Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 040943
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
343 AM MDT TUE AUG 4 2015

.DISCUSSION...

TODAY THROUGH THURSDAY...WATER VAPOR IMAGERY REVEALS A CLOSED
UPPER LEVEL CIRCULATION CENTERED OVER WYOMING WITH A TROUGH AXIS
EXTENDING INTO NW MONTANA. THE UPPER LEVEL WAVE IS ALIGNING WITH
AN ELONGATED LEE SURFACE TROUGH AS THE COUPLED FEATURES WILL NOW
PROGRESS INTO THE NORTHERN PLAINS. BRISK WEST WINDS WILL DEVELOP
BEHIND THIS TROUGH AS TEMPERATURES LOWER NEAR AVERAGE INTO THE
LOWER 80S. SCATTERED RAIN SHOWERS CONTINUE OVER SOUTHWEST MT
CLOSER TO THE CENTER OF CIRCULATION. THESE SHOWERS WILL DEVELOP
INTO WIDESPREAD THUNDERSTORMS THIS AFTERNOON GENERALLY ALONG AND
EAST OF A LINE FROM HAVRE TO BOZEMAN. SEVERE WEATHER IS NOT
EXPECTED DUE TO LACK OF SHEAR...BUT SOME SLOW MOVING CELLS COULD
PRODUCE MODERATE TO HEAVY RAIN. THE LINE OF SHOWERS CLEARS TO THE
EAST THIS AFTERNOON. LIGHT SHOWERS ARE FORECAST TO ACCOMPANY A
PASSING JET STREAK THROUGH SOUTHWEST MONTANA TONIGHT...WITH DRY
CONDITIONS EXPECTED ELSEWHERE. MODELS HAVE COME INTO GENERAL
AGREEMENT THAT A WAVE OF PACIFIC MOISTURE WILL CROSS SOUTHWEST AND
CENTRAL MONTANA LATE WEDNESDAY. AREAS OF RAIN WITH EMBEDDED
THUNDERSTORMS WILL DEVELOP WITH THIS FEATURE AND PRODUCE MODERATE
TO HEAVY RAIN IN SOME AREAS. THE ROCKY MOUNTAIN FRONT AND WESTERN
PORTIONS OF THE HILINE WILL NOT RECEIVE PRECIPITATION FROM THIS
SYSTEM. DRY AIR ARRIVES ON THURSDAY AS A BROAD CLOSED UPPER LEVEL
LOW NUDGES SOUTHEAST FROM BRITISH COLUMBIA. SHOWERS ARE POSSIBLE
ALONG THE INTERNATIONAL BORDER...AND TEMPERATURES WILL DROP INTO
THE MID 70S AS THE FLOW TURNS WESTERLY. NUTTER

THURSDAY NIGHT THROUGH TUESDAY...MEDIUM RANGE MODELS ARE ONCE AGAIN
IN RELATIVELY GOOD AGREEMENT FOR LATE THIS WEEK THROUGH EARLY NEXT
WEEK AND FORECAST CONFIDENCE REMAINS MODERATE. A SHORTWAVE TROUGH
WILL BE EXITING THE REGION AS THE PERIOD BEGINS ALLOWING FOR MOSTLY
DRY CONDITIONS THROUGH FRIDAY NIGHT. AN UPPER LEVEL TROUGH ALONG THE
WEST COAST WILL EJECT SHORTWAVE ENERGY INTO THE NORTHERN ROCKIES BY
SATURDAY EVENING FUELING SCATTERED SHOWERS AND THUNDERSTORMS OVER
SOUTHWEST MONTANA THAT WILL MOVE INTO CENTRAL MONTANA OVERNIGHT.
MODEL SOLUTIONS HAVE EVOLVED SOMEWHAT FROM WHAT WAS SEEN YESTERDAY
AND MODELS NOW KEEP THIS UPPER TROUGH IN PLACE THROUGH THE REMAINDER
OF THE FORECAST PERIOD. AS A RESULT, MONTANA WILL REMAIN BENEATH A
SOMEWHAT UNSTABLE SOUTHWEST FLOW ALOFT WITH ISOLATED SHOWERS AND
THUNDERSTORMS EXPECTED AT TIMES, MAINLY OVER THE MOUNTAINS.
TEMPERATURES WILL ALSO REMAIN AT OR NEAR SEASONABLE AVERAGES THROUGH
THE PERIOD. MPJ

&&

.AVIATION...
UPDATED 0540Z.

VFR CONDITIONS PREVAIL THROUGH THE PERIOD...ALTHOUGH MVFR CONDITIONS
WILL BE POSSIBLE UNDER THUNDERSTORMS MID-DAY TUESDAY NEAR KHVR/KLWT.
A FRONTAL BOUNDARY WILL MOVE THROUGH CENTRAL AND SOUTHWEST MONTANA
OVERNIGHT...FOLLOWED BY A SHIFT TO WESTERLY WINDS. SCATTERED SHOWERS
AND THUNDERSTORMS ARE PRESENT NEAR KHLN EARLY TONIGHT. SHOWER
ACTIVITY WILL DISSIPATE SOMEWHAT OVERNIGHT...THEN DEVELOP STRONGLY
ALONG A LINE FROM KHVR TO KLWT TUESDAY AFTERNOON. CONFIDENCE IN THE
TIMING OF THIS LINE IS LOW. PRECIPITATION CLEARS MOST OF THE AREA
TUESDAY EVENING. A SECONDARY DISTURBANCE WILL CAUSE ADDITIONAL LIGHT
SHOWERS OVER FAR SOUTHWEST MONTANA TUESDAY NIGHT...POSSIBLY
AFFECTING KBZN. NUTTER

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  83  57  78  54 /  20  10  40  40
CTB  85  52  80  50 /  10  10  20  20
HLN  86  55  75  51 /  20  20  50  30
BZN  83  53  76  50 /  40  30  50  50
WEY  73  43  71  38 /  50  20  50  60
DLN  81  52  71  47 /  20  20  60  40
HVR  82  57  84  55 /  50  20  20  40
LWT  77  55  80  52 /  70  20  50  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

WEATHER.GOV/GREATFALLS


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