Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 230356
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
956 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.
Plenty 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 06Z TAFS through 06Z Wednesday night)
Issued at 946 PM MDT Tue May 22 2018

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

MVFR to lower end VFR ceilings and visibilities will continue at
the TAF sites through the initial few hours of the forecast
period. Will keep in borderline MVFR/low end VFR ceilings/visibility
values at KJAC through the forecast period and at KNPA until
around 16Z Wednesday. VCTS will be possible at KBPI until around
02Z Thursday and expect at least VCSH at KJAC,KPNA and KRKS
through the balance of the forecast period. Mountains will be
obscured at times. Wind gusts to 30 knots and small hail will
occur with any stronger storms.

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

Widespread showers and isolated TSRA is expected tonight during
the initial portion of the forecast. At KRIW, KLND and KWRL, the
SHRA probabilities will decrease with time toward 10Z. MVFR
ceilings to lower end VFR ceilings are expected through be balance
of the forecast period. VCTS is expected at KWRL until around 02Z
Thursday.

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 through Wednesday morning for WYZ002-004-006-008-009-
015-016.

&&

$$

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


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