Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 230933
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
333 AM MDT WED APR 23 2014

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT

A STRONGLY FORCED COLD FRONT SHOULD BE SWEEPING EAST OF THE FORECAST
AREA EARLY IN THE MORNING. THE MAIN TROUGH WILL BE MOVING THROUGH
EARLY WITH SOME DECENT QG FORCING REMAINING A PLAYER...POPS WERE
KEPT BROAD ACROSS THE STATE THIS MORNING TO ACCOUNT FOR THE
LINGERING UPPER LEVEL FORCING ALONG WITH THE TROUGH...IN ADDITION TO
THE DYNAMICS ASSOCIATED WITH THE COLD FRONT. THE SURFACE LOW IS
PRETTY FAR NORTH AND FLOW REMAINS WEST TO NORTHWESTERLY...WHICH IS
MOST FAVORABLE FOR THE HIGHER ELEVATIONS AND NORTHERN BIGHORN BASIN
BUT POPS WERE KEPT BROAD FOR THE MORNING. IT WILL BE CONSIDERABLY
COOLER TODAY BEHIND THE FRONT WITH MOUNTAIN SNOW
SHOWERS...DECREASING TO SCATTERED RAIN OR SNOW SHOWERS IN AND NEAR
THE FOOTHILLS AND MORE ISOLATED OUT IN THE BASINS AND SOUTH. SOME
MEASURABLE SNOW IS STILL POSSIBLE TODAY IN THE WRN MOUNTAINS AND
BIGHORNS...BUT THE STEADIEST AND HEAVIEST PRECIPITATION WILL CEASE
EARLY THIS MORNING.

WIND WILL BE QUITE STRONG AGAIN TODAY IN THE SINKING MOTION
ASSOCIATED WITH THE BACK SIDE OF THE TROUGH...ESPECIALLY IN THE
MOUNTAINS AND EAST OF THE DIVIDE. ANOTHER WAVE ASSOCIATED WITH A
SEPARATE LOW PRESSURE SYSTEM JOGGING ALONG THE CANADIAN BORDER WILL
GRAZE THE NORTHERN ZONES EARLY ON THURSDAY...BRINGING ANOTHER CHANCE
FOR PRECIPITATION TO THE NORTHWESTERN MOUNTAINS...BIGHORNS AND
NORTHERN BIGHORN BASIN. FLAT RIDGING BUILDS IN QUICKLY BEHIND THIS
WAVE BY THURSDAY AFTERNOON WITH WARM AND DRY CONDITIONS EXPECTED TO
HOLD FOR MOST OF THE FORECAST AREA...WITH SOME MOISTURE ALREADY
ARRIVING IN THE FAR WEST AHEAD OF THE NEXT PACIFIC SYSTEM.

THE NEXT DIGGING TROUGH ALONG THE WEST COAST WILL SEND OUT A LEADING
SHORT WAVE SET TO ARRIVE IN THE WEST EARLY ON FRIDAY AFTERNOON. RAIN
AND SNOW WILL BLANKET THE WESTERN MOUNTAINS AND VALLEYS BY FRIDAY
EVENING. MILD SOUTHWEST FLOW WILL CONTINUE THROUGH THE NIGHT WITH
SNOW LEVELS REMAINING HIGH. THERE IS SOME DISAGREEMENT ON HOW MUCH
RAIN COULD FALL ACROSS THE WEST BUT THERE IS POTENTIAL FOR OVER ONE
QUARTER OF AN INCH OF RAIN IN SOME LOW ELEVATION AREAS.

.LONG TERM...SATURDAY THROUGH TUESDAY

00Z GLOBAL MODELS HAVE TRENDED FARTHER SOUTH WITH THE MAIN ENERGY
WITH THE TROUGH IMPACTING THE ROCKIES THIS WEEKEND. BY 12Z
SATURDAY...THE MAIN ENERGY/UPPER LOW WITH THE WESTERN TROUGH IS
PROGGED BY MODELS TO BE OVER SOUTHERN CALIFORNIA/NORTHERN BAJA AREA.
THIS UPPER LOW GRADUALLY SLIDES ACROSS ARIZONA/NEW MEXICO SATURDAY
AND SATURDAY NIGHT...EMERGING ACROSS SE COLORADO/W KANSAS SUNDAY
MORNING. AT THE SAME TIME...SOME WEAKER ENERGY IN THE TROUGH COULD
IMPACT THE NORTHERN ROCKIES. THIS MORE SOUTHERLY TRACK IS LESS
CONDUCIVE FOR WIDESPREAD SIGNIFICANT PRECIPITATION ACROSS THE
FORECAST AREA. HOWEVER TIMING OF THE BEST CHANCE FOR PRECIPITATION
HAS NOT CHANGED MUCH FROM PREVIOUS FORECASTS. IT LOOKS LIKE THE
BEST SHOT WEST OF THE DIVIDE WILL SATURDAY INTO SATURDAY
EVENING...SHIFTING EAST OF THE DIVIDE SATURDAY NIGHT INTO SUNDAY
MORNING...AS A COLD FRONT MOVES ACROSS THE AREA. ALSO LATE
SATURDAY NIGHT INTO SUNDAY SOME MOISTURE WRAPPING AROUND THE UPPER
LOW...IN COMBINATION WITH SOME LOW LEVEL UPSLOPE COULD ENHANCE
PRECIPITATION OVER THE EXTREME EAST. GLOBAL MODELS...WITH THE MORE
SOUTHERN TRACK HAVE ALSO HAVE WARMED THE TEMPERATURE PROFILE WITH
LOWER ELEVATIONS REMAINING MAINLY RAIN...ESPECIALLY EAST.

THE UPPER LOW IS EXPECTED TO SHIFT SLOWLY EAST SUNDAY NIGHT AND
MONDAY...ONLY REACHING SOME WHERE BETWEEN CENTRAL KANSAS TO SE IOWA.
PRECIPITATION DIRECTLY RELATED TO THIS UPPER LOW SHOULD END SUNDAY
EVENING. HOWEVER SOME ENERGY IN THE NORTHWEST FLOW ON ITS BACKSIDE
COULD RESULT IN SOME CONVECTIVE SHOWER ACTIVITY THROUGH THE DAY
MONDAY.

RIDGING IS THE EXPECTED TO BUILD ACROSS THE WEST TUESDAY AND
WEDNESDAY...WITH THE GFS FARTHER EAST WITH THE RIDGE AXIS THAN THE
ECMWF. BOTH SOLUTIONS RESULT IN MAINLY DRY WEATHER...BUT THE GFS IS
MUCH WARMER.

&&

.AVIATION.../12Z ISSUANCE/

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

VFR CONDITIONS WILL OCCUR THROUGH 12Z THURSDAY. ISOLATED SHOWERS
WILL OCCUR UNTIL 13Z AS THE COLD FRONT MOVES EAST ACROSS THE AREA.
GUSTY WIND FOR MUCH OF TODAY IN MANY PLACES WITH ONLY ISOLATED
SHOWERS OVER THE NORTH. SOME RAIN AND SNOW SHOWERS OVER THE BIGHORN
MOUNTAINS THROUGH 00Z THURSDAY WITH LOCAL MVFR CONDITIONS. SEE
INDIVIDUAL TERMINAL SITES FOR MORE DETAILS.

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

SNOW WILL BE LIKELY OVER THE WESTERN MOUNTAINS UNTIL 15Z. THEN SNOW
SHOWERS WILL BE LIKELY OVER THE NORTHWEST MOUNTAINS THROUGH 06Z
THURSDAY...WITH SCATTERED SNOW SHOWERS OVER THE REST OF THE WESTERN
MOUNTAINS. EXPECT MVFR TO IFR CONDITIONS OVER AND NEAR THE
MOUNTAINS. THE KJAC TERMINAL SITE WILL SEE SOME SNOW UNTIL
11Z...THEN SNOW SHOWERS IN THE VCNTY MUCH OF THE DAY AND EVENING.
THE SOUTHWEST AND SOUTH WILL SEE ISOLATED RAIN AND SNOW SHOWERS
UNTIL 12Z. THEN MOSTLY DRY CONDITIONS AFT 12Z WITH A GUSTY WIND. SEE
INDIVIDUAL TERMINAL SITES FOR MORE DETAILS.

&&

.FIRE WEATHER...

A STRONG COLD FRONT WILL EXIT THE AREA EARLY THIS MORNING WITH
STRONG WINDS TURNING WEST AND A FEW SHOWERS. IT WILL BE CONSIDERABLY
COOLER THAN TUESDAY BUT STILL RATHER DRY EAST OF THE DIVIDE WITH MIN
RH`S IN THE TEENS AND 20S. IT WILL BE WARMER ON THURSDAY AND IT WILL
REMAIN DRY AND BREEZY ACROSS THE SOUTHERN HALF OF THE FORECAST AREA.
RAIN SHOWERS RETURN TO THE WEST THURSDAY AFTERNOON. WARM...DRY AND
BREEZY AGAIN ON FRIDAY ACROSS MUCH OF THE STATE AHEAD OF THE NEXT
STORM SYSTEM.


&&

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

&&

$$

SHORT TERM...ALLEN
LONG TERM...WM
AVIATION...AR
FIRE WEATHER...ALLEN







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