461 FXUS65 KTFX 040258 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 855 PM MDT THU MAY 3 2012 .DISCUSSION... UPDATE FORTHCOMING. MOISTURE CONTINUES TO MOVE UP INTO THE STATE EMBEDDED WITHIN THE SOUTHWEST FLOW ALOFT. SHORTWAVE ENERGY MOVING ACROSS THE AREA PROVIDE THE LIFT FOR SHOWERS AND ISOLATED THUNDERSTORMS TO DEVELOP. THE LARGEST AREA OF SHOWER ACTIVITY IS NOW EAST OVER THE EASTERN PORTION OF THE COUNTY WARNING AREA WITH ANOTHER WEAKER AREA OF SHOWERS OVER SOUTHWEST MONTANA. THIS CONVECTIVE ACTIVITY SHOULD GRADUALLY END BY MIDNIGHT WITH THE LOSS OF SOLAR HEATING AND THE CONTINUED EASTWARD TREK OF THE SHORTWAVE. OVERNIGHT LOWS A BIT TRICKY TONIGHT AS CLOUD COVER...OR LACK OF...WILL PLAY AN IMPORTANT ROLE. GOING NUMBERS LOOK GOOD. EMANUEL && .AVIATION... UPDATED 2330Z. SCATTERED SHOWERS CONTINUE TO MOVE FROM SW-TO-NE OVER SOUTHWEST AND CENTRAL MT BUT HAVE YET TO SEE ANY EVEN MARGINALLY STRONGER CONVECTION SO HAVE DELETED MENTION OF THUNDER AT ALL TAF SITES FOR REMAINDER OF THIS EVE. PRECIPITATION SHOULD DISSIPATE SUBSTANTIALLY AROUND SUNSET WITH DECREASING WINDS. AREA REMAINS UNDER MOIST SOUTHWEST FLOW PATTERN TONIGHT SO WILL SEE BIT MORE MID-LEVEL (CEILINGS AT/ABOVE 7000 FT) CLOUD COVERAGE THRU TONIGHT THAN SEEN THE PAST FEW NIGHTS. VFR CONDITIONS EXPECTED TOMORROW BUT WILL SEE SCATTERED SHOWERS DEVELOP AGAIN WITH A CHANCE OF THUNDER VCNTY KHLN/KBZN. WARANAUSKAS && .PREV DISCUSSION...ISSUED 259 PM MDT THU MAY 3 2012 TONIGHT THROUGH SATURDAY...SHORT RANGE MODELS STILL HAVE A WIDE SPREAD OF SOLUTIONS THROUGH THE SHORT TERM PERIOD. THURSDAY AFTERNOON AND EVENING SCATTERED SHOWERS AND AN ISOLATED THUNDERSTORM WILL CONTINUE TO MOVE ACROSS THE AREA. SHOWER ACTIVITY WILL DECREASE OVERNIGHT AS THE SHORTWAVE THROUGH RESPONSIBLE FOR THE ACTIVITY WILL SLOWLY MOVE OFF TO THE EAST. BY FRIDAY AFTERNOON AND EVENING SCATTERED SHOWERS AND THUNDERSTORMS WILL RETURN...WITH AN INCREASE IN COVERAGE AS MORE MOISTURE MOVES INTO THE AREA AHEAD OF THE NEXT WEATHER SYSTEM. BY SATURDAY MORNING TEMPERATURES WILL HAVE DECREASED BEHIND THE COLD FRONT...WITH THE HIGHER ELEVATIONS RECEIVING SOME SNOW TOTALS CLOSE TO ADVISORY AMOUNTS. WIDESPREAD PRECIPITATION WILL INCREASE THROUGH SATURDAY AS THE TROUGH MOVES OVER THE AREA. SATURDAY AFTERNOON CONVECTION COULD ENHANCE SHOWERS AND PRODUCE SOME THUNDERSTORMS THROUGH THE DAY AS THE THROUGH SLOWLY MOVES ACROSS THE AREA. SUK SATURDAY NIGHT THROUGH THURSDAY...MEDIUM RANGE MODELS CONTINUE TO HAVE QUITE SUBSTANTIAL DIFFERENCES IN THEIR SOLUTIONS FOR SATURDAY NIGHT AND SUNDAY. AS BEFORE...THE GFS IS SLOWER...DEEPER AND WETTER WITH THE UPPER LEVEL SYSTEM THAN THE ECMWF. THE MOST RECENT RUN OF THE GFS HAS SLOWED THE SYSTEM EVEN MORE THAN EARLIER RUNS AND KEEPS THE INFLUENCE OF THE UPPER TROUGH OVER THE FORECAST AREA CLEAR INTO TUESDAY. AT THIS TIME I FEEL COMFORTABLE KEEPING THE EARLY PART OF THE MEDIUM RANGE PERIOD COOL AND WET IN KEEPING WITH THE GFS. HOWEVER...BELIEVE THIS LATEST RUN IS KEEPING THE LOW IN THE REGION TOO LONG SO HAVE TRENDED MORE TOWARD THE ECMWF FOR TUESDAY AND BEYOND WITH AN UPPER LEVEL RIDGE EXPECTED TO BUILD OVER THE NORTHERN ROCKIES FOR WARMER AND DRIER CONDITIONS. MPJ && .HYDROLOGY... THE SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED ACROSS THE AREA THROUGH FRIDAY MAY PRODUCE BRIEF HEAVY RAINFALL AT TIMES...WHICH MAY CAUSE BRIEF LOCALIZED FLOODING CONCERNS FOR SMALL STREAMS AND CREEKS. TEMPERATURES ARE NOT EXPECTED TO BECOME UNUSUALLY WARM FOR THIS TIME OF YEAR...SO RAPID AND SIGNIFICANT MELTING OF MOUNTAIN SNOWPACK IS UNLIKELY. STEADY SNOWMELT WILL KEEP WATERWAYS RUNNING HIGH...BUT FLOODING OF MAIN STEM RIVERS IS NOT FORECAST AT THIS TIME. A LARGER SCALE SYSTEM WILL LIKELY BRING MORE WIDESPREAD PRECIPITATION TO THE AREA FOR SATURDAY AND SUNDAY...WHICH MAY CAUSE RIVERS TO RISE FURTHER. WILL THEREFORE CONTINUE TO MONITOR THE SITUATION FOR THE NEXT SEVERAL DAYS FOR POTENTIAL HYDROLOGIC HIGHLIGHTS. COULSTON && .PRELIMINARY POINT TEMPS/POPS... GTF 40 62 38 48 / 50 30 60 70 CTB 35 58 34 48 / 60 20 20 50 HLN 37 62 36 49 / 30 40 70 70 BZN 35 61 33 48 / 30 50 80 70 WEY 32 49 29 38 / 40 40 50 60 DLN 34 59 32 45 / 30 50 70 70 HVR 39 67 40 51 / 60 20 30 50 LWT 36 61 35 45 / 60 50 70 80 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...EMANUEL/SUK LONG TERM...MPJ AVIATION...WARANAUSKAS WEATHER.GOV/GREATFALLS