Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 302133
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
333 PM MDT MON MAR 30 2015

.SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT

JUST A FEW HIGH CLOUDS SKIRTING THE AREA THIS AFTERNOON UNDER HIGH
PRESSURE. DRY CONDITIONS WILL PERSIST THROUGH THE OVERNIGHT HOURS
AS THE HIGH PRESSURE REMAINS ANCHORED OVER THE AREA. GUSTY WINDS
WILL CONTINUE ACROSS THE AREA THROUGH THIS EVENING...WITH SOME
WEAKENING EXPECTED OVERNIGHT FOR MOST AREAS...THE EXCEPTION COULD
BE THE MOUNTAIN AREAS.

AN APPROACHING WAVE OF LOW PRESSURE WILL HELP TO INCREASE CLOUD
COVER DURING THE EARLY MORNING HOURS OF TUESDAY. AS THIS SYSTEM
APPROACHES...STRONG WIND WILL DEVELOP OVER THE AREA...WITH SOME OF
THE STRONGEST WIND EXPECTED OVER THE WIND CORRIDOR OF SOUTHERN AND
CENTRAL WYOMING. WIND CURRENTLY LOOKS TO REMAIN BELOW HIGH WIND
THRESHOLDS...BUT MAY NEED TO BE WATCHED. VERY DRY CONDITIONS ARE
ALSO EXPECTED ACROSS THE AREA AHEAD OF THE APPROACHING WAVE. THIS
COMBINATION COULD RESULT IN CRITICAL FIRE BEHAVIOR ACROSS THE
AREA...WITH SOME RED FLAG WARNINGS ISSUED. PLEASE VISIT THE FIRE
WEATHER PRODUCTS FOR MORE INFORMATION. REGARDLESS TO
WARNING...ELEVATED FIRE BEHAVIOR IS ANTICIPATED ACROSS MUCH OF THE
FORECAST AREA FOR TUESDAY. THOSE PLANNING AGRICULTURAL BURNS WILL
WANT TO REVIEW CURRENT FORECAST PRODUCTS BEFORE IGNITING.

.LONG TERM...WEDNESDAY THROUGH MONDAY

MEDIUM RANGE GLOBAL MODELS ARE IN GOOD AGREEMENT ON THE OVERALL
PATTERN EVOLUTION THROUGH AT LEAST SATURDAY. DIFFERENCES DO EMERGE
AFTER THAT TIME...BUT CONFIDENCE IN THE FIRST SEVERAL DAYS IS VERY
GOOD. COLD FRONT WILL COMPLETE ITS TRANSIT OF THE FORECAST AREA
WEDNESDAY MORNING. MUCH COOLER AIR BEHIND THIS FRONT WITH 700MB
TEMPERATURES WEDNESDAY BEING 10C OR MORE COOLER THAN TUESDAY. GUSTY
NORTHWEST WIND EXPECTED EAST OF THE DIVIDE AND ACROSS SOUTHWEST
WYOMING THROUGH WEDNESDAY. DOES NOT LOOK LIKE IT WILL BE HIGHLIGHT
WORTHY...BUT COMBINATION OF COOLER TEMPERATURES AND WIND WILL MAKE
IT FEEL NOTICEABLY COOLER THAN TUESDAY. TRAILING ENERGY BEHIND THE
UPPER LEVEL LOW IN SOUTHERN SASKATCHEWAN COUPLED WITH UNSTABLE
NORTHWEST FLOW WILL KEEP SCATTERED SNOW SHOWERS GOING ACROSS THE
NORTHWEST AND BIGHORN MOUNTAINS. MODELS CONTINUE TO TREND TOWARD A
SOLUTION OF THE NEXT SHORTWAVE AND ASSOCIATED JET MAXIMA REMAINING
TO OUR SOUTH. BOTH THE ECMWF AND GFS HAVE THE SURFACE LOW EMERGING
OVER THE OKLAHOMA PANHANDLE BY 00Z/FRI. THERE DOES APPEAR TO BE A
PERIOD OF WEAK UPSLOPE FLOW LATE WEDNESDAY NIGHT AND THURSDAY
MORNING ACROSS THE CENTRAL ZONES. 700/500B LAPSE RATES AROUND
7C-8C/KM ALONG WITH SUFFICIENT MID-LEVEL MOISTURE WILL BE ENOUGH TO
GENERATE SNOWFALL ACROSS THE LOWER ELEVATIONS. THERE COULD BE SOME
ACCUMULATIONS IN THE BASINS/VALLEYS THURSDAY IF THE PRECIPITATION
STARTS EARLY AND IS MODERATE-HEAVY IN INTENSITY. RIGHT NOW...AM NOT
THAT IMPRESSED WITH WHAT THIS SYSTEM HAS TO OFFER AS BEST DYNAMICS
REMAIN TO OUR SOUTH AND UPSLOPE IS WEAK. THURSDAY DOES LOOK TO BE
THE COOLEST DAY BETWEEN NOW AND SUNDAY. RAIN/SNOW WILL DECREASE FROM
NORTHWEST TO SOUTHEAST THURSDAY NIGHT AS SHORTWAVE PULLS OUT INTO
THE CENTRAL PLAINS. EXPECT A SLIGHT WARM-UP FRIDAY BUT TEMPERATURES
ARE LIKELY TO STILL BE JUST A SHADE UNDER CLIMATOLOGICAL NORMALS AS
700MB TEMPERATURES STILL ONLY AROUND -6C TO -10C. 500MB COLD POOL
WILL PULL OUT FRIDAY MORNING EFFECTIVELY BRINGING TO AN END TO
INSTABILITY SHOWERS WITH THE POSSIBLE EXCEPTION BEING IN THE
BIGHORNS. HEIGHTS RISE SATURDAY AND TEMPERATURES FURTHER REBOUND TO
AT OR ABOVE NORMAL AS UPPER FLOW BACKS TO THE WEST-SOUTHWEST. DRY
CONDITIONS WILL PREVAIL SATURDAY AND SATURDAY NIGHT. MODELS THAN
DIVERGE BEGINNING SUNDAY. ECMWF HAS MORE OF A PROGRESSIVE OPEN-WAVE
MOVING ONSHORE IN THE PACIFIC NORTHWEST SUNDAY. MEANWHILE...THE
ECMWF HAS A CLOSED LOW REMAINING OFF THE NORTHWEST COAST.
THEREFORE...THE GFS IS MORE BULLISH AND FASTER IN BRINGING THE
SHORTWAVE AND PRECIP TO NORTHWEST WYOMING LATE SUNDAY AFTERNOON AND
NIGHT. EITHER SOLUTION WILL STILL KEEP EASTER SUNDAY A LITTLE WARMER
THAN AVERAGE WITH HIGHS 50-60F ACROSS THE FORECAST AREA. THE
DIFFERENCE WOULD BE IN THE LATE DY PRECIP CHANCES ACROSS NORTHWEST
AND FAR WEST WYOMING. EXTENDED PERIOD DISCUSSION FROM CPC INDICATES
LEANING TOWARD THE ECMWF SOLUTION RATHER THAN THE FLATTER SOLUTION
OFFERED BY THE GFS. WITH MUCH UNCERTAINTY AND AFTER COLLABORATION
WITH NORTHERN WFO NEIGHBORS...HAVE TRENDED TOWARD CLIMATOLOGICAL
PRECIP CHANCES LATE SUNDAY...SUNDAY NIGHT...AND MONDAY ALONG WITH A
SLIGHT COOL DOWN FOR MONDAY.

&&

.AVIATION.../00Z ISSUANCE/

HIGH PRESSURE WILL KEEP THE AREA VFR THROUGH AROUND 15Z TUESDAY.
PERIODS OF GUSTY WIND WILL BE POSSIBLE. AN APPROACHING AREA OF LOW
PRESSURE WILL INCREASE CLOUD COVER OVER THE AREA AFTER 15Z...WITH
WIND INCREASING ACROSS MUCH OF THE AREA. STRONG WIND WILL BE
FAIRLY COMMON AFTER 18Z TUESDAY. THIS SYSTEM MAY ALSO INTRODUCE
SOME SHOWERS AND THUNDERSTORMS WEST OF THE CONTINENTAL DIVIDE
AFTER 18Z TUESDAY...WITH CONVERGE INCREASING AFTER 21Z. ANY
SHOWERS REACHING OVER THE TERMINALS WILL BRING BRIEF PERIODS OF
MVFR CONDITIONS.

&&

.FIRE WEATHER...

HIGH PRESSURE WILL LEAVE DRY CONDITIONS OVER THE AREA THROUGH
TUESDAY...ESPECIALLY AHEAD OF THE APPROACHING WAVE OF LOW
PRESSURE. THE LOWER ELEVATIONS WILL COMMONLY SEE RELATIVE HUMIDITY
INT HE LOW TO MID TEENS. ADDITIONALLY...THE APPROACHING WAVE OF
LOW PRESSURE WILL HELP TO INCREASE WIND ACROSS THE AREA ON
TUESDAY. CRITICAL FUELS ARE INDICATED OVER PORTIONS OF CENTRAL AND
EASTERN WYOMING. MOST OF THESE AREAS WILL SEE A DANGEROUS
COMBINATION OF WIND AND RELATIVE HUMIDITY AND CRITICALLY DRY FUELS
TO CREATE RED FLAG CONDITIONS. THESE WARNINGS HAVE BEEN
ISSUED...WITH DETAILS INCLUDED IN THEIR APPROPRIATE PRODUCTS.
HOWEVER...THERE ARE ADDITIONAL AREAS WHERE A HAZARDOUS COMBINATION
OF WIND AND DRY RELATIVE HUMIDITY WILL EXIST...THOUGH FUELS ARE
NOT CRITICAL AT THIS TIME. ANYONE PLANNING TO DO AGRICULTURAL
BURNING ON TUESDAY WILL WANT TO REVIEW CURRENT CONDITIONS AND
FORECAST INFORMATION BEFORE IGNITING.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM NOON TO 9 PM MDT TUESDAY WYZ280-281.

RED FLAG WARNING UNTIL 9 PM MDT TUESDAY WYZ283.

&&

$$

SHORT TERM...BRANHAM
LONG TERM...CNJ
AVIATION...BRANHAM
FIRE WEATHER...BRANHAM




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