Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 200518
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1018 PM MST MON JAN 19 2015

.SHORT TERM...TONIGHT THROUGH TUESDAY

LIMITED MOISTURE IN NORTHWEST FLOW WILL KEEP AREAS OF VERY LIGHT
SNOW OVER THE NORTH AND WEST MOUNTAINS...OTHERWISE VARIABLE HIGH AND
MID CLOUDS WILL PASS OVER THE AREA.  TEMPERATURES WILL BE COOLER
WITH LIGHTER WINDS. OVER AND NEAR THE EAST SLOPES OF THE MOUNTAINS
AND ACROSS THE SOUTH BREEZY CONDITIONS WILL EXIST.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY

BEGINNING OF FCST...NW FLOW WITH THE LAST OF A TRAIN OF SMALL SW
DISTURBANCES...MOVING OVR THE CWA TUE NIGHT...REALLY JUST DOING SOME
SKY SCOURING...WITH VERY SMALL AMOUNTS...IF ANY...OF PRECIP BEING
PRODUCED FROM LEFT OVER MOISTURE AND LEAVING A FEW AREAS PRIMED FOR
FOG PRODUCTION BY WED AM...ESPECIALLY OVR THE JACKSON/STAR
VALLEYS...UPR GREEN BASIN...PORTIONS OF THE WIND RIVER BASIN...AND
SRN BIGHORN BASIN. COLD START TO THE MORNING ACROSS THE
FA...OTHERWISE...DRYING AND CLEARING SKIES LASTING THRU THU
MORNING.

THU THRU MON...NW TO N FLOW CONTINUES OVR THE FA WITH A TREND TOWARD
RIDGING...BEHIND FINAL UPR SW TROF THAT WILL MOVE THRU THE FA FROM N
TO S LATER OVERNIGHT WED...WITH NOT MORE THAN SOME INCREASED CLOUD
AND A WIND SHIFT EXPECTED ACROSS FAR ERN WY. SEASONALLY COOL THU
WITH SOME INCREASING MID/UPR CLOUD MOVING IN FROM THE N...LEADING TO
AN EVENTUAL INCREASE IN POPS ON FRI ACROSS THE NRN FA. MID/LR MDLS
ALREADY BEGIN TO DIVERGE FRI AS THE NEXT UPR DISTURBANCE...NOW
PICKED UP BY THE EURO AND NOT THERE BEFORE...MOVES INTO AND THRU THE
FA SOMETIME DURING THE DAY FRI. EURO IS COMPLETELY DRY WITH THIS
DISTURBANCE...THE GFS SLIGHTLY MOIST. ALTHOUGH NOTHING MUCH WILL
COME OF THIS WAVE... AS IT WILL TAKE A BIT OF WORK TO GET ENOUGH
MOISTURE BACK INTO THE CWA UNDER THE PREVIOUS RIDGE/DRY
CONDITIONS...WILL STAY WITH LOW END POPS ACROSS THE NRN ZONES AS PER
GFS AS IT HAS BEEN THE MOST CONSISTENT WITH THIS WAVE OVR THE PAST
FEW DAYS.

ODDLY...MDL DIFFERENCES BEYOND FRI NIGHT CONVERGE ONCE AGAIN AND
APPEAR TO BE GOOD THRU THE END OF THE FCST PERIOD...AS OPPOSED THE
THE PREVIOUS MANY FCSTS. WHILE THERE ARE SOME SPATIAL AND TEMPORAL
DIFFERENCES...THE GFS HAS COME WWD WITH MOISTURE FOR
SAT/SUN...PRODUCING SOME AREAS OF PRECIP...WHILE THE EURO IS MORE
BULLISH AND STEADFAST...CONTINUING TO ALLOW SOMEWHAT BETTER MOISTURE
TO WORK ITS WAY OVR THE FA. HOWEVER...BOTH MDLS KEEP THE STRONGEST
PORTION OF UPR LVL FORCING EAST OF THE CWA THRU SUNDAY. STILL
PLAYING ABOUT A 60/40 SPLIT BETWEEN EURO/GFS ATTM...WITH PRECIP CHCS
INCREASING ACROSS THE NRN/ERN FA FROM SAT THRU SUN...WITH BEST PROBS
OVR THE BIGHORNS. NOTHING SIGNIFICANT LOOKING ATTM. MONDAY...BOTH
MDLS CONTINUE TO AGREE SPECTACULARLY IN DRYING OUT AND BUMPING THE
WRN CONUS RIDGE FURTHER EAST...WARMING THINGS UP NICELY UNDER LL
W/SW FLOW.

&&

.AVIATION.../06Z ISSUANCE/

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

DISTURBANCES IN THE NORTHWEST FLOW ALOFT SHOULD RESULT IN ISOLATED
TO SCATTERED MOUNTAIN SNOW SHOWERS POSSIBLY IMPACTING THE LOWER
ELEVATIONS. ONE DISTURBANCE SHOULD EXIT BY AROUND 15Z...WHILE
ANOTHER ONE WILL IMPACT THE AREA BETWEEN 21Z TUESDAY AND 06Z
WEDNESDAY. THE BULK OF THE IMPACT FROM THIS LATTER SYSTEM WILL BE
ACROSS THE NORTHERN AND CENTRAL PORTIONS OF THE BIGHORN MOUNTAINS
WHERE IFR/LIFR CONDITIONS ARE LIKELY AT TIMES IN SNOW AND LOW
CLOUDS. TERMINALS ARE EXPECTED TO REMAIN VFR...BUT CANNOT RULE A
STRAY SNOWBAND PUSHING EAST SOUTHEAST OFF THE MOUNTAINS AND
IMPACTING A TERMINAL OR TWO AT TIMES. THE MAIN IMPACT FROM BOTH
SYSTEMS WILL BE CONSIDERABLE MIDLEVEL CLOUDINESS...WITH PARTIAL
CLEARING BETWEEN SYSTEMS. WINDS WILL GENERALLY BE LIGHT FROM THE
WEST TO NORTHWEST. THE EXCEPTIONS WILL BE BREEZY NORTHWEST WINDS AT
KDUB AND KBYG.

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

PATCHY FOG COULD DEVELOP LATE TONIGHT/TUESDAY MORNING OVER THE
VALLEYS...BUT MID LEVEL CLOUDINESS AND ISOLATED MOUNTAIN SNOW
SHOWERS SHOULD LIMIT THE EXTENT OF FOG/STRATUS. OTHERWISE...ISOLATED
MOUNTAIN SNOW SHOWERS...POSSIBLY SHIFTING INTO THE LOWER ELEVATIONS
WILL OCCUR TODAY. A BETTER CHANCE FOR STRATUS AND FOG WILL OCCUR
OVER THE WESTERN VALLEYS TONIGHT...ESPECIALLY KJAC.  WINDS WILL
GENERALLY BE LIGHT FROM THE WEST TO NORTHWEST THROUGH THE FORECAST
PERIOD.

&&

.FIRE WEATHER...

WIDESPREAD SNOW COVER WILL CONTINUE WITH COOL TEMPERATURES AND
FAVORABLE RELATIVE HUMIDITY. LIMITED MOISTURE IN NORTHWEST FLOW WILL
BRING SOME VERY LIGHT SNOWFALL TO THE NORTHERN AND WESTERN
MOUNTAINS.  SOME BREEZY AREAS WILL EXIST OVER THE SOUTH AND OVER AND
NEAR THE EAST SLOPES OF THE MOUNTAINS.  MIXING HEIGHTS WILL BE LOW
WITH GENERALLY POOR SMOKE DISPERSAL.

&&

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

&&

$$

SHORT TERM...C.BAKER
LONG TERM...BRAUN
AVIATION...WM
FIRE WEATHER...C.BAKER









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