Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 021139
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
539 AM MDT TUE JUN 2 2015

.DISCUSSION...

TODAY THROUGH THURSDAY...AN UPPER LEVEL LOW PRESSURE SYSTEM WILL BE
OVER THE PACIFIC NORTHWEST TUESDAY AND MOVE VERY LITTLE THROUGH
THURSDAY. THIS WILL LEAVE THE ZONES UNDERNEATH DISTURBED AND RATHER
MOIST SOUTHWEST FLOW ALOFT. WATER VAPOR INDICATES CONSIDERABLE
MOISTURE IN THE SOUTHWEST FLOW AHEAD OF THE SYSTEM. THIS IS
ASSOCIATED WITH A DISTURBANCE ROTATING THROUGH THE FLOW ALOFT AND
WILL BRING PRECIPITATION ACROSS MAINLY THE NORTHERN ZONES THIS
MORNING. INSTABILITY WILL NOT BE AS GREAT THIS AFTERNOON AS
YESTERDAY ALTHOUGH THE CONVECTIVE TEMPERATURE WILL BE QUITE LOW, AND
AFTERNOON AND EVENING CONVECTION IS AGAIN EXPECTED. GREATEST
INSTABILITY WILL GENERALLY BE ALONG AND SOUTH OF A GREAT FALLS TO
LEWISTOWN LINE. WEDNESDAY WILL BE A DAY BETWEEN SHORTWAVES AND
WILL NOT BE AS ACTIVE. HOWEVER, AFTERNOON INSTABILITY WILL DEVELOP
AGAIN WITH SHOWERS AND AFTERNOON THUNDERSTORMS IN THE AREA.
ANOTHER GOOD DISTURBANCE WILL MOVE THROUGH THE AREA LATE WEDNESDAY
NIGHT AND THURSDAY AND BRING SCATTERED TO NUMEROUS SHOWERS ACROSS
THE ZONES. THE AIRMASS WILL TREND COOLER THROUGH WEDNESDAY BEFORE
WARMING AGAIN THURSDAY. TEMPERATURES WILL REMAIN BELOW NORMALS
THROUGH THURSDAY. ZELZER

THURSDAY NIGHT THROUGH MONDAY...MEDIUM RANGE MODELS ARE IN VERY GOOD
AGREEMENT WITH THE OVERALL PATTERN. AN UPPER LEVEL TROUGH OF LOW
PRESSURE WILL REMAIN OVER THE WESTERN UNITED STATES THROUGH THE
PERIOD WITH ITS LOW PRESSURE CENTER INITIALLY STAYING OVER THE
CALIFORNIA COAST. THE CHANCE FOR SHOWERS/THUNDERSTORMS WILL DECREASE
THURSDAY NIGHT AS A SHORTWAVE TROUGH EXITS THE AREA. ANOTHER
SHORTWAVE WILL EJECT FROM THE TROUGH AND BRING A GOOD CHANCE OF
SHOWERS AND THUNDERSTORMS TO THE AREA AGAIN FOR FRIDAY AFTERNOON AND
EVENING. THE LOW PRESSURE CENTER WILL THEN MOVE NORTH INTO THE
WESTERN GREAT BASIN FOR SATURDAY THROUGH SUNDAY. THIS WILL KEEP A
GOOD CHANCE OF SHOWERS AND THUNDERSTORMS OVER SOUTHWEST MONTANA, BUT
WEAK HIGH PRESSURE TO THE NORTH OF THIS LOW WILL HINDER SHOWER AND
THUNDERSTORM DEVELOPMENT ACROSS NORTH CENTRAL MONTANA. THE LOW WILL
THEN WEAKEN AS IT MOVES NORTH INTO THE NORTHERN ROCKIES ON MONDAY,
BUT WITH IT MOVING OVERHEAD, THERE WILL BE A GOOD CHANCE FOR SHOWERS
AND THUNDERSTORMS FOR THE ENTIRE FORECAST AREA. TEMPERATURES WILL
REMAIN FAIRLY CONSTANT THROUGH THE PERIOD. HIGHS WILL BE NEAR NORMAL
(UPPER 60S TO LOWER 70S), BUT LOWS WILL BE QUITE MILD (MID 40S TO
LOWER 50S), REMAINING 5 TO 10 DEGREES WARMER THAN NORMAL.
COULSTON

&&

.AVIATION...

UPDATED 1111Z.

AN UPPER LEVEL LOW PRESSURE SYSTEM OVER THE PACIFIC NORTHWEST WILL
CONTINUE TO FEED MOISTURE INTO CENTRAL MONTANA AND KEEP THE AIRMASS
UNSETTLED.  AREAS OF MVFR/IFR CONDITIONS DUE TO CIGS AND VSBY WILL
CONTINUE INTO MID MORNING. AREAS OF SHOWERS ARE EXPECTED TO CONTINUE
THROUGH MOST OF THE DAY ACROSS THE NORTHERN PORTIONS OF THE REGION,
INCLUDING KCTB AND KHVR. AFTERNOON SHOWERS AND THUNDERSTORMS WILL
DEVELOP TO THE SOUTH. LOCAL IFR CONDITIONS ARE EXPECTED AGAIN
TOWARDS WEDNESDAY MORNING DUE TO LOW CIGS AND VSBY.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  62  46  66  49 /  70  40  40  60
CTB  53  41  64  43 /  90  50  20  40
HLN  67  47  69  50 /  70  40  40  60
BZN  67  44  68  47 /  60  50  30  40
WEY  62  35  62  38 /  30  20  30  50
DLN  66  43  66  44 /  50  40  50  50
HVR  59  45  69  47 /  70  60  30  50
LWT  62  45  65  48 /  70  50  40  50

&&

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

$$

WEATHER.GOV/GREATFALLS


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