Severe Thunderstorm Warning 2, NWS Grand Forks, ND

FORECAST DISCUSSION FOR EASTERN NORTH DAKOTA AND NORTHWEST MINNESOTA
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND
200 PM CDT MON MAY 3 1999

MAIN BATCH SHRA/TSRA ASSOCIATED WITH S/W THAT PASSED THRU CWA EARLY THIS
AFTERNOON LIFTED NORTH...HOWEVER SCT LOW TOPPED TSRA CONTINUE TO
DEVELOP IN RIPENING ATMOSPHERE LEFT BEHIND. AREA OF NVA HELPING SKIES
TO BREAK OUT IN FAR SOUTHERN ZONES WITH SOME CU FILLING IN...AS DEEP
SOUTHERLY FLOW TRANSPORTS SIG MOISTURE INTO CWA IN FORM OF 10 G/KG
MIXING RATIOS AND PWATS NEAR .8. GRADIENT STILL STRONG BUT SLACKENING
A BIT IN WESTERN CWA. ETA WAS A BIT BETTER IN PLACEMENT OF MORNING U/A
FEATURE AND MOISTURE...SO WILL FOLLOW SHORT TERM.

.SHORT TERM...
ADAP ALREADY INDICATING LI/S TO -4 IN SW CWA AND TONGUE OF POS THETE
ADVECTION EXTENDING SW TO NE THRU ERN ND. CAPES TO NEAR 1000 J/KG
EXPECTED TO SURGE INTO SOUTHERN ND THIS EVE IN CONJUNCTION WITH INFLUX
OF HI THETA-E AIR AND IMPRESSIVE LOW LEVEL JET. 50+ TD/S ALREADY IN
PLACE FOR AMPLE LOW LEVEL MOISTURE. STRONG BOUNDARY LAYER MOISTURE
CONVERGENCE ALONG WITH NEXT WAVE OF U/L ENERGY ROUNDING TROF WILL HELP
FIRE STORMS TO OUR WSW (IN CLEAR ZONE) AND STORM MOTION SHOULD RIDE THEM
NNE TONIGHT. APPEARS FAVORED AREAS FOR CONVECTION ARE SE ND AND THEN
ARCING NE TOWARD GFK...ESP SECOND HALF OF NIGHT AS THETA E-RIDGE POKES
IN THIS DIRECTION. FURTHER EAST...STRONGER PART OF LOW LEVEL JET
COMBINING WITH PWATS INCREASING TO 1 AND BETTER LOW LEVEL SHEAR COULD
ALSO HELP IGNITE TSRA LATER. WILL KEEP THE LIKELY POPS WEST AND GO TO
MORE CHANCY EAST. MODEST CAPES IN MOST OF THE AREA AND OVERALL LIMITED
SHEAR EXPECTED TO CURTAIL LARGE SEVERE THREAT...ALTHO LOW WBZ LEVELS AND
STRONG MID-LEVEL LAPSE RATES WITH TOTAL TOTALS AROUND 50 MAKE SCATTERED
SEVERE CELLS POSSIBLE AND ANY TSRA COULD MIX HIGHER WINDS DOWN BEFORE
SOUNDING SATURATES TUES.

.LONG TERM...
SIG RAIN AMOUNTS POSSIBLE THIS PERIOD AS VERY SLOW MOVING TROF PERSISTS
OVER CENTRAL STATES WITH JET ENERGY CONTINUING TO DIVE DOWN ON ITS
WESTERN EDGE THRU AT LEAST F+42. EXPECT MORE CONCENTRATED SEVERE THREAT
TO SHIFT MAINLY SOUTH OF CWA TUESDAY...AS BEST JET ENERGY FOCUSES
STRONGER SFC LO TO FORM NEAR NEB AS NORTHERN CIRCULATION WEAKENS AS PER
PREFERRED ETA. APPROACH OF SLOW MOVING SFC TROF HOWEVER WILL FOCUS
IMPRESSIVE BOUNDARY CONVERGENCE TUES AFTN INTO WED AS TIGHT BAROCLINIC
ZONE/STRONG H85-H7 FRONTOGENESIS APPROACHES FROM WEST LEADING TO LARGE
UVM FIELD. ALTHO BEST SEVERE PARAMETERS SOUTH TOMORROW...LEFTOVER
BOUNDARIES FROM OVERNIGHT TSRA AND ENHANCED U/L DIVERGENCE WILL LEAD TO
SOME EMBEDDED TSRA...ESPECIALLY EAST OF RRV. ALL OF CWA IN LINE FOR
DECENT SOAKING AS PERSISTENT UVM COMBINES WITH SATURATED ATMOSPHERE BY
AFTERNOON WITH K INDICES APPROACHING 40 AND PWATS OVER 1 IN EAST ON
STRONG SSE FLO. INVERTED TROF STILL CLOSE TO RRV BY 12Z WED WITH
ENHANCED CONVERGENCE MEANS MORE OVERUNNING RAINS TO PERSIST WITH SEVERE
THUNDER CHANCES LESSENING PAST TUESDAY. TEMPS COOLING A BIT EACH DAY
AND WILL STICK CLOSER TO COOLER FWC THAN WARMER FAN AS GRADIENT
SLACKENS IN COMPARISON TO PAST FEW DAYS.

.EXTENDED...MID RANGE MODELS IN REASONABLE AGREEMENT EARLY ON. MRF
FASTEST WITH DEVELOPMENT OF CLOSED 5H LOW OVER THE NORTHERN
PLAINS...WITH UKMET AND SEP CLOSING LOW SLIGHTLY LATER...WITH THE
FORMER FURTHER NORTH AND THE LATTER FURTHER EAST. ECMWF FAILS TO CLOSE
OFF LOW...BUT KEEPS 5H TROF JUST WEST OF THE FA. BIGGEST DIFFERENCE
SHOWS UP LATER ON WHERE MRF KEEPS LOW OVER NRN PLAINS...AND THEN
RETIRGRADES THIS FEATURE BACK WEST AS IT ATTEMPTS TO PHASE LOW WITH
NEXT 5H TROF MOVING INTO THE PACIFIC NORTHWEST. PREFER EURO/CANADIAN
MODELS SOLUTIONS OF KEEPING THESE FEATURES DISTINCT. ALTHOUGH EACH
DIFFER ON POSITION/STRENGTH OF THIS FEATURE...WITH PROXIMITY OF 5H
LOW/TROF WILL KEEP CHC OF SHOWERS CONTINUING WEDNESDAY NIGHT INTO
THURSDAY. ONCE TROF AXIS PASSES THROUGH FA LATE THURSDAY REGION TO DRY
OUT. BROAD TROF OVER PACIFIC NORETHWEST TO SHARPEN AS MAIN ENERGY
SLIDES DOWN WEST COAST...RESULTING IN RIDGING JUST WEST OF REGION.
NORTHERLY FLOW AT SFC TO KEEP REGION CLOSE TO SEASONAL AVERAGES.

.FGF...NONE

SOROKA/TURNER