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Office: MFR

FXUS66 KMFR 121742
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
942 AM PST Wed Dec 12 2018

.Updated Aviation Discussion.

.UPDATE...It will be a quiet day across the area, with last
night's front departing to the east and the next front still well
offshore. Other than a few showers along the coast north of Cape
Blanco, there will be little more than fog to concern us over the
next day or so. As the current forecast illustrates this well, and
observations are will in line with expected conditions, no updates
are necessary this morning. For more information on the rest of
the forecast, see the previous discussion below.

&&

.AVIATION...For the 12/18Z TAFs...Stable weather has returned and
moisture from recent rains has produced low clouds and patchy to
areas of fog in portions of the Umpqua Basin, including Roseburg,
Illinois valley and upper end of the Rogue Valley including Grants
Pass. Low clouds and fog should burn off late this morning, but
itr's possible it could linger into the early afternoon hours in the
Illinois Valley and Grants Pass. The TAF at Roseburg shows VFR
ceilings at 20Z but it's possible it could break out sooner. Clear
skies and residual moisture will likely produce significant valley
fog with LIFR conditions likely at KRBG and KMFR tonight. However
incoming high clouds this evening and tonight could delay the onset
of lower conditions and adjustments were made in the TAF's to
reflect this. Incoming high cloud and offshore winds makes fog less
likely, but not impossible, at the coast tonight. For now we'll keep
VFR ceilings through the TAF period at Klamath Falls, but low clouds
and patchy fog cannot be riled out around sunrise. Later shifts will
need to reevaluate. -Petrucelli

&&

.MARINE...Updated 845 AM PST Wednesday 12 December 2018...A
brief but high and very steep swell will arrive this morning and
then drop back to small craft advisory levels this afternoon.
Conditions hazardous to small craft, primarily from seas, will
continue tonight into Thursday. However, south winds will start to
increase Thursday afternoon as a strong front approaches. The front
will bring south gales and associated wind waves Thursday night into
Friday morning. The most recent short range guidance is for most
part in good agreement with the timing of the front. However the NAM
still shows a strong surface low developing late Thursday night into
friday morning which if correct could delay the timing of the front
and also result in stronger south winds, then west winds after the
front moves through. For now we'll lean towards the common solutions
from the GFS and ECMWF. A gale watch remains in effect for the
period. This will also coincide with the arrival of another very
high and powerful swell, the combination of which could produce
extremely high seas up to 25 feet Friday.

Additional strong fronts and periods of powerful west swell are
expected this weekend into early next week. As a result, hazards
from both wind and seas are expected to continue as well. However,
in order to avoid confusion, headlines for subsequent events have
not been issued. Mariners should be prepared for occasional
dangerous weather and sea conditions well into next week.
-Wright/Petrucelli

&&

PREV DISCUSSION... /Issued 310 AM PST Wed Dec 12 2018/

SHORT TERM...

We're watching the trough push eastward tonight. Showers still
continue behind the wave and are visible on radar. Winds are still
rather breezy, especially east of the Cascades this morning.
Klamath Falls briefly reported a wind gust around 35 mph as the
trough axis moved through, so we'll continue the wind advisory to
12z.

As for today, high pressure will begin to build with partly
cloudy skies. Temperatures should actually trend warmer as warmer
air begins to push in from the west if you look at 850 mb
temperatures. Thursday is essentially the same story, but the
moist west flow will bring a slight chance for showers along
portions of the coast. The flow is rather zonal and the ridge
begins to flatter on Thursday, so a slight chance for some rain
along the coast seems reasonable.

Friday is the big day as we have a strong low deepening east of
130 W longitude. As this low deepens, it heads farther north into
Canada. A strong cold front is expected to accompany this system
and is easily visible looking at 850mb temperatures. As this front
moves inland, winds will pick up along the coast around Friday
morning. We looked at the potential for a high wind watch along
the coast, but felt that the pressure gradient wasn't strong
enough. We felt that a watch was needed east of the Cascades as
the 700mb flow was showing 70 to 75 knots on some of the models.

The rain and snow for this system is a little underwhelming. We
don't really have that southwest jet connection to Hawaii. Right
now we're forecasting around 1 inch of rain along the coast and
roughly 0.5 inches in the west side valleys with the Rogue valley
seeing less with downslope winds. East of the Cascades will only
see a few tenths of precipitation. Snow as a result will also only
produce 1-4 inches in the mountains.

Overall, the main weather concern will be when the front moves
onshore Friday and pushes eastward across Oregon. Look for strong
winds at higher elevations on Friday.

-Smith

LONG TERM.../Issued at 3 pm December 11th 2018/

Saturday, Dec 15th through Tuesday night, Dec 19th...
At the beginning of this time period a strong trough will be
deepening in the Gulf of Alaska. This is likely to bring strong
southerly winds in the coastal waters Saturday night as a cold front
approaches the coast. Snow levels are expected to increase into the
5500-6500 foot range due to the strong southerly flow. At this point
it appears the front will bring gales to the coastal waters and some
advisory level southerly winds across some of the forecast area.
Moderate to heavy precipitation is expected along and near the
Coastal Mountains and in Siskiyou County, with light to moderate
amounts elsewhere.

Monday into Tuesday the jet stream will then take aim on the mouth of
Columbia River, with ridging then amplifying along the West Coast.
More precipitation is expected across the area, though details
regarding how much comes inland how fast and how fast snow levels
rise is in question. At this point there is some concern that snow
levels could rise from 6500 feet to 8000 feet Tuesday into Tuesday
night. Thereafter, the GFS indicates the front weakening before it
comes in whereas the ECMWF pushes a strong front coming in with a
sharp drop in snow levels Thursday. BTL

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Surf Advisory until 4 AM PST Saturday for ORZ021-022.
     High Wind Watch from Friday morning through Friday evening for
     ORZ030-031.

CA...None.

Pacific Coastal Waters...Gale Watch from late Thursday night through Friday morning for
     PZZ350-356-370-376.
     Small Craft Advisory until 4 AM PST Friday for
     PZZ350-356-370-376.
     Hazardous Seas Warning until 10 AM PST this morning for
     PZZ350-356-370-376.

$$



Office: PQR FXUS66 KPQR 121725 AAA AFDPQR Area Forecast Discussion...Updated National Weather Service Portland OR 925 AM PST Wed Dec 12 2018 Updated Aviation section .SYNOPSIS...Showers will end this morning for a mostly dry day. A warm front will produce light rain to southwest Washington and far northwest Oregon tonight and Thursday. More widespread rain is expected on Friday when a cold front moves across NW Oregon. This front may also produce strong gusty winds for the coast and coastal mountains. Most of Saturday will be dry before another frontal system arrives on Sunday. Active weather continues through early next week. && .SHORT TERM...Today through Saturday...Water vapor imagery shows the main short wave upper trough responsible for the showers overnight has moved east of the Cascades early this morning. Rain and Cascade showers are rapidly decreasing behind this shortwave, and have expired the Winter Weather Advisory for the Cascade snow. isolated to scattered showers will continue this morning, but any additional accumulations will be light. Surface temperature observations and area web cameras suggest that the snow level is 3000-3500 feet this morning. A building upper ridge should end the showers mid or late morning. A storm in the NE Pacific will generate large and powerful surf along the south Washington and north Oregon beaches this afternoon through Thursday morning, and a High Surf Advisory has been issued. Those planning on spending time near the beaches today should be on the look out for ocean water to run further up onto the beaches than normal, and high splashing waves near jetties and exposed rocks. These run ups and waves could be strong enough to sweep people into the frigid and turbulent water. A warm front will approach the south Washington coast this afternoon and possibly generate light rain across extreme SW Washington late this afternoon and evening. There is a better chance for rain associated with this front late tonight through Thursday afternoon. The rain will be mostly confined to Washington as the front stalls north of the Portland Forecast Area, but extreme NW Oregon could see occasional rain at times, mainly along the coast and the Columbia River. The snow level should remain around 3000 feet, and the south Washington Cascades could see another 4 to 8 inches of new snow this morning through Thursday afternoon. The Washington coast and the Willapa Hills can expect 0.75 to an inch of rain through Thursday afternoon with around a half of an inch for the interior valleys and Washington Cascade foothills. Areas south of Aurora will remain dry Thursday with mild temperatures. The warm front will move north Thursday evening and a moist cold front will approach the coast. When it will move onshore and how strong its associated low are the main forecast challenges with this system, as the forecast models vary on the timing and features of the low. Have leaned towards the ECMWF and NAM models which are forecasting a slower approach of the front, and a weaker low. There is potential for strong winds along the coast and for the higher terrain of the coastal mountains as the front moves onshore Friday morning. , and expect rain to reach the coast Friday morning and inland Friday afternoon. There is a lot of moisture available with this front as models suggest it will tap into subtropical moisture as it approaches the Pacific NW. However, the Upper trough elongates as it reaches the coast which will likely divert the highest moisture southward into southern Oregon and northern California. Currently expect rainfall totals to be less than a half of an inch from Friday morning through Friday night. Snow levels will be around 3500 feet, but with the lighter rainfall totals the snow accumulation will ne be very impressive (2 to 5 inches). Post-frontal showers are likely Friday night into Saturday morning, but building upper level heights should end the showers fairly rapidly, and expect most areas to be mostly dry on Saturday. ~TJ .LONG TERM...Saturday night through Tuesday...Both deterministic and ensemble models continue to show a progressive westerly flow pattern through Tuesday. A series of fronts should move across the area for a continued wet period. Several atmospheric river events are shown in the models Sunday and early next week. The ensembles are also showing high integrated water vapor transport across the area. The GFS is slower but also comes on board with high IVWT values and a stronger atmospheric river event by Tuesday. This is quite far out in the forecast period and there is some uncertainty, but we should begin to prepare for a possible heavy rain event early next week. Snow levels will remain near to just above pass levels. Schneider/TJ && .AVIATION...Predominant VFR conditions with scattered showers continuing today under onshore flow aloft. Expect showers to decrease this morning and VFR conditions remaining through much of the period. Steady rain returns this evening as a warm front approaches. Southerly gusts to 25-30 kt along the coast after around 20z. PDX AND APPROACHES...VFR cigs continue with some showers under onshore flow aloft. Lowering cigs, but likely still low VFR. Steadier rain arrives late this evening and continues overnight as the warm front lifts north. Meanwhile, south winds again become gusty late overnight/early Thursday ahead of the approaching cold front. && .MARINE...Break between systems today, but another fast moving warm front will push across the region beginning early tonight. Likely see another round of gusty southerly winds, with gusts 35 kt and seas near 20 ft across the northern waters. Models continue to show a strengthening 972 MB surface low moving northeast, but well northwest of the waters on Thursday. It does, however, bring a cold front with stronger gales and possible storm force gusts across the waters on Friday. No long term break in sight as additional systems line up across the Pacific well into next week. The strong low on Thursday night/Friday seems to be a more potent swell generator with combined seas around 25 feet, perhaps even approaching 30 feet according to the GFS. Followed the more unified picture from the NAM/ECMWF and have undercut the WW3 data by a few feet. Regardless, winds still seem to reach gales again with seas building toward 20-25 feet. The key message remains that a very active pattern will continue through the period. && .PQR WATCHES/WARNINGS/ADVISORIES... OR...High Surf Advisory from 4 PM this afternoon to 10 AM PST Thursday for North Oregon Coast. WA...High Surf Advisory from 4 PM this afternoon to 10 AM PST Thursday for South Washington Coast. PZ...Gale Warning from 4 PM this afternoon to 7 AM PST Thursday for Coastal Waters from Cape Shoalwater WA to Cascade Head OR out 60 NM Small Craft Advisory for hazardous seas until 1 PM PST this afternoon for Coastal Waters from Cape Shoalwater WA to Florence OR out 60 NM. Small Craft Advisory from 1 PM this afternoon to 10 PM PST Thursday for Coastal Waters from Cascade Head OR to Florence OR out 60 NM. Small Craft Advisory for Rough Columbia River Bar until 4 PM PST Thursday. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. This area is commonly referred to as the forecast area.
Office: PDT FXUS66 KPDT 121702 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 902 AM PST Wed Dec 12 2018 .UPDATE...Snow showers in the northern Blue Mountains/Wallowa County/Oregon Cascades will continue to taper off through noon and would anticipate allowing the current winter weather advisory for The Blues and Wallowa County expire at 10 AM. Have also canceled the winter advisory for the lower basin and northern Blue Mountains foothills this morning as winds have fallen to below advisory level and will continue to weaken as gradients relax. Will not see much of a break in snow in the northern portion of the central Cascades with remnant upslope showers this morning/afternoon and the next system approaching this evening. This will bring heavy snow above 3000 feet with 6 to 8 inches possible at Snoqualmie Pass and 4 to 6 inches at White Pass. NWS Seattle has Winter Storm Warnings in effect from 6 PM tonight through noon Thursday for these crest locations. Based on current forecast snow levels do not think we will require matching advisories/warnings below 3000 feet. The rest of the forecast area will not see much precipitation with this system with perhaps a sprinkle in the Washington Basin/Northern Blue Mountain foothills and a light dusting of snow in the northern Blues. Will see windy conditions returning to the Grande Ronde Valley Thursday afternoon/Friday as thermal contrasts from the upper Treasure Valley to the Columbia Basin. Will need at least a wind advisory there beginning midday Thursday through Friday evening. Does look to be some potential for some locally very windy conditions developing along the foothills in the immediate vicinity of the northern Blues Thursday afternoon/Friday morning with strong isentropic descent indicated by forecast models, especially Friday on morning. I did bump these up substantially in the morning update and will take a closer look with the afternoon package. Peck && .AVIATION... && .PREV DISCUSSION... /issued 354 AM PST Wed Dec 12 2018/ SHORT TERM...Today through Friday...The weather pattern will continue to be active and progressive with frequent weather systems over the next few days. The current weather system over the region is still causing snow showers over the northeast mountains and some spill over showers over the crest of the Cascades onto the east slopes. The snow over the WA Cascades should decrease with little additional snow accumulation over the WA Cascades and east slopes so will let the advisory for snow for that area expire at 4 AM. Elsewhere snow showers due to upslope winds will continue over the northeast mountains (mainly the Blues and Wallowa Mountains) and will continue the Winter Weather Advisory for that area until at least 10 AM PST...and let the day shift extend it if needed. Snow showers will likely decrease this afternoon with little additional accumulations. While the winds in the Grande Ronde Valley have diminished behind the cold front a tight pressure gradient remains over the Lower Columbia Basin of both OR and WA as well as the Foothills of the Northern Blue Mountains and north central Oregon. Decided to extend the wind advisory for those areas to 10 AM (those which were to expire at 6 AM). Will issue refreshed advisory highlight products by 4 AM PST to reflect these advisories for both snow and wind. There will be a short break between systems tonight and Wednesday morning, but then the next system will arrive Wednesday night into Thursday morning with more rain and mountain snow, and then another system late Friday going into the extended forecast period. Will hold off on any highlights that might be needed for these systems until the current advisories expire on the day shift. Temperatures will be above seasonal normals despite the cold front which move through the region last evening. 88 LONG TERM...Friday Night through Wednesday...Friday night a weak front will cross the area with snow levels around 3500 feet. This will give the lower elevations a slight chance of rain and the mountains a chance of snow. An exception will be the Columbia Basin which will remain dry. Precipitation amounts will be light with rain amounts of just a few hundredths of an inch with less than an inch of snow in the mountains. Saturday will be a break between systems and the area will be dry aside from a few upslope rain and snow showers along the Cascade crest. Saturday night and Sunday a front and trough will begin to move ashore but it will make slow progress as it tries to dislodge a ridge over the Rockies. Saturday night will see a chance of mainly rain move across the Cascades with snow levels rising to around 5000 feet. Sunday and Sunday night will see the trough move overhead and then off to the east Monday as the system steadily weakens. Snow levels will remain around 4500 to 5500 feet and there will be a chance of lower elevation rain and mountain rain and snow Sunday and Sunday night. Monday will see just a slight chance of light rain in the lower elevations with a chance of light rain and snow showers in the mountains. Though models begin having timing differences at this point, it appears that another system will move in right behind the departing system Monday night and Tuesday with another chance of lower elevation rain and mountain rain and snow. Snow levels will be around 5000 feet Monday night and rise to 6000 feet Tuesday. Tuesday night and Wednesday a moist westerly flow with embedded disturbances will keep a chance of lower elevation rain and mountain rain and snow continuing. Snow levels will remain around 5000 to 6000 feet. Saturday through Monday temperatures will be in the lower to mid 40s with mainly 30s in the mountains. Tuesday and Wednesday temperatures will warm to the mid to upper 40s with upper 30s to lower 40s in the mountains. Perry AVIATION...12Z TAFs...A cold front has just about left the area with a trailing trough crossing the area behind it. Showers have ended or nearly so at TAF sites but rain and snow showers will continue over the mountains this mountain. Skies will have a brief clearing for the next few hours then become broken to overcast above 5000 feet this afternoon and tonight. KPDT will continue to have westerly winds of 20 to 30 kts with gusts to 35 kts this morning before dropping to 10 to 20 kts with gusts to 25 kts this afternoon and then to below 10 kts tonight. Other TAF sites will remain at 10 to 20 kts with a few higher gusts today then below 15 kts tonight. Perry && .PRELIMINARY POINT TEMPS/POPS... PDT 45 34 51 33 / 0 10 20 0 ALW 45 35 48 33 / 10 20 20 0 PSC 48 36 49 32 / 0 20 10 0 YKM 44 30 44 29 / 0 30 20 10 HRI 48 34 49 32 / 0 10 10 0 ELN 42 31 43 30 / 10 40 30 10 RDM 43 29 51 30 / 0 0 10 0 LGD 39 29 39 30 / 30 10 20 0 GCD 37 28 42 30 / 30 0 10 0 DLS 46 34 47 34 / 0 20 20 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory until 10 AM PST this morning for ORZ050- 502. WA...Winter Weather Advisory until 10 AM PST this morning for WAZ030. && $$ 74/84/84 FXUS66 KPDT 121737 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 940 AM PST Wed Dec 12 2018 .UPDATE...Snow showers in the northern Blue Mountains/Wallowa County/Oregon Cascades will continue to taper off through noon and would anticipate allowing the current winter weather advisory for The Blues and Wallowa County expire at 10 AM. Have also canceled the winter advisory for the lower basin and northern Blue Mountains foothills this morning as winds have fallen to below advisory level and will continue to weaken as gradients relax. Will not see much of a break in snow in the northern portion of the central Cascades with remnant upslope showers this morning/afternoon and the next system approaching this evening. This will bring heavy snow above 3000 feet with 6 to 8 inches possible at Snoqualmie Pass and 4 to 6 inches at White Pass. NWS Seattle has Winter Storm Warnings in effect from 6 PM tonight through noon Thursday for these crest locations. Based on current forecast snow levels do not think we will require matching advisories/warnings below 3000 feet. The rest of the forecast area will not see much precipitation with this system with perhaps a sprinkle in the Washington Basin/Northern Blue Mountain foothills and a light dusting of snow in the northern Blues. Will see windy conditions returning to the Grande Ronde Valley Thursday afternoon/Friday as thermal contrasts from the upper Treasure Valley to the Columbia Basin. Will need at least a wind advisory there beginning midday Thursday through Friday evening. Does look to be some potential for some locally very windy conditions developing along the foothills in the immediate vicinity of the northern Blues Thursday afternoon/Friday morning with strong isentropic descent indicated by forecast models, especially Friday on morning. I did bump these up substantially in the morning update and will take a closer look with the afternoon package. Peck && .AVIATION...18Z TAFs...Currently mostly clear skies this morning will gradually become broken to overcast above 5000 feet this afternoon and tonight. Breezy westerly winds 12-20kts continue through early afternoon at KPDT, KDLS, KPSC and KALW with gusts 20- 30 kts dropping to 7-12 kts during the mid to late afternoon hours and continuing into tomorrow. KBDN, KRDM and KYKM will generally see winds 6-10 kt through the period. An outside shot of a shower near KDLS, KYKM, KPSC, KPDT and KALW tonight as a weak disturbance pushes through. && .PREV DISCUSSION... /issued 354 AM PST Wed Dec 12 2018/ SHORT TERM...Today through Friday...The weather pattern will continue to be active and progressive with frequent weather systems over the next few days. The current weather system over the region is still causing snow showers over the northeast mountains and some spill over showers over the crest of the Cascades onto the east slopes. The snow over the WA Cascades should decrease with little additional snow accumulation over the WA Cascades and east slopes so will let the advisory for snow for that area expire at 4 AM. Elsewhere snow showers due to upslope winds will continue over the northeast mountains (mainly the Blues and Wallowa Mountains) and will continue the Winter Weather Advisory for that area until at least 10 AM PST...and let the day shift extend it if needed. Snow showers will likely decrease this afternoon with little additional accumulations. While the winds in the Grande Ronde Valley have diminished behind the cold front a tight pressure gradient remains over the Lower Columbia Basin of both OR and WA as well as the Foothills of the Northern Blue Mountains and north central Oregon. Decided to extend the wind advisory for those areas to 10 AM (those which were to expire at 6 AM). Will issue refreshed advisory highlight products by 4 AM PST to reflect these advisories for both snow and wind. There will be a short break between systems tonight and Wednesday morning, but then the next system will arrive Wednesday night into Thursday morning with more rain and mountain snow, and then another system late Friday going into the extended forecast period. Will hold off on any highlights that might be needed for these systems until the current advisories expire on the day shift. Temperatures will be above seasonal normals despite the cold front which move through the region last evening. 88 LONG TERM...Friday Night through Wednesday...Friday night a weak front will cross the area with snow levels around 3500 feet. This will give the lower elevations a slight chance of rain and the mountains a chance of snow. An exception will be the Columbia Basin which will remain dry. Precipitation amounts will be light with rain amounts of just a few hundredths of an inch with less than an inch of snow in the mountains. Saturday will be a break between systems and the area will be dry aside from a few upslope rain and snow showers along the Cascade crest. Saturday night and Sunday a front and trough will begin to move ashore but it will make slow progress as it tries to dislodge a ridge over the Rockies. Saturday night will see a chance of mainly rain move across the Cascades with snow levels rising to around 5000 feet. Sunday and Sunday night will see the trough move overhead and then off to the east Monday as the system steadily weakens. Snow levels will remain around 4500 to 5500 feet and there will be a chance of lower elevation rain and mountain rain and snow Sunday and Sunday night. Monday will see just a slight chance of light rain in the lower elevations with a chance of light rain and snow showers in the mountains. Though models begin having timing differences at this point, it appears that another system will move in right behind the departing system Monday night and Tuesday with another chance of lower elevation rain and mountain rain and snow. Snow levels will be around 5000 feet Monday night and rise to 6000 feet Tuesday. Tuesday night and Wednesday a moist westerly flow with embedded disturbances will keep a chance of lower elevation rain and mountain rain and snow continuing. Snow levels will remain around 5000 to 6000 feet. Saturday through Monday temperatures will be in the lower to mid 40s with mainly 30s in the mountains. Tuesday and Wednesday temperatures will warm to the mid to upper 40s with upper 30s to lower 40s in the mountains. Perry && .PRELIMINARY POINT TEMPS/POPS... PDT 45 34 51 33 / 0 10 20 0 ALW 45 35 48 33 / 10 20 20 0 PSC 48 36 49 32 / 0 20 10 0 YKM 44 30 44 29 / 0 30 20 10 HRI 48 34 49 32 / 0 10 10 0 ELN 42 31 43 30 / 10 40 30 10 RDM 43 29 51 30 / 0 0 10 0 LGD 39 29 39 30 / 30 10 20 0 GCD 37 28 42 30 / 30 0 10 0 DLS 46 34 47 34 / 0 20 20 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory until 10 AM PST this morning for ORZ050- 502. WA...Winter Weather Advisory until 10 AM PST this morning for WAZ030. && $$ 74/84/84