Moderate Risk, NE, Sunday 6/19 & Monday 6/20

[Dave]

MESOSCALE DISCUSSION 1333
NWS STORM PREDICTION CENTER NORMAN OK
0902 PM CDT MON JUN 20 2011

AREAS AFFECTED...SERN SD...SWRN MN...NERN NEB...WRN IA

CONCERNING...TORNADO WATCH 526...

VALID 210202Z - 210300Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 526 CONTINUES.

NWD-PROPAGATING PORTION OF 600+ MILE LONG QLCS HAS BOWED ACROSS SERN
SD...WITH COMMA HEAD CENTERED OVER HUTCHINSON COUNTY. ALTHOUGH
CURRENT PROPAGATION WILL RESULT IN MOVEMENT INTO A LESS UNSTABLE AIR
MASS WITH NRN EXTENT...DAMAGING WIND/ISOLATED TORNADO THREAT SHOULD
DEVELOP N OF WW 526...AND MAY NECESSITATE A WFO WW EXTENSION.

FARTHER S...TSTM DEVELOPMENT HAS OCCURRED ALONG QUASI-STATIONARY
FRONTAL AXIS JUST E OF BOWING SEGMENT THAT RECENTLY PASSED ALONG AND
N OF THE OMAHA METRO AREA WITH MEASURED SEVERE WIND GUSTS. WITH A
VERY UNSTABLE AIR MASS LYING S OF THE FRONTAL BOUNDARY...AND
ENLARGING LOW-LEVEL HODOGRAPHS EVIDENT IN DES MOINES VWP
DATA...GREATEST RELATIVE DAMAGING WIND/TORNADO RISK SHOULD EVOLVE
ACROSS PORTIONS OF THE I-80 TO US-20 CORRIDORS IN W-CNTRL IA.

[WeatherGuesser]

Fairly sparse areas affected as far as I can tell.


http://www.omaha.com/article/20110621/NEWS01/110629979

[Dave]

[Dave]

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1208 AM CDT TUE JUN 21 2011

VALID 211200Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN
PLAINS...OZARKS...MID-MS VALLEY...UPPER MS VALLEY...OH VALLY AND
CNTRL APPALACHIAN MTNS...

...MID TO UPPER MS VALLEY...
AN UPPER-LEVEL LOW WILL MOVE SLOWLY ENEWD ACROSS THE MID-MO VALLEY
TODAY. AHEAD OF THE UPPER-LEVEL LOW...A CORRIDOR OF MODERATE TO
STRONG INSTABILITY SHOULD DEVELOP BY MIDDAY FROM CNTRL MO NNWWD INTO
ERN IA...SRN WI AND NCNTRL IL. A LINEAR MCS WITH A WIND DAMAGE
THREAT SHOULD BE ONGOING THIS MORNING ON THE WRN EDGE OF MODERATE
INSTABILITY. THIS LINE COULD WEAKEN OR REGENERATE AS SFC HEATING
TAKES PLACE. IN THE WAKE OF THE MCS...MODEL FORECASTS AGAIN
DESTABILIZE THE AIR MASS AHEAD OF A COLD FRONT WITH SCATTERED TO
NUMEROUS THUNDERSTORMS INITIATING THIS AFTERNOON. FORECAST SOUNDINGS
AT 21Z JUST AHEAD OF THE FRONT SHOW 0-6 KM SHEAR VALUES IN THE 35 TO
45 KT RANGE WHICH ALONG WITH MLCAPE IN THE 1500 TO 2500 J/KG WILL BE
SUFFICIENT FOR SUPERCELL DEVELOPMENT. HOWEVER...THE DOMINANT STORM
MODE REMAINS QUESTIONABLE AND THE CONVECTION MAY TEND TO ORGANIZE
INTO LINES ESPECIALLY AS LOW-LEVEL CONVERGENCE INCREASES ALONG THE
BOUNDARY LATE THIS AFTERNOON. A 30 PERCENT WIND PROBABILITY IS
FORECAST ACROSS ERN IA...FAR SE MN...SRN WI...NE MO AND IL WHERE THE
MORNING MCS IS FORECAST TO TRACK AND SEVERE STORMS ARE FORECAST TO
REDEVELOP LATER IN THE DAY. A FEW TORNADOES CAN NOT BE RULED OUT
ESPECIALLY IF DISCRETE CONVECTION CAN DEVELOP LATE THIS AFTERNOON AS
THE LOW-LEVEL JET STRENGTHENS.

...SRN PLAINS/ARKLATEX/OZARKS...
AN UPPER-LEVEL TROUGH WILL MOVE ACROSS THE SRN PLAINS TODAY AS A
COLD FRONT ADVANCES SEWD ACROSS THE REGION. AHEAD OF THE
FRONT...MODERATE TO STRONG DESTABILIZATION SHOULD TAKE PLACE ALONG A
CORRIDOR FROM CNTRL AND ERN TX NNEWD ACROSS ERN OK INTO WRN AR. SFC
HEATING AND INCREASING LOW-LEVEL CONVERGENCE ALONG THE FRONT SHOULD
RESULT IN SCATTERED THUNDERSTORM INITIATION WITH THUNDERSTORM
DEVELOPMENT POSSIBLE AS FAR WEST AS FAR WEST TX. FORECAST SOUNDINGS
LATE THIS AFTERNOON FROM THE ARKLATEX SWWD INTO THE TX HILL COUNTRY
SHOW 0-6 KM SHEAR VALUES IN THE 30 TO 40 KT RANGE WITH MLCAPE VALUES
IN THE 2000 TO 3000 J/KG RANGE. THIS ENVIRONMENT SHOULD BE
SUPPORTIVE OF SUPERCELLS AND LARGE HAIL WILL BE POSSIBLE WITH THE
MORE INTENSE STORMS. THE GREATEST HAIL THREAT MAY EXIST FROM WRN AR
SWWD ACROSS SE OK INTO NE TX WHERE THE STRONGEST INSTABILITY IS
FORECAST ON THE NERN EDGE OF A PLUME OF STEEP MID-LEVEL LAPSE RATES.
HOWEVER...WIND DAMAGE WILL ALSO BE POSSIBLE ESPECIALLY IF THE STORMS
CAN CONGEAL INTO A LINE AS LOW-LEVEL CONVERGENCE INCREASES ALONG THE
FRONT DURING THE EARLY EVENING.

...OH VALLEY/CNTRL APPALACHIAN MTNS...
AN UPPER-LEVEL RIDGE WILL MOVE EWD ACROSS THE GREAT LAKES REGION AND
UPPER OH VALLEY AS AN UPPER-LEVEL LOW MOVES EWD INTO THE UPPER
MIDWEST. ON THE WRN SIDE OF THE UPPER-LEVEL RIDGE AXIS...AN AXIS OF
MODERATE INSTABILITY IS FORECAST TO DEVELOP FROM SRN LOWER MI SEWD
ACROSS OH INTO THE CNTRL APPALACHIAN MTNS WHERE MODEL FORECASTS
INITIATE SCATTERED THUNDERSTORMS THIS AFTERNOON. FORECAST SOUNDINGS
AT 21Z ALONG THIS CORRIDOR SHOW MLCAPE VALUES IN THE 2000 TO 2500
J/KG RANGE ALONG WITH 30 KT OF DEEP LAYER SHEAR SUGGESTING THE
ENVIRONMENT WILL SUPPORT SEVERE STORMS. UNIDIRECTIONAL WIND PROFILES
AND STEEP LOW-LEVEL LAPSE RATES MAY RESULT IN A WIND DAMAGE THREAT
AS CELLS OR SHORT LINE-SEGMENTS ORGANIZE IN THE MID TO LATE
AFTERNOON.

[Dave]

Note: KIND NWS Indianapolis IN radar was struck by lightning and is down for maintenance at this time.

[OverlandHurricane]

Star Tribune is reported a confirmed tornado touchdown somewhere in Coon Rapids, MN.

The line of storms northwest of MSP is fast, fairly compact, and hasn't taken the humidity down one iota. Ball games cancelled all over the place tonight.