986 FXUS65 KBYZ 100900 AFDBYZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BILLINGS MT 300 AM MDT TUE SEP 10 2013 .SHORT TERM...VALID FOR TDY AND WED... QUIET WEATHER PATTERN FOR THE NEXT SEVERAL DAYS AS A RIDGE OF HIGH PRESSURE BUILDS IN OVER MONTANA AND BRINGS A DRY NORTHWEST FLOW OF AIR. THE BUILDING RIDGE OF HIGH PRESSURE WILL BRING INCREASING HEIGHTS ALOFT AND THIS WILL ALLOW TEMPERATURES TO WARM TO SLIGHTLY ABOVE SEASONAL VALUES. AN UPPER LOW PRESSURE SYSTEM WILL MEANDER OVER THE DESERT SOUTHWEST THROUGH THE PERIOD THEN WILL BEGIN LIFTING SLOWLY TO THE NORTHEAST AS ANOTHER TROUGH MOVES IN TOWARD THE PACIFIC WEST COAST. THIS WILL BRING INCREASING MOISTURE TO OUR SOUTHERN MOUNTAINS BY WEDNESDAY NIGHT ALONG WITH WEAK VORTICITY MOVING IN. GFS/WRF DO BRING SOME WEAK Q VECTOR FORCING OVER THE MOUNTAINS AND WILL ADD ISOLATED SHOWERS TO THESE AREAS AFTER 06Z WEDNESDAY. DRY WEATHER CAN BE EXPECTED OVER THE LOWER ELEVATIONS THROUGH THE PERIOD. RICHMOND .LONG TERM...VALID FOR THU...FRI...SAT...SUN...MON... UPPER LOW CURRENTLY OVER CALIFORNIA WILL SLOWLY DRIFT NORTH AND WILL BE LOCATED OVER UTAH BY THURSDAY. ACCOMPANYING MONSOON MOISTURE WILL DRIFT NORTHWARD WITH THIS LOW INTRODUCING A SLIGHT CHANCE OF POPS FOR SOUTHERN BORDER MOUNTAIN LOCATIONS. ALSO ON THURSDAY...NORTHWESTERLY FLOW ALOFT EAST OF THE FORECAST AREA WILL ALLOW FOR LOW-LEVEL SOUTHEASTERLY FLOW TO BE BECOME STRONGLY ESTABLISHED. THE LOW-LEVEL FLOW WILL FEATURE SLIGHTLY COOLER 850 MB TEMPERATURES AND SOME INCREASING BUT STILL MEAGER GULF MOISTURE FOR THE SOUTHEAST CORNER OF THE STATE. THEREFORE HAVE MADE SURE THE TEMPERATURE FORECAST REFLECTS THIS THINKING...WITH THE SOUTHEAST CORNER OF THE STATE RUNNING SLIGHTLY COOLER THAN THE REST OF THE FORECAST AREA. FOR FRIDAY THE FLOW PATTERN WILL REMAIN THE SAME...BUT WITH THE UPPER LEVEL LOW DRIFTING FARTHER NORTH THE MOISTURE WILL BECOME MORE ESTABLISHED IN THE FORECAST AREA. FURTHERMORE...WEAK QG FORCING ASSOCIATED WITH THIS UPPER LOW SHOULD COUPLE WITH THE INCREASED MOISTURE TO DEVELOP SOME ISOLATED TO SCATTERED SHOWERS AND POSSIBLY A THUNDERSTORM. THE MOUNTAINS WILL BE MOST LIKELY TO SEE SOME SCATTERED SHOWER ACTIVITY THANKS TO ENHANCED OROGRAPHIC ASSENT...BUT CANNOT RULE OUT A FEW SHOWERS MAKING IT OFF THE MOUNTAINS AND TRACKING ACROSS THE PLAINS BY FRIDAY EVENING/NIGHT. BY SATURDAY...THE ISOLATED/SCATTERED SHOWER AND THUNDERSTORM THREAT SHOULD SHIFT TO EASTERN MONTANA AND INTO THE DAKOTAS AS THE UPPER-LEVEL LOW SHIFT EASTWARD. THE FLOW WILL SHIFT AROUND TO THE NORTHWEST BEHIND THE LOW ALLOWING FOR DRIER AND SLIGHTLY COOLER AIR TO TAKE HOLD ACROSS WESTERN PORTIONS OF THE FORECAST AREA. THE GFS AND ECMWF DIFFER ON THE MAGNITUDE OF THE COOLER 850 MB AIR BEHIND THE SYSTEM FOR SUNDAY...WITH THE LATEST RUN OF THE EC SHOWING 850 MB TEMPS OF 8C FOR BAKER VS THE GFS WITH TEMPS OF 14C. THE PREVIOUS RUN OF THE EC WAS NOT THIS COOL THUS HAVE NOT REFLECTED THESE MUCH COOLER TEMPERATURES IN THE FORECAST FOR NOW...BUT IT WILL WORTH WATCHING HOW THE MODELS EVOLVE WITH THE MAGNITUDE OF THE COOLER AIR. GLOBAL MODELS CONTINUE TO EVOLVE TROUGHING OFF THE NORTHWEST COAST BY MONDAY INTO TUESDAY...INDUCING SOUTHWESTERLY FLOW ACROSS THE FORECAST AREA. GFS AND ECMWF BOTH PLACE 700 MB TEMPERATURES AT 10 TO 12 C ACROSS THE FORECAST AREA FOR THE START OF THE WORK WEEK. GIVEN THE PERSISTENCE IN BOTH MODELS...HAVE REFLECTED THE WARMING TREND IN THE FORECAST BY SHOWING HIGH TEMPERATURES RUNNING IN THE MID 80S. THE FLOW ALSO APPEARS FAIRLY DRY AND DOWNSLOPE SO THE FORECAST WILL STAY DRY. CHURCH && .AVIATION... VFR CONDITIONS WILL PREVAIL TODAY. A FEW AREAS OF LOW LYING FOG DEVELOPMENT ARE POSSIBLE AROUND SUNRISE INCLUDING IN THE VICINITY OF THE BIL...SHR...AND MLS TAF SITES. CHURCH && .PRELIMINARY POINT TEMP/POPS... TDY WED THU FRI SAT SUN MON ------------------------------------------------------- BIL 083 055/083 057/082 056/082 058/081 057/080 058/085 0/U 00/U 00/U 12/T 22/T 21/B 11/U LVM 085 046/084 050/085 045/084 048/082 049/080 051/086 0/U 00/U 12/T 23/T 31/B 11/B 11/U HDN 085 053/085 055/083 057/083 058/081 053/081 056/088 0/U 00/U 00/U 12/T 22/T 21/U 11/U MLS 083 055/083 056/083 057/083 058/080 054/080 058/085 0/U 00/U 00/U 12/T 22/T 21/B 11/U 4BQ 083 053/084 055/078 055/080 056/079 050/079 054/086 0/U 00/U 00/U 12/T 22/T 22/T 11/U BHK 079 052/080 053/078 051/078 053/076 052/075 051/080 0/U 00/U 00/U 12/T 22/T 22/T 11/U SHR 081 049/083 051/079 052/078 052/078 047/078 051/086 0/U 00/U 10/B 12/T 22/T 21/B 11/U && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...NONE. WY...NONE. && $$ WEATHER.GOV/BILLINGS