315 FXUS65 KRIW 290550 AFDRIW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 1150 PM MDT FRI JUN 28 2013 .SHORT TERM...TONIGHT THROUGH SATURDAY HIGH PRESSURE CONTINUES TO DOMINATE THE WEATHER ACROSS THE AMERICAN WEST WITH HIGHER THAN NORMAL TEMPERATURES EXPECTED TO REMAIN...WITH NEAR RECORD HIGHS IN SWEETWATER AND LINCOLN COUNTY POSSIBLE THIS AFTERNOON AND AGAIN TOMORROW...WITH TEMPERATURES 5 TO 10 DEGREES ABOVE NORMAL ELSEWHERE. A FEW CLOUDS MANAGED TO POP UP OVER THE HIGHER TERRAIN THIS AFTERNOON...THEY WILL DISSIPATE SHORTLY AFTER SUNSET. HEIGHTS WILL FALL SLIGHTLY THIS EVENING AS A SHORT WAVE MOVES AROUND THE PERIPHERY OF THE RIDGE IN MT...WHICH WILL EVENTUALLY SEND DOWN A WEAK FRONT WITH INCREASED MOISTURE AND COOLER TEMPERATURES EAST OF THE DIVIDE. THE RIDGE RE-SURGES TOMORROW...BUT A LITTLE FURTHER SOUTHWEST...THE FALLING HEIGHTS WILL ENTERTAIN THE POSSIBILITY OF SOME CONVECTION TOMORROW AS IT USES THE AVAILABLE MOISTURE DURING PEAK HEATING TO PRODUCE SOME SHOWERS AND THUNDERSTORMS OVER THE HIGHER TERRAIN. THE BETTER INSTABILITY WILL BE OVER THE SOUTHWEST...BUT IT WILL BE TOO DRY AND THE CONVECTION WILL BE TOO SHALLOW FOR SEVERE THUNDERSTORMS...A FEW 25 TO 30 MPH OUTFLOWS ARE POSSIBLE BUT IT WILL BE DIFFICULT TO MUSTER MORE THAN THAT WITH THE LIMITED VERTICAL DEVELOPMENT. THE BETTER SHEAR AND MOISTURE WILL BE EAST OF THE DIVIDE BUT INSTABILITY IS LACKING. THERE COULD BE A FEW SHOWERS AND STORMS KICKING OFF A BIT LATER WHEN A SHORT WAVE ROTATES AROUND THE RIDGE...BUT THE LOSS OF PEAK HEATING WILL NOT HELP. SO...WHILE THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS ON SATURDAY THE INGREDIENTS FOR STRONG STORMS DO NOT COME TOGETHER FAVORABLY IN ANY ONE PLACE. .LONG TERM...SATURDAY NIGHT THROUGH FRIDAY SATURDAY NIGHT...UPPER TROUGH AXIS CENTERED NEAR/ALONG WRN WY BORDER WITH SOME NW FLOW OVER THE ERN HALF OF THE CWA. SOME LOW END MOISTURE AND INSTABILITY ACROSS NWRN QUARTER OF THE CWA WITH LITTLE HELP FROM THE MOUNTAINS AND A SHORTWAVE RIDING THE RIDGE...CURRENTLY NEAR SRN CALIFORNIA THIS AFTERNOON...AROUND THE UPPER HIGH AND NEAR OUR WRN CWA SATURDAY...WILL GIVE THE CHANCES FOR PRECIP IN THIS REGION THROUGH THE EVENING PERIOD. SHEAR WILL BE QUITE LOW AND EXTENT AND LONGEVITY OF ANY STORM SHOULD BE ON THE BRIEF SIDE OF THINGS. THE ERN CWA HAS BETTER SHEAR...BUT REALLY LACKS MUCH IN THE WAY OF ANY USEFUL FORCING...SO NOT EXPECTING MUCH OF ANYTHING EXCEPT VERY ISOLATED OVER THE BIG HORN MOUNTAINS WITH EVEN LESS CHANCES OVER CASPER MOUNTAIN. NO SEVERE WX EXPECTED...AS ALL THAT IS NEEDED IS NOT COMING TOGETHER. BEST THAT CAN BE EXPECTED ATTM IS SOME ISOLATED GUSTY WINDS < 30 KTS AND 1/4 INCH OR LESS SIZE HAIL. SUNDAY WILL HAVE SIMILAR WX INDICES BUT LESS IN THE WAY OF ANY UPPER FORCING...SO ALL SMALLER CHANCES FOR CONVECTION WHICH LOOK TO BE MAINLY ISOLATED TO WIDELY SCATTERED OVER THE MOUNTAINS ONLY. THE BASIC IDEA FROM SUNDAY AND INTO THE BEYOND IS THAT A HIGHLY AMPLIFIED AND SLOWLY RETROGRADING UPPER LEVEL RIDGE ACROSS THE WESTERN CONUS WILL CONTINUE TORTOISE PACE TO THE WEST THROUGH MID WEEK BEFORE BEING EITHER UNDERCUT BY RETROGRADING LOW...GFS...OR SIMPLY SHOVING AGAINST AND DISSOLVING INTO EACH OTHER...THE ECMWF...THE BY WEEKS END. EXCELLENT MODEL AGREEMENT WITH THE LR MODELS THROUGH NEXT WEDNESDAY BEFORE ALL FALLS APART. HOWEVER...EVEN WITH THE MODELS PARALLELING EACH OTHER...UNFORTUNATELY WE...AS IN WY...ARE RIGHT ON THE DIVIDING LINE BETWEEN THE TWO LARGE AIR MASSES. IN THE LONG RUN...A COOL OFF LOOKS EMINENT BY MID WEEK NEXT FOR AT LEAST A DAY OR TWO. THE BIGGER QUESTION HAS TO DO WITH CHANCES FOR PRECIP. RIGHT NOW WED LOOKS TO BE IN THE BEST POSITION FOR UPPER LEVEL FORCING...BUT WHAT ELSE WILL BE AVAILABLE SUCH AS MOISTURE IN THE BOUNDARY LAYER...ETC? JUST KEEPING LOWER END POPS ACROSS THE REGION WITH BEST CHANCES ONCE AGAIN OVER THE HIGH ELEVATIONS...SO WHAT'S NEW? AFTER THAT THE THE EXTENDED PROCEDURE PUTS MID CHANCES FOR CONVECTION FOR THURSDAY AND FRIDAY...WHICH I DIALED BACK SOME AS THIS IS THE PERIOD OF THE FORECAST WHERE THERE IS MUCH DIVERGENCE...AND THE SOLUTIONS VARY WIDELY. DRY VS WET? DRIER CONDITIONS WILL MOST LIKELY WHEN OUT IN THIS CASE. ONE SIDE NOTE IN ALL OF THIS...REGARDLESS OF WHAT HAPPENS BY THE END OF NEXT WEEK...THIS YEARS MONSOON LOOKS TO BE PUSHED BACK BY AT LEAST ANOTHER WEEK OR TWO. HOPEFULLY IT WON'T BE TOO LATE FOR US ALTOGETHER. && .AVIATION.../06Z ISSUANCE/ VFR CONDITIONS AND UNLIMITED CIGS WILL PREVAIL THROUGH SATURDAY MORNING. A COUPLE OF WEAK UPPER LEVEL DISTURBANCE WILL ROTATE INTO NW WYOMING AND SOUTH ALONG THE DIVIDE SATURDAY AFTERNOON AND EVENING. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL DEVELOP MAINLY VCNTY OF THE DIVIDE AND WEST WITH STORM MOTION S-SE AT 5-10KTS. THE BEST COVERAGE OF THESE STORMS WILL BE BTWN 23Z SAT-04Z SUN. SURFACE HIGH PRESSURE TO THE NE AND LOW PRESSURE TO THE SW WILL RESULT IN A PREVAILING NE-E SFC WIND FIELD. THIS WIND FIELD WILL BECOME INCREASINGLY DOMINATED BY CONVECTIVE OUTFLOWS ACROSS WESTERN WYOMING LATE SATURDAY AFTERNOON AND EVENING. && .FIRE WEATHER... HOT...DRY AND UNSTABLE ACROSS RAWLINS AND SOUTHERN TETON DISPATCH THIS WEEKEND...WITH A HAINES INDEX OF 6 EACH DAY...SLIGHTLY MORE MOISTURE AND LESS INSTABILITY WILL EXIST OVER NORTHERN TETON DISPATCH AND IN YELLOWSTONE. THERE WILL BE SOME BREEZY PERIODS BUT EXCESSIVELY WINDY CONDITIONS ARE NOT EXPECTED UNDERNEATH THE RIDGE. A SLUG OF MID LEVEL MOISTURE ARRIVES ON SATURDAY EVENING... ALLOWING RH TO RECOVER NICELY OVERNIGHT AS WELL AS BRING IN A CHANCE OF SHOWERS AND PERHAPS A THUNDERSTORM OR TWO...WITH ANOTHER CHANCE ON SUNDAY. ELSEWHERE...A COOL FRONT MOVING IN TODAY AND TONIGHT WILL MODERATE RHS AND TEMPERATURES ACROSS CASPER AND CODY DISPATCH WITH AN ISOLATED SHOWER OR THUNDERSTORM ACROSS THE LOW ELEVATIONS ON SATURDAY AND SUNDAY...WIDELY SCATTERED ACTIVITY EXPECTED OVER THE HIGHER TERRAIN. ON SUNDAY...A SLOW COOLING TREND WILL BEGIN ALONG WITH A GRADUAL INCREASE IN LATE DAY THUNDERSTORM ACTIVITY AS CLOUDS AND MOISTURE GET WRAPPED UP INTO THE CLOCKWISE CIRCULATION IN THE HIGH PRESSURE CENTER MEANDERS AROUND TO OUR WEST. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...ALLEN LONG TERM...BRAUN AVIATION...AEM FIRE WEATHER...ALLEN