Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 292102
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
302 PM MDT FRI MAY 29 2015

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SUNDAY...
CANADIAN SURFACE HIGH PRESSURE THAT IS GIVING A FALL-LIKE FEEL TODAY
WILL PUSH EAST AS FLOW INCREASES OVER THE PACIFIC NW...INTRODUCING
UPPER DISTURBANCES THAT BEGIN TO MOVE THROUGH THE AREA STARTING
SATURDAY EVENING.

MAINLY CLEAR SKIES WITH DEWPOINTS IN THE 30S TONIGHT SHOULD ALLOW
FOR ANOTHER COOL NIGHT BUT WILL BE LIMITED WITH INCREASING CLOUDS
FROM THE NORTHWEST. TEMPS SHOULD DROP INTO THE 30S EAST AND NORTH
AND 40S ELSEWHERE.

CLOUDS CONTINUE INCREASING SATURDAY AHEAD OF A DISTURBANCE ALONG
WITH SOUTHEAST WINDS. SPEEDS OF 15 TO 30 MPH WILL BE STRONG ENOUGH
FOR A LAKE WIND ADVISORY.

WARM AIR ADVECTION WILL ALSO HELP TO GENERATE THUNDERSTORMS AND
SOME COULD BE STRONG AS LOW -LEVEL SHEAR INCREASES...MID LEVELS
ARE UNSTABLE (>7*C/KM) AND LOW AND MID LEVEL MOISTURE INCREASES.
SPC HAS AREA IN A MARGINAL RISK FOR SEVERE THUNDERSTORMS. HAVE
LEFT MENTION IN FOR SMALL HAIL AND GUSTY WINDS IN THE SOUTHWESTERN
ZONES.

SYSTEM EXITS INTO THE DAKOTAS SUNDAY MORNING. ATMOSPHERE SHOULD BE
CAPPED AND SHOULD MAINLY BE DRY. HOWEVER DIDN/T HAVE ENOUGH
CONFIDENCE TO DROP SLIGHT CHANCE OF SHOWERS/TSTORMS YET AS SOME
INSTABILITY REMAINS. TFJ

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
MINOR ADJUSTMENTS MADE TO GOING FORECAST. CHANCES OF SHOWERS OR
THUNDERSTORM THROUGH MOST OF NEXT WEEK WITH A LONG WAVE TROF
SETTING UP OVER THE WEST COAST STATES SENDING MOISTURE AND ENERGY
INTO THE STATE ON THE SOUTHWEST FLOW ALOFT. EBERT

PREVIOUS LONG TERM DISCUSSION...SYNOPTIC SET UP... THE LONG RANGE
BEGINS WITH A LARGE RIDGE RUNNING FROM WESTERN MEXICO THROUGH THE
FOUR CORNERS AND INTO WYOMING. THE TOP OF THE LARGE RIDGE IS
BLUNTED INTO ZONAL FLOW ACROSS EASTERN MONTANA BY A WEAK TROUGH
OVER THE CANADIAN PRAIRIES. A VERY WEAKENED SPUR JUTS UP INTO
WESTERN MONTANA AND SOUTHERN BRITISH COLUMBIA. WEST OF THE SPUR IS
A STRONG PACIFIC TROUGH OVER THE COAST OF OREGON AND WASHINGTON
WHICH IS SENDING SHORTWAVES... JETS... AND PACIFIC MOISTURE INTO
MONTANA.

THE RIDGE SPUR OVER THE WESTERN MONTANA WILL BE KNOCKED DOWN
QUICKLY SUNDAY NIGHT WITH SOUTHWEST FLOW THEN STAYING IN PLACE
THROUGH ALMOST THE WHOLE OF THE LONG TERM. THIS WILL PRIME THE
ATMOSPHERE WITH CONVECTION FOR ALMOST EVERY AFTERNOON LASTING
INTO THE EVENING UNTIL NEXT WEEKEND. POPS WERE RAMPED UP ABOVE
CLIMO FOR THIS VERY MOIST SET UP.

THE SHAPE OF FLOW OF THE JET STREAM AND PLACEMENT OF STRONGER
SURFACE HEAT JUST AHEAD OF IT MAKES MONDAY AND ESPECIALLY TUESDAY
LOOK LIKE SEVERE WEATHER DAYS FROM PATTERN RECOGNITION. WHILE THE WHOLE
PATTERN WILL NOT CHANGE QUICKLY... THE MESOSCALE DETAILS WHICH
DEFINE GENERAL THUNDER OR SEVERE WEATHER... AND HOW MUCH RAIN IS
POSSIBLE... COULD EASILY CHANGE IN FUTURE FORECASTS. UNTIL THEN...
HAVING ALTERNATE PLANS IN PLACE FOR AFTERNOON OUTDOOR ACTIVITIES
WILL PROBABLY BE A GOOD IDEA THROUGH NEXT WEEK. GAH

&&

.AVIATION...
VFR CONDITIONS ARE EXPECTED OVERNIGHT WITH HIGH PRESSURE OVER THE
NORTHERN PLAINS. CLOUDS WILL BEGIN TO INCREASE AND LOWER THROUGH
THE DAY ON SATURDAY...WITH SHOWERS AND THUNDERSTORMS MOVING OUT OF
CENTRAL MONTANA LATE IN THE AFTERNOON.

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY FROM 9 AM TO 9 PM MDT SATURDAY FOR FORT PECK
LAKE FOR CENTRAL AND SOUTHEAST PHILLIPS...CENTRAL AND SOUTHERN
VALLEY...GARFIELD...MCCONE...PETROLEUM.

&&

$$

WEATHER.GOV/GLASGOW





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