Flash Flooding and Hail in Montana, June 20 to 21, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
820 PM MDT MON JUN 20 2005

.SHORT TERM...FOR NORTHEAST MONTANA TONIGHT...
SEVERE THUNDERSTORM WATCH #507 REMAINS IN EFFECT UNTIL 11 PM MDT FOR
OUR WESTERN ZONES.  SO FAR THIS EVENING THERE HAS ONLY BEEN ONE
GAME IN TOWN...A SEVERE STORM ACROSS NORTHERN BLAINE COUNTY THAT IS
CROSSING OVER INTO NORTHERN PHILLIPS COUNTY...AND THE KGGW 88-D
INDICATING THAT THIS STORM IS CAPABLE OF PRODUCING A TORNADO.

THE ACTIVITY FROM LAST NIGHT/S MCS APPEARED TO TRACK RIGHT ALONG THE
PERIPHERY OF A STRONG SUMMERY LOOKING UPPER RIDGE THAT IS CENTERED
JUST EAST OF THE 4-CORNERS REGION.  THE UPPER FLOW ACROSS THE
NORTHERN HIGH PLAINS IS OUT OF THE WEST/SOUTHWEST...BUT VEERS MORE
INTO THE WEST/NORTHWEST ACROSS THE EASTERN DAKOTAS AND UPPER
MISSISSIPPI VALLEY.

THE 18Z NAM12 SEEMS TO BE PICKING UP WELL ON THE CONVECTION ACROSS
NORTHERN BLAINE/PHILLIPS COUNTIES.  IT INTENSIFIES THE CONVECTION AND
DEVELOPS AN MCS ACROSS OUR NORTHERN ZONES LATER THIS EVENING AND
PUSHES IT OUT INTO WESTERN NORTH DAKOTA BY MORNING.  THIS CERTAINLY
SEEMS REASONABLE GIVEN THE UPPER PATTERN AND WHAT HAPPENED LAST
NIGHT.  INTERESTING TO NOTE THAT THE 00Z NAM DOES NOT DEVELOP AN MCS
AS IT APPARENTLY TRIES TO KEEP THE AREA MORE CAPPED.

THE BIGGEST CHANGE TO THE DATABASE WAS TO LOWER THE CLOUD COVER INTO
THE M/CLEAR RANGE AND DROPPED THE POPS ACROSS OUR EASTERN ZONES AS
IT APPEARS THAT IT WILL BE AT LEAST ANOTHER FEW HOURS BEFORE ANY
CLOUDS AND CONVECTION MAKE IT THAT FAR EAST.  THE 00Z KGGW AND KBIS
SOUNDINGS SEEMS TO SUPPORT THIS WITH A MODEST CAP IN PLACE AT AROUND
800MB.

LATEST MESO ANALYSIS INDICATED PLENTY OF INSTABILITY WITH MLCAPE
VALUES OVER 2000J/KG AND LI/S BELOW -6C.  THE PRIMARY UNCERTAINTY AT
THIS JUNCTURE IS IF THERE IS ENOUGH SHORTWAVE ENERGY IN THE FLOW TO
INITIATE CONVECTION.  SHOULD THE CONVECTION FIRE THE PRIMARY THREATS
ARE LIKELY TO BE LARGE HAIL AND DAMAGING STRAIGHT LINE WIND WITH BOW
ECHOS...BUT ISOLATED TORNADOES ARE ALSO A THREAT...ESPECIALLY IN
LIGHT OF THE GOOD ROTATION SHOWING UP ON OUR RADAR WITH THE STORM IN
NORTHERN PHILLIPS COUNTY. CB

.PREVIOUS DISCUSION...FOR NORTHEAST MONTANA...TON THRU WED...
WARM AND ACTIVE PATTERN SETTING UP FOR EARLY THIS WEEK WITH MORE
THAN ONE ROUND OF SEVERE WEATHER POSSIBLE. FIRST ROUND EXPECTED TO
COME TONIGHT WITH PATTERN NOT TO DIFFERENT FROM LAST NIGHT. LATEST
NAM...WHICH PICKED UP WELL ON LAST NIGHTS ACTIVITY...IS DEVELOPING
YET ANOTHER THUNDERSTORM COMPLEX AND SENDING IT ACROSS NORTHEAST
MONTANA...WITH A LITTLE EARLIER TIMING THAN PREVIOUS RUN. KGGW 18Z
SOUNDING SHOWING DECENT CAP...BUT WITH WARMING AND INCREASING
SURFACE MOISTURE THIS SHOULD ERODE THROUGH THE AFTERNOON. MAIN
THREATS WILL BE LARGE HAIL AND DAMAGING WINDS...BUT GIVEN SUPERCELL
ENVIRONMENT CANNOT RULE OUT AN ISOLATED TORNADO.

FOR TUESDAY INSTABILITY AXIS SETS UP ACROSS NORTHEAST ZONES WITH
IMPRESSIVE CAPE VALUES. SOUNDINGS SHOWING THAT THERE MAY BE
SOMETHING OF A CAP...BUT IF ANY WAVES CROSS ENVIRONMENT THAT SHOULD
BE ENOUGH TO SET OFF AT LEAST ISOLATED THUNDERSTORMS...AND WILL KEEP
POPS HERE. ANYTHING THAT DOES DEVELOP WILL LIKELY BE SEVERE...SO
WILL CONTINUE WITH SEVERE MENTION. SHOULD ALSO SEE CONVECTION
INITIATING OF HIGHER TERRAIN BY LATE TUESDAY AFTERNOON AND PUSH INTO
WESTERN ZONES BY EVENING. NOT REALLY CONFIDENT HOW LONG ACTIVITY
WILL LAST INTO THE NIGHT...SO HAVE PUSHED POPS INTO SOUTH CENTRAL IN
CASE DEVELOPING LOW LEVEL JET AND WAVE ENERGY SUPPORTS THEM PAST
SUNSET. ON WEDNESDAY FRONT APPROACHES THE AREA...AND EXPECT THAT
THUNDERSTORMS WILL AGAIN DEVELOP OFF OF HIGHER TERRAIN AND PUSH INTO
THE AREA BY AFTERNOON. AT THIS TIME SEVERE WEATHER NOT LOOKING QUITE
AS FAVORABLE...BUT CANNOT RULE IT OUT WITH SIMILAR PATTERN. FOR NOW
WILL NOT MENTION IN FORECAST.

OTHERWISE EXPECT HOT AND RATHER HUMID CONDITIONS OVER NEXT COUPLE OF
DAYS. HIGH TEMPERATURES WILL CLIMB INTO THE UPPER 80S AND 90S...WITH
LOWS AT NIGHT ONLY IN THE 60S. JJZ

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...
VERY LITTLE CHANGES AGAIN WERE MADE TO THE EXTENDED PERIOD
ESPECIALLY BEYOND THURSDAY. SOUTHWEST FLOW ALOFT WAS PROGGED BY THE
ALL OF THE MEDIUM RANGE MODELS WITH A POOLING OF HIGHER MEAN
RELATIVE HUMIDITY ACROSS MT THROUGH MUCH OF THE PERIOD.

LIMITING FACTOR FOR WEDNESDAY NIGHT AND THURSDAY HOWEVER LOOKS TO BE
LACK OF GOOD SHEAR AND LOW LEVEL MOISTURE AS MAIN SURFACE LOW WILL
HAVE LIFTED NORTH INTO CANADA. HOWEVER MODELS ARE NOT IN AGREEMENT
WITH THE STRENGTH OF THIS.

ONE THING FOR SURE TO OCCUR DURING THIS PERIOD IS A COOLER AIRMASS
TO MOVE IN. TEMPERATURES SHOULD BE MUCH CLOSER TO NORMALS.  JAMBA

.PREVIOUS LONG TERM DISCUSSION...
NO CHANGES MADE TO THE EXTENDED FORECAST THIS MORNING WITH MODELS
STILL IN GOOD AGREEMENT WITH MAINLY SOUTHWEST FLOW PERSISTING
THROUGH NEXT WEEK. SINCE GOOD THUNDERSTORM PATTERN SIMILAR TO THE
PAST FEW DAYS...SEE NO REASON TO CHANGE BROADBRUSH SLIGHT CHANCE
POPS THROUGH THE ENTIRE PERIOD. TEMPERATURES TO REMAIN AT OR
SLIGHTLY ABOVE NORMAL...ALREADY HANDLED JUST FINE IN THE GRIDS.
EVERYTHING ALSO ON TRACK WITH MORE SEVERE WEATHER LIKELY IN AT LEAST
A PART OF THE EXTENDED PERIOD. JAZ

&&

AVIATION...
VFR CONDITIONS WITH A SCATTERED TO BROKEN CEILING OF ABOUT 8
THOUSAND WILL QUICKLY GIVE WAY TO SCATTERED THUNDERSTORMS EARLY THIS
EVENING. LOCALLY HEAVY RAIN WITH LARGE HAIL A GOOD POSSIBILITY
WITH THESE STORMS...WHICH WOULD BRING IFR CONDITIONS. CONDITIONS
SHOULD IMPROVE BY DAYBREAK TUESDAY AS STORMS MOVE OUT OF THE AREA.
LIGHT WINDS AWAY FROM THUNDERSTORMS ARE EXPECTED.  JAMBA

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...SEVERE THUNDERSTORM WATCH
#507 IN EFFECT UNTIL 11 PM MDT FOR PHILLIPS...PETROLEUM...GARFIELD...
AND VALLEY COUNTIES.

&&

WEATHER.GOV/GLASGOW

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GLASGOW MT
426 PM MDT MON JUN 20 2005

MTZ016-017-021-022-059>061-211200-
CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-
PETROLEUM-GARFIELD-NORTHERN PHILLIPS-SOUTHWEST PHILLIPS-
NORTHERN VALLEY-
426 PM MDT MON JUN 20 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MONTANA.

.DAY ONE...TONIGHT
A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR A PORTION OF
NORTHEAST MONTANA THROUGH 11 PM TONIGHT. PLEASE REFER TO
GTFWCNGGW OR WWUS65 KGGW FOR ADDITIONAL INFORMATION.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY
ISOLATED TO WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP
ACROSS THE AREA DURING THE AFTERNOON AND EVENING HOURS TUESDAY
THROUGH SUNDAY. SOME OF THESE STORMS COULD BECOME SEVERE...PRODUCING
DAMAGING WIND AND LARGE HAIL. ISOLATED TORNADOES ARE ALSO
POSSIBLE.

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

MTZ018>020-023>027-062-211200-
DANIELS-SHERIDAN-WESTERN ROOSEVELT-MCCONE-RICHLAND-DAWSON-PRAIRIE-
WIBAUX-EASTERN ROOSEVELT-
426 PM MDT MON JUN 20 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST
MONTANA.

.DAY ONE...TONIGHT
SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS THE AREA
LATER THIS EVENING AND TONIGHT. SOME OF THESE STORMS COULD BECOME
SEVERE...PRODUCING DAMAGING WIND AND LARGE HAIL. ISOLATED
TORNADOES ARE ALSO POSSIBLE.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY
ISOLATED TO WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP
ACROSS THE AREA DURING THE AFTERNOON AND EVENING HOURS TUESDAY
THROUGH SUNDAY. SOME OF THESE STORMS COULD BECOME SEVERE...PRODUCING
DAMAGING WIND AND LARGE HAIL. ISOLATED TORNADOES ARE ALSO
POSSIBLE.

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

JJZ