Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 011143
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
540 AM MDT SAT AUG 1 2015

UPDATED AVIATION DISCUSSION

.DISCUSSION...
TODAY THROUGH MONDAY NIGHT...AN UPPER RIDGE WILL BE DEVELOPING
OVER THE PACIFIC NORTHWEST TODAY AND WILL GRADUALLY MOVE EAST AND
BY MONDAY SHOULD BE OVER CENTRAL MONTANA. A WEATHER DISTURBANCE
ALOFT WILL DEVELOP OVER THE GREAT BASIN SUNDAY AND WILL MOVE
TOWARDS SOUTHWEST MONTANA ON MONDAY. IT WILL THEN MOVE THROUGH
SOUTHWEST MONTANA MONDAY EVENING AND BE OVER CENTRAL MONTANA BY
LATE MONDAY NIGHT. MONSOONAL MOISTURE AHEAD OF THE DISTURBANCE
WILL MOVE INTO SOUTHWEST MONTANA SUNDAY NIGHT AND SPREAD OVER THE
REMAINDER OF THE FORECAST AREA MONDAY. THE APPROACH OF THE
DISTURBANCE COMBINED WITH WEAK INSTABILITY WILL LEAD TO SCATTERED
THUNDERSTORMS OVER SOUTHWEST MONTANA THROUGH THE ROCKY MOUNTAIN
FRONT MONDAY AFTERNOON. THEN SCATTERED SHOWERS AND A FEW
THUNDERSTORMS WILL SPREAD OVER THE REMAINDER OF THE FORECAST AREA
AHEAD OF THE DISTURBANCE MONDAY NIGHT. UNTIL THE MONSOONAL
MOISTURE MOVES INTO THE FORECAST AREA EXPECT NO PRECIPITATION AND
THERE WILL BE SOME NEAR RECORD HIGH TEMPERATURES. A CANADIAN
AIRMASS WILL MOVE INTO THE NORTH LATE THIS AFTERNOON AND TONIGHT
AND SHOULD PROVIDE A FEW DEGREES OF COOLING IN THAT REGION SUNDAY.
BLANK

TUESDAY THROUGH SATURDAY...THERE SHOULD BE A SOUTHWEST FLOW ALOFT
UNTIL LATE IN THE WEEK WITH A FEW EMBEDDED WEATHER DISTURBANCES.
THE GFS AND ECMWF DIFFER WITH DETAILS OF THE ASSOCIATED
PRECIPITATION SO WILL CONTINUE WITH THE ISOLATED TO SCATTERED
THUNDERSTORM FORECAST IDEA. TOWARDS THE WEEKEND THERE ARE INDICATIONS
THAT A DRIER WESTERLY TO NORTHWESTERLY FLOW ALOFT COULD DEVELOP.
DID LOWER THE INHERITED CHANCES OF PRECIPITATION FORECAST SLIGHTLY
FOR FRIDAY BUT DID NOT REMOVE THE MENTION OF PRECIPITATION.
TEMPERATURES WILL BE QUITE A BIT COOLER THAN THOSE OF THIS
WEEKEND WITH HIGHS IN THE UPPER 70S TO LOWER 80S BY WEDNESDAY. BLANK


&&

.AVIATION...
UPDATED 1140Z.

THERE WILL BE VFR CONDITIONS WITH GENERALLY CLEAR SKIES. SURFACE
WINDS WILL REMAIN LIGHT THROUGH THIS MORNING WITH WEST TO NORTHWEST
WINDS OF 10 TO 15 KTS THIS AFTERNOON EXCEPT FOR SOUTHWEST MONTANA.
THE POSITION OF A CANADIAN COLD FRONT WILL AFFECT FORECAST WIND
DIRECTIONS TONIGHT OVER THE PLAINS WITH SOME GUIDANCE KEEPING IT NE
OF A KCTB-KGTF-KLWT LINE WHILE OTHER GUIDANCE HAS IT SW OF THAT
LINE. CONFIDENCE AT THIS POINT IS HIGHER IN THE LATTER SOLUTION THAN
THE FORMER SOLUTION. BLANK

&&

.FIRE WEATHER...
HOT AND DRY CONDITIONS WILL CONTINUE OVER THE REGION THROUGH
SUNDAY WITH WARMEST TEMPERATURES AND LOWEST AFTERNOON HUMIDITY
OVER THE PLAINS EXPECTED TO PEAK SATURDAY AFTERNOON. OVERNIGHT
HUMIDITY RECOVERY WILL BE POOR AT MID-SLOPE TO RIDGETOP LOCATIONS
AS OVERNIGHT INVERSIONS/THERMAL BELTS PERSIST. A VERY WEAK
WEATHER DISTURBANCE ALOFT AND DEEP MIXING WILL BRING A PERIOD OF
BREEZY WINDS SATURDAY AFTERNOON AND EARLY EVENING. WESTERLY WINDS
OVER THE ROCKY MOUNTAIN FRONT AND NEARBY PLAINS SHOULD REACH AT
LEAST 15 MPH WITH GUSTS OF 20-25 MPH. THIS COMBINED WITH EXTREMELY
LOW RELATIVE HUMIDITIES IN THE 5 TO 10 PCT RANGE WILL LEAD TO
CRITICAL FIRE WEATHER CONDITIONS AND HAVE UPGRADED THE FIRE
WEATHER WATCH THERE TO A RED FLAG WARNING. FARTHER EAST WINDS WILL
BE OUT OF THE NORTHWEST AND MORE IN THE RANGE OF 10 TO 15 MPH.
HOWEVER WITH VERY LOW RELATIVE HUMIDITIES OF 5 TO 15 PCT HAVE
DECIDED TO ALSO UPGRADE THE REGION TO A RED FLAG WARNING. A WEAK
WEATHER SYSTEM MOVING INTO THE REGION FROM THE SW WILL BRING A
CHANCE FOR THUNDERSTORMS LATE MONDAY AND THE INCREASE IN LIGHTNING
AND POTENTIAL FOR GUSTY THUNDERSTORM WINDS FOLLOWING THIS PERIOD
OF VERY WARM AND DRY CONDITIONS MAY LEAD TO ADDITIONAL FIRE
WEATHER CONCERNS ON MONDAY. HOENISCH/BLANK

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  97  56  93  58 /   0   0   0   0
CTB  94  49  90  54 /   0   0   0   0
HLN  98  56  98  57 /   0   0   0   0
BZN  94  52  94  54 /   0   0   0  10
WEY  84  41  86  43 /   0   0  10  10
DLN  92  51  92  55 /   0   0  10  10
HVR  94  56  91  57 /   0   0   0   0
LWT  92  56  90  57 /   0   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM NOON TODAY TO 9 PM MDT THIS EVENING FOR
MTZ112>115-117.

&&

$$

WEATHER.GOV/GREATFALLS


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