Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 210012 CCA
AFDCYS

Area Forecast Discussion...Corrected
National Weather Service
Cheyenne WY 606 PM MDT Fri Apr 20 2018

.UPDATE...
Issued at 602 PM MDT Fri Apr 20 2018

Latest web cams are showing some accumulating snow taking place
between Wagonhound and Cooper Cove. Latest model trends are
showing this snowfall persisting through much of the night. As a
result, we are going to issue a Winter Weather Advisory for the
Arlington zone through 15z.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 233 PM MDT Fri Apr 20 2018

Snow amounts continue to be the forecast challenge in the short
term. Currently, band of heavier precip ahead of low pressure has
moved off into Nebraska this afternoon. Did get some pretty good
rainfall amounts over the Panhandle this afternoon. Sidney got
some much needed rainfall with .3 inches observed. Alliance
received .21 inches. Looks like precip has pretty much ended
across the Panhandle. Upper low over western Colorado this
afternoon with precip breaking out across northwest Colorado into
the mountains of southern Carbon County. Here along and east of
the Laramie Range, a dry slot continues, but am seeing cooling
cloud tops over central Colorado, working their way north.

Made no changes to the ongoing headlines and forecast for tonight
into Saturday. Area is forecast to fill in with rain and mountain
snow this evening as upper low tracks into eastern Colorado.
Similar snow amounts from the overnight forecast.

Precip ends from northwest to southeast Saturday late morning.
Still need to watch the southern Panhandle as heavier precip band
from wrap around moisture just south of Cheyenne County through
the day.

.LONG TERM...(Saturday night through Friday)
Issued at 233 PM MDT Fri Apr 20 2018

The remainder of the weekend will be quiet w/ dry zonal flow aloft
and a lack of any notable mid-level disturbances. The GFS/ECM both
suggest a fast-moving short wave tracking across the Intermountain
West on Monday/Tuesday, likely bringing our next chance for rain &
snow to the area. Trending warmer and drier afterwards.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 540 PM MDT Fri Apr 20 2018

The main concern with this TAF issuance are the potential for low
ceilings overnight and where the bands of snowfall will be.

Latest radar loop was showing several clusters of snowfall mainly
between Cheyenne and Elk Mountain. This is in response to good
upslope flow from the closed upper low in northern Colorado. Would
expect these bands of precipitation to expand east during the
remainder of the evening and overnight. Meanwhile, there is some
bands of precipitation trying to develop near Sterling and Sidney.
This appears to be in response to the large scale diffluence and
an approaching jet streak moving through eastern Colorado. This
may cause ceilings to drop to the LIFR category in KSNY and KAIA
this evening with more snow developing after 05z and persisting
through the night. KBFF and KCDR will be tricky with lower
ceilings possible after 03z in KBFF, due to upvalley flow.

The rest of the TAF sites will most likely experience low LIFR
ceilings with periods of low visibility from snowfall and fog through
much of the night before some improvement occurs around mid
morning.


&&

.FIRE WEATHER...
Issued at 233 PM MDT Fri Apr 20 2018

No fire weather concerns. A cool/unsettled weekend ahead with good
chances for measurable rain/snow across all of southeast Wyoming &
the western Nebraska Panhandle.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Warning until 9 AM MDT Saturday for WYZ114.

     Winter Weather Advisory until 9 AM MDT Saturday for WYZ112.

     Winter Weather Advisory until noon MDT Saturday for WYZ116.

NE...None.
&&

$$

UPDATE...REC
SHORT TERM...GCC
LONG TERM...MJ
AVIATION...REC
FIRE WEATHER...CLH



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