Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 290535
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1135 PM MDT THU MAY 28 2015

.UPDATE...
SURFACE COLD FRONT THAT HAS BEEN MAKING ITS WAY THROUGH THE REGION
THIS AFTN/EVE IS NOW LOCATED JUST NORTH OF BOZEMAN. MUCH OF THE
PRECIPITATION THAT WAS AHEAD OF THE FRONT DID NOT SUSTAIN
ITSELF AND ONLY PRECIP CURRENTLY ON RADAR IS A PATCH OF LIGHT RAIN
OVER CENTRAL LEWIS & CLARK/MOST OF CASCADE/WESTERN JUDITH BASIN
COUNTIES. COULD STILL SEE A FEW LIGHT RESIDUAL SHOWERS OVERNIGHT
OVER CENTRAL/SOUTHWEST MT BUT WIDESPREAD PRECIP NOW LESS LIKELY...
SO HAVE REDUCED PRECIP CHANCES ACROSS THE REGION THROUGH THE
OVERNIGHT HOURS. HAVE ALSO ADDED MENTION OF FOG TONIGHT AND INTO
FRI MORNING FOR THE HILINE ALONG WITH TETON/CHOUTEAU/NORTHERN
FERGUS COUNTIES AS PARTIAL CLEARING AND COOLING BEHIND THE FRONT
WILL PUSH OVERNIGHT TEMPS CLOSE TO DEWPOINTS THAT REMAIN IN THE
LOW- TO MID 40S THANKS TO EARLIER PRECIP TODAY.
WARANAUSKAS

&&

.AVIATION...
UPDATED 0535Z.

HIGH PRESSURE ALOFT WILL CONTINUE TO BUILD INTO THE AREA FROM THE
WEST, WHICH WILL CAUSE REMAINING SHOWERS TO DIMINISH BY 10Z.
HOWEVER, LOW LEVEL MOISTURE WILL LINGER ACROSS THE AREA THROUGH THE
EARLY MORNING HOURS (AROUND 15Z), CAUSING LOW VFR/HIGH MVFR CEILINGS
AND OCCASIONAL IFR CONDITIONS IN FOG TO CONTINUE TO OBSCURE
MOUNTAINS ACROSS NORTH CENTRAL MONTANA (INCLUDING KGTF KLWT) AND
SOUTHWEST MONTANA (INCLUDING KHLN AND KBZN). ALONG THE HI-LINE
ACROSS NORTH CENTRAL MONTANA (INCLUDING KCTB KHVR) SKIES ARE
BEGINNING TO CLEAR FROM THE NORTH. HOWEVER, THERE IS LOW LEVEL
MOISTURE THERE AS WELL, SO OCCASIONAL MVFR/IFR CONDITIONS ARE
POSSIBLE THERE IF THERE IS FOG DEVELOPMENT, MAINLY BETWEEN 09Z AND
15Z. THE LOW LEVELS OF THE ATMOSPHERE WILL BEGIN TO DRY OUT AFTER
15Z, ALLOWING SKIES TO AT LEAST PARTIALLY CLEAR AND BRING WIDESPREAD
VFR CONDITIONS. HOWEVER, A WEAK DISTURBANCE WILL MOVE THROUGH THE
HIGH PRESSURE ALOFT, BRINGING ISOLATED SHOWERS/THUNDERSTORMS TO THE
MOUNTAINS OF WESTERN AND SOUTHWEST MONTANA (KHLN KBZN) AND TO THE
EAST SLOPES OF THE ROCKIES (KCTB KGTF) AFTER 22Z.  COULSTON

&&

.PREV DISCUSSION...
/ISSUED 600 PM MDT THU MAY 28 2015/
TONIGHT THROUGH SATURDAY...AN UPPER TROUGH FROM NORTHWESTERN WYOMING
THROUGH EASTERN MONTANA THURSDAY AFTERNOON WILL CONTINUE MOVING EAST
AND THE FORECAST AREA WILL FALL UNDER THE INFLUENCE OF AN UPSTREAM
UPPER RIDGE LATER TONIGHT. EXPECT SCATTERED SHOWERS AND A FEW
THUNDERSTORMS EARLY THIS EVENING TO GRADUALLY DIMINISH OVERNIGHT.
NOT SURE HOW MUCH CLEARING WILL GO ON IN THE NORTH BUT HAVE
DECIDED TO MENTION PATCHY FOG FOR LATE TONIGHT AND EARLY FRIDAY
MORNING. THE UPPER RIDGE JUST MENTIONED WILL MOVE OVER THE
FORECAST AREA BY FRIDAY AFTERNOON. THIS WILL LEAD TO LESS SHOWER
AND THUNDERSTORM ACTIVITY THAN ON THURSDAY BUT THERE WILL STILL BE
SOME AFTERNOON INSTABILITY SO WILL CONTINUE THE MENTION OF A
CHANCE OF SHOWERS OR THUNDERSTORMS OVER THE WESTERN MOUNTAINS.
SATURDAY A WEATHER DISTURBANCE ALOFT WILL MOVE TO CENTRAL MONTANA
BY LATE AFTERNOON. THIS DISTURBANCE COMBINED WITH GENERALLY
GREATER INSTABILITY WILL RESULT IN AN INCREASE IN SHOWER AND
THUNDERSTORM ACTIVITY. IN FACT THE ENVIRONMENT OVER CENTRAL
MONTANA AND TO A LESSER EXTENT OVER SOUTHWEST MONTANA LOOKS
FAVORABLE FOR STRONGER BUT NOT NECESSARILY SEVERE THUNDERSTORMS.
BLANK

SATURDAY NIGHT THROUGH WEDNESDAY...A WESTERLY FLOW ALOFT OVER
MONTANA THIS WEEKEND RESULTS AS A GRADIENT BETWEEN A WESTERN
CANADIAN TROUGH AND AN GREAT BASIN RIDGE. MINOR IMPULSES IN THIS
FLOW...COMBINED WITH SURFACE DEWPOINTS IN THE UPPER 40S AND A NEARLY
LINEAR SHEAR PROFILE WILL MAINTAIN SCATTERED SHOWERS AND
THUNDERSTORMS SATURDAY NIGHT. WEAK RIDGING ALOFT ON SUNDAY WILL
SUPPRESS ALL BUT ISOLATED AFTERNOON SHOWERS AS THE UPPER LEVEL FLOW
TURNS MORE SOUTHWESTERLY. WIDESPREAD THUNDERSTORMS ARE INDICATED
MONDAY AFTERNOON WITH A CLOSED UPPER TROUGH APPROACHING FROM THE
PACIFIC. AN ACCOMPANYING SURFACE LOW FORMING IN SOUTHEAST MONTANA
WILL SUPPORT A HUMID EASTERLY FLOW OVER THE NORTH CENTRAL PLAINS.
DIVERGENT SOUTHWEST FLOW ALOFT WILL YIELD AN INCREASINGLY UNSTABLE
ENVIRONMENT. CONVECTIVE PARAMETERS DO NOT SUPPORT SEVERE STORMS...
BUT THE SETUP DOES WARRANT ATTENTION FOR A FEW STRONGER STORMS
INCLUDING SMALL HAIL AND GUSTY WINDS. TIMING WILL BECOME AN
IMPORTANT FACTOR TO CONSIDER. THE WAVE OPENS ON TUESDAY AND
WEDNESDAY AS DIFFERENCES BEGIN TO APPEAR AMONG MODEL SOLUTIONS.
HOWEVER THE OVERALL PATTERN REMAINS UNSETTLED THROUGH THE PERIOD
WITH CONTINUING SHOWERS AND ISOLATED THUNDERSTORMS. TEMPERATURES
TREND BELOW NORMAL THROUGH MIDWEEK. SNOW LEVELS COULD LOWER TO
AROUND 7500 FT MSL WEDNESDAY MORNING ALONG THE CONTINENTAL
DIVIDE...BUT AS YET VERY LITTLE CONFIDENCE IN THE POTENTIAL FOR ANY
ACCUMULATION. NUTTER

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  70  50  73 /  40  20  10  50
CTB  40  67  43  71 /  10  20  20  50
HLN  47  74  51  75 /  40  20  20  40
BZN  44  68  47  71 /  40  20  20  40
WEY  35  63  39  65 /  30  30  20  30
DLN  44  70  48  72 /  30  20  30  50
HVR  38  69  45  76 /  10  10  10  30
LWT  42  65  47  73 /  40  20  10  60

&&

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

$$

WEATHER.GOV/GREATFALLS


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