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Office: BOU

FXUS65 KBOU 201102

Area Forecast Discussion
National Weather Service Denver/Boulder CO
402 AM MST Tue Feb 20 2018

.SHORT TERM...(Today and tonight)
Issued at 350 AM MST Tue Feb 20 2018

Very light snowfall continues to diminish across northeast
Colorado this morning as the upper jet responsible for the snow
has moved northeast into the northern high plains. Only some
lingering light banded snowfall across far northeast Colorado and
over portions of Douglas and Elbert counties remains. Appears
this will also diminish before sunrise. Will let the wind chill
advisory run its course through early this morning as observations
still showing wind chill readings in the -12 to -27 degrees below
zero, coldest up along the Wyoming border and over Jackson county.
Decided to also add remainder of far northeast Colorado and
extending down to Lincoln county as well as winds are still brisk
there. As winds continue to relax after sunrise, wind chill
issues will diminish.

Despite the exiting weather maker, there still remains lingering
troughiness across the Great Basin this morning and a weak wave
will push across the area this afternoon and evening. This will
result in continued scattered snow showers in the mountains and
some of this expected to spill east over the adjacent plains this
afternoon under shallow upslope flow. Moisture depth is rather
shallow so expect any accumulation's on the plains less than 1/2
inch of snow. Improving conditions later tonight with clearing

Temperatures will remain quite cold today under the influence of
cold surface high pressure building south and east across the
central plains. Readings will struggle to get out of the teens
from Denver northward.

.LONG TERM...(Wednesday through Monday)
Issued at 320 AM MST Tue Feb 20 2018

Active weather pattern for the long term with persistent pieces of
energy moving around the base of an elongated, nearly stationary
upper trough. The trough extends from the North into Canada south
across the Great Basin and into the Pacific wear it wobbles but
stays persistent through Saturday with the help of a strong,
nearly 590 decameter high over the Atlantic. The synoptic pattern
will keep SW flow over the State keeping decent moisture moving
into the SW and central mountains with slightly less for the
Northern mountains and adjacent plains. For Wednesday moisture
and SW flow ahead of the upper trough will help to keep a slight
chance of snow for the central mountains with dry conditions on
the plains. Temperatures will rebound slightly from Tuesday but
highs will still be hovering around freezing. Light snow will fall
in the mountains into the early morning with little accumulation.

For Thursday a piece of energy moves up with the SW flow providing
enough lift for increasing snow chances for the high country. Cld
air will continue to dominate the plains with increasing clouds
and temperatures staying around or just below the freezing mark.
Thursday into Thursday evening moisture deepens with high RH
levels through the 350 mb level. Friday another upper trough will
drop out of the Pacific NW and settle into the Great Basin
maintaining the SW moist flow into the state. the upper jet will
shift slightly northward helping to increase the chances of a more
convective CSI set-up for Friday snow. The main thing that seems
to be lacking is a strong cold push with the small chances of
freezing drizzle where there is increased drying. Will have to
monitor model consistency with Friday's set-up.

Over the weekend, the GFS and to an extent the EC shows the trough
that brought weather to the region on Friday move eastward over
the central US. This will be followed up with more zonal flow as
a new trough develops over the Pacific NW. Models still hinting at
some CSI produced precip returns into Saturday morning before
stabilizing and drying out Sunday. Temperatures for the weekend at
this time look to be in the 30s reaching into the 40s by Sunday.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 320 AM MST Tue Feb 20 2018

Varying MVFR cigs early this morning with still some very light
snow/flurries remain at KDEN/KAPA. This should all be ending
before sunrise. Expect some improvement in low stratus deck this
morning. Expect additional light snow/flurries to move back into
terminals mid afternoon through evening, especially at kbjc/kapa
and may also make it to KDEN as well. Looks real light so any
accumulations will be under a half inch. Gradual clearing later
tonight as surface winds return to drainage.


Wind Chill Advisory until 8 AM MST this morning for COZ030-035-



SHORT TERM...Entrekin

Office: PUB FXUS65 KPUB 200659 AFDPUB Area Forecast Discussion National Weather Service Pueblo CO 1159 PM MST Mon Feb 19 2018 .UPDATE... Issued at 1159 PM MST Mon Feb 19 2018 Updated forecast to increase intensity/coverage of snow into the early morning hours. UPDATE Issued at 938 PM MST Mon Feb 19 2018 Banded snow along and east of the mountains onto the plains has been rather vigorous this evening, with spotty 1-3 inch accums already from Pueblo up into nrn El Paso County. Still have a couple hrs to go before bands shift east and begin to dissipate, so have increased pops along I-25 and portions of the plains, with another inch or two of snowfall possible, mostly before midnight. && .SHORT TERM...(This evening through Tuesday) Issued at 325 PM MST Mon Feb 19 2018 ...Strong winds and Heavy snow to continue across the southwest mountains tonight... Mean trof across the Great Basin will continue to gradually shift eastward towards western CO overnight. First round of energy will be lifting out across CO in strong southwest flow aloft this evening. Its been snowing hard across the southwest mountains through the day given strong orographics. Visibilities have been abysmal at times across Wolf Creek Pass and La Manga Pass. Even Cochetopa Pass in the La Garitas has seem some poor visibilities at times but overall looks like there has been less snow the farther north one goes. Winter weather highlights across the mountains still look on target. Even seeing some isolated thunder across southwest locally intense snowfall with convective snow bursts will be possible. Have introduced some thunder into the grids to account. Overall another foot of snow looks likely across the eastern San Juans by morning with lesser amounts for the Sawatch/Mosquito and crest of the Sangres and Pikes Peak. Meanwhile...lapse rates steepen aloft late this afternoon through tonight and already seeing convective snow showers across the southeast mountains, a few of which are developing/spreading into the adjacent plains. Gusty winds will be the main concern with these over the mountains...but as they shift eastward over the arctic airmass in place across the plains...this threat will be less likely. High res models have caught on to farther south position of the front across the plains and suggest convective snow showers will override the cold air across the far eastern plains this evening. They will be moving pretty fast though and this should help limit accumulations. But locations to watch will be Kiowa and possibly Prowers counties later this evening. A quick inch of accumulation would not be out of the question. Otherwise...precipitation should wind down quickly for most of the plains overnight although retreating cold front will make another southward push through the plains overnight and will likely see stratus break but reform and lower again towards early Tuesday morning across the plains. Always difficult to say what the extent of any flurries, or freezing drizzle/fog will be behind the front. Models have had a tough time capturing the southern penetration of the front and depth of cold air lately and today was no exception. Have introduced some low pops along/north of highway 50 late tonight/early Tuesday morning...though suspect that drying aloft may limit precipitation efficiencies more so tomorrow morning. Upper trof lingers across the great basin and western CO on Tuesday as more energy drops in from the Pacific northwest. Moisture shallows out quite a but, though it will still remain unstable enough to maintain scattered pops along the Continental Divide. Another impulse lifts out across the area during the afternoon...and with continued southerly upslope into the Palmer Divide, the Pikes Peak region may see some more light snow during the afternoon as snow showers develop over the mountains and spread eastward. Overall, accumulations look light. Dropped MaxT forecast across the plains quite a bit, anticipating a farther south cold front position and less warming than guidance suggests. -KT .LONG TERM...(Tuesday night through Monday) Issued at 325 PM MST Mon Feb 19 2018 Tuesday night and Wednesday...As the upper trough axis swings east, pcpn is forecast to come to an end over the central mts and Pikes Peak region Tue night around midnight, while light upslope flow across the plains will keep the east chilly. As the next upper shortwave approaches from the west late Wed afternoon, isolated snow showers return to the continental Divide. West to southwest winds across the higher elevations will remain breezy to strong, while the lower elevations will remain under cool easterly flow. Highs are expected to only climb into the upper 20s to upper 30s for most locations. Thursday and Friday...The next upper low pressure system drops out of the Pacific NW and crosses the Great Basin on Thu, then sweeps across the region on Fri. The GFS and EC models disagree on placement of this low, with the GFS placing this system farther south which would have a greater impact on the cwa into the weekend. Since the models differ on low placement but agree on a system moving across the region during the same time frame, will hold with high pops for the mts areas starting late Wed night through Fri, then isolated pops for the plains Thu and Fri. as the location gets pinned down better over the next day, the forecast will become more specific on snow amounts and location. Look for highs in the 30s to lower 40s for the high valleys, and 40s to mid 50s for the plains. Saturday through Monday...Plenty of upper level activity to keep Colorado occupied over the weekend, though beyond Friday the models are having a very tough time deciphering the upper track. Will keep the mention of snow over the central mts over the weekend because that seems to be a safe bet under this pattern, and partly cloudy skies elsewhere. Extended models are not indicating any llvl cold air intrusions for the east, so look for max temps each day in the upper 30s to mid 40s for the high valleys, and mid 40s to mid 50s for the plains. Moore && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1030 PM MST Mon Feb 19 2018 Light snow will come to an end 08z-10z at KCOS and KPUB, although IFR conditions may linger through the morning and into the afternoon Tue as weak easterly winds keep low clouds and patchy fog in place. Gradual improvement to VFR then expected from late afternoon into the evening at both sites. At KALS, VFR expected overnight and through the day Tue, with sw winds continuing to gust in the 20-30 kt range through most of the next 24 hrs. Over the mountains, IFR widespread with snow and low cigs, some vis improvement expected late Tue as snow diminishes, though most higher terrain will remain obscured by clouds into the evening. && .PUB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 8 AM MST Tuesday for COZ058-061- 065>067-073-075-082. Winter Storm Warning until 8 AM MST Tuesday for COZ060-068. && $$
Office: GJT FXUS65 KGJT 201056 AFDGJT Area Forecast Discussion National Weather Service GRAND JUNCTION CO 356 AM MST Tue Feb 20 2018 .SHORT TERM...(Today through Wednesday) Issued at 356 AM MST Tue Feb 20 2018 Been able to shave off some of the winter highlights as winds and heavy snow threat has been diminishing with the jet and large scale ascent shifting northeast. However plenty of other meso- scale features keeping snow going over the area. Up north seeder feeder seems to be keeping light snow going. EPV in a fairly distinct lapse rate gradient is keeping some decent convective bands coming off the UnCo into the Olathe to Montrose region and may have a sunrise surprise definitely impacted along Hwy 50 at times. This also probably associated with the mid level front pushing through. Much of the southern mountains have shut off except for some isolated showers. Cold air continues to spill in overhead as the main trough swings through which means convective bands of snow continue through the day. Mainly centered on the terrain but some of the showers are likely to drift into the valleys at times. Where? Yes. Much cooler today though less breezy. Clearing and cold tonight as we get a short break between the next system. New snow cover and drier air will mean some spots will really be dropping off and could be the coldest reading of the winter in some spots up north. Wednesday with the cold start and cold air in place still cooler than normal temperatures stay in place. This will set the stage for another snow event as the next trough digs to or west and pushes moisture and southerly flow into the Colorado mountains late in the day. More on that below. .LONG TERM...(Wednesday night through Monday) Issued at 356 AM MST Tue Feb 20 2018 The long term period will be dominated by a long wave trough that is carved out over the western states, centered over the Great Basin. Temperatures through Sunday will remain quite cool as H7 temps throughout the period remain within the -10C to -14C range from south to north respectively. Southwest flow will dominate through Friday, with some showers possible over mainly the higher terrain Wednesday night into Thursday with a weak shortwave ahead of the main upper level trough. Not expecting too significant of precipitation with these showers as QPF amounts remain fairly light. This is similar in design to a warm advective regime, without the warm air. The main upper level trough will kick out of the Great Basin and move through the area Friday into Saturday morning, bringing another round of snowfall. Breezy to windy conditions are anticipated across the area Thursday night into Friday afternoon ahead of this system, which looks fairly convective once again as we head into the Spring months. The pattern remains progressive as another trough will move through in northwest flow Sunday into Monday morning. Temperatures look to moderate heading into the coming week with a return to above normal temps as a ridge tries to move in and influence our weather beyond this coming weekend. Models seem to be in fairly good agreement overall on the timing of these systems but differences as always lie in the fine details. Regardless, this progressive active pattern looks promising for more snowfall across the mountains continuing what has been a snowy February. && .AVIATION...(For the 12Z TAFS through 12Z Wednesday morning) Issued at 356 AM MST Tue Feb 20 2018 Expect conditions to slowly improve today as the main part of this storm has shifted east. However unstable air means showery precipitation and this could again quickly drop VFR to LIFR as snow moves through. This most probably in the KASE and KTEX areas but can not rule this out of most of the western Colorado TAF sites. Winds could gusts near the showers but overall wind conditions will be much improved over yesterday. Overnight much colder and clear conditions move in which could lead to some fog issues but this airmass is quite dry so confidence very low on timing and locations. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Winter Storm Warning until 8 AM MST this morning for COZ009-012. Winter Weather Advisory until 8 AM MST this morning for COZ008- 010-017. UT...None. && $$ SHORT TERM...15 LONG TERM...MDA AVIATION...TGJT