Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 011700
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1100 AM MDT SUN MAY 1 2016

.SHORT TERM...SUNDAY THROUGH TUESDAY NIGHT

FINALLY SOME IMPROVING CONDITIONS ACROSS THE AREA AND A RETURN OF
SOME SUNSHINE FOR SOME MUCH NEEDED DRYING OUT. THERE ARE STILL A FEW
SHOWERS ON THE RADAR THIS MORNING BUT THESE SHOULD DIMINISH BY EARLY
AFTERNOON AND THEN FEATURE...SHOCKING...INCREASING AMOUNTS OF
SUNSHINE THROUGH THE DAY AS DRIER AIR MOVES IN FROM THE NORTH AS
HIGH PRESSURE DROPS IN FROM MONTANA. TEMPERATURES WILL
STILL BE BELOW NORMAL...BUT WARMER THAN RECENT DAYS AND WITH THE
SUNSHINE IT WILL FEEL MUCH BETTER THAN RECENT DAYS. THE MAIN CONCERN
THIS MORNING WILL BE SOME PATCHY FOG WHERE CLEARING MAY TAKE PLACE.
CONTINUITY HAD THAT COVERED FAIRLY WELL SO WE LEFT IT. IN
ADDITION...THERE WILL STILL BE GUSTY WINDS ACROSS SOUTHERN
WYOMING. HOWEVER...NOT HIGH ENOUGH TO WARRANT ANY HIGH WIND
HIGHLIGHTS. TONIGHT LOOKS MAINLY DRY AND COOL. THERE COULD BE SOME
FOG IN PLACES...SO WE ADDED PATCHY FOG FOR LATE TONIGHT IN AREAS THAT
HAD SUBSTANTIAL RAIN OVER THE PAST FEW DAYS WITH NARROW TEMPERATURE-
DEW POINT SPREADS EXPECTED.

THERE IS A BIT OF UNCERTAINTY FOR MONDAY HOWEVER AS A FLY HAS
ENTERED THE SOUP FOR MONDAY AFTERNOON. THAT FLY IS SHORTWAVE THAT
WILL MOVE RAPIDLY DOWN FROM CANADA AND INTO THE STATE MONDAY
AFTERNOON AND EVENING. THE NAM RETROGRADES THE WAVE INTO WYOMING AND
BRINGS SOME CONVECTION TO PORTIONS OF THE STATE. THE GFS IS WELL
EAST OF THE AREA WITH THE WAVE. THE EUROPEAN IS IN THE MIDDLE BUT
STILL KEEPS IT EAST OF THE AREA. FOR NOW...AS A COMPROMISE WE
INTRODUCED SOME ISOLATED TO THE HIGHER ELEVATIONS EAST OF THE
DIVIDE. TEMPERATURES WILL CONTINUE TO BE ON THE UPWARD
SWING...FINALLY APPROACHING SEASONAL NORMALS.

THERE IS THE SAME DILEMMA FOR TUESDAY. THE NAM HAS CONVECTION OVER
SOUTHERN WYOMING WITH THE LOW STALLED OVER THE AREA. MEANWHILE...THE
GFS AND EUROPEAN ARE DRY WITH A RIDGE FIRMLY IN CONTROL. AGAIN...WE
ADDED SOME SLIGHT POPS ACROSS THE SOUTH BUT MOST AREAS WILL BE DRY
MOST OF THE TIME. THERE WILL FINALLY BE SOME SPRING LIKE
TEMPERATURES FOR THE FIRST TIME IN OVER A WEEK. MANY LOWER
ELEVATIONS SHOULD SEE HIGH TEMPERATURES RISE INTO THE 70S.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

SYNOPSIS...UPPER RIDGE WILL BRING DRY AND MILD WEATHER ACROSS THE
AREA ON WEDNESDAY.  ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
WILL PUSH INTO THE WEST THURSDAY AHEAD OF THE NEXT PACIFIC STORM
SYSTEM...WHILE CENTRAL WYOMING WILL SEE UNSEASONABLY MILD AND MAINLY
DRY WEATHER.  THE PACIFIC STORM SYSTEM WILL MOVE INTO THE GREAT
BASIN FRIDAY AND LINGER THROUGH THE WEEKEND...BRINGING CHANCES OF
SHOWERS AND THUNDERSTORMS ACROSS THE AREA ALONG WITH A COOLING
TREND.

DISCUSSION...GFS SHOWS BETTER RUN-TO-RUN CONTINUITY THAN ECMWF WITH
THE GFS DEVELOPING A REX BLOCK OVER THE ROCKIES/GREAT BASIN NEXT
WEEKEND.  THE ECMWF HAS SHOWN WIDELY VARYING INTERACTIONS WITH SW
LOW AND NORTHERN STREAM OVER THE LAST FEW RUNS.  GFS/GEFS MEAN WAS
USED FOR THIS FORECAST PERIOD.

OMEGA BLOCK BEGINS THIS PERIOD WITH UPPER RIDGE ACROSS THE ROCKIES
FLANKED BY LOWS OFF THE WEST COAST AND ACROSS THE EASTERN U.S. UPPER
RIDGE SHIFTS EAST INTO THE PLAINS ON THURSDAY/THURSDAY NIGHT AS
WESTERN UPPER LOW SLOWLY MOVES INTO THE LAS VEGAS AREA BY 0Z
SATURDAY.  GFS HAS TRENDED SLIGHTLY WARMER OVER LAST FEW RUNS WITH
H7 TEMPS NEAR 10C ACROSS CENTRAL WYOMING ON THURSDAY...SO FORECAST
CONTINUES TO TEND TEMPERATURES WARMER WITH SOME HIGHS IN THE LOWER
80S ACROSS THE LOWER CENTRAL BASINS ON THURSDAY.  MOISTURE AND
SLIGHT INSTABILITY IN SOUTHERLY DIFLUENT FLOW WILL BEGIN TO SPREAD
SOME SHOWERS AND THUNDERSTORMS NEAR AND WEST OF THE DIVIDE THURSDAY.
EASTERLY LOW LEVEL FLOW WILL BRING BETTER MOISTURE...INSTABILITY AND
SHEAR INTO CENTRAL AREAS ON FRIDAY WITH THE POTENTIAL FOR SOME
STRONG TO SEVERE THUNDERSTORMS.  A MORE WIDESPREAD PRECIPITATION
EVENT IS SETTING UP FOR NEXT WEEKEND WITH CUTOFF UPPER LOW OVER THE
GREAT BASIN WITH LOW LEVEL UPSLOPE FLOW EAST OF THE DIVIDE.  AT THIS
POINT...SNOW LEVELS ARE PROGGED TO REMAIN >=9KFT SO IMPACTS ON
TRAVEL SHOULD BE MINIMAL.  HOWEVER...SIGNIFICANT RAINFALL ON
MOUNTAIN SNOWPACK MAY ELEVATE FLOODING CONCERNS.


&&

.AVIATION.../18Z ISSUANCE/

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

VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD. GUSTY EAST TO
NORTHEAST WIND TO CONTINUE NEAR AND WEST OF KRKS INTO THIS EVENING.

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

LINGERING RAIN OR SNOW SHOWERS IN CENTRAL WY WILL CONTINUE TO
DISSIPATE THROUGH 20Z. SOME LOW CLOUDS WILL REMAIN IN PLACES WITH
MVFR CONDITIONS UNTIL 02Z MONDAY. OTHERWISE VFR CONDITIONS WILL
PREVAIL THROUGH THE PERIOD.

&&

.FIRE WEATHER...

FIRE DANGER SHOULD REMAIN LOW TODAY. ANY SHOWERS SHOULD END THIS
MORNING WITH INCREASING AMOUNTS OF SUNSHINE THROUGH THE DAY. A GUSTY
EASTERLY WIND WILL BLOW FROM THE RATTLESNAKE RANGE ACROSS SOUTHERN
WYOMING. HOWEVER...RELATIVE HUMIDITY VALUES WILL REMAIN WELL ABOVE
CRITICAL LEVELS. EXPECT WARMING AND DRIER CONDITIONS THROUGH AROUND
WEDNESDAY WITH THE EXCEPTION OF THE MOUNTAINS WHERE AN ISOLATED
AFTERNOON THUNDERSTORM MAY FIRE. EXPECT MAINLY LIGHT WINDS FROM
MONDAY INTO THE MIDDLE OF THE WEEK.
&&

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

$$

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



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