Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 181032
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
332 AM MST Sun Feb 18 2018

.SHORT TERM...(Today and tonight)
Issued at 330 AM MST Sun Feb 18 2018

Strong winds are still being reported across parts of southeast
Wyoming this morning. Cooper Cove WYDOT site out by Arlington had
a wind gust of 78 mph just about an hour ago with widespread 60+
mph gusts in that zone. Deer Creek had a gust of 67 mph around
midnight and a CWOP site just south of Douglas currently has wind
gusts to 55 mph. Will keep current wind headlines going as
forecast. Exception, I extended the High Wind Warnings for the
South Laramie Range west to Arlington until 1PM this afternoon as
Craig to Casper 850/700mb height gradients remain above 60mtrs.
Looking at forecast soundings, winds right off the surface at
Laramie are forecast to 60kts at 15Z and 55kts at 18Z, so though
maybe extending the warnings for a while this morning was prudent.
Day shift can pull down the headlines as they get a look at winds
after mixing.

Arctic boundary currently lies across extreme southwestern South
Dakota, northwest to Sheridan and up into southwestern Montana
this morning. Getting snow reported at Sheridan, Cody and points
north into Montana at this time. Expecting snow to begin in
earnest across northern Converse County as early as 15Z this
morning as the arctic boundary sags to near a line from Chadron to
Douglas to Casper. By 00Z, the front lays along a line from Sidney
to Chugwater to Muddy Gap with widespread snow north of the front.

Did upgrade all watches to Winter Storm Warnings as we are in that
timeframe for upgrade. Dayshift will need to make a call on what
to do with Laramie County and the southern Panhandle today. GFS
was a little more bullish on QPF over the SREF and ECMWF. SHould
its solution hold true, we will need to add Laramie and most of
the southern Panhandle counties into possibly a warning, but more
likely Advisories are going to be needed. Decided to let the day
shift take one last look before issuing anything.


.LONG TERM...(Monday through Saturday)
Issued at 302 AM MST Sun Feb 18 2018

Most affected/impacted area are going to be where the warnings are
currently in place as the front stalls over the area and
persistent snow fall over our western and northern zones. Guidance
in pretty good agreement on this placement.

Brutally cold Monday and Monday night as 700mb temperatures fall
to -17C over the Panhandle to -22C out by Carbon County. Snow
looks to slowly end from northwest to southeast by late morning
Tuesday. We may need to extend the end time of our warnings to
reflect the slower clearing. Windchills well below warning level
Monday night/Tuesday morning, so expect Windchill headlines after
the Winter Storm Warnings come to an end.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday evening)
Issued at 1000 PM MST Sat Feb 17 2018

Strong westerly winds with gusts 35-50 kt will continue through
Sunday morning along and west of Interstate 25. Moderate to severe
mountain wave turbulence can be expected. VFR will prevail at all
terminals until Sunday afternoon and early evening when CIG/VIS
lower to MVFR-IFR as an Arctic cold front progresses south across
southeast Wyoming and western Nebraska. Snow develops from north to
south during the afternoon and evening. Winds shift to the north-
northeast with gusts around 25 kt.

&&

.FIRE WEATHER...
Issued at 302 AM MST Sun Feb 18 2018

Strong winds this morning will ease across southeast Wyoming by
early afternoon as an arctic front moves into the area. Widespread
wind gusts in excess of 60 mph this morning, turning north and
northeast with gusts to 20-25 mph this afternoon. Widespread snow
event to unfold from north to south over the next 36 hours behind
the front with very cold temperatures moving in behind the front
as well. Significant snow accumulations across entire area of
southeast Wyoming and Nebraska Panhandle before snow ends Tuesday
morning. No fire weather concerns expected.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Warning from 6 PM this evening to midnight MST
     Monday night for WYZ106>117.

     High Wind Warning until 1 PM MST this afternoon for WYZ104>107-
     109-110-113-115>117.

     Winter Storm Warning from 9 AM this morning to midnight MST
     Monday night for WYZ101>105.

     High Wind Warning until 9 AM MST this morning for WYZ101-103.

NE...Winter Storm Warning from 6 PM this evening to midnight MST
     Monday night for NEZ002-003-095-096.

&&

$$

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



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