Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 251524
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
924 AM MDT Mon May 25 2020

.UPDATE...
Issued at 913 AM MDT Mon May 25 2020

No updates planned at this time. Some lingering low clouds over
the Palmer Divide and far eastern plains this morning. Latest HRRR
keeps any showers or possible storms west of Interstate 25 this
afternoon, similar to what is already in the grids.

&&

.SHORT TERM...(Today and tonight)
Issued at 435 AM MDT Mon May 25 2020

The short wave trough responsible for a nice rain across most of
north central and northeast Colorado is moving east. The trough
axis is roughly over I-25 now. Area radars and GOES-16 satellite
have shown all the precipitation have shifted into Kansas and
Nebraska so have dropped PoPs across the far northeast plains the
remainder of the morning. There is a decent cold pool aloft
associated with the ejecting trough, staying between -16 and -18
degC at 500 mb through today. This will provide instability,
especially across the high country, during the afternoon hours.
Convective initiation in the mountains should be between 11 AM
and 1 PM, and storms will move out of the WNW to the ESE
throughout the day. Surface winds out of the north and northwest
across the plains will push the low-level moisture out of our
area, resulting in dewpoints in the low to mid 30s. Thus, any
showers that move off the mountains will have a hard time
maintaining themselves. PoPs today likewise will drop off quickly
from west to east across the plains, and any rain that does fall
east of the foothills will be light. Any showers that form in the
mountains and foothills are likely to have thunder given the
instability with SBCAPEs in the 500 J/kg range. Moisture at all
levels is lacking, with under 0.50" precipitable water across most
of our area, so rainfall amounts will be light in the mountains
and foothills as well. In terms of snow chances, 700 mb temps warm
from -3 deg to around +2 degC by mid afternoon today, limiting
any potential accumulating snow to above 10,000 feet, and even
then only up to an inch is possible.

High temperatures will be much warmer than Sunday but still well
below normal given the cool 700 mb temps. Downslope warming will
help some, and the sun will be out across the plains into early
afternoon, resulting in highs in the mid to upper 60s. In the
mountain valleys expect highs in the 50s, but only in the 30s and
40s above 10,000 ft.

Precipitation chances drop after 9 PM pretty much everywhere as
the cold pool aloft moves east. Clearing skies will result in
below freezing temperatures for the mountain valleys, and upper
30s in the cool spots across the plains to mid 40s for the urban
heat islands. Frost is unlikely tonight but it could come close in
the low spots in Lincoln County, especially for Limon.

.LONG TERM...(Tuesday through Sunday)
Issued at 435 AM MDT Mon May 25 2020

Drier air, in WNW flow aloft, will be over the area on Tue with
warmer temps. Highs will reach the 75 to 80 degree range over
nern CO.

On Wed, a disturbance embedded in the WNW flow aloft, will move
across late in the day or at night. Cross-sections show
increasing moisture with this feature. MLCAPE values are only in
the 300-500 j/kg range, however, will see a chc of showers and
storms, across the higher terrain, as the above mentioned feature
moves across. At lower elevations will keep in a slight chc
showers and storms for Wed night as a cold front moves across. As
for highs, readings will be in the upper 70s to mid 80s over the
plains.

On Thu, an upper level high will begin to build over the Great Basin
into the swrn US.  This will leave nrn CO in NW flow aloft with some
moisture embedded in the flow. At this time, there appears to be
enough instability to keep in a chc of aftn showers and storms,
over the higher terrain, with a slight chc along the I-25
Corridor. Highs will be cooler, over the plains, as readings stay
mainly in the 70s.

Little change is expected on Fri, as there will be enough moisture
and instability, to keep in a chc of aftn showers and storms,
over the higher terrain, with a slight ch along the I-25
Corridor. Highs will rise into the lower to mid 80s over nern CO.

By Sat, the upper level high will move into CO with weak flow aloft.
Both the ECMWF and GFS show quite a bit of subtropical moisture
rotating around the high. Thus will keep in a chc of convection
mainly over the higher terrain, with a slight chc at lower
elevations. Highs will remain above normal.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 913 AM MDT Mon May 25 2020

VFR conditions are expected. Low probability of ILS conditions at
DEN late this afternoon 050-060. Light northerly wind this
morning, then a little stronger this afternoon, 10-15 kts. Gusts
20-25 kts possible by 23z-01z remaining that way into the evening
hours. Winds shouldn`t be much of an issue this evening with a
normal drainage wind pattern tonight after midnight (SSW DEN/APA,
W at BJC) and speeds will be 10 kt or less.

&&

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

$$

UPDATE...Cooper
SHORT TERM...Schlatter
LONG TERM...RPK
AVIATION...Cooper


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