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000
FXUS65 KRIW 230527
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1127 PM MDT WED MAY 22 2013

.SHORT TERM...TONIGHT THROUGH THURSDAY (ISSUED AT 306 PM MDT)

TODAY...STILL CAUGHT BETWEEN DUELING UPPER LOWS WITH RIDGE IN
BETWEEN TRYING TO REACH BIG BROTHER OFF TO THE NORTH IN CENTRAL
CANADA. SFC LOW POSITION MORE ELONGATED AND STRENGTH AND
PROGRESSION LOOKS TO BE JUST SLIGHTLY BEHIND AND LESS VIGOROUS THAN
THE PAST COUPLE OF DAYS. STILL...WE SHOULD STILL BECOME SOMEWHAT
ACTIVE BY LATE THIS AFTERNOON...THUNDERSTORM-WISE...FROM THE SALT
AND GREEN MOUNTAINS...WESTERN WIND RIVER MOUNTAINS TO THE NORTHWEST
EDGE EDGE OF THE WIND RIVER BASIN AND ON UP TO THE WEST AND NORTH
BORDERS...WITH THE BIG HORN BASIN POSSIBLY MAKING OUT AS WELL.

SOUTHEASTERLY FLOW HAS FINALLY SET UP TODAY...WITH DEW POINTS THAT
STARTED OUT THIS MORNING WITH 30S AT LOWER ELEVATIONS AND 20S
MOUNTAINS...ONLY MAINTAINING OR INCREASING A POINT OR TWO THIS
AFTERNOON. THE REGION SOUTH OF THE WIND RIVER MOUNTAINS AND BASIN HAS
SOME DRYING OCCURRING AS SOUTHERN WARM/DRY PUSH WHICH HAS DEVELOPED
AHEAD OF SFC INVERTED TROF TRYING TO MAKE ITS WAY INTO WESTERN WY
AND IN RESPONSE TO UPPER LEVEL FORCING. A MINI WEAK DRY LINE PUSH.
BIG HORN MOUNTAINS AND ADJACENT EASTERN AREAS WILL BE PRIVY TO MORE
BOUNDARY LAYER MOISTURE...BUT WILL ALSO BE QUITE CAPPED THROUGH MOST
OF THE DAYTIME AND EARLY EVENING PERIOD...SO WILL NOT PRODUCE MUCH
IN THE WAY OF SHOWERS OR THUNDER DURING THE FIRST HALF OF THE FIRST
PERIOD OF THE FORECAST...EXCEPT PERHAPS RIGHT OVER CLOUD PEAK.
HOWEVER...THAT SAID...UPPER LEVEL DIVERGENCE AND SUPPORT WILL ARRIVE
OVER THE BIGHORNS LATER OVERNIGHT AND POSSIBLY SPARK A ROUND OF
SHOWERS THAT COULD LINGER THROUGH TOMORROW`S MORNING PERIOD.

FOR NORTHERN CWA TODAY...FORECAST SHEAR AND HODOGRAPHS CONTINUE TO
SHOW A MEAN VALUE OF 35 KTS AND MODERATE CLOCKWISE TURNING
RESPECTIVELY...WHICH SHOULD HELP TILT ROTATE AND SUSTAIN STORMS A
BIT LONGER WITH STORM MOTION RIGHT OF THE MEAN FLOW. A CATEGORY FOR
SOME STRONG STORMS...AND HARD TO GET TO VERY OCCASIONAL AND
MARGINAL SEVERE. STORMS SHOULD BE LOW TOPPED AND TOP OUT AT AROUND
35K FT MSL FOR THE STRONGER STORMS. FOR HAIL...FIRST LOOK FOR SEVERE
VIL OF THE DAY WILL BE BETWEEN 45 AND 50 TO CALCULATE VIL DENSITY
FROM. WILL HARD TO GET SEVERE HAIL IF WE DON`T JUICE UP A BIT.
MOSTLY WE CAN LOOK FOR PEA SIZE HAIL 80% OF TIME. FCST DCAPE RUNNING
BETWEEN 700 AND 800 J/KG OVER EASTERN FREMONT...HOT SPRINGS AND
WASHAKIE COUNTIES...AND SOMEWHAT LESS TO THE NORTH THROUGH THE REST
OF THE BIG HORN BASIN...THE USUAL CONVECTIVE WIND PRODUCING
SUSPECTS. SO WILL WATCH FOR SOME MODERATE BOWING SIGNATURES THIS
AFTERNOON/EVENING. EXPECT FIRST CONVECTION OVER THE SALT
RIVER/WYOMING AND ABSAROKA RANGES.

TONIGHT AND THURSDAY...OVERNIGHT SHOWERS WILL LINGER ACROSS NORTHERN
COUNTIES...AND AS MENTIONED ABOVE...START OVER AND NEAR THE BIG HORN
MOUNTAINS. THURSDAY DAYTIME...LESSER CHANCES FOR PRECIP AND THUNDER
WITH SCATTERED SHOWERS AND ISOLATED THUNDER NORTHWEST AND ISOLATED
SHOWERS AND THUNDER FROM BIGHORN BASIN AND MOUNTAINS SOUTH THROUGH
NATRONA COUNTY. MUCH OF THE SOUTHWEST PORTION OF THE CWA WILL BE
FREE FROM THUNDER ACTIVITY AND UNDER RATHER DRY SOUTHWEST FLOW. ONE
NOTE FOR TOMORROW...NATRONA COUNTY MAY FALL AT THE CROSS ROADS OF
JUST ENOUGH INSTABILITY TO GET A COUPLE OF STORMS OVER AND NEAR THE
MOUNTAINS...BUT THE STORMS SHOULD BE QUITE ELEVATED AND RELATIVELY
DRY...AND CAPABLE OF PRODUCING STRONG TO SEVERE WINDS. WILL HAVE TO
MONITOR AND WATCH THIS CONDITION OVER THE NEXT 36 HRS.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY NIGHT

AN UPPER LEVEL LOW PRESSURE TROUGH WILL EXTEND FROM THE PACIFIC NORTHWEST
SOUTH SOUTHEAST INTO THE GREAT BASIN WITH DRYING SOUTHWEST FLOW
ALOFT OVER WESTERN AND CENTRAL WYOMING THURSDAY EVENING.  MOISTURE
AND INSTABILITY WILL BE LIMITED TO THE NORTH AND WESTERN MOUNTAINS
WHERE SOME EVENING SHOWERS AND THUNDERSTORMS ARE POSSIBLE.  SOME
LIGHT SHOWERS WILL BE OVER THE FAR NORTH OVER NIGHT. OVERALL
TEMPERATURES WILL BE MILD. THE DRY SOUTHWEST FLOW WILL INCREASE ON
FRIDAY WITH BREEZY TO WINDY CONDITIONS AND WARMING.  THE DRY AND
BREEZY CONDITIONS WILL CONTINUE FRIDAY NIGHT.  THE PACIFIC TROUGH
WILL INCH CLOSER TO WESTERN WYOMING ON SUNDAY WITH SOME MOISTURE
INCREASING OVER THE NORTH AND WEST WITH SPOTTY AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS OVER THE NORTHERN AND WESTERN MOUNTAINS.
THE SOUTH...CENTRAL AND EAST WILL REMAIN DRY AND BREEZY TO WINDY
WITH TEMPERATURES REMAINING WARM.  SOME CLOUDS WILL MOVE INTO THE
WEST  SATURDAY NIGHT AND SUNDAY WITH THE RATHER STRONG SOUTHWEST
FLOW ALOFT CONTINUING.  SUNDAY AFTERNOON AND EVENING SPOTTY SHOWERS
AND THUNDERSTORMS WILL RETURN TO THE NORTHERN AND WESTERN MOUNTAINS.
CLOUDS WILL INCREASE ACROSS THE SOUTH...CENTRAL AND EAST THROUGH
SUNDAY WITH A SLIGHT COOLING OF TEMPERATURES.  A PORTION OF THE
PACIFIC TROUGH WILL SEPARATE FROM THE MAIN TROUGH AND MOVE EAST
SUNDAY NIGHT WITH CLOUDS AND SHOWERS INCREASING ACROSS THE NORTH AND
WESTERN MOUNTAINS WITH A SURFACE COLD FRONT MOVING SOUTH FROM
MONTANA COOLING TEMPERATURES.  MONDAY WILL BE COOLER WITH INCREASED
CLOUDS AND SHOWERS OVER THE AREA AND ISOLATED AFTERNOON AND EVENING
THUNDERSTORMS. MONDAY NIGHT THE COLD FRONT WILL PASS SOUTH WITH
NORTH TO NORTHEAST WINDS AND COOLER TEMPERATURES.  CLOUD COVER AND
SHOWERS WILL CONTINUE TO INCREASE OVER THE AREA.  THE TROUGH WILL
REMAIN OVER THE AREA ON TUESDAY WITH CLOUDS AND SHOWERS...AND
ISOLATED AFTERNOON AND EVENING THUNDERSTORMS MAINLY OVER THE
MOUNTAINS. TEMPERATURES WILL CONTINUE COOLER. THE TROUGH WILL WEAKEN
AND EJECT NORTHEAST OF THE AREA TUESDAY NIGHT AND WEDNESDAY WITH
DRYING AND INCREASING SOUTHWEST FLOW ALOFT WITH DECREASING CLOUDS
AND SHOWERS THROUGH TUESDAY NIGHT AND WEDNESDAY MORNING.  ANOTHER
PORTION OF THE PACIFIC TROUGH WILL MOVE EAST WEDNESDAY AFTERNOON
WITH CLOUDS...SHOWERS AND ISOLATED THUNDERSTORMS INCREASING
WEDNESDAY AFTERNOON AND EVENING.  SLIGHT WARMING WILL OCCUR WITH THE
INCREASING SOUTHWEST FLOW...ESPECIALLY OVER AREAS EAST OF THE
CONTINENTAL DIVIDE. CLOUDS AND SHOWERS WILL LINGER THROUGH THE NIGHT
WEDNESDAY NIGHT.

&&

.AVIATION.../06Z ISSUANCE/

AREAS OF LOW CLOUDS WITH MVFR TO IFR CONDITIONS WILL OCCUR UNTIL 17Z
FROM BUFFALO TO CASPER AND FROM CASPER TO RIVERTON. ISOLATED SHOWERS
ARE POSSIBLE OVER THE NW WY MOUNTAINS UNTIL 18Z. AFTER 18Z SHOWERS
AND THUNDERSTORMS WILL FORM OVER NW WY AS WELL AS AROUND THE BIGHORN
MOUNTAINS. THIS ACTIVITY WILL PERSIST THROUGH 06Z FRIDAY. SMALL HAIL
AND GUSTY WIND TO 40 KNOTS WILL OCCUR WITH SOME STORMS. LOCAL MVFR
CONDITIONS WILL OCCUR IN STORMS.

&&

.FIRE WEATHER...

RELATIVELY ACTIVE WEATHER PATTERN RETURNS TO THE AREA TODAY AFTER
A BRIEF RESPITE. A LARGE UPPER LEVEL DISTURBANCE BRINGS A GOOD
CHANCE FOR THUNDERSTORMS...ESPECIALLY IN THE NORTHWEST FIRE ZONES.
THESE STORMS WILL BE CAPABLE OF VERY GUSTY AND ERRATIC WINDS AND
SMALL HAIL. WINDS WILL LARGELY BE FROM THE SOUTH TO EAST 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...BRAUN
LONG TERM...C.BAKER
AVIATION...AR
FIRE WEATHER...BRAUN