Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 191133
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
433 AM MST Sun Nov 19 2017

.SHORT TERM...(Today through Tuesday)
Issued at 300 AM MST Sun Nov 19 2017

Currently...Mostly clear skies seen on IR imagery this morning
with light winds east of the Laramie Range. West of the Laramie
Range, we are seeing wind gusts to 45 mph at Arlington. System
moving through eastern Washington/northern Idaho this morning
looks to be the trigger for increasing winds across the CWFA this
evening into Monday.

Going to get windy again and could become quite widespread. GFS
700mb winds increase to 45kts across Carbon County by 00Z today
and increase to 55kts by 12Z Monday. Local high winds guidance
showing 850/700mb Craig to Casper height gradients ramping up this
evening...exceeding 60mtrs by 06Z on the NAM and 03Z on the GFS.
Given we are already getting strong winds at Arlington and
Bordeaux with gradients 50/40mtrs respectively at 850/700mb,
decided to start High Wind Warnings at 00Z.

Looking at GFS and NAM soundings for Monday for Douglas/Laramie/Rawlins
and Cheyenne, I do have concern for winds to be more widespread.
Have 50kts forecast right off the surface at all 4 locations at
18Z Monday with the possibility of mixing well up to 700mb.
Decided on a High Wind Watch for these locations. Will let the day
shift take another look before issuing any upgrades. As a note,
winds were not this strong with the last strong wind event last
week and we did hit at Rawlins and parts of the Laramie Valley, so
I would caution the day shift to not just cancel the watches if
they deem an upgrade is not needed. Let the Watch run and I will
take another look tonight.

Weak backdoor cold front moves to the east slopes of Laramie Range
Monday night, so should see winds ease some at least on this side
of the Laramie Range.

.LONG TERM...(Tuesday Night through Saturday)
Issued at 156 AM MST Sun Nov 19 2017

Wednesday...Near perfect travel day for the Thanksgiving holiday
with a large ridge aloft over the Great Basin and Rockies and
northwest flow aloft our counties with relatively high heights.
Breezy to windy day and mild for this time of year with 700 mb
temperatures near 4 Celsius, yielding maximum temperatures in the
60s east of I-25.

Thanksgiving...Flow aloft backs slightly to northwest and with
decent surface lee troughing and plenty of sunshine, expect another
mild day. Low and mid levels too dry to support any precipitation.

Friday...The flow aloft backs a bit more to almost due westerly and
with strengthening flow aloft, a windy day on tap with our wind
prone locations possibly nearing high wind criteria. Nevertheless,
continued dry and mild due to lack of low and mid level moisture and
700 mb temperatures near 7 Celsius.

Saturday...Fast moving shortwave trough aloft and its associated
weak cold front pass by, making for a cooler day with only a slight
chance of precipitation at select locations due to scarcity of low
and mid level moisture and lack of lift.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 431 AM MST Sun Nov 19 2017

VFR. Wind gusts from 20 to 34 knots through 00Z. Wind gusts to 33
knots at Laramie after 06Z.

&&

.FIRE WEATHER...
Issued at 300 AM MST Sun Nov 19 2017

Fairly light winds today with minimal fire weather concerns. But
that changes tonight into Monday as winds begin to increase and
become strong. A low pressure system tracks through southern
Montana tonight and into the Dakotas Monday. This is a favorable
wind producers for southeast Wyoming and Nebraska Panhandle.
Afternoon humidity could become critical across the southern
Panhandle and FWZ 310 in extreme southeast WYoming Monday for
elevated to locally critical fire weather conditions Monday
afternoon. Winds ease Tuesday as a backdoor cold front moves into
the area from the northeast.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning from 5 PM this afternoon to 8 PM MST Monday
     for WYZ106-110-116-117.

     High Wind Watch from Monday morning through Monday afternoon for
     WYZ101-104-105-107-109-115-118.

NE...None.
&&

$$

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



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