Area Forecast Discussion
Issued by NWS Great Falls, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KTFX 280609
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1205 AM MDT FRI AUG 27 2015

.DISCUSSION...

ONLY MINOR UPDATES TO THE FORECAST THIS EVENING. THUNDERSTORM
ACTIVITY HAS DECREASED ACROSS SOUTHWEST MONTANA, AND NEVER
DEVELOPED ACROSS CENTRAL MONTANA (LIKELY DUE TO THE SMOKE KEEPING
THE AIRMASS FROM BECOMING TOO UNSTABLE). HAVE THEREFORE MOSTLY
REMOVED THUNDERSTORM MENTION, EXCEPT FOR SCATTERED POPS BETWEEN
BUTTE AND BOZEMAN TO ACCOUNT FOR A WEAKENING STORM MOVING THROUGH
THAT AREA. HAVE ALSO DECREASED CLOUD COVER FROM MOSTLY CLOUDY TO
PARTLY CLOUDY, EXCEPT FOR WHERE THE WEAKENING STORM IS. OTHERWISE,
THE GOING FORECAST FOR TEMPERATURES AND WINDS APPEAR TO BE IN
GOOD SHAPE.  COULSTON

&&

.AVIATION...
UPDATED 06Z.

VFR TO MVFR CONDITIONS ARE EXPECTED ACROSS THE AREA AS SMOKE
CONTINUE TO CREATE OBSCURATIONS CEILING GROUPS THAT BORDER ON
LIMITING FLIGHT CATEGORIES. A FEW THUNDERSTORMS MAY DEVELOP AGAIN
OVER SOUTHWEST MONTANA DURING THE AFTERNOON HOURS ON
FRIDAY...HOWEVER DIRECT IMPACT TO ANY TAF SITE IS NOT ANTICIPATED.
SOME GUSTY WINDS COULD DEVELOP NEAR ANY STORM THAT DOES OCCUR. SUK

&&

.FIRE WEATHER...

SATURDAY WILL BE A NEAR CRITICAL FIRE WEATHER DAY AS AN
APPROACHING DRY COLD FRONT WILL CREATE THE POTENTIAL FOR GUSTY
WINDS WITH LITTLE TO NO MOISTURE ASSOCIATED WITH THE FRONT.
HUMIDITY WILL FALL INTO THE 15 TO 25 PERCENT RANGE, AS GUSTY
SOUTHERLY WINDS ON SATURDAY SHIFT MORE WESTERLY BEHIND THE COLD
FRONT BY EARLY SATURDAY EVENING. HAVE THEREFORE ISSUED A FIRE
WEATHER WATCH FOR SATURDAY AFTERNOON AND EVENING FOR FIRE WEATHER
ZONES 112, 114, 116, 117, 118, WHICH INCLUDES THE ROCKY MOUNTAIN
FRONT, THE ADJACENT PLAINS, AND AREAS SOUTH TO HELENA.
SUK/COULSTON

&&

.PREV DISCUSSION...
/ISSUED 550 PM MDT THU AUG 27 2015/
TONIGHT THROUGH SATURDAY...GUSTY SOUTHWEST WINDS AND LOW HUMIDITY
ARE CAUSING CRITICAL FIRE WEATHER CONDITIONS AT SOME LOCATIONS
THIS AFTERNOON ALONG THE ROCKY MOUNTAIN FRONT AND ADJACENT PLAINS.
THE RED FLAG WARNING WILL CONTINUE FOR FIRE WEATHER ZONE 112
THROUGH THIS EVENING. SMOKE HAS THICKENED THIS AFTERNOON AND IS
LIKELY TO PERSIST WITH DEEP WEST-SOUTHWESTERLY FLOW. SCATTERED
SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP THIS EVENING
ACROSS CENTRAL AND SOUTHWEST MONTANA. SOME OF THIS ACTIVITY COULD
PRODUCE ERRATIC GUSTY WINDS AND FIRE STARTS FROM LIGHTNING. HEAVY
RAIN IS POSSIBLE UNDER STRONGER STORMS FOR THE SOUTHWEST...WHILE
OTHERS REMAIN WEAK WITH ONLY LIGHT PRECIPITATION. CONDITIONS
STABILIZE ON FRIDAY WITH SHORTWAVE RIDGING AND DRY AIR ALOFT
PASSING THROUGH THE REGION. DRY AND WARM CONDITIONS WILL CONTINUE
THROUGH THE DAY SATURDAY WITH WINDS INCREASING AHEAD OF A DRY COLD
FRONT THAT WILL MOVE THROUGH THE AREA BRINGING GUSTY WINDS AND LOW
HUMIDITY VALUES AHEAD OF THE FRONT. THE LACK OF MOISTURE WITH THE
FRONTAL PASSAGE WILL LIMIT SHOWER AND THUNDERSTORM
DEVELOPMENT...BUT THERE IS ALMOST NO SIGNIFICANT PRECIPITATION
EXPECTED WITH THIS FRONTAL PASSAGE. ADDITIONAL FIRE WEATHER
HIGHLIGHTS MAY BECOME NECESSARY AS THIS FRONT APPROACHES. NUTTER

SATURDAY NIGHT THROUGH THURSDAY...MEDIUM RANGE MODEL SOLUTIONS
REMAIN IN RELATIVELY GOOD AGREEMENT THROUGH MUCH OF THE FORECAST
PERIOD. HOWEVER, BOTH HAVE TRENDED TOWARD A SOMEWHAT DRIER FORECAST
SO HAVE AGREED WITH SURROUNDING OFFICES TO PULL BACK POPS A BIT. AS
NOTED YESTERDAY, THE MAIN PLAYERS IN THE FORECAST ARE AN UPPER LEVEL
TROUGH OVER THE GULF OF ALASKA/SOUTHEAST ALASKA AND RIDGING OVER THE
HIGH PLAINS. MONTANA REMAINS BENEATH AN SOMEWHAT UNSTABLE SOUTHWEST
FLOW ALOFT THROUGH THE PERIOD AND BOTH MODELS ATTEMPT TO SLOWLY
PROGRESS THE UPPER TROUGH INTO WESTERN CANADA. THE ECMWF IS A BIT
MORE AGGRESSIVE WITH THIS THAN THE GFS BUT IT APPEARS THAT BOTH
MODELS MAY BE OVERDOING HOW FAR EASTWARD THIS FEATURE CAN MOVE GIVEN
THE UPPER RIDGE AND THE VERY WARM LATE SUMMER TEMPERATURES THAT WILL
TEND TO SUPPORT RIDGE STABILITY OVER THE PLAINS. HAVE MADE ONLY
MINOR CHANGES TO THE GOING FORECAST PACKAGE, MAINLY TO EASE BACK ON
POPS AND SURFACE WIND SPEEDS. TEMPERATURES FROM MONDAY ONWARD ARE
EXPECTED TO BE NEAR OR SLIGHTLY ABOVE SEASONAL AVERAGES AS GUIDANCE
FROM BOTH MODELS SUPPORT COOLER TEMPERATURES THAN THOSE OF THIS
WEEK. MPJ

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  58  90  62  90 /   0   0  10  10
CTB  54  88  56  85 /   0  10  10  20
HLN  52  90  55  90 /  10  10  10  20
BZN  50  87  53  91 /  30   0  10  10
WEY  37  79  41  81 /  30   0  10  20
DLN  49  86  53  87 /  10  10  10  10
HVR  57  90  58  94 /   0   0   0  10
LWT  56  88  60  93 /  10   0   0  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
FIRE WEATHER WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY
EVENING FOR MTZ112-114-116>118.

&&

$$

WEATHER.GOV/GREATFALLS



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.