National Weather Service Forecast Discussion

000
FXUS65 KBOU 051055
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
355 AM MST Fri Mar 5 2021

.SHORT TERM...(Today and tonight)
Issued at 355 AM MST Fri Mar 5 2021

Clouds associated with the departing low have dropped southeast of
Limon and Colorado Springs a few hours ahead of schedule. Fog has
formed in most valley areas west of the Front Range. This should
be shallow, but may persist through mid morning. There could be a
few patches of fog further east, but the areas that had
significant precipitation cleared later and have a little westerly
wind so there`s probably not much fog on the plains.

Today we`ll have drying/warming/subsidence aloft with light winds.
Southwest flow aloft starts to develop overnight tonight, but
there`s only a little moisture increase so probably not much cloud
cover yet by Saturday morning. We`ll have a bit more west and
southwest drainage winds in places prone to that, keeping low
temperatures a little warmer in and near the foothills. We made
some minor adjustments for cooler temperatures in the mountain
valleys and warmer lows tonight along the base of the foothills.

.LONG TERM...(Saturday through Thursday)
Issued at 355 AM MST Fri Mar 5 2021

Overall quiet weather through much of the extended period with
persistent ridging into early next week, then mainly mountain snow
showers mid week onward ahead of an approaching Pacific low.

Sharp 500 mb ridging across the region early Saturday with
departing low to the east and progressive open wave shortwave
trough exiting California. Ridge shifts east and is centered over
CO/KS line by 18z Saturday. Will see clouds increase in the
mountains Saturday morning, and with west to SW flow could see
some wave type clouds spread onto the adjacent plains. Downslope
flow will provide some drying further east on the plains. Surface
lee trough on the plains will turn winds southerly & become gusty,
with gusts over 30 mph in the far east. Fire weather concerns
will be elevated on Saturday with minimum RH 15-20 percent and the
gusty winds, albeit offset by last evening`s precip. Given
marginal RH and recent rainfall will not raise any fire weather
headlines. For max temps Saturday, bumped up a few degrees over
initial blend guidance on the eastern plains. 700 mb temps warmer
Saturday than Sunday, while initial guidance had Saturday cooler
than Sunday. Saturday night the shortwave trough passes across
Colorado with most energy remaining to the north. Limited moisture
with this feature, and cloudiness Saturday night with no precip
forecast.

Weak ridging redevelops Sunday with continued warm temperatures
through Tuesday. Meanwhile a closed low moves near the California
coast, providing a moisture source that reaches the Western Slopes
late Tuesday. Upslope flow and increasing lapse rates from
cooling aloft with break out chance pops for snow showers Tuesday
evening. California low opens up and moves slowly east Wednesday
and Thursday, turning upper flow more southwesterly. 100+kt jet at
300 mb noses into Colorado Wednesday morning, with much of
forecast area in favorable left exit region for ascent. Terrain
plays a key role with precip, with westerly mid level flow and
downslope a limiting factor on the plains. Chance pops Wednesday
and Thursday mainly in the mountains, with slight chance pops
relegated to the adjacent & northern plains.

Cooling trend begins Wednesday with precip in the mountains,
lowering heights in advance of Pacific low, and increasing cloud
cover. High mountain valleys will see highs 35-40, near 40
foothills, and 50s on the plains. Canadian and to lesser extent
ECMWF bring in a cold front Wednesday during the day across the
plains, while GFS is a bit slower. Despite initial timing
differences of front, all models show further cooling Thursday,
with highs 30-35 mountains and in the 40s on the plains.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 355 AM MST Fri Mar 5 2021

VFR in the Denver area with light winds today, then normal S/W
drainage winds tonight.

&&

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

$$

SHORT TERM...Gimmestad
LONG TERM...Hanson
AVIATION...Gimmestad

NWS BOU Office Area Forecast Discussion