Possible tornado outbreak for June 20th.
Posted: Sun Jun 20, 2010 8:48 am
...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF NEB...SD...IA...SW
MN...NRN MO...AND NW IL...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
AREA...FROM THE NRN AND CNTRL HI PLNS TO THE MID MS VLY...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF NEW ENGLAND AND
THE MID ATLANTIC CST...
...SYNOPSIS...
UPR RIDGE WILL HOLD FIRMLY OVER THE SRN PLNS THROUGH MON AS LEAD
IMPULSE/JET STREAK ASSOCIATED WITH ORE/NV UPR LOW...NOW OVER
UT...SHEARS E/NE INTO THE NRN PLNS THIS EVE...AND ACROSS THE UPR MS
VLY EARLY MON. PATTERN WILL THEREFORE REMAIN FAVORABLE FOR NUMEROUS
STRONG TO SVR STORMS...WITH EPISODIC MCS DEVELOPMENT LIKELY
THROUGHOUT THE PERIOD.
...CNTRL/NRN HI PLNS TO MID MS VLY TODAY THROUGH EARLY MON...
CLUSTERS OF SLIGHTLY ELEVATED TSTMS EXPECTED TO PERSIST THROUGH AT
LEAST MIDDAY OVER ERN NEB AND SRN SD ESE INTO PARTS OF NE KS/IA AND
MO...SUPPORTED BY WEAKENING WAA ATOP EXISTING CONVECTIVE OUTFLOW.
SUFFICIENT MUCAPE AND CLOUD LAYER SHEAR LIKELY WILL EXIST FOR
SPORADIC INSTANCES OF SVR HAIL AND PERHAPS LOCALLY DMGG WIND. SOME
REGENERATIVE/UPSTREAM DEVELOPMENT ALSO MAY PERSIST ON WRN FRINGE OF
EXISTING ACTIVITY...I.E. OVER CNTRL NEB AND SRN SD.
APPROACH OF UT UPR IMPULSE...ASSOCIATED INCREASE IN SW FLOW
ALOFT...AND SFC HEATING SHOULD DEEPEN SFC LOW OVER ERN CO TODAY.
THIS WILL SERVE TO STRENGTHEN LOW LVL ESELY UPSLOPE FLOW N OF LOW
ACROSS THE CNTRL/NRN HI PLNS AND ADJACENT PORTIONS OF WRN NEB AND
THE WRN DAKOTAS. COUPLED WITH STRONG SFC HEATING... EXPECT NUMEROUS
STRONG TSTMS TO FORM BY MID TO LATE AFTN OVER SE MT AND ERN WY SSE
INTO WRN SD...WRN NEB AND NE CO. OTHER STORMS MAY FORM A BIT LATER
ON DRY LINE/LEE TROUGH SEGMENTS OVER NRN/WRN KS SWD INTO THE SRN HI
PLNS.
POTENT COMBINATION OF RICH LOW LVL MOISTURE BENEATH DEEP EML WITH
40-50 KT DEEP WSWLY SHEAR AND INCREASING ASCENT WITH UT UPR
DISTURBANCE SHOULD SUPPORT VIGOROUS SUPERCELLS. THESE WILL BE
CAPABLE OF VERY LARGE HAIL AND A FEW TORNADOES...ESPECIALLY FROM ERN
WY INTO ADJACENT PARTS OF SD...NEB...AND POSSIBLY NE CO/NRN KS LATE
THIS AFTN INTO EARLY TONIGHT.
AIDED BY A STRENGTHENING/BROADENING LLJ...RICH MOISTURE
INFLOW...ASCENT WITH CONTINUED ENE MOVEMENT OF UPR IMPULSE...AND LOW
LVL UPLIFT ALONG REMNANT OUTFLOW BOUNDARIES/WARM FRONT...THE STORMS
LIKELY WILL MERGE BY MID EVE INTO SEVERAL SVR MCSS OVER SD AND NEB.
THE POTENTIAL WILL EXIST FOR ONE OR TWO OF THESE CLUSTERS TO EVOLVE
INTO A LARGER SCALE BOW MCS/DERECHO...WITH THE SYSTEM INITIALLY
MOVING MAINLY ESE INTO SRN MN AND IA...AND THEN MORE SEWD ACROSS SRN
WI AND NRN/CNTRL IL EARLY MON.
...NRN RCKYS/INTERMOUNTAIN REGION...
IN ERN QUADRANT OF ORE UPR LOW...SUFFICIENT MOISTURE /PW AROUND .75
IN/ SHOULD EXIST TO SUPPORT SCTD AFTN/EVE STORMS FROM WRN MT SWD
INTO NW WY AND CNTRL/ERN ID...GIVEN STEEP LOW TO MID LVL LAPSE
RATES. WITH 30-35 KT SWLY MID LVL FLOW AND UPR DIFFLUENCE AHEAD OF
LOW...EXPECT SOME SUSTAINED/ORGANIZED ACTIVITY CAPABLE OF SVR
HAIL/WIND. SOME OF THIS ACTIVITY MAY SPREAD INTO CNTRL MT THIS EVE.
FARTHER W...A CLUSTER OF REGENERATIVE/BACK-BUILDING STORMS MAY
PERSIST THROUGH TONIGHT/EARLY MON OVER CNTRL/NRN ID AND WRN MT...N
OF UPR LOW.
...NEW ENGLAND AND SERN NY/NJ TODAY...
WV IMAGERY SHOWS A FAIRLY WELL-DEFINED SHORTWAVE IMPULSE...NOW OVER
SRN QUE...THAT SHOULD DRIVE DIFFUSE COLD FRONT AND PREFRONTAL TROUGH
E/SE OFF THE N ATLANTIC CST EARLY TONIGHT. MODERATE DESTABILIZATION
LIKELY WILL OCCUR AHEAD OF FRONT/TROUGH THIS AFTN...WITH SBCAPE
INCREASING TO AROUND 1500-2000 J/KG FROM SRN NEW ENGLAND INTO ME.
THIS SHOULD SUPPORT INTENSIFICATION OF EXISTING STORMS ALONG
TROUGH...AND NEW DEVELOPMENT ALONG FRONT/TROUGH BY EARLY AFTN.
COUPLED WITH 30-35 KT WLY MID LVL FLOW AND ASCENT WITH UPR
DISTURBANCE...EXPECT A FEW BROKEN LINES/SMALL CLUSTERS OF MULTICELLS
AND POSSIBLY A FEW MARGINAL SUPERCELLS WITH LOCALLY DMGG WIND/SVR
HAIL THROUGH SUNSET.
...GULF CST/FL/CAROLINA CSTL PLN THIS AFTN...
SCTD STRONG DIURNAL STORMS ARE EXPECTED FROM THE CNTRL/ERN CAROLINAS
SWWD INTO FL TODAY...ALONG LEE TROUGH AND SEA BREEZE BOUNDARIES.
SOMEWHAT MORE WDLY SCTD ACTIVITY MAY OCCUR ALONG THE CNTRL/ERN GULF
CST. STEEP LOW LVL LAPSE RATES AND HIGH PW /AROUND 2 INCHES/ MAY
SUPPORT ISOLD WET MICROBURSTS/LOCALLY DMGG WIND GUSTS IN THE VERY
WEAKLY SHEARED ENVIRONMENT TIL SUNSET.
...SRN HI PLNS LATE THIS AFTN/EARLY EVE...
ISOLD SVR LATE AFTN/EVE TSTMS CAPABLE OF LARGE HAIL/LOCALLY DMGG
WIND MAY ONCE AGAIN OCCUR ALONG LEE TROUGH/DRY LINE SEGMENTS IN ERN
NM/W TX...WHERE STEEP LOW TO MID LVL LAPSE RATES AND MOISTURE WILL
PERSIST BENEATH BAND OF ENHANCED UPR FLOW/WEAK ASCENT SKIRTING NW
SIDE OF UPR HIGH.
It really looks like the same forecast that spawned the tornado outbreak 3-4 days ago, I'm guessing we'll have a strong initial line with a few tornadoes, but mostly high winds and hail, and then it'll backbuild, and that's where we'll see the tornadoes.
