Severe Thunderstorm Warning 89, NWS Grand Forks, ND

FORECAST DISCUSSION FOR EASTERN NORTH DAKOTA AND NORTHWEST MINNESOTA
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND
145 PM CDT TUE JUN 22 1999

...MAIN FORECAST PROBLEM CHC OF THUNDERSTORMS THIS EVENING...

MODELS SIMILAR IN HANDLING 5H FEATURES WITH SOME MINOR DIFFERENCES
CONCERNING PLACEMENT/STRENGTH OF VORT MAXES. ONCE AGAIN RUC DOING THE
BEST IN THE SHORT TERM WITH ETA IN CLOSE SUPPORT. ETA ALSO A BIT BETTER
AT THE SFC AND WITH LOW LEVEL THERMAL FIELDS THUS WILL FOLLOW ETA THIS
PACKAGE.

.SHORT TERM...CONVECTIVE ACTIVITY OVER WRN ND IN ASSOCIATION WITH 850
MB FRONT MAKING SLOW EASTWARD PROGRESS THIS AFTERNOON. HOWEVER...BEST
SFC CONVERGENCE SHOWN MOVING INTO ERN ND AND CENTRAL SD...WITH
THUNDERSTORMS FIRING IN SOUTH CENTRAL SD ATTM ALONG WEAK S/W MOVING UP
FROM THE SW. CONVECTIVE INHIBITION LIMITING THIS ACTIVITY CURRENTLY...
BUT ETA SHOWS CIN DIMINISHING OVER FA BY LATE AFTERNOON. BEST SFC
CONVERGENCE ALONG PRE FRONTAL TROF...WHICH SHOULD BE LOCATED OVER ERN
ND BY 0Z. THUS THUNDERSTORMS SHOULD CONTINUE TO BECOME MORE WIDESPREAD
OVER THE WESTERN HALF OF THE FA LATE THIS AFTERNOON...AND SPREADING
EAST OVER NW MN DURING THE EVENING.

WHILE MAIN S/W TO PUSH INTO RRV BY 12Z...THIS FEATURE TO TRAIL WELL
BEHIND SFC FRONT. FRONT TO STRETCH ACROSS CENTRAL MN BY 12Z. AS A
RESULT...BEST MOISTURE TO BE SHUNTED OUT OF ALL BUT FAR ERN ZONES BY
THEN. LOSS OF MOISTURE TO INHIBIT CONVECTIVE DEVELOPMENT DESPITE DECENT
DYNAMIC FORCING. WILL END PRECIPITATION FROM WEST TO EAST OVER ALL BUT
ERN FA IN ZONES FOR TONIGHT. DRIER AIR ON WESTERLY FLOW TO ALLOW TEMPS
TO DROP INTO THE 50S WEST WITH LOWER TO MIDDLE 60S ALONG AND AHEAD OF
FRONT.

.LONG TERM...MAIN DYNAMIC FORCING TO BE OVER ERN FA DURING THE MORNING
BEFORE LIFTING OUT BY MIDDAY. ALTHOUGH SFC FRONT STILL IN THIS AREA
BEST MOISTURE TO BE EAST OF THIS AREA. WILL MENTION OF MORNING SHOWERS
THIS AREA WITH ACTIVITY ENDING AS SYSTEM LIFTS NE. ETA SHOWS WEAK S/W
WRAPPING AROUND 5H SYSTEM BUT WITH LOWER LEVELS DRIED OUT THIS SHOULD
ONLY PRODUCE MID/HIGH CLOUDS OVER THE NRN FA. CAA BEHIND FRONT TO KEEP
REGION AOB SEASONAL NORMALS WITH FWC NUMBERS GENERALLY ACCEPTED. WITH
SFC TO 5H FLOW NEARLY UNIDIRECTIONAL WILL SEE BREEZY CONDITIONS SET UP
OVER MUCH OF FA. THERMAL GRADIENT TO TAKE A N/S ORIENTATION WITH FWC
NUMBERS AGAIN ACCEPTABLE.

.EXTENDED...MRF AND UKMET STILL IN AGREEMENT ALTHOUGH MRF IS MUCH
STRONGER WITH S/W MOVING INTO NRN PLAINS THIS WEEKEND. WARM FRONT TO
MOVE THROUGH THE AREA ON FRIDAY WITH INCREASE IN LOWER LEVEL MOISTURE.
ALTHOUGH MRF HAS WASHED OUT WEAK S/W THAT IT HAD ADVERTISED MOVING
THROUGH FA ON FRIDAY...WILL CONTINUE TO MENTION CHC OF THUNDERSTORMS
OVER ALL BUT FAR NE ZONES. MAIN S/W TO ARRIVE ON SATURDAY...BUT FRONT
TO AGAIN MOVE THROUGH REGION BEFORE BEST DYNAMIC FORCING ARRIVES. WILL
CONTINUE MENTION OF THUNDERSTORMS OVER THE FA FOR SATURDAY BUT
CONFIDENCE IN THIS HAS BEEN DIMINISHED. HIGH PRESSURE BUILDS IN SUNDAY
WITH ASSOCIATED CAA WHICH WILL DROP TEMPS BELOW NORMAL.

.FGF...NONE.

TURNER