Mesoscale Discussion 677

Issued

May 1, 2011, 1:16 AM CDT (06:16 UTC)

Expired

May 1, 2011, 2:15 AM CDT

In force

59 min

Issued by

the Storm Prediction Center

The Little Rock radar (KLZK), 117 km from the middle of the area, began a volume at 06:19 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

• Tornado Watch 260May 1, 4:45 AM CDT

959 
ACUS11 KWNS 010616
SWOMCD
SPC MCD 010616 
TNZ000-MOZ000-ARZ000-MSZ000-LAZ000-TXZ000-OKZ000-010715-

MESOSCALE DISCUSSION 0677
NWS STORM PREDICTION CENTER NORMAN OK
0116 AM CDT SUN MAY 01 2011

AREAS AFFECTED...PORTIONS NE TX...SWRN THROUGH CENTRAL/NERN
AR...EXTREME SERN MO...WRN TN...EXTREME NWRN MS.

CONCERNING...TORNADO WATCH 257...258...

VALID 010616Z - 010715Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 257...258...CONTINUES.

HOWEVER...SVR THREAT SHOULD DIMINISH SUCH THAT REMAINDER WWS CAN BE
ALLOWED TO EXPIRE AS SCHEDULED AT 07Z.  REF SPC MESOSCALE DISCUSSION
676 FOR COVERAGE OF NEAR-TERM THREAT FROM ELEVATED HAILSTORMS W OF
WW 257 ACROSS N TX.

SFC MESOANALYSIS SHOWS COLD FRONT FROM ERN OZARKS OF SERN MO SWWD
NEAR PHF...MCCURTAIN COUNTY OK...HENDERSON COUNTY TX...WHICH SHOULD
BECOME QUASISTATIONARY WITH LOCALIZED SEWD DRIFT THROUGH 09Z. 
PERSISTENT LOW-LEVEL CONVERGENCE/CONVECTIVE ZONE WAS EVIDENT FROM
MCCURTAIN COUNTY ENEWD ACROSS NRN PORTIONS LIT METRO AREA TO NEAR
JBR...AND ONWARD OVER EXTREME WRN KY...BULK OF CONVECTION BEING N OF
ITS AGGREGATE GUST FRONT.  EARLIER/ISOLATED SUPERCELL OVER CASS
COUNTY TX DISSIPATED...AMIDST STEADILY INCREASING MLCINH.  SFC
OBS...MODIFIED RAOBS AND RUC SOUNDINGS SUGGEST WEAK THETAE ADVECTION
HELPING PARCELS TO REMAIN EFFECTIVELY SFC-BASED FOR DEW POINTS 70
F...WITH STEADILY INCREASING MLCINH AS TEMPS GRADUALLY COOL TO
LOW-MID 70S.  CORRIDOR OF MLCAPE 1000-2000 J/KG WITH MLCINH UNDER 50
J/KG PERSISTS FROM CENTRAL AR TO NE TX...SO ISOLATED/ADDITIONAL
DEVELOPMENT STILL MAY OCCUR.  OTHERWISE...ANY LINGERING SVR THREAT
SHOULD BE ASSOCIATED WITH BAND OF CONVECTION OVER AR...PRIMARILY FOR
ISOLATED INSTANCES OF DAMAGING GUSTS AND MRGL SVR HAIL.

WHILE TORNADO STILL CANNOT BE RULED OUT...ESPECIALLY GIVEN RELATIVE
MAX IN EFFECTIVE SRH EVIDENT BENEATH LLJ OVER CENTRAL/SRN
AR...PROBABILITIES MAY BE DIMINISHING WITH TIME AND BELOW WW
INDICATIONS AS MAIN MCS HAS ASSUMED MESSY/MULTICELLULAR MODE WITH
PRIMARY THREAT OF HEAVY RAINFALL.  REGIME ELABORATED UPON IN EARLIER
MESOSCALE DISCUSSION 675 PERSISTS WITH RAIN RATES
OCCASIONALLY/LOCALLY EXCEEDING 2 INCHES/HOUR IN TRAINING TSTMS.

..EDWARDS.. 05/01/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PAH...MEG...LZK...SHV...TSA...FWD...

LAT...LON   31899550 32689558 33079557 33889533 34289513 34829442
            35639251 36439012 36438986 36358942 35618947 34449058
            34039216 33679322 32399425 31819487 31899550

Mesoscale Discussions in Arkansas, 2011Mesoscale Discussions in Texas, 2011Mesoscale Discussions in Tennessee, 2011Every mesoscale discussion in 2011

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.