Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 212211
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
311 PM MST WED JAN 21 2015

.SHORT TERM...TONIGHT THROUGH THURSDAY

LIGHT SNOW SHOWERS FROM THIS MORNING HAVE DIMINISHED TO A FEW
LINGERING LOW TO MID LEVEL CLOUDS ACROSS SOUTHERN WYOMING. THIS
DISTURBANCE WILL EXIT THE REGION THIS EVENING. DRY AIR...WHICH IS
CURRENTLY VISIBLE ON WV IMAGERY...IS EXPECTED TO MOVE IN OVERHEAD
TONIGHT. THIS DRY AIR WILL BRING MAINLY CLEAR SKIES TONIGHT...AND
COMBINED WITH WAA...COULD CAUSE A FEW AREAS OF PATCHY FOG...OR LOW
CLOUDS TO DEVELOP ACROSS THE VALLEYS AND BASINS OF WESTERN AND
CENTRAL WYOMING. WAA WILL PUSH OUT THE COLD 700 MB TEMPS
TONIGHT...AND REPLACE THEM WITH SLIGHTLY WARMER TEMPS OF -5 TO -10
C FOR THURSDAY. ALTHOUGH LOW TEMPS FOR TONIGHT WILL BE SIMILAR TO
THE PREVIOUS NIGHT...THIS WAA WILL BRING SLIGHTLY WARMER DAYTIME
HIGHS FOR THURSDAY...ESPECIALLY ACROSS AREAS WITH AMPLE MIXING DUE
TO GUSTY WINDS. THESE GUSTY WINDS WILL OCCUR FROM EASTERN
SWEETWATER COUNTY TO KAYCEE...AS A LEE SIDE TROUGH BRINGS A
TIGHTENED PRESSURE GRADIENT FOR THURSDAY. HIGH WIND CRITERIA IS
NOT EXPECTED...HOWEVER...WIND GUSTS COULD REACH AROUND 35 TO 40
KNOTS BY THURSDAY AFTERNOON. DRY CONDITIONS WILL BE IN PLACE
ACROSS THE FORECAST AREA THROUGH THE DAY THURSDAY...WITH ONLY A FEW
MID TO HIGH LEVEL CLOUDS EXPECTED.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY

BEGINNING OF THE FCST...DRY NW TO N FLOW...WITH WRN CONUS RIDGE
FOLDING ACROSS THE STATE WITH THE AXIS STRETCHING FROM SW TO
NE...CONTINUES OVR THE FA...TRANSITIONING TO ALL NW FLOW...AND LESS
RIDGE INFLUENCE...BY FRI MORNING. NEXT UPR SW MOVING QUICKLY THRU
THE FLOW WILL ALSO ARRIVE NEAR THE NRN ZONES FRI
MORNING...INCREASING POPS FRI ACROSS THE NRN FA. AS IT WILL TAKE A
BIT OF WORK TO GET ENOUGH MOISTURE BACK INTO THE NRN CWA UNDER THE
PREVIOUS RIDGE/DRY CONDITIONS...ONLY EXPECTING LOW END POPS/QPF
ACROSS THE NRN ZONES...WHICH IS CONSISTENT WITH PREVIOUS SHORT AND
MID RANGE MDL RUNS OVR THE PAST FEW DAYS. BY FRI NIGHT...WRN CONUS
RIDGE BEGINS TO RE-FOLD OVR WY...WHILE AN UPSTREAM SW CRESTS THE
RIDGE WHILE IN BC AND TAKES AIM ON THE NWRN CORNER OF THE
FA...ARRIVING BY SAT MORNING. CONTENT AND TRAJECTORY OF
MOISTURE...ALTHOUGH ORIGINATING FROM THE EPAC...NOT ALL THAT
IMPRESSIVE...WITH THE BETTER AVAILABLE MOISTURE TRACKING N AND E OF
THE FA THRU THE DAY SAT. ATTM...NOTHING TOO SIGNIFICANT CONCERNING
THIS SYSTEM...WITH ONLY A FEW INCHES ACCUMULATING IN THE NRN
MOUNTAINS THRU SUNDAY MORNING.

SUNDAY THRU WEDNESDAY...WRN CONUS RIDGE ON TRACK TO PROPAGATE
EWD...LARGELY PROTECTING THE FA FROM INCLEMENT CONDITIONS...EXCEPT
FOR PERHAPS SOME TRAPPED COLD(ER) AIR ACROSS THE THE WRN VALLEYS FOR
A COUPLE OF DAYS. WARMING AND DRYING FOR MOST LOCATIONS IN THE CWA
THRU TUE NIGHT...AHEAD OF THE NEXT WX MAKER...A COL STUCK W OF
BAJA...WHICH IS SCHEDULED TO KICK INTO THE SWRN/WRN ZONES ON WED.
WHILE THIS IS REPRESENTED IN THE FCST FOR WED...THIS WILL REMAIN A
VERY LOW CONFIDENCE EVENT FOR A WHILE AS THE WAVE THAT IS FCST TO
CUT OFF IS STILL CAUGHT UNDER A TROF WELL INTO THE PAC ATTM...WITH
NO HINT THAT A PAC HI WILL OVER RUN THAT WAVE WHEN IT REACHES SWRN
CONUS...EFFECTIVELY CUTTING IT OFF BY LATER ON SAT. NOT MUCH OF A
PROBLEM WITH THE LEAD IN/DEVELOPMENT SCENARIO OF THE COL...BUT MORE
WITH THE TIMING AND TRAJECTORY OF THE KICKED/EJECTING LOW SOMETIME
NEXT TUE. LOTS OF IF/ANDS/BUTS HERE. HOWEVER...ASSUMING THAT
SCENARIO PLAYS OUT...EVEN THIS SYSTEM LOOKS RELATIVELY MOISTURE
CHALLENGED. THE WAIT AND SEE GAME IS ON.

&&

.AVIATION.../00Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

DECREASING CLOUDINESS IS EXPECTED FROM NORTH TO SOUTH AFTER 00Z
THIS EVENING AS THIS MORNINGS DISTURBANCE EXITS THE REGION. CLEAR
SKIES AND LIGHT WINDS TONIGHT COULD ALLOW FOR PATCHY FOG TO
DEVELOP IN BASINS AND VALLEYS AFTER 06Z. ANY PATCHY FOG THAT
DEVELOPS WILL DIMINISH BY 15Z THURSDAY...GIVING WAY TO FEW/SCT
HIGH CLOUDS AND VFR CONDITIONS THROUGH THE AFTERNOON. GUSTY WINDS COULD
ALSO DEVELOP AFTER 09Z THURSDAY...AND CONTINUE THROUGH THE
AFTERNOON...MAINLY NEAR KCPR. WIND GUSTS OF 30 TO 35 KNOTS ARE
GENERALLY EXPECTED...WITH SOME GUSTS UP TO 40 KNOTS POSSIBLE.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

LOW TO MID DECK ACROSS SOUTHERN WYOMING WILL SCATTER/LIFT DURING
LATE AFTERNOON AND EARLY EVENING HOURS. OTHERWISE...THE MAIN
CONCERN WILL BE SOME LOW CEILINGS AND FOG OVER THE FAR WESTERN
VALLEYS TONIGHT INTO EARLY THURSDAY MORNING. HOWEVER THE EXPECTED
EXTENT ONLY WARRANTS A VCFG FOR NOW AT KJAC...WHILE A LIGHT VRB
WINDS SHOULD KEEP KBPI AND KPNA FROM FOG/LOW CLOUDS IMPACTING
THOSE TERMINALS. ANY FOG THAT DEVELOPS WILL LIFT BY 15Z
THURSDAY...AND MAINLY VFR CONDITIONS ARE EXPECTED THROUGH THE REST
OF THE DAY...ALONG WITH SOME SCT MID TO HIGH LEVEL CLOUDS.

&&

.FIRE WEATHER...

MIXING/INVERSION HEIGHTS WILL CONTINUE TO REMAIN ON THE LOW SIDE
THROUGH AT LEAST FRIDAY. ACCUMULATING PRECIPITATION IS NOT
EXPECTED ANYWHERE OVER THE FORECAST AREA UNTIL POSSIBLY THIS
WEEKEND...MAINLY ACROSS THE NORTH AND NORTHEAST DISPATCH ZONES.
GUSTY WINDS COULD DEVELOP THURSDAY FROM EASTERN SWEETWATER COUNTY
TO KAYCEE.

&&

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

$$

SHORT TERM...ANGLIN
LONG TERM...BRAUN
AVIATION...ANGLIN
FIRE WEATHER...ANGLIN




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