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000
FXUS65 KRIW 131708
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1108 AM MDT THU MAR 13 2014

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT
A DRY MILDER DAY IS IN STORE FOR TODAY AS H7 TEMPS WARM TO A FEW
DEGREES BELOW ZERO C. THEN ON FRIDAY SIMILAR TEMPS CAN BE EXPECTED
WITH INCREASING CLOUDS IN THE AFTERNOON AS THE NEXT UPSTREAM TROUGH
APPROACHES. SNOW WILL DEVELOP FRIDAY NIGHT IN THE WEST AS THE FLOW
OUT AHEAD OF THIS DEEPENING TROUGH BECOMES VERY DIFLUENT. THE
COMBINATION OF DIFLUENT FLOW AND THE WESTERLY UPSLOPE COMPONENT WILL
DELIVER A FEW INCHES OF SNOW TO THE FAR WEST FRIDAY NIGHT AND INTO
SATURDAY. AN ASSOCIATED COLD FRONT WILL SLING SNOW TO AREAS EAST OF
THE DIVIDE AFTER MIDNIGHT FRIDAY NIGHT. RAIN AND SNOW WILL WILL
GRADUALLY DIMINISH EAST AND WEST OF THE DIVIDE BY SATURDAY
AFTERNOON. MOST OF THE ENERGY WITH THIS SYSTEM WILL PROPAGATE WELL
TO THE SOUTH OF US OVER THE 4 CORNERS AREA SATURDAY SO NOT EXPECTING
MUCH MORE THAN 4 INCHES OR SO OF SNOW ANYWHERE IN THE WEST FOR NOW
WITH PERHAPS 3 TO 6 INCHES IN THE BIG HORN MTNS WITH THE TROUGH AND
ASSOCIATED COLD FRONT AND LESS ELSEWHERE. CLEARING IS EXPECTED
SATURDAY NIGHT. WITH H7 TEMPS IN THE MINUS LOW TEENS SATURDAY...MOST
MTN LOCATIONS WILL BE HARD PRESSED TO BREAK FREEZING. MOS GUIDANCE
NUMBERS FOR RIVERTON/BUFFALO SUSTAINED POST FRONTAL WINDS ON
SATURDAY ARE OVER 30 KNOTS. HOWEVER THE GRADIENT DOES NOT LOOK
IMPRESSIVE AT THE SFC OR AT H7 AND NEITHER DO THE SFC PRESSURE RISES
BEHIND THE FRONT. WILL NOT INDICATE HIGH WINDS FOR THOSE AREAS IN
THE GRIDS FOR NOW.

.LONG TERM...SUNDAY THROUGH THURSDAY

UPPER RIDGE OVER THE REGION ON SUNDAY INTO SUNDAY NIGHT LEADS TO A
DRY DAY AND NIGHT FOR ALL. THE GFS AND ECMWF SHOW A NW FLOW ALOFT
FOR MONDAY AND TUESDAY. A WEATHER SYSTEM IN THE NW FLOW MOVES
ACROSS THE ROCKIES MONDAY NIGHT INTO TUESDAY. 00Z ECMWF HAS GONE
BACK TO A MORE DIGGING SYSTEM AGAIN VERSUS THE FLATTER GFS. GFS
WOULD HAVE IMPROVING CONDITIONS TUESDAY AFTERNOON WHILE THE ECMWF
HAS MOUNTAIN SHOWERS THROUGH TUE AFTERNOON. HAVE BEEN SIDING WITH
THE ECMWF MODEL PAST FEW NIGHTS AND WILL NOT CHANGE THIS IDEA
UNTIL IT CHANGES ITS SOLUTION. THUS A CHANCE OF RAIN AND SNOW MON
NIGHT AND TUESDAY SPREADING FROM NORTH TO SOUTH ACROSS THE REGION.
TUESDAY NIGHT AND WEDNESDAY LOOK DRY BY BOTH MODELS AS THE SYSTEM
DEPARTS. THE GFS MODEL THEN TAKES THE NEXT WEATHER SYSTEM INTO THE
WESTERN U.S. WED NIGHT AND THURSDAY. FLOW ALOFT BACKS TO THE SW
AND MOISTURE INCREASES OVER THE WEST WED NIGHT THROUGH THURSDAY.
EAST OF THE DIVIDE STAYS DRY WED NIGHT AND THURSDAY. THE 13/00Z
ECMWF MODEL HAS A RIDGE OF HIGH PRESSURE OVER THE REGION WITH DRY
WEATHER EVERYWHERE AND NO HINT OF A STORM SYSTEM OVER THE WESTERN
U.S. AS IT DID ON ITS 12/12Z MODEL RUN. AT THIS POINT I WILL SIDE
WITH THE GFS SOLUTION FOR WED NIGHT AND THURSDAY. THAT MEANS
BRINGING IN A CHANCE OF RAIN AND SNOW THE WEST. MOSTLY DRY IN THE
EAST FOR NOW. AS FOR TEMPS...A MILD DAY IS IN STORE FOR SUNDAY AS
700MB TEMPS ARE SLIGHTLY WARMER THAN PREVIOUS RUNS. MONDAY WILL BE
A LITTLE COOLER BUT STILL MILD. COLDER TUESDAY...THEN MODERATION
NEXT WED AND THURS BASED ON CURRENT THINKING OF THE GFS MODEL.

&&

.AVIATION.../18Z ISSUANCE/

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

VFR CONDITIONS THROUGH 18Z FRIDAY. THE LEE SIDE OF MOUNTAINS...IN
THE FOOTHILLS AND WIND CORRIDOR FROM KRKS TO KCPR WILL BE BREEZY
WITH WEST TO SOUTHWEST WINDS GUSTING 30 TO 45 KTS AT TIMES THROUGH
23Z TODAY.

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

VFR CONDITIONS THROUGH 18Z FRIDAY...WITH A REMOTE POSSIBILITY OF
ISOLATED FOG IN THE UPPER GREEN VALLEY. OTHERWISE...MOST BASINS AND
VALLEYS WILL SEE LIGHT WINDS THROUGH THE PERIOD WHILE THE LEE SIDE
OF MOUNTAINS...FOOTHILLS AND WIND CORRIDOR FROM KRKS TO KCPR WILL BE
BREEZY WITH WEST TO SOUTHWEST WINDS GUSTING 30 TO 45 KTS AT TIMES
THROUGH 23Z TODAY.

&&

.FIRE WEATHER...

MILD AND DRY WEATHER CAN BE EXPECTED TODAY AND FRIDAY. WEST
SOUTHWEST WINDS WILL INCREASE SOMEWHAT FROM ROCK SPRINGS TO CASPER
TODAY AND FRIDAY. A PACIFIC TROUGH WILL DELIVER SOME ACCUMULATING
SNOW TO FAR WESTERN WYOMING BY FRIDAY NIGHT AND WILL SPREAD TO AREAS
EAST OF THE DIVIDE WITH ACCUMULATING SNOW IN BIG HORN MOUNTAINS LATE
FRIDAY NIGHT AND INTO SATURDAY WITH LESS RAIN AND SNOW AT THE LOWER
ELEVATIONS. THE PRECIPITATION WILL TAPER OFF SATURDAY WITH CLEARING
EXPECTED SATURDAY NIGHT. TEMPERATURES WILL WARM SUNDAY AND MONDAY.

&&

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

&&

$$

SHORT TERM...LIPSON
LONG TERM...AR
AVIATION...JFB
FIRE WEATHER...LIPSON