Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 221815
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1215 PM MDT Tue May 22 2018

.SHORT TERM...This evening through Friday
Issued at 1212 PM MDT Tue May 22 2018

Upper low lifting nwd across far ern NV with approaching nose of
strong jet and mid level QG forcing. This area of forcing moves into
Central WY about 00z and then lifts slowly nwd through the night.
Models are also showing a H7 low lifting nwd through Central WY
tonight. The GFS is a little further east with it than the NAM and
thus the difference in the QPF maxes. Bottom line is very favorable
upper support (nose of strong jet, upper divergence/diffluence and
mid level QG forcing (e-w band) lifting nwd late this afternoon
through tonight. Enough instability (1000-1500 J/kg) and upper
support for strong to locally severe thunderstorms (especially nrn
half) along with flooding/flash flooding potential where heavy rain
persists or falls on saturated ground from recent storms. Main upper
low lifts gradually nwd and exits off into srn MT by Wed aftn. Plent
of showers/tstorms still around the low track through Wed
(especially nw mtns). Weak shortwave ridging Thursday with afternoon
convection in and near the mountains. A few will likely move across
the lower elevations of the north half late in the day or evening
but nothing like today`s action. Ridging strengthens Friday for a
generally dry and warm day.

.LONG TERM...Friday night through Tuesday
Issued at 1212 PM MDT Tue May 22 2018

A weather system will settle over the Great Basin of Nevada and
western Utah Saturday and remains there Sunday and even Monday
(Memorial Day). For Saturday, most of the area will be dry with
some showers and thunderstorms over the western mountains and
valleys in the afternoon and evening. Another warm day expected
with 70s and 80s, a few lower 90s in the Big Horn basin. The
potential for showers and thunderstorms increases for Sunday and
Monday as disturbances rotate from south to north through our
area. Timing these features this far out is tough and will no
doubt change each day. For now, be prepared for periods of
unsettled weather with many dry hours in between on Sunday and
Monday. Sunday high temps will be in the 70s to lower 80s east of
the divide with 60s to lower 70s west of the divide. Monday looks
to cool down with 60s in the west and 70s in the east. Next
Tuesday could be cooler with a chance of showers and storms as the
weather system is forecast to get closer to our area.

&&

.AVIATION...For the 18Z TAFS through 18Z Wednesday
Issued at 1212 PM MDT Tue May 22 2018

West of the Continental Divide...KJAC/KBPI/KPNA/KRKS

VFR conditions to prevail into this afternoon. Scattered SHRA/TSRA
are expected to develop at the TAF sites after 20Z with more
predominant TSRA expected toward 01Z, continuing through around
the 06Z-07Z time frame. MVFR ceilings and rain showers are
expected toward the end of the forecast period with thunderstorms
expected to slowly dissipate after 07Z. Mountains will be obscured
at times. Wind gusts to 30 knots and small hail will occur with
stronger storms.

East of the Continental Divide...KCPR/KCOD/KRIW/KLND/KWRL

Expect showers and thunderstorms to be on the increase by this
afternoon with widespread showers and thunderstorms expected tonight.
Some storms will be quite strong to possibly severe, especially in
the eastern zones. MVFR ceilings will be predominant at most
locations after 02Z.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.

&&

.FIRE WEATHER...
Issued AT 1212 PM MDT Tue May 22 2018

A surge of moisture lifting northward across Wyoming through the
night will bring scattered to numerous showers and thunderstorms
across the area. The chance of showers/storms will decrease in the
south this evening but continue in the north half all night. Some
heavy rain is possible with these storms with a good chance of a
wetting rain where storms set up. Flooding is possible where heavy
rain persists. Winds should remain light to moderate except in and
near any shower or thunderstorm. Relative humidity will remain above
critical levels. Mixing and smoke dispersal will range from poor in
the basins and good in the breezier areas. On Wednesday, widespread
showers and some thunderstorms will continue in the northwest with
only isolated showers elsewhere.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 6 PM MDT this evening through Wednesday morning
for WYZ002-004-006-008-009-015-016.

&&

$$

SHORT TERM...Skrbac
LONG TERM...Hulme
AVIATION...Hulme
FIRE WEATHER...Skrbac



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