Expires:No;;539416 FXUS65 KBYZ 222047 AFDBYZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BILLINGS MT 247 PM MDT WED MAY 22 2013 .SHORT TERM...VALID FOR THU AND FRI... LARGE UPPER LEVEL LOW WILL BE STATIONARY OVER THE PACIFIC NORTHWEST STATES THIS AFTERNOON THROUGH THURSDAY NIGHT. THIS WILL PROVIDE A SOUTHERLY AND DIVERGENT FLOW ALOFT TO OUR FORECAST AREA THROUGH THURSDAY. SEVERAL DISTURBANCES WILL ROTATE THEIR WAY AROUND THE LOW AND EJECT ACROSS MAINLY THE WESTERN HALF OF OUR FORECAST AREA. BEST UPPER LEVEL DYNAMICS WILL BE WEST OF BILLINGS THROUGH TONIGHT BEFORE SLOWLY SHIFTING EAST THURSDAY INTO THURSDAY NIGHT. WILL CONTINUE WITH CHANCE TO LIKELY POPS FROM BILLINGS WEST FROM LATE THIS AFTERNOON THROUGH THURSDAY. SOUNDINGS SHOW A CAP ACROSS THE ENTIRE AREA THIS AFTERNOON DUE IN PART BY AN EASTERLY SURFACE WIND WHICH HAS ALLOWED A LOW STRATUS DECK TO REMAIN IN PLACE ACROSS OUR CENTRAL AND WESTERN LOCATIONS KEEPING TEMPERATURES ON THE COOL SIDE. LIVINGSTON HAS REMAINED IN THE 40S ALL DAY EXCEPT THE PAST HOUR WHEN THEY BROKE 50 DEGREES. DEWPOINTS ARE A BIT LOW AND ONLY IN THE UPPER 30S TO LOWER 40S. SOUNDINGS DO SHOW THE CAP OVER THE LIVINGSTON AREA WEAKENING THIS EVENING SO CAN'T RULE OUT AN ISOLATED SEVERE THUNDERSTORM WEST OF BILLINGS AS SHEAR REMAINS QUITE GOOD. HOWEVER...CAPE IS QUITE LIMITED AND MAINLY OVER THE BEARTOOTH/ABSAROKA MOUNTAINS AND THERE IS ALSO NOT MUCH OF ANY DISTURBANCE MOVING OVERHEAD TO TRIGGER TOO MUCH AT THIS TIME. SAME PATTERN HOLDS THURSDAY WITH THE FOCUS SHIFTING SLIGHTLY FURTHER EAST TOWARD BILLINGS AS THE UPPER LEVEL DIVERGENCE AND WIND SHEAR SHIFT INTO THE CENTRAL AND EASTERN ZONES. HOWEVER...A VERY STRONG LOW LEVEL JET WILL BE IN PLACE RESULTING IN SUSTAINED WINDS IN THE 20 TO 35 MPH RANGE WITH GUSTS NEAR 50 MPH FOR FALLON AND CARTER COUNTIES. SOUNDINGS SHOW A VERY STRONG CAP ACROSS OUR EASTERN AREAS THROUGH THE DAY THURSDAY AND INTO THURSDAY NIGHT. AT THIS TIME...GIVEN UPPER LOW PLACEMENT WELL WEST OF THE AREA...NO STRONG DISTURBANCE LOOKS TO MOVE ACROSS THE EAST TO HELP ERODE THE CAP SO THUNDERSTORM ACTIVITY LOOKS LIMITED. UPPER LOW BEGINS TO SHIFT NORTH INTO CANADA FRIDAY. MODELS SHOW QUITE A BIT OF DRYING AT MID AND LOWER LEVELS SO HAVE LOWERED POPS QUITE A BIT TO JUST A SLIGHT CHANCE FOR THE DAY FRIDAY AND INTO FRIDAY NIGHT. HOOLEY .LONG TERM...VALID FOR SAT...SUN...MON...TUE...WED... UNSETTLED SW FLOW WILL BE OVER THE FORECAST AREA THROUGH THE EXTENDED PERIOD AS SEVERAL UPPER LOWS MOVE THROUGH THE PACIFIC NW. THE AIRMASS WILL BE MOIST...AS PACIFIC MOISTURE AND GULF MOISTURE MERGE OVER THE REGION. IN ADDITION...THERE WILL BE PERIODS OF STRONG INSTABILITY BASED ON MODEL LIFTED INDICES AND BUFKIT SOUNDINGS. THE STRONGEST INSTABILITY WILL BE OVER AREAS E OF KBIL THROUGH MON. A FAIR AMOUNT OF SHEAR WILL ACCOMPANY THE INSTABILITY...SO THE POSSIBILITY EXISTS FOR SEVERE THUNDERSTORMS. RAINFALL COULD BE HEAVY AT TIMES OVER CENTRAL AND EASTERN AREAS BASED ON HIGH PRECIPITABLE WATERS ON THE GFS. OTHERWISE...THERE WAS A MODERATE TO HIGH AMOUNT OF MODEL SPREAD IN TERMS OF POPS...AS THE GFS AND ECWMF VARIED IN HOW THEY HANDLED THE ENERGY IN THE SW FLOW. INHERITED FORECAST OF SCATTERED POPS THROUGH MOST OF THE PERIOD HANDLED THE SITUATION WELL AND HAVE MADE ONLY A FEW ADJUSTMENTS BASED ON NEW MODEL DATA. TEMPERATURES IN THE UPPER 70S TO LOWER 80S WERE ALSO ON TRACK GIVEN FORECAST 700 MB MIXDOWN TEMPERATURES. ARTHUR && .AVIATION... SHOWERS AND THUNDERSTORMS WILL INCREASE OVER AREAS W OF KMLS THROUGH THIS EVENING. THE BEST CHANCES FOR PRECIPITATION WILL BE FROM HARLOWTON TO RED LODGE W. ISOLATED TO SCATTERED SHOWERS WILL OCCUR W OF KMLS OVERNIGHT AND THU MORNING. THUNDERSTORMS WILL REDEVELOP OVER THE SAME AREAS THU AFTERNOON. EXPECT VFR TO MVFR CONDITIONS. IFR TO LIFR WILL BE POSSIBLE IN SOME OF THE STRONGER STORMS. SURFACE WINDS WILL BE E AT 15 TO 25 KT ACROSS THE AREA THROUGH TONIGHT. ON THU...WINDS WILL INCREASE FROM THE SE OVER AREAS E OF KBIL TO 25 TO 35 KT. LOW-LEVEL WIND SHEAR WILL BE POSSIBLE LATE TONIGHT AND EARLY THU OVER KMLS. ARTHUR && .PRELIMINARY POINT TEMP/POPS... THU FRI SAT SUN MON TUE WED ----------------------------------------------------------- BIL 049/073 050/075 049/077 053/080 053/077 051/078 053/077 34/T 42/T 12/T 33/T 33/T 33/T 33/T LVM 045/065 041/070 039/078 041/080 042/078 041/076 043/075 66/T 62/T 22/T 23/T 33/T 33/T 33/T HDN 048/077 050/078 047/079 053/082 052/080 051/080 054/080 22/T 22/T 12/T 33/T 33/T 33/T 33/T MLS 049/072 051/078 052/079 057/083 058/079 054/080 058/080 11/N 22/T 23/T 33/T 44/T 33/T 33/T 4BQ 046/074 052/079 049/081 055/085 052/081 052/082 054/081 11/N 12/T 12/T 33/T 33/T 33/T 33/T BHK 044/066 047/075 050/073 056/077 056/077 052/077 057/077 11/N 12/T 24/T 43/T 33/T 33/T 33/T SHR 045/074 046/075 045/079 048/083 048/079 046/077 051/078 22/T 22/T 12/T 22/T 23/T 33/T 33/T && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...NONE. WY...NONE. && $$ WEATHER.GOV/BILLINGS