Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 101124
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
424 AM MST Tue Jan 10 2017

.SHORT TERM...(Today and tonight)
Issued at 356 AM MST Tue Jan 10 2017

Wly flow aloft will continue over the area today and tonight.  Cross-
sections still show decent moisture and favorable lapse rates thru
the aftn in the mtns so will continue to see periods of snow and
gusty winds over the higher passes.  There could be a brief lull
early this morning but it could increase again by late morning into
the aftn especially along along and north of I-70.  Tonight with
lapse rates becoming more stable snowfall may decrease this
evening although gusty winds will continue over the passes.

Over nern CO it will be dry thru the aftn with highs in the mainly
in the upper 40s to lower 50s across the plains.  As for high wind
potential not sure how tings are going to evolve later this aftn and
tonight.  Cross-sections do show lapse rates becoming more stable by
early this eveining and continuing overnight with a mtn wave
developing.  Component along winds are fcst in the 50-60 kt range so
there is some threat for high winds in the foothills so will issue a
watch.  Below 6000 ft not sure if stronger winds will mix down into
zns 38 and 39 so will hold off on a watch at this time.

.LONG TERM...(Wednesday through Monday)
Issued at 356 AM MST Tue Jan 10 2017

A 110-140 knot west-southwesterly jet maximum is over the
forecast area continually Wednesday through Thursday. By Thursday
night, the flow aloft becomes southwesterly but still stays in the
100-120 knot range. For much of the time, the QG Omega fields
have weak upward synoptic scale energy over the forecast area all
four periods. On Wednesday morning, a cold front and some upslope
moves into the northeast corner but it never makes it all the
westward to the foothills. All the models show that. Usually these
airmasses make it across all the planes. Drainage and downsloping
predominated Wednesday night. On Thursday, another cold front
with easterly upslope makes through all the plains into the lower
foothills by midday. The upslope lasts into the evening, then
gives way to normal drainage patterns by midnight. There is a
mountain wave set-up on the cross section again, Thursday morning.
Winds will blow in favored areas but they should not get fierce
in speed. There is decent moisture to continue over the mountains
on Wednesday and by later afternoon, there may be some low level
cloudiness getting into the plains with the upslope. The moisture
deepens in the mountains later Wednesday night and continues
Thursday and Thursday night. There is a bit of mid and upper level
moisture over the plains Wednesday night. There is pretty decent
moisture over the plains on the GFS Thursday and Thursday night,
less on the NAM but more in the lower levels those two periods.
The QPF fields have fairly decent snowfall amounts in the
mountains on Wednesday into the evening. Amounts decrease later
Wednesday night and continue with just a tad Thursday and Thursday
night. The orographic enhancement is poor from Thursday onward
with poor mountain top wind directions and speeds are down too.
There is a tiny bit of measurable precipitation out over some of
the plains Wednesday afternoon and again Thursday afternoon and
evening. For pops in the mountains will go with 60-100%s on
Wednesday, then 30-80%s Wednesday night through Thursday night.
The orographic snow models points to perhaps advisory amounts of
snowfall in the high mountains, at least Zone 31. This could be
addressed after this morning`s Winter Storm Warning expires at
18Z for the mountains. For pops on the plains will go with 0-
10%s Wednesday afternoon, then 0-25%s Thursday afternoon and
night. For temperatures on Wednesday, highs will be similar to
today`s but up to 10 C colder over the far northeast corner.
Thursday`s highs are 6-9 C colder then Wednesday`s. For the later
days, Friday through Monday, models keep the strong southwesterly
flow aloft on Friday and Friday night, then it decreases slowly
Saturday and Saturday night. A weak upper trough moves across
Colorado Sunday and Sunday night. The ECMWF has an upper closed
circulation with this going right across eastern Colorado Sunday
night. the GFS has this feature well south and southeast for the
state during that time. There is weak east and northeasterly winds
aloft on monday. If the ECMWF solution pans out there will be
more clouds and a shot at some scattered light snow for the CWA.
If the GFS is correct, it will be mostly clear.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 356 AM MST Tue Jan 10 2017

Winds were wsw early this morning and should stay that general
direction thru late morning.  By early aftn winds will become more
wly with some gusts to 30 mph.  By 00z winds are fcst to decrease
and then become more sse by both the hrrr and rap thru the evening
hours.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from 2 PM MST this afternoon through late
tonight for COZ035-036.

Winter Storm Warning until 11 AM MST this morning for COZ031-033-
034.
&&

$$

SHORT TERM...RPK
LONG TERM...RJK
AVIATION...RPK



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