Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 300134
AFDGGW

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

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SUNDAY...

EVENING UPDATE...
CHANGE FOR THE FORECAST FOCUSED ON AN INCOMING MID LEVEL BOUNDARY
THAT DRAGS EXTRA PACIFIC MOISTURE IN BEHIND IT AROUND 12 TO 18Z.
SHOWERS WITH THIS BOUNDARY WILL BE ISOLATED. Q-VECTOR CONVERGENCE
AROUND 700 MB AND SURFACE QPF ACROSS MULTIPLE MODELS SEEMS TO SHOW
IT OFF THE BEST. HOWEVER... THIS ISOLATED MORNING SHOWER ACTIVITY
WILL ONLY BE THE PRELUDE TO WHAT COMES AFTER.

DIRECTLY BEHIND THIS BOUNDARY WILL BE AN UNSTABLE ENVIRONMENT
THAT JUST NEEDS SOME DAYTIME HEATING TO BUBBLE AND COULD LEAD INTO
IOSLATED SEVERE CELLS DURING THE AFTERNOON. THE SPC HAS PLACED A
MARGINAL ZONE OVER THE DAY2 OUTLOOK ACROSS THE SOUTHWEST ZONES OF
THE CWA FOR THIS AND WILL LIKELY BE FOLLOWING SUIT WITH THE
OVERNIGHT PACKAGE.

REMAINING CHANGES FOR THIS EVENING AND OVERNIGHT PERIODS WERE
PERFORMED OVER WIND... SKY... AND QPF FIELDS. WITH CHANGES IN
THESE FIELDS BEING MINOR... TEMPERATURES WERE UNTOUCHED. GAH


PREVIOUS SHORT TERM DISCUSSION...
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...
SYNOPSIS: INCREASING CLOUD COVER THROUGH THE PERIOD AS HIGH
PRESSURE EXITS THE REGION AND A LEE TROUGH DEVELOPS ACROSS CENTRAL
MONTANA ON SATURDAY.

WIND: THE WIND WILL CONTINUE OUT OF EAST AND INCREASE FROM LIGHT
TO 10 TO 20 KNOTS DURING THE DAY ON SATURDAY FOR THE FORECAST AREA.

WX: A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS EXIST ON SATURDAY
WEST OF A KGGW-KJDN LINE.         PROTON

&&

.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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