Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 270457
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1055 PM MDT WED AUG 26 2015

UPDATE...ADDED 06Z AVIATION DISCUSSION

.SHORT TERM...TONIGHT THROUGH THURSDAY

TWO MAIN DISTURBANCES TO DEAL WITH IN THE SHORT TERM WITH THE FIRST
ELONGATED VORT MAX STRETCHING FROM WCNTRL UT INTO WCNTRL WY AROUND
MIDDAY. THIS SYSTEM WILL SLOWLY MOVE NEWD INTO TONIGHT AND THEN
GRADUALLY EXIT THURSDAY MORNING AS IT ROUNDS THE RIDGE AND MOVES
EAST. THE SECOND DISTURBANCE/CIRCULATION IS MOVING NNE FROM SERN UT
AND SHOULD SLIP OUR SERN ZONES TONIGHT BEFORE EXITING OFF THE TO
THE E/SE THURSDAY MORNING. NICE...COOL...SHOWERY WX SPREADING NWD
ACROSS THE FAR WEST TODAY WITH OUR FIRST SYSTEM WITH TEMPERATURES
ONLY IN THE 50S AND 60S. PLENTY OF SHOWERS AND SOME TSTMS ALONG
ITS PATH THROUGH TONIGHT...LINGERING INTO THURSDAY MORNING IN THE
NERN ZONES. THE SRN SYSTEM WILL CREATE INCREASING SHOWERS AND SOME
TSTMS IN OUR SOUTH AS THE LATE AFTN AND EVENING WEARS ON...NOT
ENDING UNTIL THURSDAY MORNING. WITH UPPER 40S AND 50S DEW POINTS
SURGING UP FROM THE SOUTH...A FEW OF THESE SHOWERS/TSTMS WILL
CONTAIN SOME HEAVY RAIN. THURSDAY AFTERNOON SHOULD SEE NEW STORMS
FIRING IN THE WEST WITH COOLER MID LEVEL TEMPERATURES...DEW POINTS
STILL IN THE 40S AND WARMER AFTN TEMPS. MODIFIED SOUNDINGS AT KJAC
WITH TEMPS IN THE MID 70S AND SFC DEW POINTS IN THE LOWER 40S
GENERATE CAPES OVER 700 J/KG. MOST AREAS NEAR AND WEST OF THE
DIVIDE ARE GENERATING ENOUGH CAPE/INSTABILITY FOR AFTN
TSTMS...EVEN ACROSS CENTRAL WYO AFTER THEY BUILD OVER THE
ABSAROKAS AND WINDS. MOISTURE AND FRONTAL BOUNDARY ON THE BACK
SIDE OF OUR CURRENT SYSTEM WILL AID IN AFTN SHOWERS AND MAYBE A
TSTM IN THE FAR ERN ZONES. INCREASED THE POPS QUITE A BIT ACROSS
THE WEST THURSDAY...ESPECIALLY WCNTRL/NWRN AREAS.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY

THE DISTURBANCE EXPECTED TO BRING SHOWER ACTIVITY ACROSS THE AREA ON
WEDNESDAY WILL CONTINUE TO MOVE THROUGH EASTERN WYOMING THURSDAY
EVENING...WITH SHOWER ACTIVITY CONTINUING INTO THE OVERNIGHT HOURS.
THE NORTHWESTERN MOUNTAINS LOOK THE MOST FAVORABLE TO EXPERIENCE
CONTINUED ACTIVITY.

RIDGING STRENGTHENS OVER THE AREA FRIDAY MORNING...WITH GENERALLY
DRY CONDITIONS EXPECTED FRIDAY. MODELS DO VARY ON THE SPEED OF THE
AXIS OF THE RIDGE INITIALLY...WITH THE GFS BEING MORE AGGRESSIVE.
MODELS DO GENERALLY COME INTO AGREEMENT BY THE TIME THE AXIS IS OUT
OUTSIDE OF THE FORECAST AREA...WITH STRENGTHENING SOUTHWEST FLOW
NOTED BY SATURDAY MORNING. THIS SOUTHWEST FLOW WILL PERMIT
ADDITIONAL MOISTURE TO MOVE OVER WESTERN AND CENTRAL WYOMING...WITH
A RETURN OF AFTERNOON SHOWERS AND THUNDERSTORMS THIS WEEKEND.

THIS SCENARIO WILL CONTINUE FOR THE REMAINDER OF THE FORECAST
PERIOD...WITH SHOWER COVERAGE INCREASING EACH AFTERNOON.
TEMPERATURES WILL VARY WITH NO CLEAR TREND OVER THE NEXT FEW DAYS.
UNDER THE PERIODS OF RIDGING INFLUENCE...EXPECT SOME WARMING...BUT
THE SURGES OF SOUTHWEST FLOW WILL INCREASE CLOUD COVER HELPING TO
KEEP TEMPERATURES SLIGHTLY COOLER. REGARDLESS...TEMPERATURES TO
REMAIN GENERALLY SEASONABLE.

&&

.AVIATION.../06Z ISSUANCE/

AN UPPER LEVEL LOW PRESSURE SYSTEM WILL CONTINUE TO DRIFT EAST
ACROSS CENTRAL AND EASTERN WYOMING OVERNIGHT...INTO THE HIGH PLAINS
THURSDAY MORNING.  PARTIAL CLEARING WILL OCCUR OVER WESTERN WYOMING
WITH PATCHY FOG DEVELOPING ALONG WITH PARTIAL TERRAIN OBSCURATIONS
THROUGH 15Z.  FOG DEVELOPMENT IS MOST FAVORABLE VCNTY KJAC WHERE ONE-
HALF INCH OF RAIN FELL ON WEDNESDAY.

AN AREA OF SHOWERS ASSOCIATED WITH THE UPPER LEVEL LOW WILL PUSH
EAST OF A VCNTY KRIW-KWRL LINE BY 11Z...AND EAST OF KCPR 16Z-18Z
THURSDAY.  LCL MVFR CIGS AND HIGHER MTN OBSCURATIONS WILL BE
ENCOUNTERED IN THIS AREA OF SHRA.

AN UPPER LEVEL DISTURBANCE WILL PUSH SE VCNTY OF THE CONTINENTAL
DIVIDE THURSDAY AFTERNOON AND EVENING WITH WDLY SCT SHRA/TSRA
DEVELOPING ACROSS MAINLY VCNTY AND WEST OF A KPOY-KWRL-KRKS LINE
THROUGH AROUND 03Z FRIDAY.  BRIEF MVFR CONDITIONS AND ERRATIC WIND
GUSTS NEAR 30KTS WILL BE THE MAIN HAZARDS WITH STRONGER STORMS.
CLEARING...VFR CONDITIONS WILL PREVAIL AFTER 03Z FRIDAY.

&&

.FIRE WEATHER...

...ELEVATED FIRE DANGER ACROSS THE ACROSS THE FAR NORTHERN AND
EASTERN ZONES UNTIL DEEPER MOISTURE ARRIVES THIS EVENING...

ISOLATED SHOWERS AND THUNDERSTORMS IN THE FAR WEST WITH MIN RH`S IN
THE TEENS BEFORE HIGHER RH ARRIVES THIS EVENING ALONG WITH A BETTER
CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS. WIDESPREAD SHOWERS AND
A FEW THUNDERSTORMS ALONG AND WEST OF THE DIVIDE THROUGH THIS
EVENING WITH LOCALLY HEAVY RAIN. A FEW MORNING SHOWERS THURSDAY
BEFORE AFTERNOON SHOWERS AND THUNDERSTORMS FIRE UP IN THE WEST WITH
A FEW MOVING OFF THE MOUNTAINS INTO AREAS EAST OF THE DIVIDE. MIN
RH`S WILL GENERALLY BE IN THE 20S EAST OF THE DIVIDE THURSDAY WITH
MID 20S TO MID 30S WEST ACROSS THE LOWER ELEVATIONS.

&&

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

&&

$$

SHORT TERM...PS
LONG TERM...BRANHAM
AVIATION...AEM
FIRE WEATHER...PS


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