Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 152349
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
449 PM MST Thu Feb 15 2018

.SHORT TERM...(Tonight - Saturday Night)
Issued at 225 PM MST Thu Feb 15 2018

Snow is quickly diminishing over the Snowy and Sierra Madre ranges
this afternoon, as indicated by recent trends in radar and GOES-16
satellite imagery. Winter Storm Warnings will likely be allowed to
expire or possibly cancelled early. Otherwise, still a possibility
of a few snow showers across the CWA through this evening. Little/
no accumulation is expected.

High winds return for Friday and Saturday. Low-level gradients are
expected to increase markedly after 18z Fri, with notable pressure
falls spreading across eastern MT and western SD. H7 & H85 CAG-CPR
gradients from both the NAM/GFS climb to over 60 meters during the
afternoon/evening hours on Friday, and to between 70 and 80 meters
by early Saturday. By 12z Saturday, the GFS suggests widespread 55
to 65 knot H7-H8 flow over much of southeast WY along w/ excellent
subsidence in the RFQ of a 120-130 knot H25 jet streak. Expect low
level mixing to be quite good as well per forecast soundings, so a
fairly widespread high wind event appears likely. Wind prone areas
will likely strike first, with Arlington possibly seeing gusts 60+
MPH as early as Friday afternoon. The I-80 summit and Bordeaux may
be somewhat delayed into the evening and overnight until we see an
eastward progression of the surface trough and a stronger pressure
gradient along the spine of the Laramie Range. High winds may also
spread into Laramie & Cheyenne overnight into early Sat morning w/
models suggesting significant downward omega. A High Wind Watch is
in effect from Friday afternoon through early Sunday morning.

.LONG TERM...(Sunday - Thursday)
Issued at 240 AM MST Thu Feb 15 2018

Guidance very consistent on next cold front entering area from the
northwest Sunday afternoon/evening. Expect snow to start up by
Douglas by Sunday mid afternoon and then spread south through the
evening hours. This is looking like a widespread heavy snow event
with Converse County possibly seeing a foot of snow and Cheyenne
maybe seeing 3-5 inches. We will need to start getting the word
out on this event and will post something on social media about it
this morning.

Very cold behind the front for Monday and Tuesday as 700mb
temperatures fall to -18 to -20C. Single digit highs for Monday
with lows well below zero for most areas Monday night. These cold
temperatures look to stay with us through at least Wednesday
before westerly winds return to start warming up temperatures
Thursday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 439 PM MST Thu Feb 15 2018

Latest surface analysis was showing the cold front just north of
Laramie which should pass through that area during the next hour
or so. Latest radar loop was showing a few snow showers along and
behind this front, but this precipitation should not last long,
due to a dry air mass in place and that area become more stable as
sunset approaches. The rest of the evening, we should see
diminishing wind speeds. However, wind speeds will be kicking back
up again tomorrow morning across the Wyoming TAF sites, as another
shortwaves approaches the region and induces pressure falls.



&&

.FIRE WEATHER...
Issued at 240 AM MST Thu Feb 15 2018

No fire weather concerns seen through the weekend with cool to
mild temperatures. Colder across the area today into Friday
morning then warmer temperatures return for the weekend, along
with some strong winds around the mountains as well.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Warning until 6 PM MST this evening for WYZ112-114.

     High Wind Watch from Friday evening through late Saturday night
     for WYZ106-116-117.

     High Wind Watch from Friday afternoon through late Saturday
     night for WYZ110.

     High Wind Watch from late Friday night through Saturday morning
     for WYZ107-115-118.

NE...None.
&&

$$

SHORT TERM...CLH
LONG TERM...GCC/CLH
AVIATION...REC
FIRE WEATHER...RE



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