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Area Forecast Discussion (AFD)

Issued by Cheyenne, WY (CYS)

FXUS65 KCYS 141117 CCA

Area Forecast Discussion
National Weather Service Cheyenne WY
517 AM MDT Sat Sep 14 2019

.SHORT TERM...(Today through Sunday night)
Issued at 400 AM MDT Sat Sep 14 2019

The latest WV/IR imagery depicted a near-zonal flow in the mid/upper
levels. Some Pacific moisture was spreading east across the northern
Rockies and high plains associated with a shortwave trough over
Montana. Surface high pressure was the dominant weather feature for
the CWA with generally clear skies. Winds were west to southwest 
around 10 mph, except gusting to 25 mph through the wind corridor 
between Laramie and Rawlins. Temperatures were milder compared to 
24 hours ago, with 40s and 50s prevailing.

Current model/ensemble blends prog the near-zonal flow aloft to 
continue today, with the Montana upper trough tracking east across
North Dakota and northern Minnesota. 700mb temperatures will warm
to 8 to 12 degrees Celsius this afternoon, resulting in high 
temperatures from the mid 70s to lower 80s. A surface trough
developing over the high plains later this morning will deepen
this afternoon. West to southwest winds sustained will increase
to 15 to 25 mph, with gusts to 35 mph across much of southeast
Wyoming. Humidities will fall into the lower to mid teens this
afternoon. Most fuels have cured over southeast Wyoming, and the
high fire danger will exist into Sunday. The high plains pressure
gradient weakens Sunday, so winds will not be as breezy, with 
gusts of 20 to 25 mph over portions of Carbon and Albany counties.
700mb temperatures rise into the mid teens Celsius Sunday afternoon,
yielding high temperatures in the 80s to around 90 east of the
Laramie Range.

.LONG TERM...(Monday through Friday)
Issued at 400 AM MDT Sat Sep 14 2019

Little change gleaned from latest model/ensemble blends with the
large scale pattern next week. Upper ridge dominates the eastern
CONUS, with upper troughiness over the western CONUS. The lead
Pacific trough moves inland Monday, and pivots northeast through 
the northern Rockies and High Plains Tuesday. This trough will 
push a Pacific cold front across the CWA by Wednesday morning. 
Models indicate an initial surge of moisture and upslope over the 
higher terrain of southern Wyoming Monday afternoon and evening. A
secondary surge of moisture and lift arrives Tuesday afternoon 
and evening, with scattered showers and isolated thunderstorms. 
The upper ridge rebuilds over the Great Plains Wednesday with only
isolated convection mainly confined to the I-80 corridor. A 
stronger upper trough enters the Intermountain West Thursday and 
lifts northeast toward the northern Great Plains Friday, with 
widely scattered convection forecast. QPF has been trending on the
lower end for accumulating precipitation with these troughs. 
After above normal temperatures Monday, it will cool back to 
seasonal normals as we approach the autumnal equinox.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 517 AM MDT Sat Sep 14 2019

VFR conditions expected through the period. Some gusty winds
mainly affecting KRWL to KCYS this afternoon with gusts around
25 knots, diminishing around 00Z.   


Issued at 238 AM MDT Sat Sep 14 2019

West to southwest winds gusting 25 to 35 mph combined with low humidity
will contribute to Red Flag conditions for much of southeast Wyoming
this afternoon. On Sunday, wind speeds will be more marginal, combined
with low humidity for potential critical fire weather conditions over
portions of Carbon and Albany counties in the afternoon. Conditions
will begin to improve late Monday as Pacific moisture spreads northeast
into southeast Wyoming ahead of an approaching upper level low pressure
trough and cold front from the west. Cooler temperatures, higher humidity
and chances for wetting rainfall are expected Tuesday through Friday.


WY...Red Flag Warning from 11 AM this morning to 8 PM MDT this 
     evening for WYZ303-304-306-308>310.

     Fire Weather Watch from Sunday morning through Sunday evening 
     for WYZ303-308.