Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 110311
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
911 PM MDT THU JUL 10 2014

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SATURDAY...
UPDATE...ADDED SMALL HAIL TO THE ZONES FOR THIS EVENING AS SMALL
HAIL HAS BEEN REPORTED NEAR VAL MARIE AND NORTH OF WHITEWATER THIS
EVENING. DID NOT CONTINUE IT AFTER MIDNIGHT WOULD EXPECT ANY
STORMS OVERNIGHT TO HAVE GUSTY WIND AND BRIEF HEAVY RAIN. REST OF
THE FORECAST ELEMENTS ARE IN GOOD SHAPE.    PROTON

PREVIOUS DISCUSSION...SYNOPTIC SET UP... A LARGE HOT HIGH PRESSURE DOME EXISTS
OVER THE INTERMOUNTAIN WEST AND ROCKY MOUNTAINS. TWO RIDGES EXTEND
UP FROM THIS DOME... ONE RUNS UP THROUGH WYOMING... THE DAKOTA...
AND MANITOBA WHILE THE OTHER RIDGE RUNS UP THROUGH BRITISH
COLUMBIA INTO EASTERN ALASKA. A LARGE TROUGH RESIDES OVER ALBERTA
AND SASKATCHEWAN WITH COOLER INFLUENCE REACHING OVER THE
INTERNATIONAL BORDER INTO NORTHERN MONTANA. FARTHER WEST... A
CLOSED LOW EXISTS OVER THE ALEUTIANS WITH A WEAK TROUGH EXTENDING
DOWN TO OFF THE COAST OF CALIFORNIA.

THIS AFTERNOON AND EVENING... CLEAR SKIES AND DRY CONDITIONS ARE
ANTICIPATED AS A COLD FRONT MOVES THROUGH THE AREA AND STABILIZES
OUT THE SURFACE LAYER. MEANWHILE... A SHORTWAVE DISTURBANCE WILL
MAKE ITS WAY ACROSS THE PACIFIC NORTHWEST.

FRIDAY MORNING... PAC NORTHWEST DISTURBANCE WILL HIT THE HIGH
PLAINS OFF THE FRONT RANGE AND FORM A FEW ISOLATED TO SCATTERED
SHOWERS AND THUNDERSTORMS. THESE ARE EXPECTED TO REACH PHILLIPS
AND PETROLEUM COUNTY BORDER AROUND MIDNIGHT AND THEN PASS OVER THE
REST OF THE CWA DURING THE MORNING HOURS.

FRIDAY AFTERNOON THROUGH SATURDAY... TROUGH TO THE NORTH WILL FORM
INTO A CLOSED LOW AND CONSISTENTLY DRAG DOWN COOLER AIR OVER THE
AREA. THIS AIR WILL IN CONFLICT WITH AN INTENSIFYING HEAT DOME
OVER THE INTERMOUNTAIN WEST. DUE TO THE COMPACT THERMAL GRADIENT
TEMPERATURES COULD EASILY SWING WARMER OR COOLER THAN ANTICIPATED
DURING THIS TIME. SO... HAVE GONE WITH A CENTER OF THE ROAD APPROACH.

GAH


.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
THE GOING FORECAST WAS IN OVERALL GOOD SHAPE...AND MODEL
CONSISTENCY REMAINS GOOD THROUGHOUT THE EXTENDED. WITH NO BIG
SYSTEMS ON THE HORIZON...THE ONLY CHANGE WAS TO CONTINUE TO TREND
THE FORECAST TOWARD THE MODEL CONSENSUS WHICH IS A BIT COOLER ON
MONDAY AND TUESDAY AS A COOL UPPER TROUGH REMAINS OVERHEAD.
OTHERWISE NO OTHER NOTEWORTHY CHANGES WERE MADE. GILCHRIST

PREVIOUS LONG TERM DISCUSSION...NORTHEAST MONTANA REMAINS SETUP
BETWEEN A PERSISTENT CLOSED LOW NEAR HUDSON BAY AND AN UPPER RIDGE
OVER THE WEST ANCHORED BY DESERT HIGH PRESSURE ACROSS THE GREAT
BASIN. THE NORTHWEST FLOW ALOFT SATURDAY NIGHT AND SUNDAY IS A DRY
PATTERN. THE MAIN QUESTION WILL BE TEMPERATURE. BOTH THE GFS AND
THE EC HAVE NORTHEAST MONTANA ON THE BOUNDARY BETWEEN THE NORTHERN
COOLER AIR AND THE HOT SOUTHWEST AIR. GUIDANCE SUGGESTS CLOSE TO
NORMAL TEMPERATURES FOR SUNDAY. HOWEVER ON MONDAY AN EMBEDDED
DISTURBANCE KNOCKS DOWN THE THE RIDGE AND LOCAL THICKNESS HEIGHTS
DROP SIGNIFICANTLY. THE WIND PROFILE ALOFT TO THE SURFACE IS FOR
NORTHERLY WIND. SO GUIDANCE SUGGESTS BELOW AVERAGE TEMPERATURES
FOR MONDAY.

BY TUESDAY THE EMBEDDED DISTURBANCE MOVES SOUTHEAST OUT OF MONTANA
TO ALLOW THE UPPER RIDGE TO REBOUND. THIS TAKES ANY STORM ENERGY
AWAY FROM EASTERN MONTANA AND WILL ONCE AGAIN ESTABLISH A DRY
NORTHWEST FLOW ALOFT PATTERN FOR WEDNESDAY AND THURSDAY.

OVERALL THE MODELS ARE IN AGREEMENT WITH A MOSTLY DRY PERIOD WITH
TEMPERATURES THAT DO NOT DEVIATE FAR FROM NORMAL. THERE WILL BE NO
PERIODS OF STRONG WIND. CONVECTIVE PARAMETERS WILL ALSO REMAIN
WEAK FOR LIMITED SHOWER THUNDERSTORM ACTIVITY. AS SUCH...POP GRIDS
ARE DRY. SCT


&&

.AVIATION...
FLIGHT CATEGORY: MAINLY VFR. ISOLATED IFR POSSIBLE.

OVERNIGHT SHOWERS AND THUNDERSTORMS: A WEAK DISTURBANCE IS
ANTICIPATED TO PASS OVER THE AREA AFTER MIDNIGHT AND WILL GENERATE
SCATTERED SHOWERS AND THUNDERSTORMS AGAIN WITH AN ISOLATED CHANCE
AT IFR DUE TO VISIBILITY REDUCTIONS FROM BRIEF INTENSE SHOWERS.
CHANCES ARE BELOW 50 PERCENT AND HAVE THEREFORE GONE WITH VCSH
UNTIL THE STORMS DEVELOP LATER TONIGHT.

AREA WINDS: VEERING TO THE NORTHWEST AND INCREASE 10 TO 20 KTS THIS
AFTERNOON... THEN CALMING TO LESS THAN 10 KTS AND VEERING FARTHER
TO THE NORTH TO NORTHEAST AFTER SUNSET.

GAH


&&

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

&&

$$

WEATHER.GOV/GLASGOW




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