000 FXUS65 KTFX 140938 COR AFDTFX SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 337 AM MDT TUE OCT 14 2003 .DISCUSSION... TODAY THROUGH WEDNESDAY...THE PROGRESSIVE WESTERLY FLOW ALOFT WILL CONTINUE OVER MONTANA THROUGH AT LEAST WEDNESDAY. CLEARING SKIES WITH LOW LEVEL MOISTURE FROM SHOWERS YESTERDAY AND OVERNIGHT HAVE CAUSED PATCHY FOG TO DEVELOP THIS MORNING...WITH THE FOG BURNING OFF BY LATE MORNING. A DISTURBANCE WITH CONSIDERABLE MOISTURE AND LIFT WILL THEN MOVE INTO WESTERN MONTANA THIS MORNING AND ACROSS THE TFX CWA THIS AFTERNOON AND TONIGHT. THIS WILL BRING SCATTERED MOUNTAIN SNOW SHOWERS WITH ISOLATED RAIN SHOWERS OVER THE PLAINS THIS AFTERNOON...INCREASING TO LIKELY MOUNTAIN SNOW SHOWERS AND SCATTERED RAIN AND SNOW SHOWERS OVER THE PLAINS THIS EVENING. THE DISTURBANCE WILL MOVE EAST OF THE CWA AFTER MIDNIGHT TONIGHT...FOR DECREASING SHOWERS FROM THE WEST. WINDS WILL BE GENERALLY LIGHT AND SHIFT TO A MORE NORTHERLY DIRECTION THIS AFTERNOON AND TONIGHT AS SURFACE HIGH PRESSURE BUILDS SOUTHWARD FROM CANADA. THIS WILL CAUSE WEAK UPSLOPE CONDITIONS FOR A SLIGHTLY BETTER CHANCE FOR PRECIPITATION ALONG THE NORTH AND EAST FACING SLOPES OVERNIGHT. WEAK UPPER LEVEL RIDGING WITH MID LEVEL MOISTURE WILL THEN MOVE INTO MONTANA FROM THE WEST ON WEDNESDAY...FOR MOSTLY CLOUDY SKIES BUT DRY CONDITIONS. SURFACE HIGH PRESSURE WILL CONTINUE TO MOVE SOUTH OVER THE CWA AND SHIFT THE LIGHT WINDS MORE EASTERLY. TEMPERATURES WILL REMAIN FAIRLY CONSISTENT IN SOUTHWEST MONTANA TODAY AND WEDNESDAY...WITH HIGHS STAYING IN THE LOWER 40S TO MID 50S. HOWEVER...THE SURFACE HIGH PRESSURE WILL BRING COOLING TEMPERATURES TO NORTH CENTRAL MONTANA... AS HIGHS FALL FROM THE MID 40S TO MID 50S TODAY INTO THE UPPER 30S AND 40S FOR WEDNESDAY. LOWS TONIGHT WILL REACH THE 20S TO LOWER 30S ONCE AGAIN. COULSTON WEDNESDAY NIGHT AND THURSDAY...A WEAK UPPER LEVEL DISTURBANCE CROSSES THE ROCKIES OVERNIGHT AND MOVES EAST OF THE ZONES BY LATE THURSDAY. A SURFACE LOW PRESSURE CENTER OVER SOUTHERN MT AND WY WILL HELP SPREAD A CHANCE OF PRECIP ACROSS THE CENTRAL AND SOUTHERN ZONES...WHILE THE NORTHERN ROCKIES WILL ALSO CONTINUE TO SEE A CHANCE OF PRECIP MAINLY FROM THE WEST FLOW ALOFT. FRIDAY THROUGH SUNDAY...AN UPPER LEVEL HIGH PRESSURE RIDGE BUILDS OVER THE ZONES AND WILL KEEP THE AIRMASS WARM AND DRY. LOWER SURFACE PRESSURE IN SOUTHERN ALBERTA WILL CONTINUE TO KEEP BREEZY WEST WINDS AT THE SURFACE IN THE FORECAST. ZELZER MONDAY AND TUESDAY...PACIFIC LOW PRESSURE MOVES ACROSS NORTHERN CANADA MONDAY. THE SYSTEM FLATTENS THE RIDGE RIDGE OVER MONTANA... CREATING ALMOST ZONAL FLOW ACROSS THE STATE. SHORT WAVES MOVING THROUGH THE FLOW BRING CLOUDS AND A SLIGHT CHANCE OF SHOWERS MONDAY EARLY. THE UPPER RIDGE REBUILDS OVER THE NORTHWEST AS THE CANADIAN LOW MOVES EAST. SURFACE HIGH PRESSURE PUSHES INTO MONTANA EARLY TUESDAY. THE BUILDING UPPER LEVEL RIDGE BRINGS THE WESTERN PART OF THE STATE UNDER DRY NORTHWEST FLOW. THE EASTERN PART OF THE AREA REMAINS UNDER THE INFLUENCE OF THE LOW PRESSURE CIRCULATION TO THE EAST...KEEPING HEAVIER CLOUD COVER AND NORTHERLY FLOW ON THE SURFACE. DAYTIME TEMPERATURES ARE WARM FOR THE FORECAST PERIOD...BUT NEARER TO SEASONAL NORMS ON TUESDAY. CLOUD COVER IN THE EAST WILL MODERATE MINS. PREWITT .CCF NUMBERS GTF EE 054/030 049/031 056 10250 BNBUU 042/067 044/070 040/068 038/061 031 22000000000 CTB EE 050/028 046/030 052 10250 ENBUU 040/066 042/068 039/064 034/060 030 22000000000 HLN EE 053/034 054/034 055 10240 BNBUU 037/064 039/068 035/065 037/060 029 330000000-0 BZN EE 057/033 057/031 053 10230 BBBUU 035/065 034/067 032/069 038/063 029 33000000010 WEY BE 047/021 048/022 051 10230 EBUUU 025/056 028/057 025/063 034/058 025 33000000000 DLN EE 056/033 056/031 055 10230 BBBUU 034/067 037/066 036/069 036/061 028 330000000-0 HVR BB 055/029 053/029 054 10030 BNBUU 038/068 045/071 040/072 038/066 034 11000000000 LWT BE 054/030 048/031 055 10-50 BNBUU 040/064 040/068 038/068 037/063 029 22000000000 .TFX...NONE. $$