Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 221754
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1154 AM MDT MON AUG 22 2016

.SHORT TERM...(Today through Wednesday)
Issued at 330 AM MDT Mon Aug 22 2016

Water vapor loop showed an upper low over central British Columbia
with a trough into the Pacific Northwest. A weaker upper low was
situated over western Arizona. A broad upper ridge dominated the
Rockies and high plains. A surface trough axis extended from
central Montana through central and southeast Wyoming, and eastern
Colorado. South to southwest winds 5-15 mph prevailed. Skies were
mostly cloudy as cirrus spread north into southern Wyoming.
Temperatures were 5-10 degrees milder than 24 hours ago with 50s
and 60s.

There is good agreement from the short range models progging the
upper ridge axis to progress east across the Great Plains and
Midwest through Tuesday. The British Columbia upper low will
also track east across southern Alberta and Saskatchewan. The
southwest flow aloft will increase through the next 12 to 24
hours with 700mb winds 30-35 kt this afternoon. Fairly steep
lapse rates with mixing up to 600mb during peak heating will
create rather breezy west-southwest surface winds across much
of southeast Wyoming and the northern Nebraska Panhandle this
afternoon. These winds combined with low humidities will create
critical fire weather conditions. Also, isolated convection will
develop over the mountains near the Colorado border and move
east-northeast along weak surface boundary into far western
Nebraska Panhandle later this afternoon. This will be high-based
convection with inverted-v soundings indicating gusty/erratic
outflow winds, lightning and very little rainfall. Very warm
temperatures are forecast this afternoon with highs into the 90s
east of I-25. Convection will wane early this evening.

Surface low progged to develop over the western Dakotas early
Tuesday, with its trailing cold front pushing southeast across
the CWA during the morning. winds will shift to northwesterly
and become breezy behind the front. Temperatures will be at least
10 degrees cooler with highs in the 70s and 80s. Subtropical
moisture will begin to spread northward along the Front Range
Tuesday afternoon, with more scattered convection developing
over the mountains. The nearby valleys and plains of southeast
Wyoming can expect isolated convection later in the afternoon.
Low levels will still be rather dry, with limited rainfall and
gusty/erratic outflow winds from convection.

Wednesday will be quite cool by August standards with highs in the
mid 60s-mid 70s with northeasterly winds. Cooler air aloft, upslope
low level flow and lingering monsoon moisture will trigger isolated
to scattered convection for much of southeast Wyoming, mainly during
the afternoon. Low levels will be more moist, with better chances
for wetting rainfall from convection.

.LONG TERM...(Wednesday night through Sunday)
Issued at 310 AM MDT Mon Aug 22 2016

Mild temperatures will continue Thursday and Friday with the upper
pattern featuring a general troughiness over the northern Rockys
and northern plains. A couple impulses in the flow will help to
set off widely scattered showers and tstms over the CWA both days
with some monsoonal moisture brought up to enhance the activity.
Drier and warmer weather should return for Friday into the weekend
as the upper flow turns westerly behind the departing upper trof
axis and monsoonal moisture gets shunted to the south and east of
the CWA. Convective activity looks to be more isolated and mainly
over the mtns Saturday and Sunday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1151 AM MDT Mon Aug 22 2016

VFR conditions will occur across the region through the TAF period
with SCT/BKN coverage of clouds around 10-15k feet AGL. Gusty wind
can be expected this afternoon with a few gusts to 30 kts possible
at KRWL, KLAR, KCDR, and KAIA.

&&

.FIRE WEATHER...
Issued at 245 AM MDT Mon Aug 22 2016

Critical fire weather conditions will be more widespread this
from late morning through early evening for much of southeast
Wyoming and the northern Nebraska Panhandle. Expect sustained
southwest winds 15 to 20 mph with gusts of 25 to 35 mph combined
with minimum humidities of 8 to 15 percent. The potential for
dry thunderstorms exists over southern portions of fire weather
zones 309 and 310, as well as zones 311 and 312. Thunderstorms
will produce very little rainfall and gusty winds. A cold front
will move southeast across the districts Tuesday morning with
cooler temperatures, higher humidities and increasing chances
for wetting rainfall.

&&

.CYS Watches/Warnings/Advisories...
WY...Red Flag Warning until 8 PM MDT this evening for WYZ301>304-306-
     308>310.

     Fire Weather Watch from Tuesday morning through Tuesday evening
     for WYZ301>304-306-308.

NE...Red Flag Warning until 8 PM MDT this evening for NEZ311-312.

&&

$$

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


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