Area Forecast Discussion
Issued by NWS Cheyenne, WY

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352
FXUS65 KCYS 230849
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
249 AM MDT Sun Apr 23 2017

.SHORT TERM...(Today through Tuesday)
Issued at 200 AM MDT Sun Apr 23 2017

A few forecast challenges in the short term. Strong winds a
concern today and Monday with precip timing/type as a front moves
into the area.

Currently...Water vapor showing a pretty strong system moving into
Oregon this morning, just about to move into western Idaho. Ridge
axis just about overhead at this time. Radar is PPINE at this time
with clear skies over the CWFA at this time.

For Today...Ridge axis shifts east and southwest winds begin to
increase. GFS soundings for Rawlins showing possibility of mixing
winds from 550mbs this afternoon, which are around 45kts. Craig to
Casper 850/700mb gradients increase to 32/35mtrs respectively
this afternoon and up to 44/41mtrs Monday. So definitely a windy
day especially out west. Did bump up winds, but kept winds around
40-45kts on gusts. At the same time, increasing clouds and mid
level moisture should begin to limit mixing.

Convection spreads into the CWFA from west to east this evening
into Monday. Mountains out west (Snowy/Sierra Madre) getting hit
pretty good on GFS and ECMWF Monday afternoon into the evening
hours. Latest HPC snow forecast for these mountains around 8-10
inches for snowfall through 12Z Wednesday. Later shifts will need
to consider Advisories for these two zones.

.LONG TERM...(Tuesday night through Saturday)
Issued at 1213 AM MDT Sun Apr 23 2017

Tuesday night/Wednesday...Initial shortwave trough aloft continues
to move to our southeast with decreasing areal coverage of showers
after midnight, confined mainly to the mountains. On Wednesday, the
next shortwave trough aloft moves across western Wyoming, spreading
clouds and showers from west to east across our counties, especially
in the afternoon, with decent orographics expected over our Snowy
and Sierra Madre Ranges.

Thursday...Quite a wet pattern setting up as the initial shortwave
trough aloft moves off to our east, with another stronger shortwave
developing over western Wyoming in the afternoon, and decent upper
level diffluence setting up over southeast Wyoming along with plenty
of low and mid level moisture, setting the stage for scattered to
numerous showers to develop late in the day.

Friday...Models similar in depicting a slow moving upper low over
western Colorado with deep and moist low and mid level upslope flow
over our counties, producing scattered to numerous showers with
mountain snows. Quite a cool and raw day with plenty of rain
falling. If this pattern verifies, we will expect a cool and cloudy
day with widespread showers and plenty of snow for the mountains.

Saturday...The slow moving upper low progged to move to northeast
Colorado by late in the day, with scattered to numerous showers to
continue across our counties in the wraparound precipitation band.
Continued quite cool with temperatures hovering mainly in the 40s at
lower elevations.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1128 PM MDT Sat Apr 22 2017

VFR. Winds gusting 23 to 35 knots after 13Z Sunday, with winds
decreasing after 00Z, except at Rawlins and Laramie where winds
will gust up to 28 knots.

&&

.FIRE WEATHER...
Issued at 200 AM MDT Sun Apr 23 2017

Strong winds today as high pressure moves off to our east and a
front begins to move in from the west. Could see southwest winds
gusting close to 50 MPH in the wind prone areas today.
Fortunately, afternoon humidities should remain above critical
thresholds. As the front moves into Carbon County late this
afternoon, we will see increasing chances for wetting rains and
mountain snow. Pretty unsettled weather for most of the upcoming
week with daily chances for wetting rains and mountain snow.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

$$

SHORT TERM...GCC
LONG TERM...RUBIN
AVIATION...RUBIN
FIRE WEATHER...GCC



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