Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 212023
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
223 PM MDT SUN AUG 21 2016

.SHORT TERM...(This evening through Tuesday)
Issued at 223 PM MDT Sun Aug 21 2016

Forecast challenges deal mainly with critical fire weather
conditions over the next 24 hours.

Currently...1011mb low on surface analysis over southern Albany
County this afternoon looks to be assisting in enhancing winds out
across Carbon and Albany Counties this afternoon. Getting wind
gusts to 30+ MPH at numerous WYDOT sites along I-80 with close to
30MPH at Saratoga. Further off to the west, water vapor imagery
showing next low pressure system pushing into southeastern
Vancouver Province with upper level ridge axis located from
central Montana into western Wyoming and eastern Utah.

Both the GFS and ECMWF 12Z guidance showing the upper low tracking
slightly further south Monday and Monday night as compared to
yesterday. This is a good track for gusty winds here in southeast
Wyoming and confidence is growing that we should see stronger
winds tomorrow. Went ahead and extended the Fire Weather Watch
further south to include FWZs 309, 310 and 312 as well as most
fire zones that were already in the watch. Evening shift should
probably upgrade these watches once the current red Flag warnings
expire at 8PM tonight.

Timing of front pretty consistent between the GFS and ECMWF as
well. Both bring the front into the northern CWA around 06Z
Tuesday and into the southern portion of the CWA by 12Z. 850MB
winds out in the Panhandle Tuesday quite strong,GFS showing 35-
possibly 40kts behind the front. Could be looking at wind
advisories out there for late Tuesday morning and afternoon.

.LONG TERM...(Tuesday night through Sunday)
Issued at 223 PM MDT Sun Aug 21 2016

The front pushes well south and east of our forecast area by
Tuesday evening with some lingering instability being denoted in
the models across the higher terrain and mountains when we hold on
to chance PoPs for evening showers and thunderstorms. The pattern
gets fairly messy synoptically mid through late week with a
lingering upper trough lingering over Idaho, Nevada and Arizona
and several hard to time pieces of midlevel shortwave energy
ejecting east across the central Rockies through Friday. Right now
we kept most PoPs out across the western zones Wednesday into
Thursday with a trend for an increase in PoPs Friday into Saturday
along and east of the Laramie range and onto the high plains
Friday into Saturday as we see a broader plume of midlevel
moisture and deeper instability as the midlevel flow increases
from the southwest and becomes more active. We should be trending
warmer again by next weekend after a cooler post frontal pattern
midweek.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1117 AM MDT Sun Aug 21 2016

VFR category expected to continue for all airports. Generally
lighter winds will turn more southerly over the NE Panhandle
later this afternoon and evening before resuming a southwesterly
flow by tomorrow. A bit higher southwesterly winds expected for
Rawlins this afternoon where greater mixing will occur. Generally
clear skies with no visibility restrictions expected through tonight
into tomorrow morning.

&&

.FIRE WEATHER...
Issued at 223 PM MDT Sun Aug 21 2016

Critical fire weather conditions fairly widespread this afternoon across
Carbon County with wind gusts of 25 to 30 MPH widespread and humidities
in the 10 to 15 percent range. Will continue the Red Flag Warning through
8 PM as advertised. More widespread winds Monday to cover much of southeast
Wyoming and the northern half of the Nebraska Panhandle and Fire Weather
Watches are in effect for much of the area. Cold front that is causing
these winds will finally move into the area Tuesday morning with colder
air and increased chances for wetting rains. Should see fire weather
conditions ease behind the front.

&&

.CYS Watches/Warnings/Advisories...
WY...Fire Weather Watch from Monday morning through Monday evening
     for WYZ301>304-306-308>310.

     Red Flag Warning until 8 PM MDT this evening for WYZ303-304-306-
     308.

NE...Fire Weather Watch from Monday morning through Monday evening
     for NEZ311-312.

&&

$$

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


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