Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 310252
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
852 PM MDT WED JUL 30 2014

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH FRIDAY...
UPDATE...MINOR ADJUSTMENT MADE TO WEATHER AND POP GRIDS BASED ON
CURRENT TRENDS. A WEAK AREA OF THUNDERSHOWERS ACROSS SOUTHERN
SASKATCHEWAN... AS PER THE HRRR... ARE EXPECTED TO HOLD TOGETHER
AND CROSS INTO NORTHEASTERN MONTANA OVERNIGHT. OTHERWISE MINOR
TWEAKS TO OTHER ELEMENTS TO REFRESH THE CURRENT TIME PERIOD.  PROTON

PREVIOUS DISCUSSION...THE UPPER RIDGE THAT HAS BEEN THE MAIN FOCUS FOR DRY AND
WARMER WEATHER OVER THE REGION WILL SLOWLY BEGIN TO BREAK DOWN.
DURING THE SHORT TERM...THE RIDGE WILL LARGELY BE IN PLACE
BRINGING CONTINUED WARM AND DRY CONDITIONS. HOWEVER...CURRENT
MODEL GUIDANCE IS SUGGESTING THAT SOME WEAK SHORTWAVE ENERGY MAY
HAVE A BIT MORE IMPACT THAN PREVIOUS FORECASTS...AND CHANCES FOR
PRECIPITATION HAVE BEEN ADDED.

FOR TONIGHT...WEAK SHORTWAVE ENERGY APPEARS TO BE ENOUGH TO FORCE
SOME CHANCES OF PRECIPITATION THIS EVENING AND POSSIBLY OVERNIGHT
IN THE NORTHEAST. HIGH RES SHORT TERM MODELS ARE PLACING SOME QPF
IN THE GLASGOW AREA AS WELL AS AREAS EAST OF GLASGOW AND NORTH OF
THE MISSOURI RIVER. LEFT POPS IN FROM THE PREVIOUS FORECAST BUT
EXPANDED FURTHER WEST TO MATCH UP WITH HIGH RES MODEL GUIDANCE TO
REPRESENT THE CHANCE FOR PRECIP TONIGHT.

THURSDAY SHOULD BE DRY TO START WITH A STATIONARY BOUNDARY FEATURE
AND WEAK UPPER LEVEL SUPPORT NEAR THE NORTH DAKOTA AND MONTANA
BORDER. THIS LOOKS TO BE THE FORCING MECHANISM FOR YET ANOTHER
CHANCE FOR SHOWERS AND THUNDERSTORMS MAINLY SOUTH OF INTERSTATE 94
BY 00Z. THE NAM LOOKS TO BE BUYING INTO THIS SOLUTION THE
MOST...WITH THE ECMWF NOT FAR OFF...SO PUT IN SLIGHT CHANCE POPS
FOR THE TIME BEING. AGAIN CHANCES ARE SLIM AT BEST FOR NOW...BUT
ENOUGH OF A POSSIBILITY FOR A MENTION ATTM.

FRIDAY SHOULD HAVE THE BETTER SHOT AT PRECIP...AGAIN WITH THE NAM
AND ECMWF PLACING QPF OVER THE REGION DURING THE AFTERNOON. EXPANDED THE
POP REGION A BIT TO REFLECT THIS...BUT NOT TOO CONFIDENT YET SINCE
ALL GUIDANCE IS NOT ON BOARD. SYNOPTIC FORCING IS STILL A BIT WEAK
SINCE SHORTWAVE ENERGY IS TAKING A BIT TO BREAK DOWN THAT
PERSISTENT UPPER RIDGE. 500 MB FLOW IS STILL QUITE WEAK...AND 850
TEMPS ARE NOT INDICATING MUCH FRONTAL FORCING...SO LOOKS TO BE
MAINLY DIURNALLY DRIVEN CONVECTION POSSIBLE IN THE AFTERNOON. CAPE
VALUES ATTM ARE PRETTY WEAK ALONG WITH SHEAR VALUES...SO WILL HAVE
TO SEE HOW THE EVENT EVOLVES IF AT ALL. KEPT THE POP TREND IN THE
SHORT TERM GOING WITH SLIGHT CHANCE TO REFLECT THE POSSIBILITY.
BARNWELL

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...

EVEN THOUGH THE WESTERN STATES RIDGE OF HIGH PRESSURE DOES AN
IMPRESSIVE JOB AT TRYING TO HOLD ON AS LONG AS IT CAN...LATE
FRIDAY NIGHT SEEMS TO BE THE BEGINNING OF THE END FOR THIS RIDGE
AS A SERIES OF SHORT WAVE DISTURBANCES FROM THE PACIFIC NORTHWEST
ERODE THE RIDGE AWAY INTO MORE OF A ZONAL FLOW ALOFT FOR NORTHEAST
MONTANA. IN FACT...BY THE END OF THE FORECAST PERIOD...WE FIND
OURSELVES UNDER THE PERIPHERAL INFLUENCE FROM THE HUDSON BAY LOW.

UNFORTUNATELY...MODEL STILL SHOW QUITE A BIT OF DISAGREEMENT
REGARDING PRECIP TIMING AND PLACEMENT. YES...AFTER THIS
WEEKEND...WE FIND OURSELVES IN A SLIGHTLY MORE MOIST FLOW
REGIME...BUT IT LOOKS LIKE MORE OF A MESSY DISORGANIZED PATTERN
WITH SCATTERED OR HIT AND MISS SHOWERS AND THUNDERSTORMS WITH
TEMPERATURES A BIT COOLER.      BMICKELSON

PREVIOUS LONG TERM DISCUSSION...THE EXTENDED PERIOD BEGINS FRIDAY
NINTH WITH A LARGE UPPER LEVEL RIDGE ACROSS THE WESTERN U.S. AND A
TROUGH ACROSS THE GREAT LAKES REGION. THIS PLACES THE REGION UNDER
NORTHWEST FLOW ALOFT AS A DEPARTING UPPER SHORTWAVE PUSHES EAST
INTO NORTH DAKOTA/SOUTHERN MANITOBA. WILL KEEP SLIGHT CHANCE
MENTION PRIMARILY ALONG THE INTERNATIONAL BORDER AS THIS SYSTEM
PUSHES AWAY. ADDITIONAL SHORTWAVES WILL RIDE THROUGH THE RIDGE
THROUGH THE WEEKEND WHICH WILL MAINTAIN SLIGHT CHANCES FOR SHOWERS
AND THUNDERSTORMS. WITH THE RIDGE LARGELY IN PLACE...DO EXPECT
CONTINUED SUMMERTIME TEMPERATURES WITH HIGHS NEAR 90 THROUGH THE
WEEKEND.

ENHANCED MONSOONAL FETCH OF MOISTURE MAY PRODUCE BETTER CHANCES
FOR SHOWERS OR THUNDERSTORMS HEADING INTO EARLY NEXT WEEK IF
TIMING AND TRACK OF SHORTWAVES IS FAVORABLE. FOR NOW MAINTAINED
SLIGHT CHANCES THROUGH THE PERIOD UNTIL MODEL CONSENSUS BETWEEN
THE ECMWF AND GFS IMPROVES WITH REGARD TO THESE DETAILS. THESE
SHORTWAVES MAY ALSO KNOW DOWN THE RIDGE ALLOWING FOR SOMEWHAT
COOLER TEMPERATURES AS THE EXTENDED PERIOD COMES TO A FINISH
ALTHOUGH HIGHS SHOULD GENERALLY STILL REACH THE 80S. MALIAWCO


&&

.AVIATION...
FLIGHT CATEGORY: VFR.

SYNOPSIS: AN UPPER RIDGE TO THE WEST WILL CONTINUE LIGHT NORTHERLY
FLOW OVER NORTHEAST MONTANA. THIS EVENING A REMOTE CHANCE FOR SOME
LIGHT THUNDERSTORM ACTIVITY REMAINS POSSIBLE FROM 03-12Z FOR THE
TERMINAL LOCATIONS.     PROTON

&&

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

&&

$$

WEATHER.GOV/GLASGOW





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