000 FXUS65 KBYZ 250925 AFDBYZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BILLINGS MT 325 AM MDT MON JUN 25 2007 .SHORT TERM...VALID FOR TDY AND TUE... SEVERE WEATHER THREAT APPEARS OVER FOR THIS MORNING. CANCELLED THE SEVERE THUNDERSTORM WATCH FOR NORTHEAST ZONES. ANOTHER CHANCE OF POTENTIALLY SEVERE THUNDERSTORMS WILL OCCUR THIS AFTERNOON INTO THE EARLY EVENING FROM ROSEBUD COUNTY EAST AS MAIN COLD FRONT AND UPPER LEVEL TROF MOVE OVER THE AREA...MAIN THREAT WILL BE LARGE HAIL WITH ML CAPE VALUES OVER 2000 J/KG. CANT RULE OUT AN ISOLATED STRONG THUNDERSTORM OVER THE FAR SOUTHEAST THIS MORNING EITHER. THERMAL CAP IN PLACE BUT STRONG SW TO NE ORIENTED JET IS RIGHT OVER THIS AREA AND ITS POSSIBLE A DISTURBANCE COULD INDUCE ENOUGH LIFT TO BRIEFLY BREAK THIS BARRIER...HOWEVER ONLY A VERY SLIGHT CHANCE. MORE ENERGY AND UPPER DIVERGENCE MOVING INTO WESTERN ZONES EARLY THIS MORNING AS MAIN SYSTEM MOVES INTO THE FORECAST AREA FROM THE WEST. TRENDED FORECAST TO FOLLOW PROGRESSION OF THE FRONT THROUGH THE AREA WITH ASSOCIATED PRECIPITATION CHANCES. NAM-WRF DID VERY WELL WITH LAST NIGHTS CONVECTION COMPARED WITH THE GFS WHICH KEPT ALL PRECIP WELL NORTH OF THE FORECAST AREA. THUS LEANING TOWARD ITS SOLUTION. EXPECT MAIN COLD FRONTAL BOUNDARY TO PUSH INTO NORTHWEST ZONES BY LATE MORNING AND THROUGH THE SOUTHEAST BY MID EVENING. BEHIND THE FRONT STRONG PRESSURE RISES WILL INDUCE GUSTY NORTHWEST WINDS. LATEST MODELS A BIT WEAKER WITH THE WIND SPEEDS COMPARED TO LAST NIGHTS RUNS...BUT STILL LOOKING AT GUSTS TO 35 MPH MOST LOCATIONS THIS AFTERNOON INTO THE EVENING. TEMPERATURES LOOK SIMILAR TO LAST FEW MODEL RUNS WITH HIGHS FROM THE UPPER 60S NORTHWEST TO THE UPPER 80S SOUTHEAST. TONIGHT...WINDS WILL DIMINISH OVERNIGHT AS SURFACE HIGH BUILDS INTO THE AREA. CONVECTION SHOULD EXIT THE AREA BY MIDNIGHT AT THE LATEST. OVERNIGHT LOWS SHOULD BE CONSIDERABLY COOLER THAN THE PAST SEVERAL NIGHTS WITH DRIER AIRMASS AND MOSTLY CLEAR SKIES. TUESDAY LOOKS VERY PLEASANT WITH HIGHS IN THE 70S MOST LOCATIONS. A FEW AFTERNOON CUMULUS CLOUDS SHOULD BE THE EXTENT OF THE CLOUD COVER. WEST TO NORTHWEST WINDS MAY GET A BIT BREEZY IN THE EAST DURING THE AFTERNOON BUT WELL BELOW WINDY MENTION. TUESDAY NIGHT WILL BE MOSTLY CLEAR WITH LOWS IN THE 40S AND LOWER 50S. CHAMBERS .LONG TERM...VALID FOR WED...THU...FRI...SAT...SUN... RIDGING PATTERN ACROSS THE AREA FOR WEDNESDAY AND THURSDAY TRANSITIONS INTO A SOUTHWEST FLOW ALOFT PATTERN WITH CONTINUED WARM WEATHER FOR THE WEEKEND. BIGGEST FORECAST QUESTION THIS MORNING IS HOW MUCH RETURN FLOW THUNDERSTORM ACTIVITY TO START ON WEDNESDAY AND HAVE KEPT LOW POPS IN BUT CAPPING SHOULD BE PRETTY PRONOUNCED. MOISTURE SHOULD BE DEEPER ON THURSDAY BUT STILL SEE CAPPING ISSUES SO HAVE KEPT ACTIVITY ISOLATED. PATTERN LOOKS A LITTLE BIT WETTER FOR FRIDAY HEADING INTO THE WEEKEND BUT MAINLY FOR DIURNAL HEATING INITIATING OFF THE HIGHER TERRAIN ESPECIALLY WITH DYNAMICS STAYING NORTH OF THE AREA. ECMWF AND GS IN PRETTY DECENT AGREEMENT ON HOW LONG TO KEEP THE RIDGE IN THE AREA WITH THE FLOW VEERING A BIT MORE FOR SUNDAY AS THE RIDGE AXIS SLIPS FURTHER TO THE EAST INTO THE DAKOTAS. EXPECT TO SEE PLENTY OF 90 DEGREE READINGS LATER THIS WEEK. BORSUM && .AVIATION... SURFACE LOW PRESSURE OVER WESTERN SOUTH DAKOTA WILL ALLOW A FRONT TO MOVE THROUGH THE AREA TODAY. THIS WILL BRING A SWITCH FROM EASTERLY TO WESTERLY WINDS AND START A DRYING TREND FOR MOST OF THE AREA. SOUTH AND EAST OF KMLS THUNDERSTORMS WILL DEVELOP AND POSSIBLY BECOME SEVERE THIS AFTERNOON. THUNDERSTORMS WILL DECREASE IN THE EVENING. BORSUM && .PRELIMINARY POINT TEMP/POPS... TDY TUE WED THU FRI SAT SUN ------------------------------------------------------- BIL 076 050/074 051/083 059/090 060/092 058/092 060/092 2/T 00/U 02/T 22/T 22/T 22/T 22/T LVM 073 041/073 044/083 050/089 053/091 053/091 052/091 2/T 00/U 02/T 22/T 22/T 22/T 22/T HDN 081 051/076 049/087 060/091 060/092 060/092 062/092 2/T 00/U 02/T 22/T 22/T 22/T 22/T MLS 080 051/075 053/084 061/088 060/090 060/090 062/090 3/T 00/U 00/U 02/T 22/T 22/T 22/T 4BQ 086 053/074 053/086 062/088 062/090 060/090 062/090 3/T 20/U 00/U 02/T 22/T 22/T 22/T BHK 084 054/073 052/082 057/085 058/088 058/088 057/088 3/T 20/U 00/B 02/T 22/T 22/T 22/T SHR 084 050/074 047/084 058/090 057/091 058/091 060/091 3/T 00/U 02/T 22/T 22/T 22/T 22/T && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...NONE. WY...NONE. && $$ WEATHER.GOV/BILLINGS