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000
FXUS65 KRIW 131745
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1145 AM MDT THU JUN 13 2013

.SHORT TERM...THURSDAY THROUGH SATURDAY NIGHT

THE SEVERE WEATHER OF YESTERDAY HAS ENDED. HOWEVER IT DOES NOT LOOK
LIKE WE ARE OUT OF THE WOODS COMPLETELY YET. RADAR DOES SHOW SOME
SHOWERS AND EMBEDDED THUNDER ACROSS EASTERN IDAHO AND INTO
NORTHWESTERN WYOMING IN ASSOCIATION WITH YET ANOTHER SHORTWAVE AND A
JET STREAK PROVIDING SOME LIFT. ORIENTATION OF THE SHOWERS AND
THUNDERSTORMS MAY BE A BIT DIFFERENT TODAY AS A COLD FRONT SLOWLY
MOVES ACROSS THE AREA AHEAD OF AN APPROACHING TROUGH. THE NAM DOES
SHOW A SURGE OF MOISTURE MOVING IN OUT OF UTAH. WATER VAPOR IMAGERY
ALSO SHOWS A SURGE OF MOISTURE WITH A BIT MORE JET ENERGY SO WE HAVE
ADDED SOME LATE MORNING AND AFTERNOON CONVECTION TO SOUTHERN WYOMING
OVER TO AROUND CASPER. FURTHER NORTH...THE ATMOSPHERE IS A BIT MORE
CAPPED SO THE SHOW MAY BE LATER THERE. HOWEVER...THIS WILL ALLOW FOR
MORE EXPLOSIVE DEVELOPMENT OF ANY THUNDERSTORMS. WITH UPPER LEVEL
DIFLUENCE AND STILL SOME GOOD DIRECTIONAL SHEAR SOME STRONG
THUNDERSTORMS ARE ONCE AGAIN POSSIBLE...MAINLY ACROSS PORTIONS OF
JOHNSON COUNTY AND ACROSS THE BIG HORN RANGE TO THE BIG HORN BASIN
WHICH IS WHERE THE DEEPEST MOISTURE AND SHEAR CONTINUE TO PRESIDE.
THE MAIN THREATS ONCE AGAIN WOULD BE LARGE HAIL AND DOWNBURST WINDS.
THE THREAT OF STORMS SHOULD TAPER OFF LATER AT NIGHT AS DRIER AIR
MOVES IN FROM THE WEST. THE OTHER THREAT TODAY WILL BE WIND.
PROBABLY NOT HIGH WIND CRITERIA...ALTHOUGH THERE COULD BE SOME GUSTS
TO 40 TO 50 MPH...MAINLY ACROSS SOUTHERN WYOMING AND NORTH INTO
PORTIONS OF FREMONT AND NATRONA COUNTIES WITH THE TIGHTENING
PRESSURE GRADIENT AHEAD OF THE COLD FRONT.

QUIETER AND COOLER WEATHER WILL BE THE RULE FOR FRIDAY AS A COOLER
AIR MASS MOVES INTO MOST OF WYOMING. PRECIPITABLE WATERS DROP
SIGNIFICANTLY TO UNDER 0.5 FOR MOST AREAS TOMORROW SO THE CHANCE OF
CONVECTION WILL BE MUCH LESS. AN APPROACHING TROUGH WILL LIFT TO THE
NORTH AND FLATTEN OUT BUT MAY BE CLOSE ENOUGH TO TOUCH OF AN
ISOLATED SHOWER OR THUNDERSTORM ACROSS FAR NORTHERN AREAS BUT MOST
AREAS WILL BE MAINLY DRY. SATURDAY ALSO LOOKS TO BE A MAINLY QUIET
DAY WITH NEAR NORMAL TEMPERATURES AS RIDGING BEGINS TO BUILD TO THE
WEST OF WYOMING ONCE AGAIN. ONE POSSIBLE SMALL FLY IN THE OINTMENT
MAY BE SOME DEEPER MOISTURE TRYING TO SNEAK INTO FAR EASTERN
PORTIONS OF THE COUNTY WARNING AREA. THIS COULD TOUCH OFF A STRAY
SHOWER OR THUNDERSHOWER BUT WE WILL KEEP THE FORECAST DRY FOR NOW.

.LONG TERM...SUNDAY THROUGH THURSDAY

AT THE START OF THIS PERIOD...AN UPPER RIDGE OF HIGH PRESSURE WILL
BE CENTERED NEAR THE CONTINENTAL DIVIDE DOWNSTREAM OF AN UPPER LOW
OFF THE NW COAST...AROUND 45N 135W.  THIS UPPER PATTERN WILL
PROGRESS SLOWLY THROUGH THIS PERIOD WITH UPPER LOW PUSHING ONTO NW
COAST TUESDAY NIGHT AND UPPER RIDGE SHIFTING INTO THE PLAINS.  UPPER
LOW THEN IS EXPECTED TO SHEAR NE UP BACKSIDE OF RIDGE ACROSS THE
NORTHERN ROCKIES ON THURSDAY.  CONTINUED OVERALL DRY CONDITIONS
ACROSS SOUTH AND CENTRAL WYOMING WILL RESULT IN HEIGHTENED FIRE
WEATHER CONCERNS.

ON SUNDAY...MOISTURE AND SLIGHT INSTABILITY WILL LIE ALONG AND NORTH
OF A STATIONARY FRONTAL BOUNDARY ACROSS THE NORTH AND EAST...WITH
ISOLATED AFTERNOON/EVENING THUNDERSTORMS NORTH OF THIS
BOUNDARY...AND DRY WEATHER WITH SEASONABLY MILD WEATHER ACROSS THE
CENTRAL AND SOUTH.

ON MONDAY...SURFACE HIGH PRESSURE BUILDING INTO THE PLAINS WILL
RESULT IN AN EASTERLY FLOW BRINGING IN BETTER MOISTURE AND
INSTABILITY/CHANCES FOR AFTERNOON AND EVENING THUNDERSTORMS...MAINLY
ACROSS NATRONA AND JOHNSON COUNTIES.

TUESDAY AND WEDNESDAY...A DRY AND WARM SW FLOW WILL PREVAIL ACROSS
MOST OF THE AREA...BREEZY TO WINDY CONDITIONS ALONG WITH INCREASING
FIRE WEATHER CONCERNS ACROSS THE SOUTH AND CENTRAL.  ISOLATED
THUNDERSTORMS WILL BE POSSIBLE ACROSS THE NORTH.

THURSDAY...COLD FRONTAL PASSAGE.  COOLER HIGH TEMPERATURES WITH A
CONTINUED SLIGHT CHANCE OF THUNDERSTORMS ACROSS THE NORTH.

&&

.AVIATION.../18Z ISSUANCE/
HIGH BASED SHOWERS AND THUNDERSTORMS WILL BE A THREAT THIS AFTERNOON
FOR ALL TERMINALS IN THE FORECAST AREA SOUTH OF A KJAC TO KCPR
LINE...WITH POSSIBLE BRIEF SEVERE WINDS IN EXCESS OF 50 KTS POSSIBLE
THROUGHOUT THE AFTERNOON AND THROUGH THE EVENING PERIOD. STORMS
NORTH OF THIS LINE WILL BE ABLE TO ATTAIN STRONGER CHARACTERISTICS
WITH BRIEF BUT VERY STRONG TO SEVERE ERRATIC WINDS AND GS POSSIBLE
ALONG WITH BRIEF MVFR/IFR CONDITIONS.


&&

.FIRE WEATHER...

A COUPLE OF UPPER LEVEL DISTURBANCES WILL SWING UP THROUGH THE
REGION TODAY WITH THE POSSIBILITY OF PRODUCING SOME STRONGER STORMS
ACROSS THE NORTHERN QUARTER OF WYOMING. THE CHANCE OF THUNDERSTORMS
MAY MOVE FURTHER SOUTH TODAY ALTHOUGH STORMS SHOULD BE ISOLATED IN
THESE AREAS. GUSTY WEST TO SOUTHWEST WINDS WILL CONTINUE ACROSS THE
FAVORED AREAS IN THE SOUTHWESTERN WIND CORRIDOR. EXPECT A QUIETER
AND COOLER DAY ON FRIDAY AFTER THE PASSAGE OF A COLD FRONT.
&&

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

$$

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