Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 192037
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
237 PM MDT Sat May 19 2018

.SHORT TERM...(This evening through Tuesday)
Issued at 216 PM MDT Sat May 19 2018

A Pacific low pressure trough extending south from the Pacific
Northwest into the Great Basin will spread moisture and instability
across the area producing scattered showers and isolated thunderstorms
with small hail and gusty winds this evening and again on Sunday.
Temperatures will begin to warm with favorable relative humidity.
Convection will increase on Tuesday as the trough shifts east.
Run off from recent heavy rainfall and snow melt will likely cause
rising river levels through Tuesday.

.LONG TERM...(Tuesday night through Saturday)
Issued at 216 PM MDT Sat May 19 2018

A weakly defined upper level low over the Great Basin Tuesday night
will be in a position to where we will be under a backing,
predominantly southerly difluent flow. This will fuel late day
convection Tuesday evening, especially over Natrona and Johnson
Counties where lifted indices will be down to -5 along with decent
capes. Currently, the GFS is indicating over two inches of precip in
this area for a six hour period. Convection, overall will be fairly
widespread. In addition, we will be underneath the LFQ of the jet
max. On Wednesday and Wednesday night, the low will become more well
defined and track east across Southern Montana. Based on the timing
of this low, it will come close to Northwest Wyoming late Wednesday
during the favorable time for convention, so the most convection will
likely occur over Northwest Wyoming where the GFS indicates a six
hour period of 1.46 inches. Behind this low/trough, the steering
flow will go northwest with slightly cooler temps Wed/Thu,
especially in the west where some additional convection will occur
through Friday. Northern Wy will also see convection Thu/Fri. By
Saturday of next week, convection is progged to be a bit more
widespread.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday)
Issued at 216 PM MDT Sat May 19 2018

West of the Continental Divide...KJAC, KBPI, KPNA, and KRKS

Surface wind of 15- 25kts from the east-northeast will prevail
through the day at KRKS. Ceilings should rise to VFR by 20Z this
afternoon with scattered afternoon showers developing. KJAC, KBPI,
and KPNA to generally remain VFR through 12Z/Sun. Weak showers to be
scattered about the area for the remainder of this afternoon before
diminishing between 00Z- 02Z/Sun with VFR conditions remaining.
Widely scattered thunderstorms are expected Sunday afternoon vcnty
JAC/PNA/BPI.

East of the Continental Divide...KCPR, KCOD, KRIW, KLND, and KWRL

Dissipating light rain and drizzle through 20Z this afternoon, but
limited in coverage. Low-level upslope flow and plenty of boundary
layer moisture will lead to persistent IFR/MVFR ceilings at all but
KWRL through 22Z or so today with gradual clearing afterward, but
persisting through 00Z Sunday vcnty CPR. Conditions to be VFR at all
terminals by early this evening. Thunderstorms not expected today
with cooler, more stable airmass in place. North to northeast
surface winds will gradually diminish through the day today.
Mainly VFR conditions are expected Sunday.

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 216 PM MDT Sat May 19 2018

A Pacific low pressure trough extending south from the Pacific
Northwest into the Great Basin will spread moisture and instability
across the area producing scattered showers and isolated thunderstorms
with small hail and gusty winds this evening and again on Sunday.
Temperatures will begin to warm with favorable relative humidity.
Convection will increase on Tuesday as the trough shifts east.
Run off from recent heavy rainfall and snow melt will likely cause
rising river levels through Tuesday. Mixing heights will be favorable
even with relatively light transport winds to produce good or
better smoke dispersal each afternoon through Tuesday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Baker
LONG TERM...Lipson
AVIATION...Lipson
FIRE WEATHER...Baker


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