Flash Flood Warning 20, NWS Glasgow, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
413 AM MDT SAT SEP 7 2013

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH MONDAY...
UPPER LEVEL CLOSED LOW ACROSS THE PACIFIC NORTHWEST WILL DRIVE
SOUTHWEST FLOW ALOFT ACROSS NORTHEAST MONTANA TODAY THROUGH
TONIGHT. SHORTWAVE ENERGY ROTATING AROUND THIS UPPER LEVEL LOW
WILL PROVIDE DYNAMICAL SUPPORT FOR VERTICAL ASCENT. IN
ADDITION...MODELS SHOW LOW LEVEL JET THROUGH THE AFTERNOON AND
EVENING HOURS WHICH WILL HELP FEED LOW AND MID LEVEL
MOISTURE...ESPECIALLY ACROSS THE EASTERN ZONES. NAM BUFKIT
SOUNDINGS SHOW PRECIPITABLE WATER VALUES EXCEEDING AN INCH AND A
HALF. UPPER LEVEL JET DYNAMICS ARE SOMEWHAT LESS FAVORABLE WITH
THE NORTHEASTERN ZONES IN AN AREA OF FAVORED LARGE SCALE
SUBSIDENCE. GUIDANCE SHOWS THAT JET WEAKENS SOME TONIGHT WHICH MAY
EVENTUALLY ALLOW SHOWER/THUNDERSTORM ACTIVITY TO SPREAD INTO THOSE
AREAS. EXCELLENT AGREEMENT OTHERWISE ON THE NAM/ECMWF/GFS BRINGING
HEAVIEST PRECIPITATION AMOUNTS IN THE EASTERN/SOUTHEASTERN ZONES.
WILL HAVE TO SEE IF THE NORTHEAST HAS A BIT OF SUPPRESSION DUE TO
LESS FAVORABLE UPPER LEVEL JET DYNAMICS AND MORE STABLE
ENVIRONMENT. THERMAL BOUNDARY REMAINING RATHER STATIONARY ACROSS
THE CWA MAY ALSO ENHANCE SURFACE CONVERGENCE AND ENABLE CONVECTION
INITIATION. IN ADDITION...SOUTH OF THIS BOUNDARY WILL BE AN AREA
OF GREATER WAA WHICH WILL ENHANCE VERTICAL ASCENT. UPWARDS OF 1000-2000
J/KG CAPE ARE EXPECTED SOUTH OF THE MISSOURI RIVER. NOT MUCH SPEED
SHEAR ACROSS THE CWA BUT NICE DIRECTIONAL SHEAR AND VEERING WIND
PROFILES IN FORECAST SOUNDINGS.  NICE THETA-E RIDGE ALSO EVIDENT
ACROSS NORTHEAST MONTANA IN MODELS FOR TODAY AND TONIGHT.

HAVING SAID ALL OF THAT...ALL SYSTEMS GO AS FAR AS WIDESPREAD
SHOWER AND THUNDERSTORM ACTIVITY TODAY AND TONIGHT. ANY STORM MAY
BE CAPABLE OF BRIEF HEAVY RAINFALL RATES AND GUSTY WINDS. SOUTH OF
THE THERMAL BOUNDARY IN THE REGION OF HIGHEST CAPE VALUES AND
GREATEST INSTABILITY IS WHERE THE GREATER CHANCE FOR A FEW SEVERE
STORMS WILL BE. THIS WILL GENERALLY BE CONFINED TO AREAS SOUTH OF
THE MISSOURI RIVER. GIVEN THE STATIONARY NATURE OF THE
BOUNDARY...AM CONCERNED ABOUT TRAINING OF STORMS IN SOME
LOCATIONS. GIVEN HIGH PRECIPITABLE WATER VALUES AND ENHANCEMENT
FROM LOW LEVEL JET...ESPECIALLY IN THE EAST...LOCALIZED FLASH
FLOODING MAY BE POSSIBLE. WILL NOT CONCERN WITH FLASH FLOOD WATCH
AT THIS TIME AS THIS SHOULD BE ISOLATED IN NATURE AND RELATIVELY
SHORT IN DURATION. IN ADDITION...PRIOR TO THIS PATTERN CHANGE IT
HAS BEEN FAIRLY DRY. WILL MENTION ISOLATED FLASH FLOODING IN THE
HWO FOR NOW HOWEVER AND LET THE DAY SHIFT REASSESS THE SITUATION.

SOME OF THE HIGH RESOLUTION FORECAST MODELS ARE ALSO INDICATING
POTENTIAL FOR GUSTY WINDS ACROSS THE CWA THIS AFTERNOON AND
EVENING. GIVEN DECENT LOW/MID LEVEL LAPSE RATES AND PRESENCE OF
LLJ...AS WELL AS POTENTIAL ENHANCED MIXING FROM SHORTWAVE ENERGY
AND ALSO FROM CONVECTIVE ACTIVITY...SUSTAINED WINDS FROM THE EAST
OF 15 TO 25 MPH AND GUSTS TO 35 MPH ARE POSSIBLE. EVEN HIGHER
GUSTS MAY OCCUR IN THUNDERSTORMS BUT FEEL THAT THE AMBIENT WIND
POTENTIAL WILL BE ENOUGH FOR CONCERNS AROUND FORT PECK LAKE.
THEREFORE...WILL HOIST A LAKE WIND ADVISORY FOR THIS AFTERNOON AND
EVENING.

SUNDAY AND MONDAY...UPPER LEVEL LOW WILL TRANSLATE EASTWARD ACROSS
THE UPPER MIDWEST FOR SUNDAY AND MONDAY PROVIDING FOR ADDITIONAL
CHANCES OF SCATTERED SHOWERS AND THUNDERSTORMS. CHANCES WILL
DECREASE EACH DAY HOWEVER AS THE SYSTEM PUSHES FURTHER EAST. THE
UPPER LEVEL TROUGH AS WELL AS ENHANCED CLOUDS/PRECIPITATION WILL
ALSO ENSURE A COOLER TEMPERATURE REGIME WITH NEAR SEASONAL NORMAL
CONDITIONS EXPECTED. MALIAWCO

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
A FEW LINGERING STORMS ARE POSSIBLE MONDAY NIGHT AT THE START OF
THE EXTENDED PERIOD AS THE WEEKEND UPPER LOW PUSHES TOWARD THE
UPPER MIDWEST. NORTHWEST FLOW EXPECTED BEHIND THIS WAVE AS AN UPPER
RIDGE BUILDS IN TO WESTERN CANADA WILL BRING COOLER AND DRIER
WEATHER INTO NORTHEAST MONTANA. HIGH PRESSURE DRIFTING FROM
WESTERN CANADA WILL KEEP CONDITIONS DRY UNTIL THE END OF THE WEEK
WHEN THE HIGH REACHES THE GREAT LAKES AND SOUTHEAST LOW LEVEL FLOW
BEGINS PULLING MOISTURE NORTHWARD. UPPER RIDGE ALSO EXPECTED TO
HAVE SHIFTED INTO THE NORTHERN PLAINS INCREASING POTENTIAL FOR A
RETURN OF THUNDERSTORMS BY NEXT WEEKEND. EBERT

&&

.AVIATION...
MAINLY VFR CONDITIONS ALTHOUGH THUNDERSTORMS ARE EXPECTED ACROSS
THE REGION TODAY AND TONIGHT. THESE STORMS MAY PRODUCE BRIEF
REDUCTION OF FLIGHT CONDITIONS ALONG WITH GUSTY WINDS.

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY FROM NOON TODAY TO 8 PM MDT THIS EVENING FOR
FORT PECK LAKE FOR CENTRAL AND SOUTHEAST PHILLIPS...CENTRAL AND
SOUTHERN VALLEY...GARFIELD...MCCONE...PETROLEUM.

&&

WEATHER.GOV/GLASGOW

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GLASGOW MT
357 AM MDT SAT SEP 7 2013

MTZ016>027-059>062-081000-
CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-
DANIELS-SHERIDAN-WESTERN ROOSEVELT-PETROLEUM-GARFIELD-MCCONE-
RICHLAND-DAWSON-PRAIRIE-WIBAUX-NORTHERN PHILLIPS-
SOUTHWEST PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT-
357 AM MDT SAT SEP 7 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MONTANA.

.DAY ONE...TODAY AND TONIGHT

SHOWERS AND THUNDERSTORMS CAPABLE OF GUSTY WINDS AND HEAVY
RAINFALL WILL OCCUR ACROSS MUCH OF NORTHEAST MONTANA THROUGH
TONIGHT. ISOLATED FLASH FLOODING IS POSSIBLE...ESPECIALLY WHERE
STORMS TRAIN OVER THE SAME LOCATIONS. A FEW OF THE STORMS MAY
ALSO BECOME SEVERE...MAINLY SOUTH OF THE MISSOURI RIVER.

EASTERLY WINDS OF 15 TO 25 MPH WITH GUSTS TO 35 MPH ARE ALSO
EXPECTED ACROSS THE REGION THIS AFTERNOON THROUGH THE EARLY
EVENING HOURS. A LAKE WIND ADVISORY GOES INTO EFFECT FROM NOON
UNTIL 8PM THIS EVENING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

SCATTERED SHOWERS AND THUNDERSTORMS MAY CONTINUE THROUGH MONDAY
UNTIL THE LARGE WEATHER SYSTEM TRANSLATES EAST OF THE REGION. THIS
ACTIVITY MAY LEAD TO ADDITIONAL LOCALIZED HEAVY RAINFALL. THE
HIGHEST RAINFALL POTENTIAL IS EXPECTED IN EASTERN PORTIONS OF THE
REGION. ISOLATED AMOUNTS EXCEEDING ONE INCH ARE POSSIBLE BY THE
END OF THE EVENT.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GLASGOW MT
659 AM MDT SAT SEP 07 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0655 AM     HEAVY RAIN       5 SW HINSDALE           48.35N 107.15W
09/07/2013  M1.20 INCH       VALLEY             MT   TRAINED SPOTTER

            MEASURED 1.2 INCHES IN ABOUT 30 MINUTES

&&

JB