Special Weather Statement, NWS Great Falls, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
550 PM MDT TUE AUG 21 2012

.DISCUSSION...
THIS AFTERNOON THROUGH THURSDAY EVENING...STRONG HIGH PRESSURE RIDGE
THAT HAS BEEN OVER OUR REGION PAST FEW DAYS BRINGING THE HOT AND DRY
CONDITIONS HAS MOVED INTO ERN MT IN RESPONSE TO SHORTWAVE TROF
MOVING INLAND ALONG THE WA/OR COAST.  COLD FRONT ASSOCIATED WITH THE
PACIFIC TROF CURRENTLY LOCATED FROM THE LOWER ID PANHANDLE TO JUST
WEST OF MISSOULA AND INTO FAR NW GLACIER COUNTY.  CLUSTER OF
THUNDERSTORMS AHEAD OF THE FRONT PUSHED THRU GLACIER NP AROUND 1PM
WITH GUSTY OUTFLOW WINDS AND ARE NOW EXITING INTO NRN TOOLE COUNTY
AND FAR SOUTHERN ALBERTA.  SECOND CLUSTER OF STORMS IS CURRENTLY
DEVELOPING OVER BEAVERHEAD/MADISON COUNTIES.  AS THE FRONT CROSSES
THE MIDDLE/SRN PORTIONS OF THE CONTINENTAL DIVIDE AROUND 6PM...
EXPECT THUNDERSTORM COVERAGE TO INCREASE OVER CENTRAL/SOUTHWEST MT
THROUGH ABOUT 10 PM.  A FEW OF THESE CELLS MAY BECOME STRONG ENOUGH
TO PRODUCE OUTFLOW GUSTS OF 40-50 MPH AND SOME SMALL HAIL.  MOST OF
THE STRONGER CELLS SHOULD DISSIPATE TOWARD MIDNIGHT BUT SHOWERS WITH
A FEW WEAKER CELLS WILL CONTINUE OVER ERN PORTIONS OF THE COUNTY
WARNING AREA INTO WED MORNING.  PRECIPITATION SHOULD END FOR GOOD BY
MIDDAY WED AS THE TROF AXIS PASSES OVERHEAD.  HIGH PRESSURE RIDGING
RETURNS ON THURS THOUGH NOT AS STRONG AS EARLIER...SO WE WILL SEE
THE MOSTLY CLEAR SKIES BUT TEMPERATURES WILL NOT BE AS WARM AS SEEN
PAST FEW DAYS.  COOLER AIRMASS BEHIND THE FRONTAL SYSTEM WILL DROP
TEMPERATURES BACK INTO THE LOW-MID 80S TOMORROW BUT CLIMB BACK TO
THE MID-UPPER 80S ON THURS AS THE AIRMASS MODERATES FROM WARMING
SOUTHWEST FLOW ALOFT.
WARANAUSKAS

THURSDAY NIGHT THROUGH TUESDAY...CONFIDENCE IN THE FORECAST IS ON
THE LOW END LATER IN THE WEEKEND AND EARLY NEXT WEEK AS MODELS
DIFFER FROM ONE ANOTHER WITH THE UPPER AIR PATTERN AND EVEN FOR A
PARTICULAR MODEL..RUN-TO-RUN CONSISTENCE HAS ON OCCASION BEEN
POOR. AN UPPER TROUGH IS FORECAST TO SWING THROUGH THE FORECAST AREA
ON FRIDAY. THE ASSOCIATED COLD FRONT WILL MOVE THROUGH THE AREA LATE
THURSDAY INTO THURSDAY NIGHT. MODELS ARE DRY WITH THE FRONT AND
TROUGH THURSDAY NIGHT/FRIDAY WITH THE POSSIBLE EXCEPTION OF NEAR THE
CANADIAN BORDER. ALTHOUGH MODELS TEND TO KEEP PRECIPITATION JUST
NORTH OF THE BORDER THE ECMWF DOES HAVE PRECIPITATION FARTHER SOUTH.
HAVE ADDED A SLIGHT CHANCE OF SHOWERS TO THE ZONES BORDERING CANADA.
FARTHER SOUTH REMOVED THE MENTION OF PRECIPITATION OVER A PORTION OF
SOUTHWEST MONTANA AS MODELS INDICATE A DRY AIRMASS. LATE SATURDAY AN
UPPER RIDGE IS FORECAST TO DEVELOP OVER THE FORECAST AREA ACCORDING
TO THE ECMWF (EUROPEAN) AND GEM (CANADIAN) MODELS BUT THE GFS DOES
NOT DO THIS UNTIL SUNDAY. BY EARLY NEXT WEEK EXPECT SOUTHWEST FLOW
ALOFT OVER THE AREA. MODELS DIFFER WITH WEATHER DISTURBANCES
EMBEDDED IN THIS FLOW. ALTHOUGH MODELS WITH THE EXCEPTION OF THE GEM
ARE ON THE DRY SIDE..DID ADD A SLIGHT CHANCE OF SHOWERS TO THE
MOUNTAINS OF SOUTHWEST MONTANA. THE MAIN CHANGE TO INHERITED
TEMPERATURES WAS TO COOL HIGHS ON FRIDAY BEHIND THE COLD FRONT.
BLANK

&&

.AVIATION...
UPDATED 2341Z.
AN UPPER LEVEL SHORTWAVE WILL CROSS THE DIVIDE TONIGHT AND MOVE INTO
EASTERN MONTANA EARLY WEDNESDAY MORNING. AN ASSOCIATED COLD FRONT
WILL CROSS THE ROCKIES AND MOVE THROUGH THE ADJACENT PLAINS AFTER
MIDNIGHT. SCATTERED EVENING THUNDERSTORMS WILL MOVE EAST AND
NORTHEAST THROUGH THE EVENING. THE MAIN THREAT FROM THESE STORMS
WILL BE LIGHTNING AND GUSTY WINDS. MVFR CONDS ARE POSSIBLE NEAR
THUNDERSTORMS...ELSEWHERE VFR CONDS ARE EXPECTED THROUGH THE NEXT 24
HOURS.

&&

.FIRE WEATHER...
COLD FRONT APPROACHING FROM THE WEST TUES EVE WILL GENERATE
SCATTERED SHOWERS AND THUNDERSTORMS...A FEW OF WHICH MAY PRODUCE
GUSTY OUTFLOW WINDS OF 40 MPH OR GREATER. WITH MOST STORMS
EXPECTED TO PRODUCE MEASURABLE RAINFALL AND MATCHING HIGHER
HUMIDITIES...THREAT OF IGNITION STARTS FROM LIGHTNING SHOULD BE
SLIGHTLY REDUCED BUT GIVEN THE CURRENT WIDESPREAD DRY SURFACE
CONDITIONS THERE IS STILL DECENT POTENTIAL FOR SOME NEW STARTS WITH
TONIGHTS STORMS. COOLER TEMPERATURES TOMORROW WILL ALLOW AFTN
HUMIDITIES TO GENERALLY REMAIN IN THE UPPER TEENS TO UPPER 20S.
NEXT CHANCE FOR FIRE WEATHER CONCERNS COMES FRIDAY WHEN A SHARP
BUT DRY COLD FRONT SWEEPS ACROSS THE STATE ACCOMPANIED BY GUSTY
WINDS. THOUGH HUMIDITIES SHOULD INCREASE IN RESPONSE TO MUCH
COOLER TEMPERATURES...THEIR IMPACT MAY BE REDUCED BY THE STRONG
WINDS...THUS INCREASING THE POTENTIAL FOR CRITICAL FIRE WEATHER
CONDITIONS AND FIRE WEATHER HEADLINES.
WARANAUSKAS

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  59  85  53  87 /  50  10   0   0
CTB  53  81  47  80 /  60  10   0   0
HLN  57  85  53  88 /  50  20   0   0
BZN  51  85  46  88 /  30  20   0  10
WEY  41  77  36  78 /  30  10   0   0
DLN  50  80  47  83 /  50  10   0  10
HVR  59  87  51  89 /  50  20   0   0
LWT  55  82  50  86 /  30  30  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL MIDNIGHT MDT TONIGHT BEAVERHEAD...
JEFFERSON...MADISON.

&&

WEATHER.GOV/GREATFALLS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREAT FALLS MT
330 AM MDT TUE AUG 21 2012

MTZ008>015-044>055-220930-
BEAVERHEAD-NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL-
CASCADE-CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON-
TOOLE-LIBERTY-EASTERN PONDERA-BLAINE-
SOUTHERN ROCKY MOUNTAIN FRONT-EASTERN TETON-JUDITH BASIN-FERGUS-
JEFFERSON-BROADWATER-MEAGHER-GALLATIN-
330 AM MDT TUE AUG 21 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
MONTANA...NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA.

.DAY ONE...TODAY AND TONIGHT

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
557 PM MDT TUE AUG 21 2012

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0537 PM     TSTM WND GST     ULM                     47.43N 111.51W
08/21/2012  E55 MPH          CASCADE            MT   NWS EMPLOYEE

&&

UTTECH

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
611 PM MDT TUE AUG 21 2012

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0557 PM     TSTM WND GST     GREAT FALLS             47.50N 111.29W
08/21/2012  E55 MPH          CASCADE            MT   BROADCAST MEDIA

&&

UTTECH

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
614 PM MDT TUE AUG 21 2012

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0552 PM     TSTM WND GST     5 WSW GREAT FALLS       47.47N 111.38W
08/21/2012  M51 MPH          CASCADE            MT   ASOS

&&

UTTECH

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREAT FALLS MT
622 PM MDT TUE AUG 21 2012

MTZ012>014-049-220100-
CASCADE MT-CENTRAL AND SOUTHERN LEWIS AND CLARK MT-CHOUTEAU
MT-EASTERN TETON MT-
622 PM MDT TUE AUG 21 2012

...SIGNIFICANT WEATHER ADVISORY FOR EASTERN LEWIS AND CLARK...EXTREME
SOUTHEASTERN TETON...SOUTHWESTERN CHOUTEAU AND CASCADE COUNTIES UNTIL
700 PM MDT...

AT 621 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
A THUNDERSTORM OUTFLOW BOUNDARY ALONG A LINE EXTENDING FROM 11 MILES
WEST OF FORT BENTON TO 8 MILES NORTH OF WOLF CREEK...AND MOVING EAST
AT 30 MPH.

WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THESE STORMS.

* LOCATIONS IMPACTED INCLUDE...
   CARTER...
   CASCADE... FLOWEREE AND  ULM...
   BLACK EAGLE... CRAIG AND  GREAT FALLS...
   FORT BENTON AND  MALMSTROM AFB...
   SAND COULEE AND  TRACY...
   CENTERVILLE... STOCKETT AND  HIGHWOOD...

IF THREATENING WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A
STURDY BUILDING.

LAT...LON 4775 11036 4700 11143 4700 11154 4692 11154
      4691 11165 4689 11160 4682 11167 4717 11222
      4799 11098
TIME...MOT...LOC 0022Z 285DEG 25KT 4788 11087 4713 11206

COULSTON