Severe Thunderstorm Warning 219, NWS Grand Forks, ND

FORECAST DISCUSSION FOR EASTERN NORTH DAKOTA AND NORTHWEST MINNESOTA
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND
257 PM CDT TUE AUG 18 1998

1ST PERIOD DISCUSSION...THREAT FOR TSRA THREAT/SVR MAIN FCST CONCERN
TNGT. CURRENT KMVX 88D INDICATING LEFTOVER SHRA AFFCTNG NW MN WHILE
STRNGR TSRA DVLPNG NR JMS AND TRACKING NE. IR LOOP SHOWS LOTS OF CLOUD
COVER ACRSS ALL OF CWA W GUD CHUNK OF AREA IN LOW MVFR AND EVEN IFR
CONDITIONS.

ADAP SHOWS GREAT INSTABILITIES/SFC MOIST CNVRGNCE OVER MUCH OF
WRN/CNTRL ND. LI/S TO -11 ALONG W SFC MXNG RATIOS UP TO 17G/KG AND GUD
THETA-E ADVCTN IN SAME AREA WHERE SUM CLRNG TOOK PLACE LEADS ME TO
BELIV SUM DVLPMNT WL STILL OCCUR PRBLY JUST E OF THERE ALNG BEST GRAD OF
CNVRGNCE/MXNG RATIONS AND LI/S THIS AFTN THRU ERY EVE AND THEN SLIDE NE
AS NOW BEGINNING TO OCCUR. NOSE OF H85 JET ALSO IN SIMILAR POSITION. SFC
LO PRES ANALYZED NR DIK...CLOSER TO NGM FRTHR N POSITION THAN MORE S
ETA. AS NGM ALSO HIT ON MRNG CNVCTN IN ASSOC W S/W BETTER...WL TEND TO
BELIV ITS FEATURES MORE FOR THIS PD.

LITTLE PVA SEEN INDICATED ON MDLS FOR TNGT AS ONE S/W EXITS INTO SRN
CAN BY 00Z AND NXT ONE DOESN/T AFFCT AREA TIL LATER PD SO SUM DYNAMICS
LACKING FOR SVR TNGT...ALTHO LARGE H250 DVRGNCE IS PROGGED OVER RRV BY
12Z. HOWEVER...LUKS LIKE NGM HITS ON AREA OF CNVCTN TO DVLP SW ND TWRD
00Z W ITS UVM PROG AND WUD AGREE BASED ON ABOVE ADAP SIGNATURES. THIS
SHUD THEN PROGRESS NE TWRD RRV AND INTO MN ZONES LATER. BEST H85
30-40KT JET HEADS INTO MN CWA TNGT AS +20C LINE REACHES DVL-FAR LINE BY
00Z AND BY 12Z H85 (CDFNT) SLIDES INTO CNRL ND W NW FLO INTO NW ND
ATTM. SFC LO SHUD TRACK ACRSS SCNTRL ND THIS EVE/TNGT W STRNG
ISENTROPIC LFT SEEN ERN ND/WRN MN AS 576 THCKNESS LINE SWINGS N. SLO
MOVING LO ONLY TO NR JMS BY 12Z AND SFC CDFNT NR DVL AS BEST UVM SWINGS
INTO WCNTRL MN.

BELIV BEST CHANCE FOR SVR TNGT WL START IN SW ZONES FRM VCY THRU SRN RRV
AND EVENTUALLY WORK INTO REST OF RRV AND THEN XTRM WRN MN ZONES.
WUD LEAVE MENTION OUT XTRM ERN ZONES WHERE BEST MOIST RTRN WL NOT OCCUR
UNTIL VRY LATE THIS PD AND MORE STABLE AIR STILL HANGING ON. BASE THIS
ON PROXIMITY OF WMFNT WHERE VERT WIND SHEAR SHUD BE STRNGST TO SUPPOR
MORE ORG ACTIVITY. CRRNT POS OF WMFNT HAS IT N OF BIS CURLING SE JUST N
OF ABR BUT SOUTH OF P67. AMNT OF LO CLOUD CUD BE LIMITING FACTOR...AS
WELL AS SUCH HI K/S INTO UPPR 30S AND PWATS 1.75 LEADING ME TO BELIV
MAINLY HVY RAIN THREAT. WUD STL MENTION SVR THREAT THO PARTS OF ERN ND
TNGT W FAR SNDG AT 06Z SHOWING LI/S TO -7 AND CAPES OVER 2000 J/KG W
REALISTIC 67F T/D AS INPUT. ALSO HELICITY VALUES GET TO NR 200 SRN RRV
LATE TNGT. WBZ LVLS QUITE HI...ALTHO SVR HAIL WAS ALRDY RPRTD THIS AM
IN CWA SO BELIV STILL PSBL AGAIN TNGT IN THIS AIRMASS.

TEMPS SHUD NOT FALL MUCH CWA WIDE TNGT W SE FLO AND CONTINUED ADVCTN OF
HIER TD/S (ALRDY MID 60S MUCH OF ND SIDE) AND CLOUD COVER. MOS BUSTED ON
HI TEMPS TDY BUT SHUD DO OK FOR MOST LO TEMPS W LITTLE DROP XPCTD.
FOLLOWING ARE FORECAST SUGGESTIONS ONLY. OFFICIAL FORECASTS FOUND IN
BISZFPND AND MSPZFPMN:

DVL/GFK: MOSTLY CLOUDY WITH SCATTERED SHOWERS AND THUNDERSTORMS...SOME
POSSIBLY SEVERE AND WITH HEAVY RAIN. LOW IN THE MID 60S. WIND SOUTHEAST
10 TO 20 MPH.

FAR: MOSTLY CLOUDY WITH SCATTERED SHOWERS AND THUNDERSTORMS...SOME
POSSIBLY SEVERE AND WITH HEAVY RAIN. LOW IN THE UPPER 60S. WIND
SOUTHEAST 10 TO 20 MPH.

MN: HCO/TVF/FSE: MOSTLY CLOUDY WITH SCATTERED SHOWERS AND
THUNDERSTORMS...SOME POSSIBLY SEVERE AND WITH HEAVY RAIN. LOW IN THE
MID 60S  WIND SOUTHEAST 10 TO 20 MPH.

FFM/DTL: MOSTLY CLOUDY WITH SCATTERED SHOWERS AND THUNDERSTORMS. LOW IN
THE MID 60S. WIND SOUTHEAST 10 TO 20 MPH.

BDE/BJI/PKD: MOSTLY CLOUDY WITH SCATTERED SHOWERS AND THUNDERSTORMS.
LOW 60 TO 65. WIND SOUTHEAST 10 TO 20 MPH.

SOROKA