Mesoscale Discussion 577

Issued

Apr 21, 2012, 1:25 PM EDT (17:25 UTC)

Expired

Apr 21, 2012, 4:00 PM EDT

In force

3 hr

Issued by

the Storm Prediction Center

The Tallahassee radar (KTLH), 172 km from the middle of the area, began a volume at 17:24 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.

013 
ACUS11 KWNS 211725
SWOMCD
SPC MCD 211725 
FLZ000-212000-

MESOSCALE DISCUSSION 0577
NWS STORM PREDICTION CENTER NORMAN OK
1225 PM CDT SAT APR 21 2012

AREAS AFFECTED...PORTIONS WRN/CENTRAL/NRN FL
PENINSULA...COASTAL-BEND AREA...COASTAL SERN PANHANDLE.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 211725Z - 212000Z

QUASI-LINEAR MCS OFFSHORE FROM FL MAY OFFER DAMAGING GUST POTENTIAL
AS IT MOVES INLAND DURING ROUGHLY 18-21Z TIME FRAME...FROM FL
COASTAL BEND REGION SSEWD TO PIE-SRQ AREAS.  NWRN FRINGE OF COMPLEX
MAY OFFER AT LEAST MRGL SVR THREAT DURING NEXT 1-2 HOURS OVER SERN
PANHANDLE AREAS NE AAF.  BRIEF TORNADO CANNOT BE RULED OUT WITH
LEWP/BOW CIRCULATIONS...HOWEVER ORGANIZED TORNADO POTENTIAL APPEARS
SMALL ATTM.  ADDITIONAL/SEPARATE CONVECTION INLAND MAY PRODUCE MORE
ISOLATED DAMAGING GUSTS. 

SFC MESOANALYSIS SHOWS VERY FRAGMENTED/VARIABLE SFC MOISTURE FIELD
ACROSS CENTRAL/NRN FL.  AREAS AROUND OCF AND GIF THAT HAVE
EXPERIENCED MORE SUSTAINED HEATING/MIXING SHOW LOW-MID 60S DEW
POINTS...WITH MID-UPPER 60S ELSEWHERE.  MORE ROBUST MOISTURE RETURN
IS UNLIKELY THROUGH REMAINDER AFTERNOON...GIVEN PRESENCE OF OUTFLOW
POOL FROM EARLIER MCS OVER S FL...KEYS AND ADJOINING ERN GULF. 
STABILIZATION FROM THAT OUTFLOW AREA ALSO WILL LIMIT SRN EXTENT OF
GULF MCS BACKBUILDING...AT LEAST FOR NEXT 4-5 HOURS.  

VIS IMAGERY SHOWS THAT AREAS OF PRIOR STG INSOLATION ARE DIMINISHING
AS PROGRESSIVELY DENSER COVERAGE AND THICKER DEPTH OF HIGH CLOUDS
SPREAD OVER CENTRAL/NRN PENINSULA...IN ADVANCE OF MCS. THIS WILL
SLOW PACE OF FURTHER DIABATIC SFC DESTABILIZATION AND MLCINH
REDUCTION...LENDING SOME UNCERTAINTY TO THERMODYNAMIC SUITABILITY OF
BOUNDARY-LAYER AIR MASS INLAND.  HOWEVER...MODIFIED RAOBS AND RUC
SOUNDINGS SUGGEST OBSERVED RANGE OF SFC TEMPS/DEW POINTS...WITH A
COUPLE MORE DEGREES F ADDED THERMALLY...WILL YIELD 1000-1500 J/KG
MLCAPE AND SFC-BASED EFFECTIVE INFLOW PARCELS.  DEEP-LAYER SHEAR
WILL CONTINUE TO WEAKEN WITH NWD AND NEWD EXTENT ACROSS FL INTO
GA...INDICATING LESSER ORGANIZATION AND MORE PULSE/MULTICELL
MORPHOLOGY.  HOWEVER...IN GROUND-RELATIVE SENSE...DEEP BULK SHEAR
WILL STRENGTHEN WITH TIME OVER FL W COAST...WITH EFFECTIVE SHEAR
MAGNITUDES 35-45 KT BECOMING COMMON BY TIME OF MCS ARRIVAL.

..EDWARDS.. 04/21/2012

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

ATTN...WFO...MLB...TBW...JAX...TAE...

LAT...LON   29598501 30188457 30558374 30398241 30098172 27758114
            26938226 27828288 28068282 28208286 28288272 28648265
            28818272 28878272 28898263 29058277 29148282 29168298
            29028311 29248307 29308320 29428322 29458334 29498340
            29638339 29738361 29898364 30088401 30058432 29918435
            29598501

Mesoscale Discussions in Florida, 2012Every mesoscale discussion in 2012

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.