Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 222345
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
545 PM MDT Sun Apr 22 2018

.SHORT TERM...(This evening through Tuesday night)
Issued at 200 PM MDT Sun Apr 22 2018

Next system set to move into the area Monday. Forecast challenges
deal with overnight fog tonight and thunderstorm locations
Monday/Monday evening.

Currently...CWFA looking good this afternoon after some fairly
widespread morning fog. Looks like all locations have finally
burned off with sunny skies just about everywhere. Still have some
low stratocu over the eastern Panhandle, but that should be gone
in the next hour or so. Next cold front moving into eastern
Oregon/central Idaho.

For tonight, still believe we have a chance at some fog
development as soils are still wet and we are going to be under
clear skies/light winds. HRRR hinting at low conditions from
Kimball County Nebraska west to Cheyenne this evening after 06Z,
persisting through sunrise. Low level winds from forecast
soundings continue to be southeast in this area, so did add areas
of fog back into the forecast for tonight. HRRR also showing some
low conditions up by Lusk tonight, so added patchy fog up there as
well.

Increasing clouds through the day as upper shortwave and
associated surface cold front move into Carbon and Converse
Counties after 18Z. Looks like the front passes through the
Cheyenne area after 00Z and through the southern Panhandle by 03Z
Tuesday. Steepening mid level lapse rates as the colder mid level
air moves into the area on the order of 8C/KM with Lifted Indices
-3C just ahead of the front. Did keep isolated thunderstorms going
 in the forecast across southeast WYoming into the Nebraska
 Panhandle Monday afternoon.

Rain to turn over to snow behind the front Monday night into
Tuesday as 700mb temperatures fall from +4C monday 18Z to -4C
Monday night. Fairly fast moving system, so do not expect headline
level accumulations of snow, but some travel impacts are possible
Monday evening into Tuesday.

.LONG TERM...(Wednesday through Sunday)
Issued at 200 PM MDT Sun Apr 22 2018

Wednesday...Northwest flow aloft and a transitory low amplitude
shortwave ridge aloft will prevail, producing a dry day. Relatively
mild temperatures with maximums in the 60s with 700 mb temperatures
near 4 Celsius.

Thursday...A bit cooler in the wake of a passing dry cold front
associated with a shortwave trough aloft passing across the Northern
Plains states. Continued dry with limited low and mid level moisture.

Friday...Warmer again as a ridge aloft builds across the Rockies.

Saturday...Next shortwave trough aloft moves into Idaho and Utah
with increasing southwest flow aloft over our counties. Looks like
enough low and mid level moisture overhead to spawn isolated
afternoon showers. Continued mild with maximum temperatures in the
60s to lower 70s with 700 mb temperatures near 8 Celsius.

Sunday...Slightly cooler with isolated showers as a shortwave trough
aloft moves overhead.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 540 PM MDT Sun Apr 22 2018

Latest water vapor loop was showing an amplified upper level trof
moving through the Pacific northwest. This feature will continue
to drive east into Wyoming during the next 24 hours. As a result,
we will see wind speeds increase a bit Monday morning as the
gradient begins to tighten up ahead of the cold front. This front
will begin to drop into the KRWL, KLAR, KCYS, KBFF and KCDR TAF
sites after 21z. Until then mostly VFR conditions are expected.
However, we may see some patchy fog around KBFF and KCYS towards
daybreak.

&&

.FIRE WEATHER...
Issued at 200 PM MDT Sun Apr 22 2018

Wetting rains and accumulating mountain snow returns to southeast
Wyoming and Nebraska Monday as a cold front moves into the area
from northwest to southeast. Just about every location should see
wetting rains Monday into Tuesday. So fire weather concerns are
going to be minor through the upcoming week. Another front
possible Thursday, but this one does not look as strong as the
front Monday/Tuesday. Warmer temperatures through the week should
help to kick off greenup across the area.

&&

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

$$

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



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