Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 021750
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1150 AM MDT MON MAY 2 2016

.SHORT TERM...MONDAY THROUGH WEDNESDAY NIGHT

THIS IS THE EASIEST NIGHT OF FORECASTING I HAVE HAD IN A WHILE AS
ALL THE WET AND COOL WEATHER IS FINALLY EXITING TO THE SOUTH AND
EAST. ALL THE PEOPLE THAT HAVE BEEN SCREAMING A RIDGE...A RIDGE...MY
KINGDOM FOR A RIDGE...WILL GET THEIR WISH GRANTED AS SOME DELIGHTFUL
SPRING WEATHER WILL MOVE IN AND GIVE MANY AREAS A CHANCE TO DRY OUT.
EXPECT A GOOD DEAL OF SUNSHINE TODAY WITH SOME HIGH CLOUDS MIXING IN
AT TIMES...BUT STILL THE WARMEST AND NICEST DAY WE HAVE HAD IN OVER
A WEEK. TEMPERATURES WILL FINALLY APPROACH THE SEASONAL AVERAGES IN
MANY AREAS. WE DID KEEP THEM A FEW BELOW GUIDANCE WITH THE WET
SOIL POSSIBLY INHIBITING THE WARMING JUST A BIT. A VORTICITY
MAXIMUM WILL BY TO THE EAST LATE THIS AFTERNOON AND EVENING BUT
ANY CONVECTION SHOULD REMAIN TO THE EAST OF THE COUNTY WARNING
AREA.

THE WARMING TREND WILL CONTINUE OVER THE NEXT COUPLE OF DAYS WITH
THE RIDGE FIRMLY IN CONTROL WITH ABOVE NORMAL TEMPERATURES
WIDESPREAD BY WEDNESDAY WITH SOME OF THE LOWER ELEVATION STATIONS
POSSIBLY APPROACHING 80 DEGREES FOR A HIGH. WITH SOME MOISTURE
AROUND...WE CAN NOT COMPLETELY RULE OUT AN ISOLATED...AND I MEAN
VERY ISOLATED...SHOWER OR THUNDERSTORM OVER THE HIGHER ELEVATIONS.
HOWEVER....OVER 95 PERCENT OF THE AREA WILL BE RAIN FREE THROUGH
WEDNESDAY NIGHT.

.LONG TERM...THURSDAY THROUGH MONDAY

SYNOPSIS...AN UPPER LEVEL LOW PRESSURE SYSTEM WILL DOWN THE WEST
COAST THURSDAY AND SLOWLY DRIFT ACROSS THE GREAT BASIN AND CENTRAL
ROCKIES THROUGH THE WEEKEND. SOME SHOWERS AND THUNDERSTORMS WILL
PUSH INTO THE WEST THURSDAY AHEAD OF THIS SYSTEM WHILE
UNSEASONABLY WARM AND MAINLY DRY CONDITIONS PREVAIL EAST OF THE
DIVIDE. SHOWERS AND THUNDERSTORMS WILL INCREASE ACROSS THE AREA
FRIDAY WITH A FEW STRONG/SEVERE STORMS POSSIBLE. MORE WIDESPREAD
RAIN AND MOUNTAIN SNOW IS THEN EXPECTED SATURDAY ACROSS CENTRAL
WYOMING WITH PRECIPITATION DECREASING IN INTENSITY AND COVERAGE
FROM THE NORTH AND WEST SUNDAY AND MONDAY.

DISCUSSION...GFS AND ECMWF IN OVERALL AGREEMENT BRINGING
CLOSED/CUTOFF LOW INTO THE FOUR CORNERS REGION OVER THE WEEKEND WITH
THE MOST SIGNIFICANT SPREAD IN THE NORTHERN STREAM. ECMWF
CONTINUES TO BRING SIGNIFICANT SHORTWAVE INTO WESTERN CANADA LATE
SATURDAY WITH MORE INTERACTION BETWEEN NORTHERN STREAM AND SW LOW.
GFS CONTINUES TO SHOW MIDWEEK OMEGA BLOCK OVER THE U.S. MORPHING
INTO A REX BLOCK OVER THE WESTERN U.S. BY SATURDAY WITH UPPER HIGH
OVER THE NORTHERN ROCKIES AND SW LOW IN THE FOUR CORNERS REGION.
FORECAST CONTINUES TO FAVOR THE GFS THAT HAS SHOWN MUCH BETTER
RUN-TO-RUN CONSISTENCY.

THE TWO MAIN CONCERNS DURING THIS FORECAST PERIOD WILL BE NUMBER
ONE...THE POTENTIAL FOR STRONG/SEVERE THUNDERSTORMS ACROSS CENTRAL
WYOMING ON FRIDAY AS COLD FRONT DROPS SOUTH TO NEAR A LANDER-CASPER
LINE WITH SE FLOW BRINGING HIGHER CAPES ALONG THE FRONT...AND
SOUTHERLY DIFLUENT FLOW ALOFT.   SECOND...DESPITE DIFFERENCES IN THE
GFS AND ECMWF...BOTH MODELS HAVE CONSISTENTLY PAINTED A BAND OF
SIGNIFICANT PRECIPITATION ACROSS CENTRAL WYOMING FRIDAY NIGHT INTO
SATURDAY ON THE NE QUADRANT OF THE FOUR CORNERS LOW.  GFS HAS COOLED
MID-LEVEL TEMPERATURES SIGNIFICANTLY OVER THE LAST 24 HOURS WHICH IS
A GOOD THING FOR HOLDING ONTO THE MOUNTAIN SNOWPACK AND ALLEVIATING
FLOODING CONCERNS WITH SNOW LEVELS FORECAST TO LOWER BELOW 9KFT
WHERE HEAVIER PRECIPITATION (>=1 INCH OF WATER) IS FORECAST.

FOUR CORNERS LOW IS EXPECTED TO GRADUALLY FILL AND LIFT ACROSS THE
CENTRAL ROCKIES INTO THE CENTRAL HIGH PLAINS SUNDAY AND MONDAY WITH
THE HEAVIER PRECIPITATION EXPECTED TO SHIFT OUT INTO THE PLAINS ON
SUNDAY...A FEW SHOWERS LINGERING MAINLY OVER THE HIGH TERRAIN ON
MONDAY.

&&

.AVIATION.../18Z ISSUANCE/

WEST OF THE CONTINENTAL DIVIDE...KJAC/KRKS/KPNA/KBPI AIRPORTS

VFR CONDITIONS TO OCCUR THROUGH TUESDAY.

EAST OF THE CONTINENTAL DIVIDE...KCPR/KCOD/KRIW/KWRL/KLND AIRPORTS

VFR CONDITIONS TO OCCUR THROUGH TUESDAY.

&&

.FIRE WEATHER...

A DRYING AND WARMING TREND WILL BEGIN TODAY AND CONTINUE INTO
WEDNESDAY. BY WEDNESDAY...RELATIVE HUMIDITY WILL FALL INTO THE TEENS
ACROSS SOME OF THE BASINS EAST OF THE DIVIDE. HOWEVER...WINDS ARE
EXPECTED TO REMAIN LIGHT TO MODERATE THROUGH WEDNESDAY NIGHT. OTHER
THAN AN ISOLATED AFTERNOON OR EVENING THUNDERSTORM OVER THE
MOUNTAINS...EXPECT DRY WEATHER THROUGH WEDNESDAY NIGHT. WITH LIGHT
WINDS...MIXING AND SMOKE DISPERSAL SHOULD REMAIN FAIR TO POOR.
&&

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

&&

$$

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



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