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000
FXUS65 KRIW 120556
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1155 PM MDT SAT MAY 11 2013

.SHORT TERM...TONIGHT THROUGH SUNDAY

CONVECTION IS FIRING OVER THE MOUNTAINS AS A WEAK WEATHER SYSTEM
IS MOVING TOWARD THE AREA IN THE NW FLOW ALOFT THIS AFTERNOON.
INSTABILITY AND CAPES ARE ENOUGH TO KEEP CONVECTION GOING BUT THE
LACK OF LOW LEVEL MOISTURE WILL KEEP MUCH OF THE RAIN FROM
REACHING THE GROUND EXCEPT IN THE HIGH COUNTRY AND NEARBY
FOOTHILLS. GUSTY WIND OF 25 TO 35 MPH WILL BE COMMON NEAR THE
SHOWERS OR STORMS THROUGH SUNSET. THE ACTIVITY WILL WIND DOWN
AFTER SUNSET AS THE WEAK SYSTEM MOVES THROUGH BUT A FEW LINGERING
SHOWERS UNTIL MIDNIGHT IS NOT OUT OF THE QUESTION IN THE SOUTH.
MILD LOW TEMPS TONIGHT WITH LIGHT WIND AFTER DARK AND AFTER THE
OUTFLOWS ARE FINISHED. SUNDAY LOOKS DRIER WITH ONLY ISOLATED
SHOWERS AND STORMS OVER AND NEAR THE MOUNTAINS IN THE AFTERNOON.
TEMPS LOOK TO BE WARM AS A MOTHER WOULD WISH ON THEIR OBSERVANCE
DAY. 700MB TEMPS LOOK TO BE THE WARMEST SO FAR THIS YEAR. SOME
LOCAL BREEZES ACROSS THE LOWER ELEVATIONS SUNDAY AFTERNOON BUT
ONLY IN THE 10 TO 20 MPH RANGE.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY NIGHT

ANY THUNDERSTORMS THAT DEVELOPED WITH THE NORTHWEST FLOW SHOULD END
DURING THE EVENING HOURS WITH A MAINLY DRY PERIOD. THEN ON MONDAY TO
QUOTE THE SONG FROM THE CLASSIC 1980S MOVIE BEVERLY HILLS COP...THE
HEAT IS ON. A RIDGE OVER THE AREA...INCREASING SOUTHWEST FLOW AND A
TIGHTENING PRESSURE GRADIENT WILL BEING THE WARMEST DAY SO FAR THIS
YEAR WITH MOST BASIN LOCATIONS SEEING HIGH TEMPERATURES RISING WELL
INTO THE 80S. THERE COULD EVEN BE SOME RECORD HIGHS THAT COULD BE
SET THAT DAY. AS FOR ANY CHANCES OF CONVECTION...IT WOULD COME LATE
IN THE DAY OR DURING THE EVENING AS THE AFOREMENTIONED COLD FRONT
MOVES ACROSS THE AREA. HOWEVER...THIS FRONT HAS VERY LITTLE MOISTURE
TO WORK WITH SO POPS WERE COMBINED LARGELY TO THE HIGHER ELEVATIONS
AND EVEN HERE LOOK FAIRLY SPARSE. THE FRONT SHOULD BE THROUGH MONDAY
NIGHT FOLLOWED BY A COOLER DAY ON TUESDAY. HOWEVER...TEMPERATURES
SHOULD ONLY FALL BACK TO NEAR TO SLIGHT ABOVE NORMAL LEVELS. AS FOR
CHANCES OF SHOWERS...NEITHER THE NAM NOR THE GFS HAS ANY QPF SO WE
REDUCED CHANCES OF AFTERNOON CONVECTION. WE DID NOT REMOVE
COMPLETELY YET BUT FUTURE SHIFTS MAY WANT TO CONSIDER IT.

BOTH THE GFS AND EUROPEAN THEN AGREE ON SOME FLAT RIDGING OVER THE
AREA FOR WEDNESDAY INTO THURSDAY. THEY DO DISAGREE ON ANY POSSIBLE
COVERAGE OF SHOWERS AND THUNDERSTORMS HOWEVER WITH THE EUROPEAN A
BIT WETTER THAN THE GFS. FOR NOW WE HAVE CONFINED ANY CONVECTION TO
THE HIGHER ELEVATIONS WITH THE ASSISTANCE OF THE HIGH ELEVATION HEAT
SOURCE. WE CAN NOT RULE OUT A THUNDERSTORM MAY DRIFT INTO THE
VALLEYS BUT THE CHANCE IS SO SMALL THAT WE LEFT THE CHANCE OUT FOR
NOW. THE VAST MAJORITY OF EACH DAY LOOKS RAIN FREE AT THIS POINT
THOUGH. LOOK FOR SOMEWHAT ABOVE NORMAL TEMPERATURES BOTH DAYS BUT
NOT AS HIGH ON MONDAY.

BY FRIDAY A TROUGH WILL BEGIN TO MAKE AN APPEARANCE IN WESTERN
WYOMING AND INCREASE THE CHANCE OF SHOWERS AND
THUNDERSTORMS...ESPECIALLY ACROSS WESTERN WYOMING BUT MOST AREAS
SHOULD HAVE A CHANCE BY THE AFTERNOON. THE WIND MACHINE WILL ALSO
BEGIN TO CRANK UP AGAIN...ESPECIALLY ACROSS THE SOUTHWESTERN WIND
CORRIDOR AS SOUTHWEST FLOW INCREASES AND THE PRESSURE GRADIENT
TIGHTENS A BIT. SATURDAY AT THIS POINT LOOKS A BIT COOLER AND
UNSETTLED WITH A SCATTERING OF SHOWERS AND THUNDERSTORMS.

&&

.AVIATION.../06Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL OVERNIGHT WITH SCT-BKN150-170 MSL CLOUD
BASES/ISOLD -SHRA DIMINISHING OVER THE NEXT FEW HOURS.

AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL BUILD OVER THE REGION
TODAY.  SLIGHT INSTABILITY AND TRAPPED MOISTURE WITHIN THIS RIDGE
WILL RESULT IN ISOLD/WDLY SCT HIGH-BASED -SHRA BLOSSOMING IN THE
AFTERNOON AND EARLY EVENING...CLOUD BASES MOSTLY 140-160 MSL.
THUNDERSTORM ACTIVITY IS EXPECTED TO REMAIN VERY ISOLATED...SIMILAR
TO SATURDAY...AND WAS NOT MENTIONED IN THE VCNTY OF ANY TERMINALS.
THE MAIN HAZARD WITH THESE HIGH-BASED SHOWERS/VIRGA WILL ERRATIC
OUTFLOW WIND GUSTS.  OTHERWISE A NW SFC WIND AT 10-20KTS WILL
PREVAIL ACROSS MOST AREAS IN THE AFTERNOON AND EARLY EVENING.

&&

.FIRE WEATHER...

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE OVER
THE REGION UNTIL LATE EVENING. GUSTY WIND TO 35 MPH AND OCCASIONAL
LIGHTNING WILL BE THE MAIN THREATS. SUNDAY WILL BE WARMER WITH
ISOLATED AFTERNOON AND EVENING SHOWERS OR THUNDERSTORMS MAINLY
OVER AND NEAR THE MOUNTAINS. A STRAY SHOWER OR STORM MAY MOVE
ACROSS THE LOWER ELEVATIONS DOWNWIND OF THE MOUNTAINS. OVERALL
SUNDAY WILL BE DRY FOR MOST LOCATIONS. MONDAY LOOKS BREEZY TO
WINDY AND VERY WARM WITH LOW RELATIVE HUMIDITY. A DRY COLD FRONT
WILL MOVE THROUGH THE WEST AND NORTH LATE MONDAY NIGHT AND THEN
ACROSS THE REST OF THE REGION TUESDAY MORNING.

&&

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

&&

$$

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