Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 031517
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
917 AM MDT THU SEP 3 2015

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SATURDAY...
UPDATE...
RADAR OBSERVATIONS SHOW INCREASING REFLECTIVITY OVER THE SOUTHWEST
ZONES THIS MORNING. IT IS UNCLEAR WHETHER OR NOT ANYTHING IS YET
REACHING THE GROUND OR IF IT IS LARGELY VIRGA. GRADUAL MOISTENING
OF THE COLUMN IS ANTICIPATED THROUGH THE DAY AND SO DID INCLUDE
SLIGHT CHANCE POPS FOR LATE THIS MORNING AND CONTINUED INHERITED
FORECAST THINKING FOR POPS THIS AFTERNOON...WITH A SMALL INCREASE
IN AREAL COVERAGE. MALIAWCO

PREVIOUS DISCUSSION...

A COLD FRONT WAS LOCATED NEAR MILES CITY... GLENDIVE AND SIDNEY
AT 08Z. THIS FRONT WILL DRIFT INTO NORTH DAKOTA THIS MORNING AND
REMAIN QUASI-STATIONARY INTO THE WEEKEND. THE FRONT WILL BE
PARALLEL TO THE SOUTHWEST FLOW ALOFT OVER THE REGION.

UPPER TROUGH/LOW WILL CONTINUE TO DIG SOUTH ACROSS THE PACIFIC
NORTHWEST TODAY AND THE BASE OF THE TROUGH WILL DIP AS FAR SOUTH
AS CALIFORNIA AND NEVADA TONIGHT. THE SW FLOW ALOFT OVER EASTERN
MONTANA WILL CONTINUE TO BE DRY FOR THE MOST PART TODAY. AN 850 MB
TEMPERATURE GRADIENT ACROSS THE REGION WILL BRING HIGHS THAT WILL
BE MAINLY IN THE 70S IN THE WEST AND 80S IN THE EAST.

A SHORTWAVE TROUGH MOVING NE THROUGH THE DAKOTAS TONIGHT WILL
BRING A BAND OF MOISTURE ACROSS THE FORECAST AREA TONIGHT WITH A
CHANCE OF SHOWERS POSSIBLY A THUNDERSTORM IF ELEVATED CONVECTION
OCCURS WITHIN AN UNSTABLE MID LEVEL.

MODELS DIFFER ON FRIDAY ON WHETHER OR NOT THERE WILL BE ANY
MOISTURE OVERRUNNING THE FRONT WHICH WILL BE ACROSS WYOMING AND
THE DAKOTAS. WILL MAINTAIN A CHANCE OF SHOWERS WITH A SLIGHT
CHANCE OF THUNDERSTORMS AS ELEVATED CONVECTION REMAINS POSSIBLE.

FRIDAY NIGHT AND SATURDAY... CHANCES OF OVERRUNNING MOISTURE
INCREASE AS LOW LEVEL FLOW TAPS INTO MOISTURE FROM THE GULF OF
MEXICO. A SURFACE LOW DEVELOPS OVER WYOMING AND MOVES INTO SOUTH
DAKOTA. UPPER TROUGH STAYS TO THE WEST KEEPING SOUTH TO SOUTHWEST
FLOW ALOFT OVER THE AREA. WILL INCREASE CHANCE OF SHOWERS TO
LIKELY LATE FRIDAY NIGHT AND SATURDAY WITH A CHANCE OF
THUNDERSTORMS AS ELEVATED CONVECTION REMAINS POSSIBLE.



.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...

SYNOPTIC SET UP... LONG RANGE BEGINS WITH A RIDGE OF HOT HIGH
PRESSURE OVER-STRETCHING FROM THE TEXAS PANHANDLE UP TO SOUTH
DAKOTA. A LARGE COOL CORE TROUGH HAS INVADED THE INTERMOUNTAIN
WEST INCLUDING WESTERN MONTANA. NORTHEAST MONTANA BEGINS UNDER
THE CLASH OF THESE TWO AIRMASSES AS A LOW PRESSURE SYSTEM HAS
WINDED UP AND TAPPED INTO COLD AIR OVER CENTRAL SASKATCHEWAN.

SATURDAY NIGHT THROUGH SUNDAY NIGHT... DEPENDING ON THE MODEL A
LOW PRESSURE SYSTEM WILL BEGIN CENTERED SOMEWHERE OVER SOUTHEAST
MONTANA TO SOUTHERN SASKATCHEWAN. PLACEMENT OF THE LOW WILL
DETERMINE WHERE STRONG WINDS AND THE TROWAL WITH EXCESSIVE
RAINFALL ON THE BACKSIDE WILL BE IN RELATION TO THE LOW`S
POSITION. CONFIDENCE IN THESE FEATURES IS LOW. HOWEVER... RAIN IS
PRESENT ON EVERY SIDE OF THE LOW. SO... CONFIDENCE IN RAIN AND
POPS DURING THESE PERIODS IS HIGH.

MONDAY TO TUESDAY NIGHT... COLD STABLE HIGH PRESSURE WILL SETTLE
INTO THE AREA AND CONDITIONS SHOULD DRY OUT WITH ONLY ISOLATED
SHOWERS POSSIBLE. FLOW ALOFT WILL BECOME ZONAL AND A MORE AUTUMN
LIKE ATMOSPHERE SHOULD SETTLE IN.

WEDNESDAY ONWARD... SYNOPTIC MODEL BREAKDOWN OCCURS AT THIS
POINT. TEMPERATURES SHOULD REMAIN SEASONAL FOR THE MOST PART... BUT
DEPENDING ON THE MODEL... SHORT TO SYNOPTIC WAVES BRING INCREASED
CHANCES FOR LIGHT RAINFALL AGAIN. GAH



&&

.AVIATION...
VFR CIGS AND VSBYS ARE TO PREVAIL THROUGH THE DAY. AN ISOLATED
SHOWER THIS MORNING AND AN ISOLATED SHOWER OR THUNDERSTORM THIS
AFTERNOON CANNOT BE RULED OUT...AND MAY BRIEFLY REDUCE MVFR IF
PASSING DIRECTLY OVER A TAF SITE. SHOWERS AND THUNDERSTORMS WILL
INCREASE IN COVERAGE TONIGHT AND ESPECIALLY BEYOND THE TAF PERIOD.
WINDS WILL GENERALLY REMAIN NORTH AND NORTHWEST AT 10 TO 20 KTS
TODAY AND SHIFT NORTHEAST TONIGHT. MALIAWCO


&&

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

&&

$$

WEATHER.GOV/GLASGOW


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