Special Weather Statement, NWS Glasgow, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
236 PM MDT SAT AUG 3 2013

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH MONDAY...
UPPER LEVEL SHORTWAVE TROUGH IS MOVING ACROSS CENTRAL MONTANA THIS
AFTERNOON. THUNDERSTORMS...SOME SEVERE HAVE DEVELOP AHEAD OF THIS
TROUGH. AIRMASS IN CENTRAL AND EASTERN MONTANA IS VERY UNSTABLE
WITH LIFTED INDICIES NEAR -4 AND CAPE 1000 TO 1500 J/KG. THE WAVE
AND STORMS WILL MOVE EAST INTO EASTERN MONTANA DURING THE LATE
AFTERNOON AND EARLY EVENING. EXPECT SCATTERED TO NUMEROUS
THUNDERSTORMS THIS EVENING EXTENDING INTO THE OVERNIGHT HOURS
MAINLY IN THE EAST.

THE WAVE WILL MOVE TO THE EAST OVERNIGHT AND SOMEWHAT DRIER
AIRMASS WILL MOVE INTO THE AREA FOR SUNDAY. ENOUGH INSTABILITY
LINGERS FOR A SLIGHT CHANCE OF THUNDERSTORMS.
UPPER RIDGE BRIEFLY EXTENDS INTO THE NORTHERN ROCKIES SUNDAY NIGHT
AND MONDAY BEFORE THE STRENGTHENING HUDSON BAY LOW COMES TO
DOMINATE OVER CENTRAL CANADA AND THE NORTHERN PLAINS. COLD FRONT
PRESSES SOUTH FROM CANADA IN THE AFTERNOON WITH A CHANCE OF
THUNDERSTORMS. FORRESTER

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...

GIVEN THE RECENT WET MODEL BIAS...I FELT IT WAS PRUDENT TO CUT
BACK POPS...ESPECIALLY WHERE RECENT MODEL RUNS HAVE SHOWN A DRY
CONSENSUS. MOST OTHER ADJUSTMENTS MADE TO THE GRIDS WERE MINOR IN
NATURE AND REFLECTED AN ALIGNMENT WITH RECENT MODEL RUNS...ETC.

LATEST MODEL DEPICTIONS OF THE MID-WEEK ARCTIC LOW SHOW A MINIMAL
IMPACT TO OUR CWA...POSSIBLY A WEAK COLD FRONT DROPPING
TEMPERATURES BY 5 TO 10 DEGREES FOR TUESDAY AND WEDNESDAY. BMICKELSON

PREVIOUS LONG TERM DISCUSSION...THE OVERALL SYNOPTIC PATTERN
ACROSS THE CONUS CONSISTS BROADLY OF AN UPPER TROUGH ACROSS THE
NORTHEAST...A RIDGE ACROSS THE SOUTHERN U.S. THAT OCCASIONALLY
PUSHES NORTH INTO THE UPPER MIDWEST...AND ANOTHER LARGE UPPER
TROUGH OVER THE PACIFIC. THIS PATTERN LOOKS TO REMAIN FAIRLY
STATIC THROUGHOUT THE EXTENDED PERIOD STARTING MONDAY NIGHT ALL
THE WAY INTO NEXT WEEKEND. TEMPERATURE TRENDS WILL DEPEND UPON
MOVEMENT OF THESE OVERALL FEATURES. PRECIPITATION CHANGES WILL
DEPEND UPON TRACK/TIMING OF SHORTWAVE FEATURES PROPAGATING THROUGH
THE FLOW ALOFT.

HAVING SAID ALL THAT...MONDAY NIGHT THROUGH TUESDAY NIGHT WILL
PLACE NORTHEAST MONTANA IN NORTHWEST FLOW ALOFT WITH THE UPPER
RIDGE TO THE WEST AND A CLOSED LOW TO THE NORTHEAST. THE 03/00Z MODEL
SUITE CONTINUES TO EJECT SHORTWAVE ENERGY ACROSS THE CWA WITH A
SURFACE COLD FRONT AND SO WILL INCREASE TO CHANCE POPS...ESPECIALLY
IN THE NORTHERN ZONES WHERE BEST DYNAMIC SUPPORT WILL BE.

WEDNESDAY THROUGH THURSDAY NIGHT...MODEL GUIDANCE CONTINUES TO KEEP
NORTHEAST MONTANA ON THE COLDER SIDE OF A THERMAL BOUNDARY WITH
850MB TEMPERATURES COOLING INTO THE SINGLE DIGITS IN THE FAR
NORTHEASTERN ZONES BY MIDWEEK. THIS IS SUPPORTIVE OF TEMPERATURES
WELL BELOW SEASONAL NORMALS FOR EARLY AUGUST. MODELS SHOW
DISAGREEMENT ON HANDLING OF WEAK DISTURBANCES IN THE NORTHWEST
FLOW ALOFT BUT GIVEN A CONTINUATION OF AN ACTIVE PATTERN WILL
MAINTAIN AT LEAST SLIGHT CHANCE POPS GOING ACROSS MUCH OF THE CWA.

FRIDAY AND BEYOND...RIDGE AXIS ACROSS WESTERN/CENTRAL MONTANA MAY
TRANSLATE EASTWARD AND OVER NORTHEAST MONTANA. THIS WOULD SUPPORT
LARGE SCALE SUBSIDENCE OVER THE CWA AND WITH RISING HEIGHTS A
GRADUAL WARMING TREND MAY INITIATE. AFTER A FEW MORE RUNS OF THE
MODELS BETTER CONTINUITY SHOULD PROVIDE BETTER CONFIDENCE ON THIS
AS IT GETS A BIT CLOSER IN TIME. FOR NOW DID ALLOW DAYTIME HIGHS
ACROSS NORTHEAST MONTANA TO FINALLY REACH THE UPPER 70S TO LOWER 80S
AGAIN IN MOST PLACES BY NEXT WEEKEND. MALIAWCO

&&

.AVIATION...

WHILE VFR CONDITIONS WILL PREVAIL FOR MOST OF THE TAF CYCLE FOR
MOST OF THE TAF SITES TODAY...STRONG TO SEVERE THUNDERSTORMS WILL
FORM AND SPREAD ACROSS THE REGION LATER THIS AFTERNOON AND
EVENING. AT THIS TIME IT SEEMS KGDV WILL MOST LIKELY BE IMPACTED
WITH STRONG WINDS AND VLIFR CONDITIONS SOMETIME BETWEEN 02Z AND
05Z TONIGHT. ALL REMAINING TAF SITES WILL LIKELY EXPERIENCE VCTS
AND MAYBE MVFR CEILINGS FROM 23Z TO 05Z. AMENDMENTS WILL BE
NECESSARY TONIGHT. VFR CONDITIONS WILL RETURN WITH SOME LINGERING
SCT CLOUDS AROUND THE AREA TOWARD THE END OF THIS TAF PERIOD.
BMICKELSON

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

WEATHER.GOV/GLASGOW

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GLASGOW MT
338 AM MDT SAT AUG 3 2013

MTZ016>027-059>062-040945-
CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-
DANIELS-SHERIDAN-WESTERN ROOSEVELT-PETROLEUM-GARFIELD-MCCONE-
RICHLAND-DAWSON-PRAIRIE-WIBAUX-NORTHERN PHILLIPS-
SOUTHWEST PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT-
338 AM MDT SAT AUG 3 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MONTANA.

.DAY ONE...TODAY AND TONIGHT

AN UPPER SYSTEM WILL MOVE ACROSS THE STATE TODAY...PRODUCING
THUNDERSTORMS ACROSS NORTHEAST MONTANA IN THE AFTERNOON AND
EVENING. SOME OF THESE STORMS MAY BECOME SEVERE WITH LARGE HAIL
AND DAMAGING WINDS. HEAVY RAIN IS ALSO POSSIBLE.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

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