Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 170839
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
238 AM MDT Tue Oct 17 2017

.SHORT TERM...(Today through Wednesday night)
Issued at 235 AM MDT Tue Oct 17 2017

Overnight GOES-R water vapor loop depicted a sharp upper trough
along the Eastern Seaboard, a weaker shortwave trough approaching
the Midwest, and deeper trough off the coast of British Columbia.
A northwest flow aloft prevailed over the CWA with some high clouds
over northern and central WY. A modest surface pressure gradient
existed between a trough over northern WY and high center over
northwest CO. This gradient was generating gusty west-southwest
winds of 25-35 mph along the I-80 corridor between Laramie and
Rawlins.

Good agreement with the 00Z models/ensembles progging a weak
shortwave passing across the CWA today. This system will enhance
the pressure gradient slightly, especially across southeast WY
this afternoon. A warm and dry air mass combined with deep layer
mixing of 25-30 kt winds to the surface will produce critical
fire weather conditions along and east of the Laramie Range into
portions of western NE this afternoon. The upper North Platte
River Basin including Saratoga may experience a period of critical
fire weather as well. Temperatures this afternoon will be similar
to Monday with highs in the 60s and 70s valleys and plains. Areas
along the North Platte Valley from Torrington to Scottsbluff could
register 80-82 degrees.

The trough to the northwest will track quickly east along the
U.S./Canadian border tonight and Wednesday, dragging a cold front
across eastern WY and western NE Wednesday. Cooler temperatures
will be more noticeable across the plains, with highs Wednesday
5-10 degrees lower compared to today.

.LONG TERM...(Thursday through Monday)
Issued at 230 AM MDT Tue Oct 17 2017

Warm and dry weather across the CWA Thursday and Friday under
southwesterly upper flow ahead of an upper trough that will move
over the Pacific Northwest by late Friday. Some breezy/windy
conditions over western parts of the CWA in the favorable
southwesterly flow. A cold front will push across the CWA Friday
night as the upper trough moves over the Rocky mtn chain, then into
the plains Saturday.
Widely scattered showers should be over mainly western and northern
parts of the CWA in association with the upper trough late Friday
into Saturday with pcpn ending with the passage of the trough late
Saturday. Mild and dry again Sunday and Monday with winds looking
like they will increase again as fast northwesterly flow sets up
over the area.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 230 AM MDT Tue Oct 17 2017

VFR over all terminals through the period with just some high
clouds at times. There will be some gusty winds this afternoon
mainly from KRWL to KCYS with gusts around 30 kts in those areas.

&&

.FIRE WEATHER...
Issued at 200 AM MDT Tue Oct 17 2017

Little change in the air mass today with warm temperatures, gusty
winds and very low humidities for most of east and southeast Wyoming
and the southern half of the Nebraska Panhandle. These critical fire
conditions will lead to rapid growth of any fire that develop. A
front will push south across southeast Wyoming and western Nebraska
Wednesday, bringing cooler temperatures, lighter winds and slightly
higher humidities.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning from noon today to 6 PM MDT this evening for
     WYZ301-306-309-310.

NE...Red Flag Warning from noon today to 6 PM MDT this evening for
     NEZ312-313.

&&

$$

SHORT TERM...MAJ
LONG TERM...RE
AVIATION...RE
FIRE WEATHER...MAJ



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