000 FXUS65 KBYZ 241342 AFDBYZ AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BILLINGS MT 642 AM MST TUE NOV 24 2009 .SHORT TERM...VALID FOR TDY AND WED... UPDATED FORECAST EARLY THIS MORNING FOR CLOUD COVER. CLOUD COVER IS MORE EXTENSIVE THAN PREVIOUSLY EXPECTED WITH AREAS UPSTREAM SHOWING CEILINGS UNDER 12KFT WHICH ARE ADVECTING INTO THE NORTHWEST PORTION OF THE FORECAST AREA. AS A RESULT WENT AHEAD AND INCREASED CLOUD COVER TO MOSTLY CLOUDY FOR MOST OF THE AREA FOR THE REST OF THE DAY. CHAMBERS PREVIOUS DISCUSSION...CONCERNS FOR THE SHORT TERM ARE THE STRONG WIND POTENTIAL OVER WESTERN ZONES THIS MORNING...AND THE ALBERTA CLIPPER SYSTEM MOVING THROUGH THIS AFTERNOON AND TONIGHT. PRESSURE GRADIENT IS UP TO 15MB ACROSS THE BEARTOOTH RANGE THIS MORNING AND WARM ADVECTION IS SPREADING OVER THE AREA ALOFT CREATING CONDITIONS FOR GAP ENHANCED WINDS FROM LIVINGSTON TO NYE. CURRENT WINDS HAVE JUMPED TO SUSTAINED IN THE LOWER 30S WITH GUSTS AROUND 50 MPH. CONSIDERED ISSUING A WIND ADVISORY FOR THESE AREAS THIS MORNING...HOWEVER THE ORIENTATION OF THE PRESSURE GRADIENT AND THE NORTHWESTERLY DIRECTION OF THE 700MB FLOW ARE NOT OPTIMAL FOR STRONG WINDS. THIS MAY BE OVERCOME IF THE PRESSURE GRADIENT CONTINUES TO INCREASE WITH ISOLATED GUSTS OVER 60 MPH BEING MORE LIKELY THAN SUSTAINED WINDS OVER 40 MPH IN THAT SCENARIO. IN ADDITION TO THE GAP FLOW AREAS...LOCATIONS FROM BIG TIMBER TO HARLOWTON SHOW SOME POTENTIAL FOR SUSTAINED WINDS AROUND 40 MPH THIS MORNING AS WELL. CROSS SECTIONS SHOW WINDS AROUND 40KTS JUST ABOVE THE SURFACE IN THESE AREAS AND CURRENT WIND SPEEDS IN HARLOWTON ARE IN THE 30 MPH RANGE. FOR WARNING TYPE WINDS IN THESE AREAS WOULD LIKE TO SEE 50 KTS JUST OFF THE SURFACE AND ALSO SEE WINDS BACKED TO THE WEST SOUTHWEST ALOFT. ABSENT OPTIMAL CONDITIONS HAVE ELECTED NOT TO ISSUE WIND HIGHLITES THIS MORNING BUT DO HAVE WINDS OF 25 TO 40 MPH WITH GUSTS TO 55 MPH IN THE GRIDS THROUGH LATE THIS MORNING. WILL MONITOR THE SITUATION CLOSELY AND WILL PULL THE TRIGGER IF CONDITIONS WARRANT LATER THIS MORNING. THIS AFTERNOON WILL BE WINDY ACROSS THE AREA AHEAD OF A COLD FRONT AND ALBERTA CLIPPER SYSTEM THAT WILL MOVE INTO THE AREA LATE THIS AFTERNOON. DAY SHIFT INCREASED EVENING POPS WITH THIS SYSTEM ACROSS CENTRAL AREAS. BASED ON LATEST MODEL TRENDS PUSHED PRECIP TIMING UP TO LATE THIS AFTERNOON FOR CENTRAL AND NORTHWEST ZONES. ONLY TWEAKED THIS EVENINGS POPS SLIGHTLY. PRECIPITATION WILL STRUGGLE TO REACH THE GROUND GIVEN DOWNSLOPE WINDS THIS AFTERNOON...WITH MOST LIKELY AREA FOR DEVELOPMENT ALONG AND EAST OF A ROUNDUP TO BILLINGS LINE OVER TO ROSEBUD COUNTY. ONCE THE SUN SETS THE MAIN 700MB FRONTOGENESIS BAND WILL SHIFT OVER THE AREA AND WITH THE DOWNSLOPE WIND INFLUENCE DECOUPLED BY THE SURFACE INVERSION DEVELOPMENT...SHOULD SEE PRECIPITATION COVERAGE INCREASE TO SCATTERED OVER CENTRAL AREAS WITH ISOLATED SHOWERS WEST AND EAST. MODELS SUGGEST THAT PRECIPITATION MAY LINGER LATE INTO THE NIGHT OVER WESTERN AND SOUTHERN AREAS AND HAVE TRENDED POP FORECAST TO ACCOUNT FOR THIS. NOT LOOKING FOR A LOT OF PRECIPITATION WITH THIS SYSTEM AS THE LOWER LEVELS LOOK PRETTY DRY...BUT MID LEVEL MOISTURE ADVECTION SHOULD BE ENOUGH THAT SOME AREAS COULD SEE .05 TO .10 INCHES OF RAIN/SNOW. THE ALBERTA CLIPPER QUICKLY PLOWS INTO THE CENTRAL PLAINS STATES EARLY WEDNESDAY WITH RIDGING DEVELOPING OVER THE AREA FOR WEDNESDAY AFTERNOON. THIS WILL BRING BREEZY...DRY AND WARM CONDITIONS TO THE AREA INTO THE END OF THE WEEK. STRONG GAP WINDS MAY DEVELOP AGAIN WEDNESDAY NIGHT FROM LIVINGSTON TO NYE AND INCREASED WINDS IN THESE AREAS TO ACCOUNT FOR THIS POTENTIAL. CHAMBERS .LONG TERM...VALID FOR THU...FRI...SAT...SUN...MON... UPPER LEVEL RIDGE WILL BE OVER THE REGION ON THURSDAY AND THURSDAY NIGHT BRINGING DRY AND WARMER CONDITIONS WITH NO CHANGES MADE. NEXT PACIFIC SYSTEM MAKES ITS WAY INTO THE REGION BY FRIDAY AFTERNOON AND FRIDAY NIGHT. BOTH MODELS IN GOOD AGREEMENT WITH THE INITIAL PUSH OF ENERGY BUT MOISTURE LOOKS FAIRLY LIMITED SO HAVE KEPT POPS ON THE LOW SIDE BUT HAVE KEPT THEM EVERYWHERE. MODELS THEN BRING A SECOND PIECE OF ENERGY AND DIG IT SOUTH INTO THE FOUR CORNERS REGION ON SATURDAY AND SATURDAY NIGHT. THE ECMWF IS SLIGHTLY FASTER WITH THIS SOLUTION. THIS SECOND PIECE OF ENERGY WOULD AT BEST BRING A CHANCE OF PRECIP TO THE WESTERN MOUNTAINS BUT HAVE CONTINUED POPS FOR EVERYWHERE FOR NOW. TEMPERATURES DURING THIS PERIOD WITH THE TROUGH WILL BE COOLER WITH HIGHS IN THE 30S AND 40S. UPPER LEVEL RIDGE BUILDING IN STARTING SUNDAY ACROSS THE WEST WHERE CONDITIONS WILL BE MOSTLY DRY. DID LEAVE SOME POPS IN THE EAST. KEPT THINGS MOSTLY DRY ON SUNDAY NIGHT AND MONDAY WITH MODELS IN GOOD AGREEMENT WITH A RIDGE IN PLACE. MODELS TRY TO BRING IN THE NEXT PACIFIC SYSTEM BY NEXT MONDAY NIGHT WITH THE GFS BEING ABOUT 6 HOURS SLOWER THAN THE ECMWF. HAVE ADDED CLIMO POPS TO THESE PERIODS FOR NOW. SOLUM && .AVIATION... GUSTY WINDS WILL CONTINUE IN THE KLVM AREA AND ALONG THE FOOTHILLS OF THE BEARTOOTH/ABSAROKA MOUNTAINS THROUGH EARLY EVENING. EXPECT GUSTS OF 40 TO 45 KNOTS WITH THESE WINDS. A STRONG STORM SYSTEM WILL PUSH INTO THE DAKOTAS TONIGHT. AS THE SYSTEM MOVES ACROSS...IT WILL BRING A SLIGHT CHANCE OF PRECIP THE AREA MAINLY ACROSS THE WESTERN AND CENTRAL ZONES. VFR CONDITIONS WILL PREVAIL THROUGH MUCH OF THE DAY WITH MVFR CONDITIONS AND MOUNTAIN OBSCURATIONS DEVELOPING WITH ANY PRECIPITATION THAT FALLS. SOLUM && .PRELIMINARY POINT TEMP/POPS... TDY WED THU FRI SAT SUN MON ------------------------------------------------------- BIL 048 032/053 037/056 033/055 029/040 021/037 023/044 1/N 31/N 00/U 00/B 22/W 20/B 00/B LVM 044 032/047 035/054 029/048 022/036 017/038 020/039 2/W 22/J 00/N 02/W 32/J 20/B 00/B HDN 051 026/053 028/057 029/057 028/045 021/039 021/046 2/W 31/B 00/U 00/B 22/W 22/J 00/B MLS 046 023/046 027/056 028/056 028/045 020/037 019/044 0/B 20/B 00/U 00/U 22/W 22/J 00/B 4BQ 046 026/046 028/056 027/056 028/044 020/038 020/044 0/N 20/N 00/U 00/U 22/W 22/J 00/B BHK 043 022/041 022/054 026/054 028/042 018/036 020/040 0/N 21/N 00/U 00/U 22/W 22/J 00/B SHR 048 025/051 027/057 026/057 025/042 018/038 018/044 0/B 33/J 00/U 00/B 22/W 22/J 00/B && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...NONE. WY...NONE. && $$ WEATHER.GOV/BILLINGS