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Office: TFX

FXUS65 KTFX 210326

Area Forecast Discussion
National Weather Service Great Falls MT
826 PM MST Tue Nov 20 2018


Mainly clear skies and dry conditions across the forecast area
this evening thanks to an upper level ridge of high pressure with
axis shifting across the Northern Rockies tonight. Surface
pressure gradient across the Rockies will maintain marginally
breezy winds along the east slopes of the Rockies tonight, which
in turn is keeping temperatures relatively mild from Cut Bank
south through Great Falls. Have raised minimum temperatures
several degrees tonight in these areas as well as winds following
observed trends this evening. Otherwise, no additional updates are
needed to the remainder of the forecast. Hoenisch


High pressure will keep the area dry through Wednesday. Breezy
westerly winds will help warm temperatures to at least 10 degrees
above normal. However, a series of weather systems will move into
the area for the latter part of the week. Clouds will increase on
Thanksgiving, but precipitation will likely remain in the
mountains. Precipitation will become more widespread Friday into
Saturday, with light accumulating snow possible down to the plains
and valley floors, as temperatures cool into the 20s and mid 30s
on Saturday. Drier and slightly warmer conditions are expected
early next week. -TP


Updated 0000Z.

VFR conditions prevail through Wednesday as an upper level ridge
shifts east across the Northern Rockies and Montana. Just some
scattered high level clouds along the northern border tonight with a
slight increase in high clouds Wednesday. Breezy west winds through
Wednesday at KCTB, KGTF and KHVR with relatively light winds at SW
MT terminals. Hoenisch


/ISSUED 430 PM MST Tue Nov 20 2018/
High pressure aloft will keep skies mostly clear through Wednesday
with only some high clouds passing overhead. Breezy westerly to
southwesterly winds aloft will continue over ridge tops and along
the Rocky Mountain Front through the period, diminishing overnight
tonight and ramping back up tomorrow morning. By Wednesday
evening, the pattern begins to shift to a more active and cooler
pattern, as low pressure from the west begins to erode the ridging
over the area through Thursday night. A series of weak
disturbances will traverse the area embedded within a moist
southwesterly flow pattern aloft, resulting in increasing cloud
cover and increased chances of precipitation over the western
mountains. Breezy westerly downslope winds will continue through
this period, which will likely keep lower elevations dry,
especially over the plains of north central Montana. Temperatures
will cool gradually with the increasing clouds and the transition
to more of a northwest flow aloft, but they should remain above
normal during this time. The precipitation may make holiday travel
difficult over mountain passes.

Friday through Saturday...This period will likely bring the best
chance for widespread travel impacts. Forecast models have come
into better agreement with moving a low pressure system from the
Gulf of Alaska southeast through Montana into the Great Plains. An
associated Canadian cold front will swing southeast through the
area Friday into Friday night, which will cool temperatures to
near freezing for most of the area on Saturday. The passage of
this system will likely bring widespread precipitation to the area
by Friday night, which will mostly be in the form of snow. At
this time, the greatest snowfall amounts will likely be south of a
Great Falls to Lewistown line, where valley locations could
receive 2 to 4 inches of snow, with 4 to 8 inches possible in the
mountains. There is lower confidence with regards to snowfall
amounts over the Northern Plains, as models have recently veered
away from bringing measurable snowfall to the area. Regardless,
given that this will be a high volume travel period, winter
weather highlights will be considered.

High pressure aloft attempts to build back into the area starting
Sunday, but another round of upper level disturbances tracking
through the area through Wednesday will keep the forecast in an
active pattern. Waves of precipitation and gusty winds are
expected as these disturbances track through our area Sunday
through Wednesday. -TP/BH


GTF  38  51  31  49 /   0   0   0   0
CTB  33  48  28  44 /   0   0   0   0
HLN  23  47  26  46 /   0   0   0  10
BZN  18  46  24  43 /   0   0   0  10
WEY   5  41  16  34 /   0   0   0  70
DLN  18  46  26  43 /   0   0   0  10
HVR  27  51  30  51 /   0   0   0   0
LWT  27  51  29  48 /   0   0   0  10




Office: MSO FXUS65 KMSO 202142 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 242 PM MST Tue Nov 20 2018 .DISCUSSION...Seasonally mild days and cold nights through should be expected through Wednesday afternoon under persistent high pressure. Valley fog will be a possibility in Northwest Montana under a stable atmosphere for both Wednesday and Thursday early morning periods, with Thursday being the least likely of the two due to high clouds and less cooling. Overnight Wednesday, expect high clouds out in front of an unsettled airmass to moderate radiational cooling. By Thanksgiving, conditions will start off wet, with a possibility of freezing drizzle in valleys west of Kalispell, and a rain/snow mix everywhere else below 4500 feet. Little to no snow accumulation is expected during this time frame below 4500 feet, however higher elevations will see between 3 to 6 inches through Friday morning. Friday will see temperatures trending colder and winds turning towards the northwest by afternoon. Snow levels will slowly drop through day, and areas that began as rain will transition to a mix and then finally all snow. By Friday evening, snow will taper off across northwest Montana. For north central Idaho, the Idaho/Montana mountain passes, and the I-90 corridor (including the southern Mission valley, Missoula valley, and Bitterroot valley) will experience periods of moderate snowfall. Snowfall amounts will range from 2 to 4 inches in the valleys, and 6 to 12 inches in higher terrain. Central Idaho valleys should see their first accumulating snowfall of the season, with around 2 to 4 inches likely from Orofino south through the Camas Prairie. We have moderate confidence that the rest of the travel weekend will see snow showers across the entire forecast area. There are hints in the models for a possibility of localized snow bands Saturday morning and afternoon. The exact location, timing, and impacts are not certain at this point, and should come into focus closer to the event. Long range, we expect unsettled weather to continue through Wednesday. The models are not in agreement on the details at this time. && .AVIATION...VFR conditions will dominate the area, with the exception of Northwest Montana. For the past two nights, localized areas of freezing fog have developed in the Flathead valley and areas north and west. It is likely these conditions will persist after midnight tonight. For terminals KMSO, KBTM, and KSMN: shallow fog may develop right at sunrise. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$
Office: BYZ FXUS65 KBYZ 210314 AFDBYZ Area Forecast Discussion...Updated National Weather Service Billings MT 814 PM MST Tue Nov 20 2018 .UPDATE... Going forecast in good shape tonight. No changes planned. Chambers && .SHORT TERM...valid for Wed and Thu... Strong upper level ridge will continue to bring dry and mild conditions through Wednesday. Temps across the region rose a bit higher than expected today, and the warming trend will continue tomorrow as the ridge axis shifts to our east. Should see some locations reach the low 60s on Wednesday. Gusty SW-W winds will continue along the western foothills, but mid level winds won't be strong enough for anything higher than gusts in the 40s. Ridge will break down as a Pacific shortwave moves thru the area Thursday into Thursday night. Downslope winds will continue so temperatures on Thanksgiving Day will remain above normal despite the cloud cover, w/ a few light showers or sprinkles possible across lower elevations by late afternoon and evening. Mountains will see a little snow w/ the shortwave. Better chance of mountain snow begins late Thursday night with the next more unstable Pacific shortwave. There is also an opportunity for a bit stronger gusts along the western foothills late Thursday night, but do not see enough potential for more than 50 mph gusts. Travel conditions Wednesday and Thanksgiving Day will be ideal with the above normal temperatures and mostly dry weather. It could be a different story for the back side of the Holiday weekend...see extended discussion for details. JKL .LONG TERM...valid for Fri...Sat...Sun...Mon...Tue... Did not make any large changes from the previous extended forecast as models are coming into better agreement with the shortwave that will affect the region Friday through Saturday. Pacific shortwave approaches the area on Friday, and moves SE toward the central plains on Saturday. Chances for mountain precipitation increase during the day on Friday, with slight chances of rain in the foothills. Models had some disagreement with QPF placement Fri. night and Saturday. In general, precipitation chances will spread W to E through the area Fri. night and will continue over the area Sat., but decrease from N to S. Expect precipitation to change to all snow Fri. night and remain mostly snow on Saturday. Will have highs in the 40s Fri. and in the 30s Saturday. The GEFS plumes showed two possible QPF scenarios Fri. night for KBIL. One scenario supported a possible couple inches of snow and the other showed several inches. Snow amounts can be refined as confidence increases with the system. Another shortwave moves SE into the area Sunday, but models did not show much QPF. Did have a slight chance of snow E of KBIL Sun. night. Monday looked drier under upper ridging. Forecast stays mainly dry through Tuesday due to the ridge. While GEFS plumes showed wide temperature spreads later in the period, model blends had 30s for Sunday and Monday, with 40s on Tuesday. Gusty WSW winds continue at times W of KBIL during the period. Have emailed customers about snow potential and travel impacts for the holiday period. Arthur && .AVIATION... VFR conditions expected to prevail over the next 24 hours. Winds gusts at KBIL and especially KLVM could be 30 to 40 knots. Reimer && .PRELIMINARY POINT TEMP/POPS... Wed Thu Fri Sat Sun Mon Tue ----------------------------------------------------------- BIL 035/057 036/052 035/048 028/037 021/037 020/037 025/043 00/U 01/E 22/R 45/O 22/S 11/B 11/B LVM 032/055 033/048 036/044 024/034 018/035 021/037 027/041 00/N 01/N 23/O 55/S 11/N 21/N 12/O HDN 024/060 026/053 031/050 026/038 019/040 018/038 021/043 00/U 01/B 21/B 35/O 21/B 21/B 11/B MLS 026/057 026/055 033/049 025/035 019/034 018/033 020/040 00/U 00/B 11/B 23/S 21/B 21/B 10/B 4BQ 026/057 027/054 032/049 025/037 019/037 018/034 019/040 00/U 00/B 11/B 24/O 21/B 21/B 10/B BHK 025/054 025/051 031/047 022/033 016/030 012/028 015/035 00/U 00/U 11/B 12/S 21/B 21/B 12/S SHR 024/058 025/053 029/048 024/034 016/037 016/037 018/043 00/U 01/E 21/B 25/S 31/B 21/B 11/B && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$
Office: GGW FXUS65 KGGW 210159 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 659 PM MST Tue Nov 20 2018 .DISCUSSION... It looks like fog will not be as widespread and thick as earlier thought, so decreased this for tonight. Backdoor front moving southwest from Canada will make temperatures and fog/weather tricky for the next 24 hours. It's currently approaching the NE zones. Models were too cool for most of the area today, which has been the case this fall when there is full sunshine in a warm air advection pattern. Hopefully 00z models will provide some insight into what will happen Wednesday. TFJ Previous Discussion... Under the ridge of high pressure, temperatures have risen to the middle and upper 50s across southwestern portions of the CWA with highs topping out in the lower 40s farther northeast over the snowpack. As we head into tonight, a stratus deck currently over northern North Dakota will retreat back to the west and lower as it does so. This will turn into fog across far northeastern Montana tonight with radiational fog developing elsewhere, most widespread north and east of Fort Peck Lake. Patchy freezing drizzle/mist may accompany the dense fog, especially across the far northeast part of the state with the retreating/lowering stratus deck. The depth of the low-level moisture will be near 1000 feet with the stratus deck and about 10 knots of wind shear is expected near the top of this layer. This is right on the fringe of whether or not freezing drizzle will occur, but even if it doesn't, the mist associated with the dense fog could be enough to cause some problems. While only trace amounts of ice would be expected in any freezing drizzle/mist, this would make for slick conditions on any untreated surface. A dense fog advisory may be needed for some areas this evening into tonight, however, there remains a little uncertainty with just how far west the stratus deck will progress and thus where the most dense fog will occur. Will therefore pass this on to the evening shift for consideration. The ridge will keep the area mild and dry (though fog for the next couple nights in the valleys remains a possibility) through the Thanksgiving holiday with highs on Thursday expected to range from the lower 40s northeast to the upper 50s southwest with clouds increasing from west to east through the day. Temperatures will cool just slightly Friday behind a weak, mostly dry front. Winds become northerly behind a stronger cold front Friday night into the weekend with notably cooler temperatures. This front will also bring a chance for some precipitation, primarily Friday night into Saturday. The brunt of the energy associated with this storm system may pass south of the area, which would greatly limit the precipitation chances. For this reason, have continued with just a chance of snow showers. Another ridge of high pressure looks to move in sometime early next week, which would keep the area dry with moderating temperatures. -Mottice && .AVIATION... FLIGHT CAT: VFR with periods of MVFR this evening through early tomorrow morning in fog and low stratus. IFR possible LIFR northeast of the TAF sites. DISCUSSION: Clear skies with fog developing this evening that will lift Wednesday morning. Wind: Variable winds with speeds 10 kts or less. See tafs for details. TFJ && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && $$