Severe Thunderstorm Warning 90, NWS Grand Forks, ND

FORECAST DISCUSSION FOR EASTERN NORTH DAKOTA AND NORTHWEST MINNESOTA
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND
210 PM CDT FRI JUN 29 2001

FORECAST CHALLENGE WILL BE TEMPS AND PRECIP CHANCES

.OVERVIEW...
LATEST SFC ANALYSIS SHOWS WEAK FRONT/TROUGH PUSHING EAST INTO MN
SIDE OF FA. SLIGHT DEWPOINT COOLING IS NOTED BEHIND FEATURE...AS
THEY DROP INTO THE LOWER 60S. ETA DID A BIT BETTER JOB INITIALIZING
MASS FIELDS...WITH AVN NOT TOO FAR BEHIND.

.SHORT TERM...
CONCERN THIS EVENING IS CONVECTIVE POTENTIAL IN EASTERN FA. TROUGH
IS PROGRESSING A LITTLE FASTER THAN MODELS HAVE PROGGED. THIS SHOULD
LIMIT SFC CONVERGENCE AS A WEST/NORTHWEST FLOW DEVELOPS AND TROUGH
AND DEVELOPING CONVECTION MAKES IT OUT OF FA AROUND 21Z. EVEN THOUGH
A 50KT SPEED MAX WILL RIDE INTO AREA AFTER 00Z...FEEL ANY SFC
FORCING WILL BE LOST WITH TROUGH PASSAGE. IN ADDITION...850MB
DEWPOINTS DRY TO AROUND +9C THIS EVENING. INSTABILITIES ALSO DROP
AFTER 00Z...SO EXPECT A DRY EVENING AND OVERNIGHT. WINDS WILL BECOME
LIGHT NORTH AFTER 06Z...COUPLED WITH RESIDUAL MOISTURE COULD LEAD TO
PATCHY FOG...ESPECIALLY IN SOUTH AND EAST WHERE HIGHER DEWPOINTS
WILL BE. WILL MENTION FOG IN HERE FOR THIS REASON.

.LONG TERM...
SIGNIFICANT COLD FRONT DROPS INTO REGION TOMORROW FROM NORTH. 850MB
TEMPS COOL TO AROUND +6C ACROSS THE NORTH...WITH THE SOUTH MUCH
WARMER AT +14C. WITH THE PASSAGE OF FRONT...AND RIGHT ENTRANCE
REGION OF 110KT 300MB SPEED MAX...EXPECT SCATTERED SHOWERS ACROSS
NORTH WHERE INSTABILITY WILL BE LIMITED. EXPECT PLENTY OF CLOUDS AS
WELL WITH CONVECTIVE TEMPS IN THE MID 60S...ANY SUNSHINE SHOULD SELF
DESTRUCT. FROM GFK SOUTH...CAPES AROUND 600 J/KG WITH LI/S TO -4C
WILL PREVAIL AFTER 18Z. IN ADDITION...SFC DEWPOINTS WILL BE AROUND
60F WITH 850MB DEWPOINTS POOLING AHEAD OF FRONT AROUND +10C. EXPECT
THUNDERSTORM DEVELOPMENT ALONG GOOD SFC CONVERGENCE NEAR FRONT BY
AFTERNOON. WITH WET BULB ZERO LEVELS DROPPING TO 9500FT...WOULD NOT
RULE OUT SOME ISOLATED SEVERE STORMS WITH LARGE HAIL. WEAK
SUBSIDENCE WILL BUILD IN SAT NIGHT BEHIND DEPARTING SHORTWAVE
PASSING NORTH OF BORDER. RELATIVE HUMIDITY PROGS SHOW DRIER AIR
WORKING INTO NORTHERN FA AS HIGH CONTINUES TO BUILD INTO ARROWHEAD.
850MB TEMPS ALSO DROP TO AROUND +2C IN NORTH...SO EXPECT TEMPS BELOW
NORMAL. TO THE SOUTH...FRONT WILL LINGER IN SOUTH DAKOTA AND EXPECT
MORE CLOUDS CLOSER TO RETURN FLOW. ON SUNDAY...LOW LEVEL JET
DEVELOPS IN WESTERN NORTH DAKOTA. SHOWALTER/S DROP TO AROUND -2C IN
WESTERN FA BY 00Z MON. STRONG 850MB WARM AIR ADVECTION MOVES INTO
THE RED RIVER VALLEY SUNDAY AFTERNOON. IN ADDITION...STRONG LIFT IN
THE 850-700MB LAYER RESULTS AHEAD OF 500MB SHORTWAVE WHICH SHOULD
AID ELEVATED CONVECTION. EXPECT SHOWERS BY LATE IN THE DAY SUNDAY IN
EASTERN FA...WHERE STABLE AIR WILL HANG ON ALL DAY. TEMPS WILL BE
COOLEST IN THE NORTHEAST...CLOSER TO DEPARTING HIGH.

EXTENDED...LONG RANGE MODELS IN PRETTY GOOD AGREEMENT...WITH MRF
TIMING COMPROMISE...SO UTILIZED FOR FORECAST. UPPER LEVEL NW FLOW
DOMINATES THROUGH EXTENDED WITH A SHORTWAVE AND SFC FRONT MOVING
THROUGH CWFA ON MON...SO KEPT CHC TSRA. UPPER LEVEL LOW AND
ASSOCIATED TROF MOVE THROUGH CWFA TUE NIGHT THROUGH WED...KEEPING
CYCLONIC FLOW OVER CWFA ON WED...SO ADDED CHC TSRA TO FORECAST. SFC
HIGH THEN BUILDS IN FOR THU AND FRI...SO KEPT DRY. AS FAR AS
TEMPS...FMR AND MEX SIMILAR...KEEPING TEMPS IN NORMAL TO SLIGHTLY
BELOW NORMAL RANGE.

.FGF...NONE.

KELLENBENZ/NG