000 FXUS65 KTFX 290450 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 1050 PM MDT TUE JUL 28 2009 .UPDATE... THE CANADIAN COLD FRONT HAS PUSHED THROUGH THE REMAINDER OF CENTRAL AND SW MT THIS EVENING WITH SHOWER AND THUNDERSTORM ACTIVITY ON THE DECREASE AS SOMEWHAT DRIER AIR MOVES IN ALOFT AND THE AIRMASS BECOMES LESS UNSTABLE. UPDATED POPS FOR THE REMAINDER OF THIS EVENING BASED ON LATEST RADAR TRENDS. EXPECT BEST CHANCE FOR ADDITIONAL PRECIP ACROSS THE CENTRAL AND SW MT MTNS WHERE UPSLOPE AND OROGRAPHIC EFFECTS ENHANCE PRECIP. HAVE DECREASED COVERAGE TO SCATTERED OR ISOLATED NORTH OF A LINE FROM GREAT FALLS TO LEWISTOWN WHERE DRIER AIR IS MOVING IN. HOWEVER...WILL STILL HAVE AT LEAST ISOLATED POPS ACROSS MUCH OF THE AREA THROUGH THE REMAINDER OF TONIGHT AS MOISTURE LINGERS IN THE LOW LEVELS AND THE ATMOSPHERE ONLY MARGINALLY STABILIZES UNDER A CYCLONIC NW FLOW ALOFT. REMAINDER OF THE FORECAST IS IN GOOD SHAPE. HOENISCH && .AVIATION... UPDATED 0447Z. A WEAK CANADIAN COLD FRONT HAS MOVED THROUGH SOUTHWEST MONTANA COOLER BUT ISOLATED SHOWERS ARE POSSIBLE THROUGH THE NIGHT. LOCAL MVFR/IFR CIGS AND VSBYS WILL DEVELOP AFTER MIDNIGHT AND DISSIPATE AFTER SUNRISE. THE AIRMASS BECOMES SLIGHTLY UNSTABLE WEDNESDAY AFTERNOON AND ISOLATED SHOWERS OR THUNDERSTORMS ARE AGAIN POSSIBLE. && .PREV DISCUSSION... /ISSUED 523 PM MDT TUE JUL 28 2009/ TONIGHT THROUGH THURSDAY NIGHT...NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS ARE CONTINUING TO DEVELOP ALONG A WEAK CANADIAN COLD FRONT THAT IS ASSOCIATED WITH AN UPPER-LEVEL LOW PRESSURE SYSTEM. WHILE SEVERE WEATHER IS NOT ANTICIPATED...THERE IS ENOUGH COOL AIR ALOFT TO SUPPORT STRONG GUSTY WINDS AND SMALL HAIL BUT HEAVY RAIN IS THE MAIN CONCERN. BREEZY CONDITIONS ALONG AND BEHIND THE FRONT WILL HELP TO PUSH THE STORMS QUICKER THAN HAS BEEN THE CASE OVER THE PAST SEVERAL DAYS. AS OF EARLY AFTERNOON THE FRONT WAS PASSING THROUGH CENTRAL MONTANA NORTH OF A LINE FROM GTF-LWT. COOLER AND CONTINUED UNSTABLE AIR BEHIND THE FRONT OVER NORTH- CENTRAL MONTANA WILL ALLOW FOR WIDESPREAD RAIN SHOWERS TO PERSIST THROUGH THIS EVENING. AS DAYTIME HEATING AND INSTABILITY WANE THIS EVENING...ANY THUNDERSTORM ACTIVITY SHOULD QUICKLY DIMINISH WITH ONLY SCATTERED SHOWERS EXPECTED THROUGH MIDNIGHT. DRIER AND CONTINUED COOL NORTHWEST FLOW WILL PERSIST THROUGH THURSDAY WITH ONLY ISOLATED MOUNTAIN SHOWERS OR THUNDERSTORMS EXPECTED AND TEMPERATURES WILL CONTINUE TO STAY BELOW AVERAGE FOR THIS TIME OF YEAR. MLS FRIDAY NIGHT THROUGH TUESDAY...NORTHWEST FLOW ALOFT WILL DOMINATE DURING THE PERIOD. FRIDAY AND SATURDAY EXPECT A COUPLE DISTURBANCES ALOFT AND ASSOCIATED MOISTURE TO AFFECT THE AREA WITH A CHANCE FOR SHOWERS AND AFTERNOON THUNDERSTORMS. STARTING SUNDAY BOTH THE GFS AND ECMWF HAVE AN UPPER RIDGE BEGINNING TO EXERT ITS INFLUENCE ON OUR AREA. THUS AGREE WITH THE MODELS DRY FORECAST OVER THE NORTHERN AND EASTERN ZONES. ANY SHOWER ACTIVITY LOOKS TO BE CONFINED TO THE SOUTHWEST DURING THIS TIME. MODELS AGREE IN BRINGING COOLER AIR DOWN FROM CANADA OVER THE WEEKEND KEEPING HIGH TEMPS A LITTLE BELOW NORMAL BEFORE RISING A LITTLE EARLY NEXT WEEK. EG && .PRELIMINARY POINT TEMPS/POPS... GTF 49 72 46 78 / 80 20 10 10 CTB 46 71 44 76 / 50 10 10 10 HLN 53 73 48 81 / 60 20 10 10 BZN 50 71 42 80 / 80 30 10 10 WEY 41 65 34 70 / 30 20 10 20 DLN 48 68 42 74 / 50 20 10 10 HVR 48 76 46 81 / 40 10 10 10 LWT 47 66 42 74 / 80 30 10 20 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ WEATHER.GOV/GREATFALLS