663 FXUS65 KBYZ 190532 AFDBYZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BILLINGS MT 1132 PM MDT FRI MAY 18 2012 .SHORT TERM...VALID FOR SAT AND SUN... WEAK UPSLOPE GRADIENT CURRENTLY EXISTS ACROSS OUR WEST...WITH LOW SFC DEWPT DEPRESSIONS AND CLEARING SKIES FROM THE NW AS SUBSIDENCE SPREADS IN BEHIND TODAYS SHORTWAVE. THOUGH THERE HAS BEEN SOME DRYING WITH NW WINDS IN WHEATLAND COUNTY...DEW PTS REMAIN IN THE 40S FROM LIVINGSTON TO BILLINGS. GIVEN THE WEAK UPSLOPE FLOW NOW AND PERHAPS VERY WEAK DRAINAGE WINDS LATER TONIGHT...BELIEVE SOME FOG IS POSSIBLE IN OUR WESTERN PARTS... INCLUDING BILLINGS. HAVE ADDED PATCHY FOG LATE TONIGHT AND EARLY SATURDAY TO COVER THIS. OTHERWISE SHOWERS CONTINUE SOUTH OF BILLINGS AND ACROSS OUR EAST. PCPN WILL SLOWLY TAPER OFF FROM WEST TO EAST TONIGHT. JKL .LONG TERM...VALID FOR MON...TUE...WED...THU...FRI... MODEL AGREEMENT REMAINS GOOD FOR MONDAY AND TUESDAY WITH A SHORTWAVE RIDGE BRINGING MUCH ABOVE AVERAGE TEMPERATURES ON MONDAY. A TROUGH BEGINS TO PUSH INTO THE REGION ON TUESDAY WHICH WILL MARK THE BEGINNING OF A COOLER AND UNSETTLED STRETCH OF WEATHER FOR THE REGION. MONDAY CONTINUES TO BE ON TRACK FOR THE WARMEST DAY OF THE FORECAST PERIOD. 700 MB TEMPERATURES ARE FORECAST TO BE IN THE +7 TO +11 C RANGE...WHICH WILL TRANSLATE TO SURFACE TEMPERATURES IN THE 80S ACROSS THE AREA. ONLY CONCERN FOR TEMPERATURES COULD BE SOME INCREASING HIGH LEVEL CLOUDS FROM WEST TO EAST AHEAD OF THE APPROACHING PACIFIC TROUGH FOR TUESDAY...ALTHOUGH EXPECT THIS TO HAVE A MINIMAL IMPACT. THE GFS AND ECMWF CONTINUE TO ADVERTISE THE SURFACE FRONT ASSOCIATED WITH THE UPPER-LEVEL TROUGH TO PUSH ACROSS THE AREA ON TUESDAY. THIS WILL BEGIN THE DOWNWARD TEMPERATURE TREND WITH HIGH TEMPERATURES EXPECTED TO BE ECLIPSED ACROSS THE WESTERN ZONES...CREATING COOLER TEMPERATURES IN THE WEST AND WARMER TEMPERATURES IN THE EAST. THE BEST PRECIPITATION THREAT ON TUESDAY WILL BE BEHIND THE COLD FRONT AS THE BETTER QG FORCING SLIDES ACROSS THE REGION AND IS COUPLED WITH THE BETTER SUPPLY OF LOW LEVEL MOISTURE. GIVEN THE INCREASING CONFIDENCE IN THE TIMING OF THIS FRONT...HAVE DECIDED TO START INCREASING POPS ON TUESDAY...TUESDAY NIGHT AND INTO WEDNESDAY. FOR THURSDAY THROUGH SATURDAY THE MODELS AGREE ON A LARGE BLOCKING RIDGE BUILDING ACROSS THE EASTERN CONUS WHICH HELPS TO LOCK IN THE BROAD CYCLONIC FLOW ACROSS THE WESTERN CONUS. WHILE THE MODELS DO NOT AGREE ON THE DETAILS OF THE EVOLUTION OF THE TROUGH... CONFIDENCE IS HIGH THAT TEMPERATURES WILL BE NEAR NORMAL OR POSSIBLY COOLER AND THE WEATHER WILL BE UNSETTLED. THE LATEST 12Z RUNS ARE TRENDING TOWARD A CUTOFF LOW ACROSS THE WESTERN CONUS BY FRIDAY...GETTING OUR AREA INTO SOUTHWEST FLOW...WHICH COULD CONTINUE A WET PERIOD FOR OUR AREA IF THIS TREND PANS OUT. CHURCH && .AVIATION... SHOWERS WILL SLOWLY TAPER OFF FROM WEST TO EAST OVERNIGHT. MVFR TO LOCAL IFR CAN BE EXPECTED IN THE SHOWER ACTIVITY FROM KSHR TO KMLS AND KBHK UNTIL THE PCPN ENDS. CLEARING CAN BE EXPECTED IN THE WEST TONIGHT. THIS ALONG WITH LIGHT WINDS COULD SUPPORT SOME FOG DEVELOPMENT AFTER 09Z. FOG IS POSSIBLE AT KLVM AND KBIL EARLY SATURDAY MORNING...AND IF IT DOES OCCUR...FLIGHT CONDITIONS COULD BE REDUCED TO MVFR OR LOWER AT THESE TERMINALS. JKL && .PRELIMINARY POINT TEMP/POPS... SAT SUN MON TUE WED THU FRI ----------------------------------------------------------- BIL 041/063 043/076 052/087 057/076 050/066 044/064 044/067 61/U 10/U 00/B 23/T 44/T 33/W 22/W LVM 033/058 035/074 043/084 049/070 042/062 037/060 038/062 61/B 10/B 00/B 45/T 44/T 33/W 22/W HDN 041/065 039/077 048/089 053/079 047/067 043/065 040/068 81/U 10/U 00/B 13/T 44/T 33/W 22/W MLS 044/066 041/076 052/089 057/083 051/071 046/066 042/070 80/U 10/U 00/U 12/T 44/T 43/W 33/W 4BQ 043/064 039/074 049/087 053/084 048/069 043/066 041/069 81/N 10/U 00/U 12/T 44/T 43/W 33/W BHK 043/064 038/071 046/084 054/083 048/069 044/064 041/067 81/N 10/U 00/U 12/T 44/T 44/W 33/W SHR 039/058 037/073 044/085 050/079 044/065 039/063 037/066 91/B 20/B 00/U 13/T 55/T 43/W 33/W && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...NONE. WY...NONE. && $$ WEATHER.GOV/BILLINGS