Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 241149
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
449 AM MST Tue Jan 24 2017

.SHORT TERM...(Today and tonight)
Issued at 428 AM MST Tue Jan 24 2017

The upper low continues to move east across Wyoming early this
morning with rapid sfc pressure falls across eastern Colorado ahead
of the main PV anomaly tracking across CO & southern portions of our
forecast area. A band of moderate snow occurred last evening across
the southern Laramie Range and across Laramie County into the
Banner/Kimball Counties, bringing a quick shot of 1-2" of snow. The
band morphed into more general snow shower activity as it crossed
north of the cold front, but moderate to heavy rates have been
observed with this shower activity across the northern panhandle
over the past couple of hours. And now, as the cold front is
making its southward trek in response to the developing low down
south, snow showers are redeveloping for our southern plains
counties. However, this activity does not appear to be as strong
as previous and shouldn`t last long, so expect perhaps an
additional inch across areas spanning from the I-80 corridor
between Cheyenne to Sidney north to US-26.

A dry slot evident on WV imagery resides over our western counties,
and over the next few hours, will see subsidence increase both aloft
as the upper low shifts east and at the sfc in downslope sfc flow.
This should reduce chances for snow in the high country as well as
to the immediate lee of the Laramie Range, although light snow
here and there cannot be ruled out. Focus of heaviest snow will
then be for northeast portions of the forecast area where dynamic
lift and the possibility of TROWAL development will maintain
chances for moderate to heavy snow here through the day. Bumped up
snow totals another inch or so for areas in the Winter Storm
Warning to follow a continued trend upward in QPF by most of the
model guidance. This puts forecast snow totals more in the to 7
to 10" range for eastern Niobrara, Sioux, Dawes, and Box Butte
Counties. Winds are still on par to increase across the plains in
response to the rapidly developing system to our east with gusts
30 to 40 mph are possible. Therefore, blowing snow concerns will
ramp up through the day.

All in all, think the winter headlines are on track for the
remainder of today. Will have to keep an eye on blowing snow for
areas along the I-80 corridor from Cheyenne to Kimball this
afternoon and whether it becomes a big enough concern to include
them in the Advisory.

.LONG TERM...(Wednesday through Monday)
Issued at 428 AM MST Tue Jan 24 2017

The models continue to be in rather good agreement through early
next week at showing a large ridge developing over the western
United States that will end the parade of Pacific storms that have
occurred over the past few weeks.  Cold northwesterly flow aloft
will be in place on Wednesday and Thursday with 700 mb temps around
-17C. Highs will struggle to get out of the 20s.  Light orographic
snows will be possible through Thursday morning over the Sierra
Madre and Snowy Ranges with no highlights anticipated.  Heights
aloft rise by Friday into the weekend with highs back into the upper
30s and low 40s by Sunday.  Breezy conditions will exist most days
across southeast Wyoming, however not expecting any high wind
threats through Sunday.  Stronger winds may occur by late Sunday
night into Monday as the llvl gradient strengthens in response to a
shortwave moving to the north of the region.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 428 AM MST Tue Jan 24 2017

Snow and IFR conditions will continue across the western Nebraska
Panhandle through at least the early afternoon. Some areas of
moderate to heavy snow and vis dropping to one quarter mile will
be possible over the Panhandle. While light snow showers will be
possible at the southeast WY sites through 18Z, prolonged IFR vis
reduction is not expected.  North to northwesterly winds will
increase after around 15Z for sites to the east of the Laramie
Range. Gusts to 20-35 kts will be common through the afternoon.

&&

.FIRE WEATHER...
Issued at 428 AM MST Tue Jan 24 2017

No concerns due to the current widespread snowfall event and cold
temperatures through the week.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 6 PM MST this evening for WYZ101-
     106>108-112-114-116.

     Winter Weather Advisory until 11 AM MST this morning for
     WYZ103>105-109>111-113.

     Winter Storm Warning until 6 PM MST this evening for WYZ102.

NE...Winter Storm Warning until midnight MST tonight for NEZ002-003-
     095-096.

     Winter Weather Advisory until midnight MST tonight for
     NEZ019>021.

&&

$$

SHORT TERM...RJM
LONG TERM...ZF
AVIATION...ZF
FIRE WEATHER...RJM



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