Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 312316
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
516 PM MDT FRI JUL 31 2015

.DISCUSSION...

TONIGHT THROUGH SUNDAY...AN UPPER LEVEL RIDGE OF HIGH PRESSURE
WILL PERSIST OVER THE NORTHERN ROCKIES AND MT THROUGH THIS WEEKEND
WHILE A THERMAL TROUGH OF LOW PRESSURE CENTERED OVER THE GREAT
BASIN GRADUALLY DEEPENS. THIS WILL MAINTAIN VERY WARM AND DRY
CONDITIONS THROUGH THE PERIOD WITH WARMEST AFTERNOON TEMPERATURES
AND LOWEST AFTERNOON HUMIDITY LIKELY TO OCCUR TOMORROW. SKIES
WILL BE GENERALLY CLEAR WITH JUST A FEW AFTERNOON CUMULUS OVER THE
MTNS. A VERY WEAK UPPER LEVEL DISTURBANCE MOVING ACROSS THE
NORTHERN TIER OF THE FORECAST AREA SATURDAY AFTERNOON WILL BRING
A SLIGHT INCREASE IN WINDS ALOFT WITH A PERIOD OF BREEZY WINDS
POSSIBLE SATURDAY AFTERNOON AND EVENING. THIS COMBINED WITH HOT
AND DRY CONDITIONS WILL PRODUCE FIRE WEATHER CONCERNS,
PARTICULARLY FOR WESTERN PORTIONS OF NORTH CENTRAL MT SATURDAY
AFTERNOON. HOENISCH

SUNDAY NIGHT THROUGH FRIDAY...SUNDAY NIGHT AND MONDAY A STRONG UPPER
RIDGE WILL BE OVER THE FORECAST AREA. A WEATHER DISTURBANCE ALOFT
WILL BE APPROACHING FROM THE SOUTHWEST ON MONDAY AND MONSOONAL
MOISTURE WILL INCREASE AHEAD OF THE DISTURBANCE. SCATTERED
THUNDERSTORMS WILL DEVELOP FROM THE ROCKY MOUNTAIN FRONT INTO
SOUTHWEST MONTANA MONDAY AFTERNOON THEN SPREAD NORTHEAST MONDAY
NIGHT INTO TUESDAY. THE GFS MODEL CONTINUES TO BE WEAKER AND FASTER
WITH THE WEATHER DISTURBANCE ALOFT THAN THE ECMWF MODEL. OTHER
DISTURBANCES EMBEDDED IN A SOUTHWEST FLOW ALOFT THROUGH THE END OF
THE WEEK WILL AIDE IN BRINGING ADDITIONAL THUNDERSTORMS TO THE
FORECAST AREA THROUGH THE WEEK. THE GFS AND ECMWF MODELS ARE IN A
LITTLE BETTER AGREEMENT WITH THEIR PRECIPITATION FORECASTS THAN
EARLIER RUNS SO HAVE RAISED THE CHANCES OF PRECIPITATION A BIT FROM
THOSE OF THE INHERITED FORECAST. THE STRONG UPPER RIDGE WILL RESULT
IN HIGHS IN THE UPPER 80S TO LOWER 90S MONDAY BUT THE UPPER RIDGE
WILL THEN WEAKEN SO TUESDAY WILL USHER IN A SPELL OF COOLER
TEMPERATURES. BLANK

&&

.AVIATION...
UPDATED 0000Z.

UPPER LEVEL HIGH PRESSURE OVER THE NORTHERN ROCKIES AND MT WILL
MAINTAIN DRY WESTERLY FLOW ALOFT WITH VFR CONDITIONS PERSISTING
THROUGH THE WEEKEND. SURFACE WINDS WILL REMAIN LIGHT THROUGH
SATURDAY MORNING AND GENERALLY AROUND 10 KTS OR LESS WITH AN
INCREASE IN WESTERLY SURFACE WINDS SATURDAY AFTERNOON. HOENISCH

&&

.FIRE WEATHER...
HOT AND DRY CONDITIONS WILL CONTINUE OVER THE REGION THROUGH
SUNDAY WITH WARMEST TEMPERATURES AND LOWEST AFTERNOON HUMIDITY
EXPECTED TO PEAK SATURDAY AFTERNOON. OVERNIGHT HUMIDITY RECOVERY
WILL BE POOR AT MID-SLOPE TO RIDGETOP LOCATIONS AS OVERNIGHT
INVERSIONS/THERMAL BELTS PERSIST. A DRY AND UNSTABLE AIRMASS
SATURDAY WILL RESULT IN HAINES INDEX VALUES OF 5 TO 6 ACROSS MOST
OF THE REGION. A VERY WEAK WEATHER DISTURBANCE ALOFT AND DEEP
MIXING WILL BRING A PERIOD OF BREEZY WINDS SATURDAY AFTERNOON AND
EVENING WITH GUSTS OF 20-25 MPH PRIMARILY EXPECTED OVER WESTERN
PORTIONS OF NORTH CENTRAL MT WHERE A FIRE WEATHER WATCH IS IN
EFFECT. A WEAK WEATHER SYSTEM MOVING INTO THE REGION FROM THE SW
WILL BRING A CHANCE FOR THUNDERSTORMS LATE MONDAY AND THE INCREASE
IN LIGHTNING AND POTENTIAL FOR GUSTY THUNDERSTORM WINDS FOLLOWING
THIS PERIOD OF VERY WARM AND DRY CONDITIONS MAY LEAD TO ADDITIONAL
FIRE WEATHER CONCERNS ON MONDAY. HOENISCH

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  59  97  60  93 /   0   0   0   0
CTB  58  94  57  92 /   0   0   0   0
HLN  57  98  60  98 /   0   0   0  10
BZN  52  94  54  94 /   0   0   0  10
WEY  40  84  43  86 /   0   0   0  10
DLN  51  92  55  92 /   0   0   0  10
HVR  57  94  56  91 /   0   0   0   0
LWT  55  92  57  90 /   0   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
FIRE WEATHER WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY
EVENING FOR MTZ112>115-117.

&&

$$

WEATHER.GOV/GREATFALLS



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