Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 270520
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1120 PM MDT THU MAR 26 2015

UPDATE...ADDED 06Z AVIATION DISCUSSION.

.SHORT TERM...TONIGHT THROUGH FRIDAY (ISSUED AT 352 PM MDT)

RIDGE WILL CONTINUE TO BUILD INTO THE AREA WITH ISENTROPIC UPGLIDE
CLOUDINESS GRADUALLY DECREASING TONIGHT LEAVING ALL BUT THE NE
CORNER SUNNY OR MOSTLY SUNNY ON FRIDAY. A FEW FLURRIES WERE NOTED
OVER THE HIGHER NRN MTNS THIS MORNING BUT THAT`S ABOUT IT. FRIDAY
WILL BE ANOTHER 8-10 DEGREES WARMER FOR MANY AREAS. BREEZY TO WINDY
NW WIND AREAS WILL CONTINUE FOR A FEW MORE HOURS BEFORE DECREASING.
THE CODY FOOTHILLS ARE SHOWING A LITTLE MTN WAVE ACTION AND MODEST
GAP FLOW POTENTIAL SO BEEFED UP THE WINDS IN THE FAVORED AREAS
TONIGHT BUT DOES NOT LOOK MORE THAN WINDY IN THE NORMAL AREAS.
SOME BREEZES RETURN FRIDAY IN THE W-NW FAVORED FLOW AREAS BUT LESS
THAN TODAY. OTHERWISE...JUST WARMER...DRIER WITH MORE SUNSHINE AND
OVERALL LESS WIND.

.LONG TERM...FRIDAY NIGHT THROUGH THURSDAY

A DRY AND MILD WEST NORTHWEST FLOW DURING THE LONG TERM WILL BE THE
DEFINING FEATURE OF THE WEATHER FOR THE NEXT SEVERAL DAYS. THE FIRST
WELL DEFINED SHORTWAVE TROUGH NOW OFF THE PACIFIC AT 145W WILL PUSH
THROUGH THE AREA SATURDAY AS A DRY WINDY TROUGH. WILL HAVE TO
MONITOR THIS EVENT CLOSELY AS THE LAST TROUGH THAT RESEMBLED THIS
ONE FIRST APPEARED IN THE MODELS AS IF THE RELATIVE HUMIDITY WOULD
REMAIN ABOVE 15 PERCENT WHERE THE FUELS ARE ALREADY CRITICAL BIT
WOUND UP APPROACHING 10 PERCENT WHEN THE DAY OF CONCERNED ACTUALLY
ARRIVED ONE WEEK PRIOR TO THIS EVENT. MOS GUIDANCE SUGGESTS THAT
THE WINDS WILL CERTAINLY BE WITHIN CRITERIA FROM RKS TO CPR AND EVEN
AT RIW ON SATURDAY. EVEN AFTER THE ASSOCIATED PACIFIC COOL FRONT
TRACKS ACROSS THE AREA EARLY SATURDAY EVENING...NW WINDS WILL
INCREASE ACROSS MOST AREAS EAST OF THE DIVIDE GIVEN THE 3 HOURLY
10MB POST FRONTAL SFC PRESSURE RISES BUT THE RH SHOULD INCREASE
WITH THESE WINDS. AS FAR AS ANY PRECIP WITH THIS FEATURE IS
CONCERNED...ONLY SPOTTY SHOWERS OF A ROUGE T SHOWER COULD OCCUR
OVER THE NW MTNS SATURDAY AFTERNOON WITH MEAGER MOISTURE AND
NEGATIVE LIFTED INDICES. THEN THE WEST NORTHWEST FLOW CONTINUES
WITH THE NEXT WEAK RIPPLE IN THE FLOW EXPECTED SUNDAY AND AGAIN
MONDAY WITHOUT MUCH FANFARE. THE NEXT TROUGH OF ANY SIGNIFICANCE
WILL ARRIVE TUESDAY IN THE FORM OF MORE DRY WINDY WEATHER.
HOWEVER...THE NW MTNS COULD AGAIN SEE ISOLD SHOWERS FROM NEGATIVE
LIFTED INDICES AND SUFFICIENT MID AND UPPER LEVEL MOISTURE. THEN
THURSDAY IS THE DAY THAT THE GFS AND THE EURO DIVERGE WITH THE GFS
INDICATING ANOTHER STRONG SHORTWAVE TRACKING ACROSS WY ALONG WITH
A WELL DEFINED MID LEVEL CIRCULATION FORMING RIGHT OVER THE CENTER
OF WY ALONG WITH ISENTROPIC LIFT FOR THE NORTHERN THIRD OF WY. THE
EURO SHOWS NOTHING...JUST A STRAIGHT WEST NORTHWEST FLOW. KEPT
POPS AS IS FOR NOW. DID NOT WANT TO RAISE THU POPS BECAUSE OF
REMAINING MODEL UNCERTAINTY AND NONE OF OUR NEIGHBORS HAVE
INCREASED THEIR POPS EITHER.

&&

.AVIATION.../06Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL ACROSS THE AREA THROUGH 12Z SATURDAY.
BKN CIGS FL120-130 VCNTY AND EAST OF A KSHR-KCPR LINE SHOULD BE EAST
OF THE AREA BY 12Z...LEAVING SKC-SCT250 ACROSS THE AREA THROUGH THE
REST OF THE PERIOD.  GUSTY W-NW WINDS ALONG THE EAST SLOPES OF THE
DIVIDE...VCNTY KCOD-KDUB-KRIW...WILL MOSTLY DIMINISH BY 15Z.

WINDS WILL INCREASE ACROSS THE WIND CORRIDOR...VCNTY 50SM NE
KRKS-KCPR...AND ALONG THE LEE SLOPES OF THE DIVIDE AFTER 06Z
SATURDAY AHEAD OF AN APPROACHING COLD FRONT.  THE COLD FRONT WILL
PUSH EAST ACROSS THE AREA LATE SATURDAY MORNING AND AFTERNOON.




&&

.FIRE WEATHER...

A RIDGE OF HIGH PRESSURE WILL CONTINUE TO MOVE CLOSER TO THE AREA
FROM THE WEST WITH DRIER AND WARMER CONDITIONS. FRIDAY WILL BE ABOUT
8-10 DEGREES WARMER THAN TODAY. WITH MIN RH`S EAST OF THE DIVIDE AND
IN THE SOUTH AND SOUTHWEST...LOWERING INTO THE 20S WITH LOCAL MIN
RH`S IN THE UPPER TEENS. THE NORTHWEST WILL BE MORE MOIST WITH MIN
RH`S IN THE 30S AND 40S. GUSTY W-NW WINDS WILL CONTINUE ALONG THE
EAST SLOPE OF MOST OF THE MOUNTAIN RANGES THROUGH FRIDAY. THE CODY
FOOTHILLS WILL ALSO SEE SOME GUSTY TO BRIEF STRONG WEST WINDS
THROUGH TONIGHT. THE UPPER GREEN RIVER BASIN FROM KBPI AND KPNA TO
KRKS WILL ALSO SEE GUSTY W-NW WIND THROUGH THIS EVENING BEFORE
DECREASING SOME. MORE WIND WILL RETURN FRIDAY BUT NOT AS STRONG AS
TODAY AND THIS EVENING.

A MORE ELEVATED FIRE RISK WILL DEVELOP ON SATURDAY EAST OF THE DIVIDE
DUE TO WARM TEMPERATURES...MIN RH`S IN THE UPPER TEENS TO LOWER 20S
AND INCREASING WEST WIND AS A COLD FRONT APPROACHES AND MOVES THROUGH.

&&

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

&&

$$

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










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