Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 032343
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
540 PM MDT MON AUG 3 2015

UPDATED AVIATION SECTION

.DISCUSSION...

TONIGHT THROUGH WEDNESDAY...A SHORTWAVE TROUGH CURRENTLY OVER THE
PACIFIC NORTHWEST AND NORTHERN GREAT BASIN WILL GRADUALLY MOVE
INTO WESTERN MONTANA TONIGHT AND THEN INTO CENTRAL MONTANA ON
TUESDAY. THIS WILL SPREAD A GOOD CHANCE FOR AT LEAST SCATTERED
SHOWERS AND THUNDERSTORMS FROM SOUTHWEST MONTANA INTO NORTH
CENTRAL MONTANA. STRONGER STORMS MAY PRODUCE GUSTY ERRATIC WINDS,
BUT RELATIVELY SLOW MOVEMENT OF THE STORMS MAY HELP THEM PRODUCE
BRIEF HEAVY RAINFALL. RELATIVELY WEAK WIND SHEAR WITH THIS SYSTEM
WILL LIMIT THE CHANCE FOR HAIL, BUT CANNOT RULE OUT A FEW OF THE
STRONGER STORMS PRODUCING VERY SMALL HAIL. A PACIFIC COLD FRONT
WILL ALSO ACCOMPANY THIS DISTURBANCE, WHICH WILL SHIFT THE BREEZY
SOUTHEAST WINDS AHEAD OF THE SYSTEM MORE WESTERLY BEHIND THE FRONT
BEGINNING LATE TONIGHT IN THE WEST AND SPREADING EAST ACROSS THE
AREA ON TUESDAY. MOST AREAS WILL ONLY RECEIVE GUSTS UP TO 30 MPH,
BUT GUSTS COULD REACH 45 MPH ALONG THE ROCKY MOUNTAIN FRONT.
CLOUDS, SHOWERS, STORMS AND WINDS WILL THEN DECREASE LATER
TUESDAY AFTERNOON INTO TUESDAY EVENING FROM THE WEST AS THE SYSTEM
EXITS AND WEAK HIGH PRESSURE ALOFT MOVES INTO THE AREA. HOWEVER,
ANOTHER SHORTWAVE TROUGH WILL MOVE INTO THE PACIFIC NORTHWEST ON
WEDNESDAY, AND THE RESULTING MOIST AND UNSTABLE SOUTHWESTERLY FLOW
ALOFT WILL BRING ANOTHER CHANCE FOR STORMS TO THE SOUTHERN HALF OF
THE FORECAST AREA. THIS SERIES OF DISTURBANCES WILL HELP KEEP
TEMPERATURES SLIGHTLY BELOW NORMAL THROUGH THE PERIOD.  COULSTON

WEDNESDAY NIGHT THROUGH MONDAY...MEDIUM RANGE MODELS REMAIN IN
RELATIVELY GOOD AGREEMENT THROUGH EARLY NEXT WEEK AND FORECAST
CONFIDENCE IS MODERATE. PERIOD STARTS OFF WITH SHORTWAVE ENERGY
ALOFT MOVING THROUGH MONTANA FOR SCATTERED SHOWERS AND
THUNDERSTORMS WEDNESDAY EVENING. AS THIS FEATURE MOVES EAST
CONDITIONS DRY OUT AS SHORTWAVE RIDGING DEVELOPS FOR FRIDAY INTO
EARLY SATURDAY. PROGRESSIVE FLOW ALOFT WILL THEN MOVE UPPER LEVEL
TROUGHING FROM THE WEST COAST INTO THE NORTHERN ROCKIES BY
SATURDAY EVENING FOR ANOTHER ROUND OF SCATTERED SHOWERS AND
THUNDERSTORMS OVER SOUTHWEST MONTANA WHILE DRIER CONDITIONS
CONTINUE ACROSS THE NORTH. UNSETTLED CONDITIONS LINGER INTO EARLY
NEXT WEEK BUT WIDESPREAD PRECIPITATION IS NOT ANTICIPATED.
TEMPERATURES WILL REMAIN NEAR SEASONAL AVERAGES THROUGH THE
MEDIUM RANGE PERIOD. MPJ

&&

.AVIATION...
UPDATED 2340Z.

VFR CONDITIONS ARE EXPECTED ACROSS THE AREA AT LEAST THROUGH THE DAY
ON TUESDAY, UNLESS OTHERWISE MENTIONED. ISOLATED SHOWERS AND
THUNDERSTORMS OVER SOUTHWEST MONTANA AHEAD OF A DISTURBANCE ALOFT
WILL INCREASE IN COVERAGE AND SPREAD NORTHEAST ACROSS NORTH CENTRAL
MONTANA THROUGH 15Z AS THE DISTURBANCE MOVES OVER THE AREA. ERRATIC
WIND GUSTS OF UP TO 35 KT ARE POSSIBLE WITH THE STORMS. BRIEF HEAVY
RAINFALL WITH ASSOCIATED MVFR CONDITIONS ARE POSSIBLE WITH SOME
STORMS, ESPECIALLY OVER THE EASTERN TERMINALS AFTER 15Z DUE TO A
MORE MOIST AIRMASS IN PLACE THERE. SHOWERS AND STORMS WILL DECREASE
FROM THE WEST AFTER 14Z AS THE DISTURBANCE BEGINS EXITING THE AREA.
A COLD FRONT WILL ALSO MOVE EAST THROUGH THE AREA AFTER 12Z,
SHIFTING WINDS MORE WESTERLY ACROSS THE AREA THROUGH 18Z.
DOWNSLOPING WIND GUSTS OF 25 TO 35 KT AT TIMES ALONG THE EAST SLOPES
OF THE ROCKIES WILL LIMIT THE CHANCE FOR SHOWERS/STORMS THERE AFTER
14Z.  COULSTON

&&

.FIRE WEATHER...

A DISTURBANCE WILL MOVE FROM OVER IDAHO MONDAY AFTERNOON ACROSS
WESTERN AND CENTRAL MONTANA THROUGH TUESDAY. THIS WILL SPREAD A
GOOD CHANCE OF AT LEAST SCATTERED SHOWERS AND A MIX OF WET AND
DRY THUNDERSTORMS OVER THE FIRE DISTRICTS THROUGH TUESDAY. THE
STRONGER AND DRIER STORMS MAY PRODUCE GUSTY ERRATIC WINDS AND WILL
INCREASE THE POTENTIAL FOR NEW FIRE STARTS. HOWEVER, THE
ADDITIONAL POTENTIAL FOR SLOWER MOVING STORMS THAT MAY PRODUCE
WETTING RAINS WILL LIKELY HINDER SIGNIFICANT SPREAD OF THESE
POSSIBLE NEW STARTS. WILL THEREFORE HOLD OFF ON ANY FIRE WEATHER
HIGHLIGHTS FOR NOW. BREEZY SOUTHEAST WINDS TODAY WILL ALSO SHIFT
MORE WESTERLY BEHIND A COLD FRONT ON TUESDAY. GUSTS WILL MOSTLY BE
UP TO 30 MPH, BUT GUSTS TO 45 MPH WILL BE POSSIBLE ALONG THE
ROCKY MOUNTAIN FRONT. HOWEVER, THE COOLER TEMPERATURES WILL KEEP
RELATIVE HUMIDITIES MOSTLY ABOVE 25 PERCENT. SO, WITH THESE
RELATIVELY HIGHER HUMIDITIES, AM AGAIN NOT ANTICIPATING A NEED FOR
ANY FIRE WEATHER HIGHLIGHTS. REGARDLESS, THE OVERALL SITUATION
WITH THUNDERSTORMS AND GUSTY WINDS WILL NEED TO BE MONITORED.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  64  82  57  83 /  10  30  20  30
CTB  61  84  51  82 /  20  20  10  10
HLN  59  84  55  81 /  20  40  20  40
BZN  57  83  53  78 /  30  50  30  40
WEY  45  73  44  71 /  50  50  30  40
DLN  54  82  52  75 /  50  30  20  40
HVR  60  81  56  85 /  10  60  20  20
LWT  59  77  55  81 /  20  60  20  40

&&

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

$$

WEATHER.GOV/GREATFALLS


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