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FXUS65 KBOU 251000
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
300 AM MST Wed Nov 25 2020

.SHORT TERM...(Today and tonight)
Issued at 315 AM MST Wed Nov 25 2020

Westerly flow aloft will increase today as a flat upper level
ridge passes across Colorado. Winds will strengthen across the
mountains with cross mountain flow of 40-45 knots. We will have a
stable layer near mountain top, but it appears from model cross
sections that the stable layer will also be quite deep with
little mountain wave enhancement. As a result, we still expect the
strong, gusty winds to be confined to the higher foothills and
Front Range Mountains. Given the strength of flow, would not be
surprised to see peak gusts around 60 mph above timberline, with
gusts around 45 mph possible in the higher foothills of Boulder
and Larimer Counties. Elsewhere, winds will be light today.

The increase in westerly flow and warm advection will bring
warmer temperatures. There are still a few pockets of deeper snow
cover on the plains, as well as an increase in mountain wave
enhanced clouds along the Front Range that should impact high
temperatures. Overall, minor temperature adjustments with highs in
the upper 40s to mid 50s across the plains. Just added a slight
bump in forecast highs over the the Palmer Divide and eastern
plains in areas that saw less snowfall and will have shallower
inversions.

For tonight, mountain areas will see an increase in moisture and
clouds, and probably enough to generate some light snow/flurries
in the northern mountains late. Elsewhere look for dry conditions
and seasonal temperatures.

.LONG TERM...(Thursday through Tuesday)
Issued at 225 AM MST Wed Nov 25 2020

For Thanksgiving Day, a positively tilted trough will be pushing into
the Great Basin with southwest flow over the region. The right
entrance region of a 100+ kt jet will stretch from the southwest to
the northeast moving northeast through the day. In the mountains,
lapse rates will increase through the morning combining with some
weak moisture to bring a chance of light snowfall. Precipitable
water values continue to be unimpressive with values of 0.10-0.20
inches across the higher terrain. Towards the surface the
predominant flow will be southwesterly with a lee side low forming
at the base of the foothills through the morning hours. This surface
low is currently projected to move southwest that would pull low
level winds more east to northeast. Overall, expect most areas
across the lower elevations to remain dry with lack of a strong cold
front and deep moisture, however with the modest upslope flow
provided by the shifting surface low and around 0.20-0.30 inches in
PW will keep a low chance of precipitation along the foothills and
into the Palmer Divide for late Thursday overnight into Friday.
Highs for Thursday will be around seasonal normals with temperatures
in the 40s for the plains and 30s in the mountains.

Friday, the models have come in better agreement with the track of
the upper low with solutions cutting it off and traversing it across
the desert southwest through the day. This will bring continued
precipitation chances for southwest Colorado but leave our county
warning area dry with high elevation snow ending early Friday.
Temperatures will stay be similar to Thursday.

For the post-Thanksgiving day weekend, the upper low will move into
the Texas panhandle with increasing subsidence over the region with
a building ridge. Temperatures will reflect this with highs on
Saturday in the 50s once again for the plains and 30s-40s in the
mountains and foothills with dry conditions. On Sunday a trough
coming out of Canada into the northern Rockies will just brush
Colorado to the north bringing only slightly cooler temperatures
with a dry cold front during the morning. Highs will drop back into
the 40s over the lower elevations with some morning cloudiness.

The start of next week will be dry as a ridge moves into place with
temperatures back into the 50s. Overall, the synoptic extended
pattern looks fairly weak for precipitation chances at least through
the fifth of December.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 315 AM MST Wed Nov 25 2020

VFR conditions will persist through the period with only a few
high clouds at times. South/southwest winds will prevail through
most of the morning. Then a more easterly diurnal component should
develop by afternoon, but local snow cover may provide light and
variable winds at times after 19Z. We expect a return to fairly
normal drainage wind patterns 01Z-03Z, and then holding most of
tonight.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...Barjenbruch
LONG TERM...Bowen
AVIATION...Barjenbruch
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