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000
FXUS65 KRIW 221734
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1134 AM MDT WED MAY 22 2013

.SHORT TERM...WEDNESDAY THROUGH FRIDAY NIGHT

AFTER A FAIRLY QUIET WEATHER DAY ON TUESDAY IT LOOKS LIKE THE
WEATHER WILL TURN ACTIVE ONCE AGAIN. SATELLITE IMAGERY SHOWS A THIN
BAND OF CLOUDS WORKING ACROSS CENTRAL WYOMING AT THIS TIME WITH A
FEW SPRINKLES BUT THIS SHOULD BE OUT OF THE COUNTY WARNING AREA BY
DAYLIGHT. AFTER THE PASSAGE OF THESE CLOUDS PRECIPITABLE WATERS
SHOULD STAY RELATIVELY LOW. HOWEVER...700 MILLIBAR FLOW WILL SLOWLY
TURN FROM SOUTH TO SOUTHEAST AND EAST THROUGH THE DAY AND INCREASE
PRECIPITABLE WATER VALUES UP TO 0.6 TO 0.7 INCHES ACROSS MANY AREAS
EAST OF THE DIVIDE WITH THE HIGHEST VALUES IN NORTHERN AND EASTERN
PORTIONS OF THE AREA. CAPE VALUES WILL ALSO BE ON THE RISE WITH
VALUES OVER 300 J/KG FROM THE ABSAROKAS THROUGH THE WIND RIVER BASIN
AND IN AREAS FROM THE BIG HORN RANGE AND EAST. IN ADDITION...LIFTED
INDICES WILL FALL TO MINUS 3 IN MANY AREAS AND THERE IS SOME
DIRECTIONAL SHEAR WITH SOUTHWEST FLOW AT 500 MILLIBARS. WITH LOW
PRESSURE PROVIDING SOME LIFT LOOK FOR ISOLATED TO SCATTERED
THUNDERSTORMS IN THE FOREMENTIONED AREAS...SOME POSSIBLY STRONG...TO
DEVELOP THIS AFTERNOON AND EVENING WITH GUSTY WINDS AND HAIL THE
MAIN THREATS. THE THREAT OF THESE STORMS SHOULD END LATE TONIGHT
WITH THE LOSS OF DAYTIME HEATING.

STILL SOME UNCERTAINTY TOMORROW AS A LOT DEPENDS ON IF A DRY SLOT
SETS UP ACROSS PORTIONS OF THE COUNTY WARNING AREA...WITH THE BEST
CHANCE OF THAT ACROSS THE SOUTHERN PORTIONS OF THE COUNTY WARNING
AREA. WITH THE UNCERTAINTY WE HAVE LEFT CONTINUITY ALONE FOR THE
MOST PART WITH THE CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS
NORTHERN AND EASTERN AREAS WHERE MOISTURE WILL BE A BIT DEEPER. WITH
INCREASED SOUTH TO SOUTHWESTERLY FLOW TEMPERATURES WILL CONTINUE AN
UPWARD TREND TO ABOVE NORMAL LEVELS. IT WILL BECOME WINDY AS WELL
ACROSS SOUTHERN PORTIONS OF THE STATE WITH THE INCREASED SOUTH FLOW
AND GOOD MIXING FROM MORE SUNSHINE. AS FOR FRIDAY...MODELS NOW
INDICATE THAT MUCH DRIER AIR WILL MOVE AS THE BEST MOISTURE GETS
SHUNTED TO THE NORTH AND EAST OF WYOMING. STILL SOME UNCERTAINTY SO
WE MAINLY NUDGED DOWN THE POPS RATHER THAN REMOVE THEM AT THIS TIME.

.LONG TERM...SATURDAY THROUGH WEDNESDAY

UPPER LOW OVER THE NW U.S. TO FILL AND LIFT INTO SOUTHERN B.C. OVER
THE WEEKEND.  THIS WILL LEAVE WYOMING IN SW FLOW BETWEEN PERSISTENT
WEST COAST TROUGH AND EXPANDING RIDGE OVER THE PLAINS.  MEDIUM RANGE
GLOBAL MODELS SHOW A SLOW PROGRESSION OF THIS OVERALL PATTERN
THROUGH THE EXTENDED PERIOD...THE GFS IS ON THE FAST END OF THIS
PROGRESSION AND THE ECMWF IS ON THE SLOW END.  FORECAST IS WEIGHTED
TOWARD THE SLOWER PROGRESSION.

AS IS TYPICAL IN WARM SEASON SW FLOW...THE MAIN SURFACE FEATURE WILL
BE A QUASI-STATIONARY SURFACE TROUGH ACROSS NORTHERN AND EASTERN
WYOMING WITH AN E-SE FLOW BRINGING IN MORE MOISTURE AND INSTABILITY
TO THE NORTH AND EAST OF THIS BOUNDARY...A DRIER SW FLOW TO THE
SOUTH.  ON SATURDAY...THIS BOUNDARY WILL BE NEAR A THERMOPOLIS TO
MIDWEST LINE...WITH SLIGHT CHANCES OF AFTN/EVE THUNDERSTORMS TO THE
NORTH.  SOME STRONGER STORMS ARE POSSIBLE IN NE JOHNSON COUNTY.

ON SUNDAY AND MEMORIAL DAY...MORE CONVECTION IS EXPECTED FROM
EASTERN IDAHO INTO FAR WEST WYOMING AHEAD OF A SLOW-MOVING COLD
FRONT.  A STRONGER SW FLOW AHEAD OF THE FRONT MAY PUSH THE SURFACE
TROUGH EAST OF THE DIVIDE FURTHER TO THE N AND E...THUNDERSTORM
INITIATION PRIMARILY FROM MEETEETSE TO BUFFALO AND NORTH.

UPPER TROUGH IS EXPECTED TO SLOWLY PROGRESS ACROSS THE GREAT
BASIN/ROCKIES TUESDAY AND WEDNESDAY WHICH WILL BRING AN INCREASING
CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS MOST OF THE AREA ALONG
WITH A COOLING TREND.

&&

.AVIATION.../18Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL ACROSS THE FORECAST AREA TODAY AND
TONIGHT...WITH THE EXCEPTION OF AREAS IN AND AROUND THUNDERSTORMS
THIS AFTERNOON AND EVENING WHEN GUSTY WINDS...SMALL HAIL AND REDUCED
VISIBILITY CAN BE EXPECTED FOR BRIEF PERIODS AND TERMINALS GO TO
MVFR. AREAS TO WATCH INCLUDE TERMINALS NEAR THE SALT AND GREEN
MOUNTAINS...WESTERN WIND RIVER MOUNTAINS TO THE NORTHWEST EDGE EDGE
OF THE WIND RIVER BASIN INCLUDING THE BIG HORN BASIN. LATER CHANCES
INPROVE FOR KCPR AND AREA NEAR SOUTHERN BIG HORN MOUNTAINS.
TOMORROW...KCPR COULD BE SUBJECT TO DRY THUNDERSTORMS AND STRONG
GUSTY STRAIGHTLINE WINDS. KRKS WILL BE THE LONE TERMINAL WITHOUT
THUNDERSTORM CHANCES TODAY.
&&

.FIRE WEATHER...

MORE ACTIVE WEATHER WILL RETURN TO THE AREA TODAY AS ANOTHER STORM
SYSTEM BRINGS A BETTER CHANCE FOR  THUNDERSTORMS IN THE NORTHWEST
FIRE ZONES ON WEDNESDAY. THESE STORMS WILL BE CAPABLE OF VERY GUSTY
AND ERRATIC WINDS. WINDS WILL LARGELY BE FROM THE SOUTH TO SOUTHEAST
ACROSS THE AREA. THE THREAT OF THUNDERSTORMS WILL REMAIN ACROSS
NORTHERN ZONES ON THURSDAY WITH WARMER...WINDY AND MAINLY DRY
WEATHER ACROSS THE SOUTHERN HALF OF THE STATE.
&&

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

$$

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