Area Forecast Discussion
Issued by NWS Cheyenne, WY

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663
FXUS65 KCYS 211717 AAA
AFDCYS

Area Forecast Discussion...UPDATED
National Weather Service Cheyenne WY
1117 AM MDT SUN AUG 21 2016

.UPDATE...for the noon aviation forecast package release.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 330 AM MDT Sun Aug 21 2016

Water vapor loop depicted a upper trough from a Hudson Bay low
south to the Missouri River valley. A broad upper ridge dominated
the western CONUS with its center over northern California. A dry
northwest flow aloft prevailed across the CWA. A surface ridge
extended north-south over the high plains, with south to southwest
winds 5-15 kt. Skies were clear and temperatures were 10 degrees
milder compared to 24 hours ago.

Short range models are in good agreement with the western CONUS
ridge progressing east across the Rockies and Great Plains through
Monday as a fairly deep upper low tracks east across southern
British Columbia and Alberta. 700-500mb winds increase to 30-35 kt
this afternoon. Model soundings indicate mixing up to 600mb this
afternoon west of the Laramie Range as temperatures peak around
80. The combination of gusty winds and low humidities will promote
high fire danger (see Fire Weather section for details). Highs
will warm into the 80s along and east of I-25, with 60s and 70s
for the mountains.

Southwesterly flow aloft will increase Monday, with 700mb winds
20-30 kt. Lee surface trough deepens with sustained west winds
15-20 kt gusting to 30 kt in the afternoon. It will be quite warm
with highs into the low-mid 90s east of I-25, with 70s and 80s
to the west. Subtropical moisture will begin to spread northward
along the Front Range into far southern Wyoming, with isolated
afternoon tstorms developing over the Snowy, Sierra Madre and
south Laramie ranges.

Low pressure over southern Montana tracks east into the Dakotas,
with a trailing cold front pushing southeast through the CWA by
midday Tuesday. High temperatures Tuesday afternoon will be 5-10
degrees cooler, with breezy northerly winds in the wake of the
cold front. Isolated to scattered showers/tstorms will develop
during the afternoon, mainly west of I-25.

.LONG TERM...(Tuesday night through Saturday)
Issued at 315 AM MDT Sun Aug 21 2016

Secondary surge of cooler air will push across the CWA Tuesday night
as an upper low tracks east across far southern Canada. A few showers
may occur behind the front mainly around the mtns Tuesday night and
Weds. Mild temperatures for Wednesday through Friday with widely
scattered showers and maybe a few storms as a positively tilted
upper trough sets up over the northwestern CONUS and several weak
shortwaves eject east across the area. Models hinting at a bit of
monsoonal moisture being pulled north over parts of the CWA which
would enhance pcpn somewhat. Dry and warmer Saturday as the upper
trough axis moves across the CWA and drier air moves into the region.

&&

.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 and Laramie this afternoon where greater mixing will
occur. Generally clear skies with no visibility restrictions
expected through tonight into tomorrow morning.

&&

.FIRE WEATHER...
Issued at 300 AM MDT Sun Aug 21 2016

Warmer...breezy and drier conditions are forecast today and Monday
as a ridge of high pressure aloft dominates the districts. Critical
fire weather conditions will develop this afternoon for much of
Carbon and Albany counties due to low relative humidities and
gusty winds. More widespread critical fire weather conditions are
probable Monday afternoon for much of southeast Wyoming and the
northern Nebraska Panhandle.

&&

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

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

NE...Fire Weather Watch from Monday afternoon through Monday evening
     for NEZ311.

&&

$$

SHORT TERM...Jamski
LONG TERM...Emanuel
AVIATION...JG
FIRE WEATHER...Jamski



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