Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 120812
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
212 AM MDT FRI SEP 12 2014

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT

PRECIP HAS MOVED EAST OF THE AREA AS THE LATER SUMMER SNOWSTORM
PULLS AWAY FROM THE AREA. QG FORCING...ISENTROPIC LIFT AND JET
DYNAMICS HAVE EXITED ALONG WITH THE TROUGH. THE MID LEVEL
CIRCULATION WILL BE TRACKING FROM NORTHERN CO TO SE WY BY 12Z FRI.
HOWEVER...LOW CLOUDS CONTINUE TO BE STACKED UP AGAINST THE EAST
DIVIDE EARLY THIS MORNING. THE FORECAST CHALLENGE THIS MORNING WILL
BE...WILL THESE LOW CLOUDS VANISH IN TIME FOR A WINDOW WIDE ENOUGH
FOR SKIES TO CLEAR AND FOG TO FORM IN THE BASINS EAST OF THE
DIVIDE. A VERY DRY LAYER OF AIR WILL BECOME ESTABLISHED ABOVE THE
INVERSIONS THIS MORNING...CONDUCIVE FOR FOG DEVELOPMENT. FOG DOES
NOT APPEAR TO BE A GOOD BET FOR THE WESTERN VALLEYS AS SFC TEMP/DEW
POINTS SPREADS ARE FAIRLY WIDE THERE. THE BIG HORN BASIN IS MORE
LIKELY TO HAVE FOG THAN THE WIND RIVER BASIN WHERE MORE WIDESPREAD
LOW CLOUDS LINGER. WILL TREND MORE WIDESPREAD FOG NORTH TO SOUTH
EAST OF THE DIVIDE. MORE PRECIP APPEARS TO HAVE FALLEN IN THE BIG
HORN BASIN THAN IN THE WIND RIVER BASIN AS WELL FOR AMPLE
CONTRIBUTING GROUND MOISTURE. NATRONA/JOHNSON COUNTIES SHOULD SEE
PATCHY FOG AS WELL ONCE LOW CLOUDS CLEAR OUT.

CONFLUENT FLOW TAKES OVER TODAY AS A HIGH PRESSURE RIDGE BUILDS IN
FROM THE WEST. THIS WILL RESULT IN A WARMING TREND THROUGH SUNDAY.
HIGHS WILL GENERALLY BE IN THE 50S TO NEAR 60 TODAY...60S TO THE LOW
70S SATURDAY AND 70S ON SUNDAY. TEMPS WILL ACTUALLY BE SLIGHTLY
WARMER WEST OF THE DIVIDE TODAY AND SATURDAY. THERE WILL BE A WELL
DEFINED SHORTWAVE TRACKING ACROSS THE CWA SATURDAY BUT WILL LACK
ANY MOISTURE AND INSTABILITY SO WILL BE TRANSPARENT FOR THE MOST
PART EXCEPT FOR SOME INCREASE IN WEST WINDS.

.LONG TERM...MONDAY THROUGH FRIDAY

AN UPPER LEVEL RIDGE HIGH PRESSURE WILL DOMINATE THE WEATHER PATTERN
ACROSS THE COWBOY STATE MONDAY THROUGH WEDNESDAY WITH DRY CONDITIONS
AND SLIGHTLY ABOVE AVERAGE TEMPERATURES. MEDIUM RANGE MODELS THEN
SHOW A TROUGH LIFTING ACROSS THE THE NORTHERN ROCKIES IN THE
THURSDAY AND FRIDAY TIME FRAME. CURRENTLY IT APPEARS THE ASSOCIATED
COLD FRONT WILL PUSH ACROSS THE FORECAST AREA THURSDAY NIGHT INTO
FRIDAY. HAVE BROAD BRUSHED SLIGHT POPS THURSDAY AND FRIDAY. THIS
SYSTEM LATE NEXT WEEK IS MUCH WARMER...THAN THE ONE THAT RESULTED IN
THE HEAVY SNOW THIS PAST WEDNESDAY NIGHT AND THURSDAY. SNOW LEVELS
EVEN BEHIND THE COLD FRONT NEXT FRIDAY ARE EXPECTED TO REMAIN ABOVE 10
KFT MSL.

&&

.AVIATION.../12Z ISSUANCE/
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES
AREAS OF FOG OR LOWER LIFR/IFR CIGS WILL PERSIST EARLY THIS MORNING
AND DISSIPATE 14Z-16Z.  MAINLY VFR/SKC CONDITIONS WILL PREVAIL
16Z FRI-12Z SAT.   SFC WINDS WILL GENERALLY BE FROM THE S-SE AT
5-10KTS THROUGH THE DAY FRIDAY.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES
THROUGH 15Z FRIDAY...SOME MVFR CIGS AROUND FL090 MAY PUSH INTO VCNTY
KRKS THROUGH 15Z. ELSEWHERE...THERE MAY BE SOME PATCHY FOG OBSCURING
THE WESTERN VALLEYS.  VFR/SKC CONDITIONS WILL PREVAIL AFTER 15Z WITH
MOSTLY LIGHT WIND OF 10 KNOTS OR LESS.

&&

.FIRE WEATHER...
THE SNOWFALL AND CLOUDS HAVE EXITED TO THE EAST LEAVING US WITH
LINGERING LOW CLOUDS AND AREAS OF FOG THROUGH MID MORNING THIS
MORNING. WITH A HIGH PRESSURE RIDGE BUILDING IN FROM THE WEST
THROUGH THE WEEKEND...WE CAN EXPECT A WARMING TREND THROUGH THE
PERIOD WITH ROUGHLY A 10 DEGREE DAILY WARM UP THOUGH SUNDAY.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FREEZE WARNING FROM 2 AM TO 9 AM MDT FRIDAY
WYZ004>006-013-016>020-023-025>030.

&&

$$

SHORT TERM...LIPSON
LONG TERM...WM
AVIATION...AEM
FIRE WEATHER...LIPSON








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