Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 230120
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
720 PM MDT TUE JUL 22 2014

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH THURSDAY...
UPDATE...THREAT OF SEVERE WEATHER HAS SUBSIDED FOR THE EVENING
HOURS...HOWEVER SCATTERED THUNDERSTORMS REMAIN POSSIBLE ACROSS THE
REGION THROUGH THE REMAINDER OF THE REGION. DID MAKE SOME
ADJUSTMENTS TO TEMPERATURES BASED ON CURRENT TRENDS.          PROTON

PREVIOUS DISCUSSION...SCATTERED SHOWERS AND THUNDERSTORMS ARE DEVELOPING
ACROSS PORTIONS OF NORTHEAST MONTANA THIS AFTERNOON. SOME OF THE
STORMS MAY PROVIDE A HAIL THREAT...PARTICULARLY SOUTH OF THE
MISSOURI RIVER. DID INCLUDE SMALL HAIL AND GUSTY WIND WORDING INTO
THE GRIDS TO COVER THAT POTENTIAL. AN ISOLATED SEVERE THUNDERSTORM
IS ALSO POSSIBLE WITH SOME CAPE IN THE SOUTHEAST ZONES...THOUGH
SHEAR IS LACKING. THIS MAY SUPPORT MULTICELLULAR CONVECTION THAT
PULSES UP AND DOWN IN INTENSITY.

UPPER LEVEL RIDGE AXIS IS EXPECTED TO TRANSLATE EAST ON WEDNESDAY
AFTERNOON AS A TROUGH/CLOSED LOW DIGS INTO THE PACIFIC NORTHWEST.
AS THE UPPER FLOW SWITCHES TO THE SOUTHWEST ACROSS THE CWA ENOUGH
MOISTURE AND INSTABILITY MAY EXIST FOR A FEW STRONG TO SEVERE
THUNDERSTORMS. SOUTHEAST SURFACE WINDS AHEAD OF THE MAIN FRONTAL
SYSTEM APPROACHING FROM THE WEST WILL ALSO INCREASE AND SO DECIDED
TO ISSUE A LAKE WIND ADVISORY FOR WEDNESDAY AFTERNOON THROUGH MUCH
OF THE NIGHT. LOW RELATIVE HUMIDITY READINGS...GUSTY SHIFTING
WINDS...AND LIGHTNING FROM THUNDERSTORMS MAY ALSO PRODUCE A FIRE
WEATHER CONCERN. THIS CONCERN WILL BECOME EVEN MORE ELEVATED ON
THURSDAY. THIS IS WHEN THE COLD FRONT IS EXPECTED TO PASS ALLOWING
FOR SURFACE WINDS TO SWITCH TO A WESTERLY DIRECTION. SOME OF THE
GUIDANCE IS POINTING TO HIGHER WINDS THAN ARE PRESENTLY FORECAST
AND SO FUTURE SHIFTS WILL NEED TO KEEP THIS IN MIND. MAY NEED TO
KEEP WATCH ON PLACES LIKE MALTA SOUTH...SOUTH SAWMILL...ETC.

REGARDLESS...EXPECT EVEN HIGHER WINDS ON THURSDAY AND A LAKE WIND
ADVISORY WILL LIKELY AGAIN BE NEEDED. AS THE UPPER TROUGH BECOMES
NEGATIVELY TILTED ACROSS SOUTHERN ALBERTA AND WESTERN MONTANA
THURSDAY AFTERNOON...EXPECT NICE DIFFLUENT UPPER SOUTHWEST FLOW
WHICH WILL CREATE UPPER LEVEL DYNAMIC SUPPORT FOR SEVERE WEATHER
POTENTIAL. MALIAWCO

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY...
THE CHANGES IN THE EXTENDED WERE FOCUSED ON FRIDAY AND THE
WINDS...WEATHER AND SKY COVER. THE GFS AND ECMWF ARE NOT IN GOOD
AGREEMENT WITH THE TIMING OF THE LOW AND THE PLACEMENT OF STORMS.
WE DIDN`T GET THE 12Z EC IN YESTERDAY AND IT IS NOT IN YET EITHER. FRANSEN
DUE TO THE IMPACT OF A STRONG SOMEWHAT NEGATIVELY TILTED UPPER LOW
MOVING INTO CANADA JUST NORTH OF MONTANA...POSSIBLY SEVERE CONVECTION
IS EXPECTED TO BE ONGOING AT THE BEGINNING OF THE LONG TERM
FORECAST THURSDAY NIGHT. GFS SHOWS A 75KT 500MB SPEED MAX ROUNDING
THE BOTTOM OF THE LOW THURSDAY NIGHT. THIS DYNAMIC WILL SUPPORT
STRONG QG FORCING OVER EASTERN MT AS WELL AS GENERATE STRONG DEEP
LAYER SHEAR.

SURFACE TROUGH AHEAD OF THE SYSTEM WILL BE CO-LOCATED WITH A
DRYLINE AND WILL BE MOVING INTO NORTH DAKOTA BY THURSDAY NIGHT
WITH STORMS EXPECTED TO HAVE FORMED ALONG AND AHEAD OF THE
DRYLINE. THERE IS STILL SOME UNCERTAINTY AS TO THE LOCATION AND
TIMING OF MOVEMENT OF THE DRYLINE...BUT IT IS ANTICIPATED THAT
EASTERN PARTS OF THE CWA WILL HAVE CONVECTION MOVING EASTWARD OUT
OF THE AREA BY THURSDAY NIGHT...PER SPC DAY3 OUTLOOK. COMBINATION
OF SHEAR AND INSTABILITY IS QUITE GOOD WITH FORECAST SOUNDINGS
SHOWING 2000 TO 3000 J/KG OF CAPE AND 45KTS OF BULK SHEAR.
SOMEWHAT LARGE DEWPOINT DEPRESSIONS AND PWAT VALUES BELOW 1 INCH
SUGGEST THE POSSIBILITY OF LOW PRECIPITATION SUPERCELLS WITH LARGE
HAIL AND MICROBURSTS POTENTIALLY THE MAIN RISKS. THE MAXIMUM CAPE
IS ALSO AROUND THE -20C LEVEL IN FORECAST SOUNDINGS...ENHANCING
HAIL GROWTH.

FOLLOWING PASSAGE OF THE THURSDAY NIGHT SYSTEM...THERE WILL ONLY
BE AN OUTSIDE CHANCE SATURDAY FOR A SHOWER IN THE EXTREME
NORTHEAST PART OF THE CWA ON THE BACK SIDE OF THE UPPER LOW AS IT
TAKES A TURN AN DIGS SOUTHEAST FROM MANITOBA TOWARDS IOWA. FROM
SATURDAY NIGHT ONWARD...RIDGE GROWS OVER THE GREAT DIVIDE LEADING
TO BENIGN WEATHER WITH CLEAR SKIES...WARM TEMPERATURES...AND LIGHT
WINDS THROUGH TUESDAY. THERE IS PRETTY STRONG MODEL AGREEMENT ON
THE PRESENCE OF THE WESTERN US RIDGE ALL THE WAY THROUGH TUESDAY.

MARTIN

&&

.AVIATION...

PREVAILING CONDITIONS WILL BE VFR. ANY REMAINING RAIN SHOWERS WILL
DIMINISH THROUGH THE NIGHT ACROSS THE REGION AND WILL LIKELY NO
LONGER AFFECT ANY OF THE TAF SITES TONIGHT. LIGHT NORTHERLY OR NORTHEASTERLY
WINDS ARE IN STORE THROUGH THE MORNING HOURS...FOLLOWED BY AN
INCREASE FROM THE SOUTHEAST....UP TO 25 KTS AFTER 15Z. BMICKELSON


&&

.FIRE WEATHER...
ISSUING A FIRE WEATHER WATCH FOR OUR WESTERN FIRE WEATHER ZONES
FROM NOON ON THURSDAY THROUGH MIDNIGHT THU/FRI. LOW RH`S...STRONG
WINDS AND THE POTENTIAL FOR DRY LIGHTNING ARE THE REASONS FOR IT.

A LOW PRESSURE SYSTEM WILL STRENGTHEN FROM ACROSS THE LEE SIDE OF
THE CANADIAN ROCKIES SOUTHWARD INTO THE GREAT BASIN. A STRONG
SOUTHEASTERLY FLOW IS IN STORE DURING THE DAY ON WEDNESDAY FOR
MOST OF NORTHEAST MONTANA WILL LIGHTER WINDS IN CENTRAL MONTANA
NEAR THE CENTER OF THE LOW. THE BEST POTENTIAL FOR THUNDERSTORMS
WILL BE WEST OF GLASGOW/WINNETT AREAS ON WEDNESDAY AFTERNOON AND
THEN EVENTUALLY MOVING EASTWARD OVERNIGHT...BUT THE MOISTURE DOESN`T
LOOK REALLY GOOD WITH THE STORMS AND IT WILL BE PRETTY HIT AND
MISS.

BY THURSDAY MORNING THE LOW PRESSURE SYSTEM WILL SLOWLY DRAG A
COLD FRONT ACROSS THE AREA. NORTHWEST WINDS WILL INCREASE BEHIND
THAT FRONTAL PASSAGE AND WIND SPEEDS FROM 15 TO 30 MPH WITH HIGHER
GUSTS CAN BE EXPECTED. MUCH DRIER AIR WILL ALSO COME INTO THE
AREA BRINGING RH`S DOWN INTO THE TEENS SOUTH OF HIGHWAY 2 AND
WEST OF GLASGOW/JORDAN. HUMIDITY RECOVERIES ARE NOT EXPECTED TO BE
VERY HIGH IN THAT AREA EITHER. WHILE THE GOING FORECAST HAS
RECOVERIES INTO THE 55 TO 70 PERCENT RANGE SOME OF THE MODELS ARE
SHOWING EVEN LOWER THAN THAT...AND IT WILL BE WORTH KEEPING AN EYE
ON IT. SOME MORE THUNDERSTORMS ARE POSSIBLE AGAIN DURING THE DAY
THURSDAY AND EVENING AGAIN BUT THE MODELS ARE NOT IN GOOD
AGREEMENT WITH TIMING AND LOCATION. THEY DO SHOW THAT ANY STORMS
IN MONTANA WOULD BE ON THE DRIER SIDE OF THINGS AGAIN.

WINDS DIE DOWN AFTER MIDNIGHT ON THU/FRI BUT THEY DO COME UP AGAIN
FROM THE WEST AGAIN ON FRIDAY...MOSTLY NORTH OF THE LAKE/MISSOURI
RIVER. RH`S ARE A BIG HIGHER THOUGH SO FOR THAT REASON HAVE OPTED
TO EXPIRE THE WATCH AT 06Z BUT IT MAY NEED TO BE EXPANDED
DEPENDING ON OBSERVED CONDITIONS THURSDAY.  FRANSEN

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
FIRE WEATHER WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY
EVENING FOR MTZ134>137.

LAKE WIND ADVISORY FROM NOON WEDNESDAY TO 4 AM MDT THURSDAY FOR
FORT PECK LAKE FOR CENTRAL AND SOUTHEAST PHILLIPS...CENTRAL AND
SOUTHERN VALLEY...GARFIELD...MCCONE...PETROLEUM.

&&

$$

WEATHER.GOV/GLASGOW




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