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000
FXUS65 KGGW 182102
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
302 PM MDT SAT MAY 18 2013

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH MONDAY...
A LARGE TROUGH HAS DUG IN OVER THE SOUTH WEST CONUS WITH A RIDGE
OVER WESTERN CANADA. VARIABLE IMPULSES OF ENERGY MOVING UP FROM
THE DOWNSTREAM PART OF THE SOUTHERN TROUGH WILL SUPPORT CONTINUED
PRECIPITATION THROUGH MONDAY AFTERNOON. RAINFALL IS ALSO SUPPORTED
BY A SURFACE LOW SOUTHEAST OF MONTANA THAT IS DRAWING LOW LEVEL
MOISTURE INTO THE AREA.

SYSTEM CONTINUES TO STRENGTHEN AND GRADUALLY MOVE EASTWARD...WITH
THE EFFECTS EXITING NORTHEAST MONTANA MONDAY NIGHT. ON
MONDAY...MOST OF THE MODELS HAVE MOST OF THE PRECIPITATION TO THE
SOUTHEAST PART OF THE CWA...BUT WITH POTENTIALLY HIGHER AMOUNTS
THAN EARLIER IN THE FORECAST. SOUNDINGS ARE VERY SATURATED WITH
AROUND AN INCH OF PRECIPITABLE WATER..LEADING TO THE FORECAST OF
MOSTLY RAIN SHOWERS. SOME INSTABILITY IN THE SOUNDINGS WILL LEAD
TO SOME LIMITED THUNDERSTORM ACTIVITY. THUNDERSTORMS ARE LIMITED
BY THE LACK OF CAP...WHICH WILL NOT ALLOW MUCH BUILD-UP OF
CONVECTIVE ENERGY. WINDS WILL PICK A LITTLE FROM THE NORTH ON
SUNDAY AS THE SURFACE LOW TIGHTENS...HOWEVER...THEY SHOULD STAY
BELOW 20KTS...WITH LOCALLY HIGHER GUSTS POSSIBLE IN OUTFLOW AREAS. MARTIN

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
THE ONLY CHANGES IN THE SHORT TERM LOOK TO BE STRONGER WINDS
THURSDAY AND THE POSSIBILITY FOR A SEVERE EVENT OR TWO AT THE END
OF THE PERIOD.

THE GFS WANTS TO RAMP UP WINDS QUITE A BIT THURSDAY AFTERNOON WITH
850 WINDS OVER THE CWA APPROACHING 50 KNOTS AS A MID LEVEL HIGH
OVER THE MINNESOTA AND ONTARIO REGION BATTLES WITH THE APPROACHING
PACIFIC NORTHWEST LOW. THE ECMWF HAS A BIT LESS AMPLIFIED GRADIENT
AND THUS A THINNER BAND OF STRONG 850 WINDS OVER THE CWA...BUT HAS
A SIMILAR UPPER PATTERN AS GFS. WENT CLOSER TO THE ECMWF SOLUTION
AS THE GFS TENDS TO HAVE WINDS A BIT HIGH OVER THE AREA.

AS THE UPPER LOW APPROACHES FOR THE WEEKEND...LOBES OF SHORTWAVE
ENERGY MAY CONTINUE TO BRING CHANCES FOR THUNDERSTORM DEVELOPMENT.
SATURDAY AFTERNOON HAS THE GFS AND ECMWF PUTTING OUT OVER 2000
J/KG OF CAPE OVER PARTS OF THE AREA...SO THERE WILL BE PLENTY OF
INSTABILITY OVER THE REGION. SUNDAY AFTERNOON AND EVENING SHOWS ROUGHLY
THE SAME SCENARIO...AND EVEN DIPS INTO MONDAY AS THE LOW SLOWLY
PROGRESSES NORTHWARD OFF TO OUR WEST AND NORTHWEST. THIS WILL
PROVIDE BROAD SOUTHWEST FLOW ALOFT FOR THE WEEKEND...WHICH SHOULD
GIVE ENOUGH UPPER LEVEL SUPPORT WITH DIFLUENT FLOW COMBINED WITH
LOBES OF SHORTWAVE ENERGY OFF THE MAIN FLOW...ESPECIALLY FOR
SATURDAY. FOR NOW...THE GFS HAS A WARM FRONT PASS THROUGH THE CWA
FRIDAY...AND THE ECMWF HAS ONE PASS SATURDAY. MORE MODEL AGREEMENT
ON TIMING WILL SHOW IF WE GET OUR FIRST SIGNIFICANT ROUND OF
STORMS THIS SEASON NEXT WEEKEND. BARNWELL

PREVIOUS LONG TERM DISCUSSION...THE EXTENDED FORECAST BEGINS
MONDAY NIGHT WITH AN UPPER LOW EXITING INTO THE UPPER MISSISSIPPI
RIVER VALLEY AND WEAK RIDGING BUILDING INTO NORTHEASTERN MONTANA.

BY WEDNESDAY MORNING ANOTHER UPPER LOW MOVES IN OVER THE PACIFIC
NORTHWEST SETTING UP DI-FLUENT SOUTHWEST FLOW ALOFT OVER THE AREA
THROUGH THE END OF THE EXTENDED.

THIS WILL CONTINUE THE COOLISH TEMPERATURES DURING THE DAY AND
NEAR NORMAL TEMPERATURES AT NIGHT. PRECIPITATION CHANCES SHOULD
RANGE SLIGHTLY ABOVE NORMAL... HOWEVER PIN POINTING ANY BETTER
DAYS THAN OTHERS WILL BE VERY HARD.

ENSEMBLES OF THE GFS AND EC SHOW HIGH CONFIDENCE IN AN UPPER LOW
OVER THE PACIFIC NORTHWEST...HOWEVER DO HAVE TROUBLE KEEPING THE
DAY TO DAY PLACEMENT OF THE UPPER LOW THE SAME. RMOP IS PRETTY
GOOD FOR UPPER LOWS OVER THE PACIFIC NORTHWEST. MODERATE TO HIGH
CONFIDENCE ON THE PATTERN. HOWEVER THE PATTERN IS MORE SHOWERY IN
NATURE NOT ALLOWING FOR THE CONFIDENCE TO DOUBLE OF CLIMO POPS AT
THIS TIME.              PROTON

&&

.AVIATION...
A MIX OF VFR WITH PERIODS OF MVFR CAN BE EXPECTED THROUGH THE
PERIOD AT ALL TERMINALS. SOUTHWEST FLOW ALOFT AND MOIST EAST TO
SOUTHEAST FLOW WILL KEEP SKIES BROKEN TO OVERCAST. CEILINGS WILL
BE TRICKY... GUIDANCE HAS A SPLIT WITH ONE GOING FOR SOLID
MVFR...THE OTHER SOLID VFR. WILL GO WITH THE PREDOMINATE OF VFR
AND PERIODS OF MVFR MAINLY FOR MORNING LOWER CEILINGS AND ANY
AFTERNOON CBS THAT FORM. LIGHT RAIN SHOWERS ARE EXPECTED ON AND
OFF THROUGHOUT THE ENTIRE TAF PERIOD.

KOLF ASOS IS NOT TRANSMITTING THE OBSERVATIONS FOR US TO SEE THEM
ONLINE AND INSTEAD WE ARE HAVING TO CALL EVERY HOUR. THEREFORE THE
TAF IS AMD NOT SKED.

PROTON/FRANSEN


&&

.HYDROLOGY...
THE NEXT FEW DAYS WILL BE RATHER WET AS AN UPPER-LEVEL TROUGH
AFFECTS THE AREA. SEVERAL DISTURBANCES ASSOCIATED WITH THIS TROUGH
WILL PASS THROUGH WHICH WILL KEEP CHANCES FOR RAIN WITH SOME
THUNDERSTORMS THROUGH EARLY NEXT WEEK. MODEL GUIDANCE DEPICTS HIGH
AMOUNTS OF MOISTURE WITH THIS SYSTEM. AT THIS POINT THE
ENVIRONMENT LOOKS FAVORABLE FOR SLOW-MOVING STORMS WITH HIGHER
PRECIPITATION IN LOCALIZED AREAS.

MOST OF THE BASINS IN NORTHEAST MONTANA WILL BE ABLE TO ACCOMMODATE
THIS AMOUNT OF MOISTURE... AT LEAST EARLY ON IN THE EVENT. THERE IS
SOME CONCERN FOR RAPIDLY RISING STREAMS...FIELD FLOODING AND
LOCALIZED FLOODING IN TOWNS AS THE EVENT PERSISTS. SOME MINOR
FLOODING MAY BECOME AN ISSUE... ESPECIALLY FOR THE AREAS FROM
GLASGOW TO CIRLE AND EASTWARD INTO NORTH DAKOTA WHERE THE POTENTIAL
FOR STRONGER THUNDERSTORMS IS HIGHER.


&&

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

&&

$$

WEATHER.GOV/GLASGOW