Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 050912
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
212 AM MST THU MAR 5 2015

.SHORT TERM...THURSDAY THROUGH SATURDAY NIGHT

THE MAINLY QUIET WEATHER PATTERN LOOKS TO CONTINUE THROUGH MOST OF
THE SHORT TERM PERIOD. THE MAIN CONCERN THIS MORNING IS THE COLD
TEMPERATURES WITH SOME OF THE BASINS ALREADY SEEING BELOW ZERO
TEMPERATURES AROUND MIDNIGHT. HOWEVER...THERE IS A BIT OF A CONTRAST
THIS MORNING. A WEAK SHORTWAVE PASSING THROUGH THE AREA IS BRINGING
SOME GUSTY BREEZES TO THE USUAL AREAS...LIKE NEAR CODY AND CASPER.
AS A RESULT...THESE AREAS HAVE TEMPERATURES THAT ARE IN SOME CASES
30 DEGREES WARMER THAN THE BASINS. THE SHORTWAVE WILL ALSO BRING
SOME MID TO HIGH LEVEL CLOUDS AT TIMES BUT NO PRECIPITATION. WITH
INCREASED MIXING...TEMPERATURES SHOULD MODERATE SOMEWHAT TODAY BUT
REMAIN BELOW NORMAL FOR MOST LOCATIONS.

TEMPERATURES WILL CONTINUE TO MODERATE INTO THE WEEKEND AS WELL.
THERE WILL BE BREEZY CONDITIONS ACROSS THE USUAL LOCATIONS BUT HIGH
WINDS ARE NOT EXPECTED AT THIS TIME. THE ONE CHANCE FOR
PRECIPITATION AND IT IS A SMALL ONE...IS A WEAK CLIPPER THAT WILL
DROP INTO THE AREA ON SATURDAY NIGHT. LIKE MOST CLIPPERS...IT IS
MOISTURE STARVED. CONTINUITY HAD ONLY SLIGHT TO LOW CHANCE POPS
ACROSS THE NORTHERN MOUNTAINS. THIS LOOKED GOOD SO WE LEFT
CONTINUITY ALONE FOR THE MOST PART.


.LONG TERM...SUNDAY THROUGH THURSDAY

A DRY NORTHWEST FLOW WILL OCCUR SUNDAY AND MONDAY. MEDIUM RANGE
MODELS THEN DIVERGE IN THE EVOLUTION OF A NORTHERN STREAM SYSTEM
PUSHING FROM THE GULF OF ALASKA EAST INTO BRITISH COLUMBIA
MONDAY/MONDAY NIGHT. THE 00Z GFS GRADUALLY CARVES OUT A BROAD TROUGH
ACROSS MUCH OF CANADA...INTO THE NORTHERN TIER OF STATES TUESDAY AND
WEDNESDAY. THIS WOULD ALLOW FOR A DECENT COLD FRONT TO DROP SOUTH
ACROSS THE AREA WEDNESDAY...WITH A SHOT OF PRECIPITATION ACROSS MUCH
OF THE AREA. ON THE OTHER HAND...THE 00Z ECMWF DOES NOT AMPLIFY THE
SYSTEM KEEPING A FAST ZONAL FLOW OVER CENTRAL/SOUTHERN CANADA. THE
ECMWF SOLUTION KEEPS THE MAIN STORM TRACK WELL NORTH OF THE AREA
THROUGH WEDNESDAY. THE 00Z ECMWF THEN SHOWS SOME PACIFIC MOISTURE
WORKING INTO THE AREA BY THURSDAY AHEAD OF CLOSED UPPER LOW OFF
THE NORTHERN CALIFORNIA COAST. THE GFS ENSEMBLES ARE SPLIT BETWEEN
THE OPERATIONAL GFS AND ECMWF SOLUTIONS WITH THE AMPLIFICATION OF
THE NORTHERN STREAM SYSTEM TUESDAY AND WEDNESDAY. HAVE ELECTED TO
KEEP SLIGHT MOUNTAIN POPS TUESDAY NIGHT AND WEDNESDAY...AND THEN
INTRODUCING SLIGHT POPS INTO THE VALLEYS WEDNESDAY NIGHT/THURSDAY
ACROSS THE FAR WEST...WHILE KEEPING THE EASTERN/SOUTHERN LOWER
ELEVATIONS DRY FOR NOW.

TEMPERATURES WILL GENERALLY BE ABOVE AVERAGE THROUGH THE
EXTENDED.

&&

.AVIATION.../12Z ISSUANCE/

VFR CONDITIONS WITH MAINLY SCT-BKN FL250 WILL PREVAIL THROUGH THE
PERIOD. AREAS OF LLWS MAY BE ENCOUNTERED ALONG THE EAST SLOPES OF
THE ABSAROKA RANGE...VCNTY KDUB-KCOD...THROUGH THE PERIOD WITH WINDS
AT FL080 30-35KT.  PATCHY FOG MAY PARTIALLY OBSCURE TERRAIN IN FAR
WEST VALLEYS AND LOWER CENTRAL BASINS DURING THE EARLY MORNING HOURS.

&&

.FIRE WEATHER...

WITH A COLD AIR MASS OVER MUCH OF THE AREA TODAY...EXPECT INVERSIONS
IN THE VALLEYS AND BASINS WITH LOW MIXING HEIGHTS AND POOR SMOKE
DISPERSAL. ACROSS NORMALLY WINDIER AREAS LIKE EAST OF THE ABSAROKAS
AND FROM ROCK SPRINGS TO CASPER...GUSTY BREEZES WILL BRING BETTER
VENTILATION AND HIGHER MIXING HEIGHTS. TEMPERATURES SHOULD CONTINUE
TO MODERATE INTO THE WEEKEND.
&&

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

&&

$$

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






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