Severe Thunderstorm Warning 39, NWS Glasgow, MT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
807 PM MDT TUE JUN 5 2007

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH THURSDAY...
CONVECTION HAS BEEN ONGOING FOR AN HOUR OR SO IN THE SOUTHWEST
PORTION OF THE CWA AS SOME STORMS HAVE BEEN MOVING INTO PETROLEUM
COUNTY FROM THE SOUTHWEST. THUS FAR STORMS HAVE SHOWN A PROCLIVITY
TO DIMINISH AS THEY ENTER PETROLEUM COUNTY AND MORE OR LESS DIE
OFF AS THEY GET ABOUT A THIRD OF THE WAY INTO GARFIELD AND
SOUTHWEST PHILLIPS COUNTIES. HOWEVER AS THE SURFACE TROF AXIS
WHICH IS NOW ACROSS PETROLEUM COUNTY MOVES FARTHER EAST TONIGHT AS
EXPECTED...THE SHOWERS AND STORMS SHOULD CONTINUE TO SUSTAIN
THEMSELVES FARTHER NORTH AND EAST. WILL BUMP POPS UP TO LIKELY
ACROSS PETROLEUM COUNTY FOR THIS EVENING. OTHERWISE CURRENT POPS
FOR TONIGHT LOOK PRETTY GOOD TO ME. WILL ALSO BUMP UP TEMPERATURES
A FEW DEGREES AS DEWPOINTS QUITE HIGH AND NOT SEEING MUCH REASON
FOR THEM TO GO DOWN TONIGHT. OTHERWISE CURRENT FORECAST LOOKS LIKE
IT HAS THINGS WELL IN HAND AND NO OTHER SIGNIFICANT CHANGES WILL
BE MADE FOR TONIGHT.

PREVIOUS DISCUSSION...
UPPER RIDGE WILL BE PASSING TO OUR EAST SHORTLY AND WITH LOW LEVEL
WARM ADVECTION STILL OCCURRING...THE AIRMASS WILL BECOME MORE
UNSTABLE AS SUBSIDENCE INVERSION AT 10K FT MSL DISAPPEARS. UPPER
FLOW TURNS SW AHEAD OF APPROACHING CLOSED LOW ON OR COAST.
MOISTURE WITH THIS SYSTEM THAT WILL BEGIN REACHING OUR AREA
TONIGHT LOOKS PLENTIFUL ON SATELLITE CHANNELS...WITHOUT ANY
SUBTROPICAL INPUT THOUGH. SCATTERED THUNDERSTORMS SHOULD BE
REACHING OUR SW ZONES BY 00Z...THEN ACROSS THE REST OF THE AREA
WITH A MODEST SHORTWAVE AND SURFACE LOW PRESSURE TROUGH TONIGHT.
SPC HAS MOST OF OUR AREA IN SLIGHT RISK OF SEVERE TONIGHT. EXPECT
A FEW STORMS COULD BECOME SEVERE AS AIRMASS BECOMES MORE
UNSTABLE...DRIVEN MORE BY STRONG DYNAMICS OF LOW PRESSURE SYSTEM WHICH
WILL BE MORE SIGNIFICANT FOR OUR AREA WED. 140 KT JET WITH THIS LOW.

MODEL FORECAST SOUNDINGS SHOW LIFTED INDEXES TO -7 AND CAPES OVER
3000 J/KG IN OUR SE WED ALONG STALLING FRONTAL SYSTEM. BY THEN...STRONG
UPPER DIFFLUENCE OVER AREA AS WELL AS CLOSED LOW MOVES TO S MT/N
WY GIVING LARGE SCALE DYNAMICS. SPC SLIGHT RISK IN OUR E LOOKS
GOOD FOR A FAIR AMOUNT OF SEVERE DAYTIME STORMS.

COOLER AND MORE STABLE AIR ARRIVES BEHIND COLD FRONT DURING THE
DAY...BUT MODELS LOOK VERY WET NOW WITH CLOSED UPPER LOW THAT
MOVES ACROSS OUR AREA...SLIGHTLY S OF PREVIOUS POSITIONS. TSTORM PATTERN
TRANSITIONS TO STEADY RAIN WITH WIDESPREAD STRONG LIFT...AND HIGH
MEAN RELATIVE HUMIDITY ACROSS THE AREA. MODELS IN GOOD AGREEMENT
WITH THIS.

MODELS SHOW WIDES READ 12HR QPF IN 4-6 RANGE..THE SELDOM SEEN 6 IS
OVER 2 INCHES. THIS SYSTEM TO BE ENHANCED BY A PUSH OF COLD AIR
FROM THE NORTH CREATING A TROUGH OR FRONTAL BOUNDARY MOVING SOUTH.
VERY TIGHT SURFACE GRADIENTS ALONG THIS WILL LEAD TO WINDY WEATHER
BEGINNING WED AFTERNOON AND CONTINUING THU. 850 MB WINDS UP TO 55KT
FORECAST BY WRF. ONE THING ABOUT THIS STY EMS THOUGH...IS THAT IT
IS PROGRESSIVE AND ENDS FROM THE NORTH THU QUICKER THAN EXPECTED
EARLIER. MEAN RH DROPS BELOW 30 PCT BY THU AFTERNOON. SIMONSEN

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY...
THE PERIOD BEGINS WITH UPPER NORTHWEST FLOW RESULTING FROM THE UPPER
TROUGH MOVING INTO THE GREAT LAKES REGION AND HIGH PRESSURE OVER
THE INTER-MOUNTAIN WEST. THE UPPER FLOW QUICKLY BECOMES MORE ZONAL
AS AN UPPER TROUGH DEVELOPS OVER THE SOUTHWESTERN STATES. BY
SATURDAY ANOTHER UPPER LOW WILL RUN INTO THE NORTHWEST COAST WHICH
WILL KEEP ANY RIDGE FROM DEVELOPING OVER THE LOCAL FORECAST
REGION. MODELS SHOW MINOR DISTURBANCES RUNNING ALONG THE QUASI-
ZONAL FLOW OVER THE WEEKEND AS THE PACIFIC LOW CLOSES OFF AND
EJECTS MOISTURE INTO THE REGION. THE TROUGH/LOW THEN SLOWLY MOVES
INTO THE LOCAL REGION BY EARLY NEXT WEEK. ONCE AGAIN THE GFS AND
ECMWF EXHIBIT DIFFERENT TIMING. GFS IS QUICKER AND CLOSES OFF THE
LOW WHILE ECMWF IS SLOWER AND KEEPS AND TROUGH OPEN LONGER. TIME
WILL TELL. THE INHERITED GRIDS REFLECT THIS PATTERN WELL SO FEW
CHANGES WERE MADE TO THE LATER PERIODS AND ONLY MINOR CHANGES TO
THE EARLIER GRIDS. SCT
PREVIOUS DISCUSSION...
UPPER LOW SLIDES ACROSS THE NORTHERN PLAINS EARLY IN THE EXTENDED
PERIOD ALONG WITH WET SURFACE STORM. TIMING WITH STRONG STORMS
SUCH AS THIS CAN BE PROBLEMATIC BUT MODELS ALL FAIRLY PROGRESSIVE
WITH BRINGING DRY AIR INTO MONTANA BY LATE THURSDAY. MODELS
SUGGEST LOW OPENS AS IT PHASES WITH WAVE ROTATING AROUND STRONG
HUDSON BAY LOW. THIS WOULD KEEP THE STORM FROM SLOWING DOWN OR
STALLING OVER THE REGION.

EXPECT GENERALLY DRY WEATHER FOR FRIDAY AND SATURDAY AS UPPER FLOW
OVER MONTANA FLATTENS. AS TROF DEVELOPS OVER THE PACIFIC NORTHWEST
EARLY NEXT WEEK...SHOULD SEE AN INCREASED THREAT FOR THUNDERSTORMS
WITH SOUTHWEST FLOW INTO MONTANA. EBERT

&&

.AVIATION...
GENERALLY VFR CONDITIONS THIS EVENING EXCEPT FOR AREAS WHERE
THUNDERSTORMS MIGHT DEVELOP. VERY UNSTABLE CONDITIONS EXIST EARLY
THIS EVENING WHICH MIGHT ALLOW SOME OF THE THUNDERSTORMS TO BECOME
SEVERE...MAINLY TOWARDS THE SOUTHWESTERN ZONES. SOME OF THESE
STORMS COULD PRODUCE HEAVY RAIN...LARGE HAIL AND STRONG GUSTY
WINDS...TEMPORARILY REDUCING CEILINGS AND VISIBILITIES. STORM
STRENGTH WILL DIMINISH AFTER MIDNIGHT. THERE WILL BE ANOTHER ROUND
OF THUNDERSTORMS WEDNESDAY AND WEDNESDAY EVENING...POSSIBLY
SEVERE...FOLLOWED BY HEAVY RAIN...MAINLY IN THE SOUTHWESTERN
ZONES. SCT

&&

.HYDROLOGY...
SOILS ARE ALREADY SATURATED OR NEARLY SO IN SOME AREAS ACROSS THE
HSA DUE TO RECENT HEAVY RAINFALLS. THE NEXT WEATHER SYSTEM WILL
MOVE IN TONIGHT WITH SCATTERED THUNDERSTORMS. PRECIPITATION
INITIALLY WILL BE SCATTERED...BUT LOCALLY HEAVY RAINFALL IS
POSSIBLE IN ANY CONVECTION.  IF A FEW STORMS WERE TO MOVE ACROSS
THE SAME AREA THERE WOULD BE THE POTENTIAL FOR FLASH FLOODING. 1
HOUR FLASH FLOOD GUIDANCE IS AS LOW AS 1.5 INCHES ACROSS THE
NORTHERN PORTION OF THE HSA.  AS THE PRECIPITATION TRANSITIONS
INTO A STEADIER RAIN ACROSS THE WESTERN PORTION OF THE HSA
WEDNESDAY AND SPREADS ACROSS THE REMAINDER OF THE AREA WEDNESDAY
NIGHT THERE IS THE POTENTIAL FOR AN INCH OR TWO OF RAIN...WITH
LOCALLY HIGHER AMOUNTS OVER A 12 TO 18 HOUR PERIOD. THERE IS THE
POTENTIAL FOR SOME SMALL STREAMS TO COME OUT OF THEIR BANKS AND
LOW LAND FLOODING. WILL CONTINUE TO MONITOR THE POTENTIAL FOR THE
MAIN STEM RIVERS. RIGHT NOW LEVELS ON THE MAIN STEMS ARE ALL WELL
BELOW FLOOD STAGE AND CONTINUING TO FALL...AND WILL CONTINUE TO
DROP OFF SOME MORE TODAY. AS THE STEADIER RAIN MOVES INTO THE AREA
WEDNESDAY AND WEDNESDAY NIGHT THE RIVERS WILL BE ON THE RISE
AGAIN...BUT RIGHT NOW IT LOOKS LIKE THEY WILL PROBABLY REMAIN
BELOW FOOD STAGE. LATER SHIFTS MAY WISH TO CONSIDER AN
AREAL/SMALL STREAM FLOOD WATCH FOR A PORTION OF THE AREA FOR
WEDNESDAY INTO WEDNESDAY NIGHT. AS THE MAIN THREAT OF SMALL
STREAM FLOODING WILL LIKELY BE WEDNESDAY NIGHT (4TH PERIOD) WILL HOLD
OFF FOR NOW. CB

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH FROM WEDNESDAY AFTERNOON THROUGH LATE WEDNESDAY
NIGHT FOR 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.

&&

WEATHER.GOV/GLASGOW

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE GLASGOW MT
342 PM MDT TUE JUN 5 2007

MTZ016>027-059>062-062145-
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-
342 PM MDT TUE JUN 5 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED STRONG THUNDERSTORMS WILL MOVE INTO THE AREA TONIGHT. A
FEW OF THESE STORMS COULD BECOME SEVERE...WITH LARGE HAIL AND
DAMAGING WINDS. THE BEST CHANCE OF SEVERE STORMS WILL BE IN VALLEY...
PHILLIPS...GARFIELD...PETROLEUM...AND MCCONE COUNTIES.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THE THREAT OF SEVERE THUNDERSTORMS CONTINUES IN NORTHEAST MONTANA
WEDNESDAY....BUT WITH THE GREATEST THREAT SHIFTING EAST TO
SHERIDAN...EASTERN ROOSVELT...RICHLAND...DAWSON...AND WIBAUX
COUNTIES. LARGE HAIL AND DAMAGING WINDS ARE POSSIBLE WITH
THUNDERSTORMS IN THESE AREAS.

THERE IS A FLOOD WATCH FOR SMALL STREAMS AND CREEKS IN NORTHEAST
MONTANA WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT. WIDESPREAD HEAVY
RAIN WILL DEVELOP ACROSS THE ENTIRE AREA BY WEDNESDAY AFTERNOON
AND CONTINUE WEDNESDAY NIGHT. RAINFALLS OF 1 TO 2 INCHES WILL BE
COMMON...CAUSING POSSIBLE MINOR FLOODING OF SMALL STREAMS...CREEKS...
COULEES...LOW SPOTS...AND POORLY DRAINED AREAS.

.SPOTTER INFORMATION STATEMENT...

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