Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 210541
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1140 PM MDT MON APR 20 2015

.DISCUSSION...

NO UPDATES TO THE GOING FORECAST. SCATTERED TO BROKEN MID LEVEL
CLOUDINESS HAS DEVELOPED IN ALBERTA THIS EVENING AND MODELS
INDICATE IT SHOULD MOVE SOUTHEAST INTO MONTANA. GOING FORECAST HAS
THIS HANDLED WELL. TEMPERATURES ARE ALSO TRENDING SIMILAR TO THE
GOING FORECAST. WITH THE LOSS OF DAYTIME HEATING, WINDS ARE
DECOUPLING AND SHOULD REMAIN FAIRLY LIGHT OVERNIGHT.
COULSTON

&&

.AVIATION...
UPDATED 0540.

VFR CONDITIONS WILL PREVAIL WITH LIGHT SURFACE WINDS UNDER HIGH
PRESSURE ALOFT. AFTERNOON HEATING WILL ALLOW FOR SOME SHOWERS TO
DEVELOP OVER THE HIGHER TERRAIN TUESDAY. SUK

&&

.PREV DISCUSSION...
/ISSUED 540 PM MDT MON APR 20 2015/

TONIGHT THROUGH WEDNESDAY...QUIET WEATHER WILL CONTINUE ACROSS
NORTH CENTRAL AND SOUTHWEST MONTANA THROUGH TONIGHT, BUT
CONDITIONS WILL BECOME A BIT MORE UNSETTLED FOR TUESDAY THROUGH
WEDNESDAY. AS AN UPPER LEVEL RIDGE OF HIGH PRESSURE APPROACHES
MONTANA FROM THE WEST, THE RESULTING NORTHWESTERLY FLOW ALOFT WILL
BE SOMEWHAT DRY, ALLOWING THE SCATTERED CLOUDINESS TO MOSTLY
DISSIPATE OVERNIGHT. A WEAK DISTURBANCE WILL THEN MOVE THROUGH THE
RIDGE AND OVER THE AREA TUESDAY AFTERNOON AND EVENING AND COMBINE
WITH WEAKLY UNSTABLE AIR TO CAUSE A FEW WEAK ISOLATED SHOWERS AND
THUNDERSTORMS TO DEVELOP OVER THE MOUNTAINS. HOWEVER, THE FLOW
ALOFT WILL BE FAIRLY WEAK, WHICH WILL KEEP ANY STORMS THAT DEVELOP
FROM MOVING MUCH OFF THE MOUNTAINS. THE CLOUDS AND SHOWERS/STORMS
WILL DISSIPATE DURING THE EVENING AS THE RIDGE AXIS MOVES INTO THE
AREA. HOWEVER, AN UPPER LEVEL TROUGH OF LOW PRESSURE WITH AN
ASSOCIATED WEAK PACIFIC COLD FRONT WILL MOVE INTO THE AREA DURING
THE DAY ON WEDNESDAY. THIS WILL BRING A BETTER CHANCE FOR
ISOLATED TO SCATTERED SHOWERS AND WEAK THUNDERSTORMS TO THE
WESTERN HALF OF THE AREA BY AFTERNOON. THESE STORMS WILL BE HIT OR
MISS, BUT PRECIPITATION AMOUNTS OF UP TO 0.10 INCH ARE POSSIBLE
FROM ANY ONE STORM. THIS PERIOD WILL ALSO SEE WARMING TEMPERATURES
WITH HIGHS OF MID 60S TO MID 70S POSSIBLE ACROSS MUCH OF THE AREA
BY WEDNESDAY. OVERNIGHT LOWS WILL ALSO REMAIN MILD FOR MOST OF THE
REGION, EXCEPT FOR IN THE HIGHER VALLEYS.  COULSTON

WEDNESDAY NIGHT THROUGH MONDAY....THE SECOND HALF OF THE WEEK
WILL CONTINUE TO HAVE AN INCREASING CHANCE OF SHOWERS AS THE
AIRMASS TRANSITIONS FROM THE HIGH PRESSURE RIDGE TO A LARGE SLOW
MOVING TROUGH. WHILE NO STRONG STORM SYSTEM IS EXPECTED TO MOVE
THROUGH THE AREA MID WEEK... THE ENHANCED INSTABILITY AHEAD OF
CLOSED LOW SYSTEM SHOULD ALLOW FOR BETTER CHANCES OF AFTERNOON
SHOWERS AND THUNDERSTORMS. BY THIS WEEKEND THE ADVANCING LOW
SHOULD MOVE TO ITS CLOSEST POINT TO THE AREA...HOWEVER MODEL
SOLUTIONS ARE NOT CONSISTENT IN HANDLING THIS LATE PERIOD SYSTEM.
HAVE KEPT POPS ABOVE CLIMATOLOGY FOR THIS BUT WILL WAIT FOR A
CONSENSUS BEFORE ATTEMPTING TO FORECAST THE TIMING AND LOCATION
OF THIS POTENTIAL SYSTEM. SUK

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  39  67  39  72 /   0   0  10  20
CTB  35  68  38  71 /   0   0  10  20
HLN  37  71  39  75 /   0  10  10  30
BZN  33  68  36  73 /   0  10  10  20
WEY  24  61  28  65 /   0  20  10  20
DLN  35  69  36  72 /   0  10  10  30
HVR  35  67  37  69 /   0   0   0  10
LWT  36  62  37  67 /   0  10  10  10

&&

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

$$

WEATHER.GOV/GREATFALLS



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