Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 022355
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
555 PM MDT WED SEP 2 2015

UPDATED AVIATION SECTION

.DISCUSSION...
TONIGHT THROUGH FRIDAY NIGHT...RAIN SHOWERS WILL DEVELOP OVER THE
NORTHERN ROCKIES TONIGHT...AND SPREAD OVER THE ADJACENT PLAINS BY
THURSDAY MORNING. DURING THE DAY ON THURSDAY PRECIPITATION SHOULD
SPREAD OVER MOST OF NORTH CENTRAL MONTANA. A TROUGH OF LOW
PRESSURE ALONG THE WEST COAST WILL PUSH INLAND ON
THURSDAY...BRINGING A STRONG FLOW OF MOISTURE TO MONTANA. THIS
SYSTEM WILL BE THE BIG WEATHER MAKER FOR THE REST OF THIS WEEK AND
INTO THE WEEKEND. SHARPLY COOLER TEMPERATURES WILL ALSO ACCOMPANY
THIS CHANGE IN THE WEATHER. DETAILS OF EXACTLY HOW MUCH RAIN WILL
FALL...AND ALSO WHERE THE HEAVIEST AMOUNTS WILL BE ARE STILL A BIT
UNCERTAIN. THE CURRENT MODEL RUNS YET SHOW SOME DIFFERENCES IN THE
SPEED AND PLACEMENT OF VARIOUS FEATURES. EVEN SO, THIS DOES LOOK
LIKE A SIGNIFICANT RAIN PRODUCER FOR MOST OF SOUTHWEST AND NORTH
CENTRAL MONTANA. DB

SATURDAY THROUGH WEDNESDAY...A DEEP UPPER LEVEL LOW PRESSURE TROF
WILL MOVE OVER THE PACIFIC NORTHWEST SATURDAY AND THE ASSOCIATED
COLD FRONT WILL MOVE THROUGH CENTRAL MONTANA. WIDESPREAD
PRECIPITATION WILL CONTINUE BEHIND THE FRONT UNDER MOIST SOUTHWEST
FLOW ALOFT. WITH THE COLD AIR ALOFT CROSSING THE ROCKIES SATURDAY,
THE AIR MASS SHOULD BECOME SLIGHTLY UNSTABLE, ESPECIALLY ACROSS
THE SOUTHERN HALF OF THE CWA. THE GFS AND ECMWF HAVE BECOME MORE
SIMILAR...STILL DIFFERENCES IN PLACEMENT BUT THE TIMING LINES UP
BETTER. A CLOSED LOW WILL BE OVER SOUTHERN IDAHO SATURDAY NIGHT
AND MOVE OVER CENTRAL MONTANA BY MID-DAY SUNDAY. THE AIRMASS WILL
BEGIN TO DRY AS THE SYSTEM MOVES EAST SUNDAY AFTERNOON ALTHOUGH A
SHORTWAVE MOVING INTO THE TROF SUNDAY NIGHT WILL KEEP THE AIRMASS
MOIST AND UNSETTLED. THIS SHORTWAVE WILL MOVE EAST OF THE ZONES BY
LATE MONDAY AND THE CHANCE OF PRECIPITATION WILL DROP MONDAY
NIGHT. THE AIR MASS WILL REMAIN QUITE DRY THROUGH TUESDAY BUT A
SHORTWAVE WILL CROSS THE ROCKIES TUESDAY NIGHT. WITH NORTHWEST
FLOW ALOFT, THIS WILL BRING SOME INCREASED CHANCES OF
PRECIPITATION ALTHOUGH COLD FRONT LOOKS QUITE WEAK. TEMPERATURES
WILL BEGIN THE PERIOD WELL BELOW SEASONAL AVERAGES BEFORE RISING
BACK TO NEAR NORMALS SUNDAY. ZELZER

&&

.AVIATION...
UPDATED 2355Z.
SOUTHWEST FLOW ALOFT WILL CONTINUE AS AN UPPER LEVEL
DISTURBANCE APPROACHES MONTANA FROM THE WEST. PRECIPITATION WILL
DEVELOP OVER THE ROCKY MOUNTAINS BY MIDNIGHT AND SPREAD EAST ACROSS
THE PLAINS ON THURSDAY. VFR CONDITIONS PREVAIL WITH INCREASING MVFR
CONDITIONS ALONG THE ROCKY MOUNTAIN FRONT AFTER 06Z AND OVER THE
PLAINS AFTER 20Z DUE TO LOW CEILINGS AND PRECIPITATION.

&&

.FIRE WEATHER... RED FLAG WARNING FOR FIRE ZONES 115...117
AND 118.

BROAD SOUTHWEST FLOW ALOFT KEEPS THE REGION WARM AND DRY WITH
BREEZY DAYTIME WINDS. A PACIFIC WEATHER SYSTEM IN WASHINGTON AND
BRITISH COLUMBIA WILL MAKE SLOW EASTWARD PROGRESS. LEADING EDGE OF
SHOWERS FROM THIS SYSTEM MAY REACH THE ROCKY MTN FRONT BY THIS
EVENING, BUT MAIN MOISTURE PLUME WILL NOT ARRIVE UNTIL THURS. BEST
CHANCE FOR RAIN WILL BE ALONG THE ROCKY MTN FRONT EAST TO THE
LITTLE BELT MTNS WITH WETTING RAINS LOOKING MORE LIKELY IN THAT
AREA. PRECIPITATION WILL BE MORE SPOTTY WITH ONLY LIGHT AMOUNTS
(LESS THAN 0.1 INCH) FOR LOCATIONS EAST AND NORTH OF THE LITTLE
BELTS ON THURS. WARANAUSKAS/SUK

&&
.PRELIMINARY POINT TEMPS/POPS...
GTF  50  66  46  60 /  20  60  70  60
CTB  45  59  42  53 /  80  90  60  80
HLN  48  68  45  62 /  10  60  70  80
BZN  48  77  45  72 /  10  20  40  40
WEY  40  70  34  69 /  10  10  20  20
DLN  48  74  43  68 /  10  40  40  50
HVR  50  72  49  67 /  20  20  50  60
LWT  48  71  44  64 /  10  20  30  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR MTZ115-117-118.

&&

$$

WEATHER.GOV/GREATFALLS


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