Tornadoes and Hail in Minnesota, May 15, 2001

FORECAST DISCUSSION FOR EASTERN NORTH DAKOTA AND NORTHWEST MINNESOTA
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND
207 AM CDT TUE MAY 15 2001

...MAIN FORECAST CHALLENGE CONCERNS TSTM POTENTIAL TONIGHT AND AGAIN
ON WED NIGHT...

MODELS IN GOOD AGREEMENT WITH FIRST SHRT WV MOVING THRU THE NRN RED
RIVER VALLEY BUT DIFFER ON TIMING OF SYSTEM CROSSING THE NRN PLAINS
WED NIGHT. NGM MORE PROGRESSIVE WITH SECOND FEATURE...WITH AVN
SLOWEST AND ETA A COMPROMISE. ETA A BIT FURTHER N THAN THE
OTHERS...AND CONSIDERING STRONG 3H JET TO IMPINGE UPON DECENT
RIDGING OVER THE ERN U.S. CAUSING JET TO TURN A BIT FURTHER TO THE
NE. THUS ETA 5H PROGS PREFERRED. AT THE SFC...AVN/RUC OUTPERFORMING
THE OTHERS IN IDENTIFYING SFC LOW OVER SE ND...ALTHOUGH IT IS A BIT
TOO WEAK AND TOO FAR E WITH THIS FEATURE. ETA PLAYS CATCH UP BY 0Z
AND STAYS CLOSE TO AVN THRU 30 HRS. WL FOLLOW ETA THIS PACKAGE...
WITH A NOD TOWARD AVN ON SFC FEATURES EARLY ON.

.SHORT TERM...AFOREMENTIONED SFC LOW TO QUICKLY TRACK E OVERNIGHT
INTO ERN WI BY 12Z AS 3H JET PUNCHES IN AND 5H TROF LIFTS NE INTO
WRN ONTARIO. COOL FRONT ENTERED INTO WRN ZONES BY 17Z AND SHOULD
PUSH QUICKLY THRU THE REGION OVERNIGHT. GOOD MOISTURE CONVERGENCE
ALONG PRE FRONTAL TROF AND ALONG WARM FRONT EXTENDING FROM SFC LOW
INTO WRN WI EVIDENT ON SFC ANALYSIS...HOWEVER UPPER AIR ANALYSIS
SHOWS LIMITED MOISTURE ABOVE THE BOUNDARY LAYER. WHILE WARM 7H TEMPS
KEEPING REGION CAPPED...THIS CAP TO BREAK DOWN BY 0Z AS COOLER AIR
PUSHES IN AT THIS LVL. THIS EVIDENT ON ETA STABILITY PARAMETERS.
EXPECT MOST UNSTABLE AIR TO BE ASSOCIATED WITH WARM FRONT AS IT
SLOWLY LIFTS N BUT THIS SAME AREA TO STAY UNDER WARMER 7H TEMPS.
THUS BEST POTENTIAL FOR TSTMS EXPECTED OVER NE ZONES INITIALLY...
WITH ACTIVITY SHIFTING SE ALONG THE WARM FRONT LATER IN THE EVE AS
COOL FRONT BLASTS THRU. ALL SAID...EVENT TO BE RATHER SHORT LIVED AS
FRONT MOVES THRU REMOVING THE BOUNDARY LYR MOISTURE AND GOOD
SUBSIDENCE BEHIND THE 5H WV COVERS THE AREA BY 6Z PER 850 TO 500 MB
Q VECTOR ANALYSIS. CONSIDERING THESE FACTORS AND SPC/S DISCUSSION...
WL MENTION POSSIBILITY OF SVR ALONG AND E OF THE VALLEY FOR THIS
EVENING. AS FOR TEMPS...WITH WINDS SLACKENING OFF LATE TONIGHT AND
WITH DRIER AIR MOVING IN...MAV NUMBERS LOOK A BIT HIGH AND WL CUT
ACCORDINGLY.

.LONG TERM...WL BE BRIEF DUE TO DEVELOPING SVR TSTM. WED TO BE DRY
AND COOLER WITH TEMPS CLOSER TO SEASONAL NORMS. THEN NEXT WV PULLS
INTO THE REGION WED NIGHT. PCPN TO LINGER INTO THU AM AND PERHAPS A
BIT LONGER OVER THE NE ZONES. TEMPS TO FALL BLO SEASONAL AVERAGES.

.EXTENDED...MRF IS STILL HAVING TROUBLE IN THE LATER PERIODS. SO
WILL GO IN BETWEEN THE ECMWF AND THE MRF. START OF THE EXTENDED
PERIOD LOOKS DRY WITH TEMPERATURES COOLING BACK TO NEAR NORMAL
TROUGH THE WEEKEND. A STRONG WAVE IS FORECAST TO DROP SOUTHEAST OUT
OF CANADA INTO MONTANA BEFORE CUTTINGl OFF FROM THE FLOW. SO LOOKS
LIKE A WET  AND SLIGHTLY COOLER PERIOD TO START OF THE BEGINNING OF
THE NEW WORK WEEK. HOWEVER...CONFIDENCE IS LOW IN THE LATER HALF OF
THE EXTENDED.

.FGF...NONE ATTM.

RJT/JRB

MNZ001>009-013>017-022>024-027>032-040-NDZ006>008-014>016-024-
026>030-038-039-049-052>054-152000-

SPECIAL WEATHER STATEMENT
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND
111 PM CDT TUE MAY 15 2001

...SLIGHT RISK OF SEVERE STORMS OVER NORTHWEST MINNESOTA FROM THE
RED RIVER AND EAST...

SYNOPSIS...AN UNSTABLE AIRMASS COMBINED WITH INCREASING LOW LEVEL
MOISTURE ACROSS EASTERN NORTH DAKOTA AND NORTHWEST MINNESOTA IS
SETTING THE STAGE FOR THUNDERSTORM DEVELOPMENT THIS AFTERNOON. ALL
OF THIS MOISTURE AND INSTABILITY IS POOLING AHEAD OF A LOW PRESSURE
SYSTEM LOCATED OVER SOUTHEAST NORTH DAKOTA AND A WARM FRONT
EXTENDING FROM THE LOW ACROSS WEST CENTRAL MINNESOTA.

AREA OF CONCERN...SLIGHT RISK OF SEVERE THUNDERSTORMS IS FORECAST
ALONG AND EAST OF THE RED RIVER.

TIME...START AROUND 3 PM AND WILL DIMINISH BY 10 PM.

TYPE OF HAZARD...THE GREATEST THREAT IS LARGE HAIL...ALONG WITH
DAMAGING DOWNBURST WINDS OVER THE ENTIRE OUTLOOK AREA. THERE IS
ALSO A VERY SLIGHT RISK OF A TORNADO ALONG AND NORTH OF THE WARM
FRONT IN WEST CENTRAL MINNESOTA.

BRAZZELL