Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 241534
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
934 AM MDT Wed May 24 2017

.UPDATE...
Issued at 934 AM MDT Wed May 24 2017

Forecast for today is on track. The thermodynamic environment
across the Plains is a bit more unstable than yesterday, but still
very dry at the surface with dewpoints in the 30s to near 40. Do
not anticipate anything more than convective cumulus development
this afternoon with no precipitation reaching the ground. This
afternoon some gusty west/west-northwest winds should occur from
I-25 and west into the foothills. Will be a warm, mostly sunny
day with highs in the low 80s Plains, 60s to low 70s in the
mountains and foothills.

&&

.SHORT TERM...(Today and tonight)
Issued at 423 AM MDT Wed May 24 2017

A sharp high pressure ridge will provide for a warm and dry day
across the forecast area. 700 mb temps warming to +12C and
downslope winds support highs pushing into the lower 80s along the
Front Range. Don`t expect anything more than scattered convective
clouds this afternoon with the ridge axis and dry airmass
overhead. By late tonight, the leading edge of cold advection
aloft will reach northwest Colorado. This should be enough to
bring a low risk of a few showers into Jackson and northern
Larimer counties late tonight. Otherwise dry and mild conditions
will persist overnight.

KFTG shows some channels of gusty west winds moving down the
foothills early this morning. Those winds will continue to spread
down the foothills and across the nearby adjacent plains today
with cross mountain flow near 30 knots, mountain top stable layer
this morning, and then better mixing this afternoon. Peak gusts
may reach 40 mph in the foothills this morning, with lighter winds
as one moves east onto the plains.

.LONG TERM...(Thursday through Tuesday)
Issued at 423 AM MDT Wed May 24 2017

Models continue to show a generally unsettled period of weather
through the holiday weekend and early next week. Thursday will
see a cold front move into northeast Colorado as a subtropical jet
aloft spreads across the southern half of the state. Moderate
levels of moisture and instability will be available to support
some thunderstorm activity in the afternoon. Model soundings show
a little more than 1000 j/kg of CAPE. Q-G diagnostics indicates
that weak subsidence will be in place, but not strong enough to
inhibit the development of showers. Daytime heating over the
mountains should be enough to initiate convection over the
mountains and foothills that moves out over the plains.

Friday still has the potential to be the more active day. Models
show an increase in moisture and instability with CAPEs
approaching 2000 j/kg. However, a good cap will also be in place.
The upper flow pattern will be similar to Thursday, but with a
little more Q-G forcing for ascent. If the cap is eroded by the
dynamic forcing aloft, then strong to severe thunderstorms will be
possible Friday afternoon.  Temperatures on both days will be in
the 70s across the plains. With the temperatures around seasonal
normals, melting of the snowpack should moderate from any drastic
rise experienced after Wednesday`s warm temperatures.

Over the weekend, an upper trough from the Pacific Northwest is
forecast to be moving over Colorado. Showers will be a good bet
Saturday, then Sunday and Memorial Day may be a little drier with
temperatures still just below seasonal normals. Cyclonic
northwesterly flow aloft will remain over the state, keeping the
threat of afternoon shower activity going into early next week.
Temperatures will be gradually warming as a ridge builds over the
southwestern U.S., however, the cyclonic flow will be slow to
yield to the rising heights, leaving the chance of showers over
the foothills and adjacent plains each afternoon.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 934 AM MDT Wed May 24 2017

VFR conditions through Thursday afternoon at the TAF sites with at
best scattered mid/high level clouds through midday Thursday. The
drainage winds have diminished presently and light west winds
should continue through early afternoon at the TAF sites. Mid
afternoon or so expect winds to increase out of the west-northwest
with some gusts over 20 kts at DEN and APA. BJC direction should
remain westerly but could also see gusts over 20 kts this
afternoon. Drainage winds again after 03Z. Tomorrow after mid-
morning winds should be east or northeast and thunderstorms are
possible after 20Z or so with variable gusty winds at the TAF
sites. Right now that is outside of the TAF window but certainly
something we will watch and probably include in this afternoon`s
TAFs.

&&

.HYDROLOGY...
Issued at 423 AM MDT Wed May 24 2017

Snowmelt will increase today with very warm temperatures, resulting
in elevated streamflows over the next couple days. At this time,
the River Forecast Center has only the Cache La Poudre near the
canyon mouth northwest of Fort Collins and the Cache La Poudre
near Greeley approaching Flood Advisory stages for minor lowland
flooding by late Thursday. Otherwise, no issues other than local
runoff from thunderstorms expected over the next several days, as
temperatures cool back down.

&&

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

$$

UPDATE...Schlatter
SHORT TERM...Barjenbruch
LONG TERM...Dankers
AVIATION...Schlatter
HYDROLOGY...Barjenbruch


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