305 FXUS65 KTFX 131555 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 955 AM MDT FRI JUL 13 2012 .UPDATE... MADE ONLY MINOR CHANGES TO POPS..SKIES..AND WIND. THE MAIN CHANGE IN THIS UPDATE WAS TO MENTION THE THREAT OF SEVERE THUNDERSTORMS OVER THE NORTHERN ROCKY MOUNTAIN FRONT AND EASTERN GLACIER COUNTY. THE ENVIRONMENT WILL BE FAVORABLE FOR SEVERE THUNDERSTORMS BUT AM CONCERNED THAT BETTER LIFT AND MOISTURE MIGHT NOT ARRIVE UNTIL LATE IN THE EVENING. WILL CONTINUE TO MONITOR THE SITUATION. BLANK && .AVIATION... UPDATED 1200Z. VFR CONDITIONS WILL GENERALLY CONTINUE ACROSS THE AREA THROUGH AT LEAST 12Z SATURDAY...UNLESS OTHERWISE SPECIFIED BELOW. THE UPPER LEVEL RIDGE OF HIGH PRESSURE OVER THE AREA WILL GRADUALLY SHIFT EAST DURING THE PERIOD AS AN UPPER LEVEL TROUGH OF LOW PRESSURE MOVES INTO THE PACIFIC NORTHWEST. THIS WILL BRING AN INCREASINGLY MOIST AND UNSTABLE SOUTHWESTERLY FLOW ALOFT TO THE AREA. ISOLATED SHOWERS AND THUNDERSTORMS DEVELOPED ACROSS THE AREA OVERNIGHT...BUT THEY HAVE BEEN WEAK AND HAVE AVOIDED THE TFX TERMINALS. HOWEVER...AM EXPECTING A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS THE AREA TODAY...MAINLY BETWEEN 18Z AND 06Z. SURFACE MOISTURE IS GREATEST ALONG THE ROCKY MOUNTAIN FRONT NEAR THE CANADIAN BORDER (INCLUDING KCTB)...WHICH WILL KEEP THE GREATEST CHANCE FOR STRONG THUNDERSTORMS WITH GUSTY WINDS IN THAT AREA. COULSTON && .FIRE WEATHER... THE AIRMASS WILL BECOME UNSTABLE THIS AFTERNOON WITH SCATTERED SHOWERS AND THUNDERSTORMS DEVELOPING MAINLY OVER THE WESTERN MOUNTAINS AND SPREADING EAST DURING THE AFTERNOON. THE AIRMASS HAS BECOME MORE MOIST AND THUNDERSTORMS ARE EXPECTED TO BE A MIX OF DRY AND WET THUNDERSTORMS. THE AIRMASS WILL CONTINUE TO MOISTEN TONIGHT AND SATURDAY. && .PREV DISCUSSION... /ISSUED 749 AM MDT FRI JUL 13 2012/ FXUS65 KTFX 131349 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 749 AM MDT FRI JUL 13 2012 UPDATE... HAVE UPDATED FOR A FEW SHOWERS AND ISOLATED THUNDERSTORMS OVER CENTRAL MONTANA FOR THE REST OF THIS MORNING. ALSO INCREASED WINDS IN THE CUT BANK AREA FOR THE REST OF TODAY. BLANK && .PREV DISCUSSION... /ISSUED 600 AM MDT FRI JUL 13 2012/ TODAY THROUGH SUNDAY...THE OVERALL WEATHER PATTERN DURING THE NEXT FEW DAYS WILL SEE MONSOONAL MOISTURE MOVING INTO THE CWA FROM THE SOUTH WHILE A LOW PRESSURE TROF OVER THE WEST COAST APPROACHES THE ROCKIES. WATER VAPOR INDICATES MONSOONAL MOISTURE ALREADY MOVING INTO SOUTHWEST MONTANA....SOMEWHAT AHEAD OF WHAT THE NAM INDICATES. INSTABILITY ACROSS PORTIONS OF THE ZONES TODAY WILL REACH CAPE VALUES GREATER THAN 2000. STRONG HELICITY...CAPE...AND EHI WILL DEVELOP OVER THE NORTHERN ROCKIES...AND SPREAD EAST ACROSS THE HILINE TONIGHT. CURRENTLY...EXPECT CONVECTION TO BEGIN OVER THE ROCKIES AND SPREAD EASTWARD INTO THE PLAINS. SURFACE HIGH PRESSURE IN ALBERTA SHOULD PROVIDE A PUSH OF SLIGHTLY COOLER AIR INTO THE NORTHERN ZONES TODAY AND CREATE A BOUNDARY WHICH ADD ANOTHER AID FOR CONVECTIVE DEVELOPMENT ACROSS THE NORTHERN PLAINS. ALONG WITH THE STRONG INSTABILITY...LOWER LEVELS WILL REMAIN DRY AND THE BEST CHANCE FOR SEVERE THUNDERSTORMS WILL LIKELY COME IN THE FORM OF STRONG GUSTS. A SHORTWAVE WILL BE MOVING THROUGH THE FLOW ALOFT THIS EVENING AND COULD KEEP CONVECTION WELL INTO THE NIGHT. BY SATURDAY...THE LOW PRESSURE TROF WILL DEVELOP A CLOSED LOW AND MOVEMENT WILL BECOME QUITE SLOW. THIS WILL GIVE TIME FOR MOISTURE TO INCREASE OVER THE ZONES...AND ESPECIALLY OVER NORTHWEST PORTIONS OF THE CWA WHERE THE AIRMASS SHOULD BECOME QUITE MOIST BY NOON. A SHORT WAVE IS FORECAST BY THE NAM TO MOVE THROUGH THE FLOW AHEAD OF THE LOW PRESSURE TROF. THIS SHOULD ENHANCE CHANCE OF CONVECTION AND PROVIDE LIFT FOR SOME WIDESPREAD PRECIPITATION FOR SATURDAY. AT THE SURFACE...A AREA OF LOW PRESSURE WILL BE OVER THE ROCKIES SATURDAY MORNING AND AND DRIFT EAST DURING THE DAY. THIS WILL BRING A NORTHERLY FLOW OF CANADIAN AIR INTO THE ZONES. THIS AREA WILL SEE WIDESPREAD CAPES ABOVE 1000 AS WELL AS STRONG DCAPES. THE UPPER LEVEL TROF WILL MOVE OVER THE IDAHO PANHANDLE SUNDAY AND GOOD SOUTHWEST FLOW ALOFT OVER THE ZONES. THE AIRMASS WILL REMAIN MOIST AND SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED. ZELZER SUNDAY NIGHT THROUGH FRIDAY NIGHT...THE MEDIUM RANGE MODELS APPEAR TO BE IN DECENT AGREEMENT WITH THE GENERAL TREND FOR THIS PERIOD. THE UPPER LEVEL LOW PRESSURE TROUGH EXTENDING FROM SOUTHERN CANADA INTO THE PACIFIC NORTHWEST WILL KEEP A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE TFX CWA THROUGH SUNDAY NIGHT. THE UPPER LEVEL RIDGE OF HIGH PRESSURE OVER THE CENTRAL CONUS WILL THEN GRADUALLY BUILD NORTHWEST BACK INTO THE AREA THROUGH THE WEEK AND FORCE THE TROUGH BACK TO THE PACIFIC NORTHWEST COAST. THE RESULTING WEAK MONSOONAL FLOW WILL THEN BRING A CHANCE OF MAINLY AFTERNOON/EVENING SHOWERS/THUNDERSTORMS TO THE AREA THROUGH THE REMAINDER OF THE PERIOD...FOR A SIMILAR PATTERN TO THAT OF THE LAST WEEK OR SO. THERE DOES NOT APPEAR TO BE ANY SIGNIFICANT DISTURBANCE IN THE FLOW TO WARRANT GOING ANY HIGHER THAN CLIMATOLOGICAL POPS FOR THIS TIME OF YEAR. TEMPERATURES ON MONDAY WILL REMAIN NEAR NORMAL AS THE UPPER RIDGE BEGINS BUILDING BACK INTO THE AREA...BUT TEMPERATURES OVERALL WILL WARM UP TO AT LEAST 5 TO 10 DEGREES ABOVE SEASONAL AVERAGES FOR THE REMAINDER OF THE WEEK AS THE RIDGE STRENGTHENS. THE WEAK DISTURBANCES IN THE FLOW ALOFT APPEAR AT THIS TIME TO PREVENT A SIGNIFICANT WARM-UP SIMILAR TO THE PAST WEEK OR SO (HIGHS IN THE 90S FOR MOST AREAS)...BUT IT IS A POSSIBILITY THAT CANNOT BE RULED OUT AT THIS TIME AND THE POTENTIAL FOR ANOTHER HOT/DRY SPELL WILL CONTINUE TO BE MONITORED. COULSTON && .PRELIMINARY POINT TEMPS/POPS... GTF 93 65 83 61 / 20 40 60 40 CTB 86 61 75 57 / 30 40 60 50 HLN 93 65 88 61 / 30 40 60 50 BZN 94 59 88 55 / 30 50 50 50 WEY 83 52 74 48 / 40 50 50 50 DLN 88 57 83 54 / 40 50 60 60 HVR 99 67 87 62 / 10 20 40 50 LWT 93 64 84 59 / 20 30 50 50 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...BLANK LONG TERM...MPJ AVIATION...LANGLIEB WEATHER.GOV/GREATFALLS