Moderate Risk for Alabama Today

The new Day One Convective Outlook has been issued by the Storm Prediction Center and it has a moderate risk for parts of West and Northwest Alabama and their standard slight risk for the rest of the state. Here is a graphic showing the slight and moderate categorical risk areas in the larger panel, the tornado probabilistic risk in the top left and the severe wind probabilistic risk in the lower left.

Click image to enlarge

Remember, the probabilities indicate the probability that that severe phenomenon will occur within 25 miles of any point in the outlooked area.

The severe hail probabilities are 30% over Northwest Alabama and 15% over the rest of the state.

Here is the text of the outlook:

SPC AC 040559

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT MON APR 04 2011

VALID 041200Z – 051200Z

…THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF WRN
TN…MS…FAR SE AR…NW AL AND A SMALL PART OF SW KY…

…THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER TO
MID-MS VALLEY…SRN PLAINS…TN VALLEY…OH VALLEY AND CNTRL TO SRN
APPALACHIAN MTNS…

…SEVERE WEATHER EVENT TODAY ACROSS THE LOWER TO MID-MS VALLEY AND
TN VALLEY…

…LOWER TO MID-MS VALLEY/TN VALLEY…
AN UPPER-LEVEL TROUGH WILL MOVE INTO THE CNTRL AND SRN PLAINS TODAY
AS A POWERFUL 90 TO 110 KT MID-LEVEL JET MOVES EWD INTO THE MID-MS
VALLEY. A LINE OF STRONG THUNDERSTORMS SHOULD BE ONGOING THIS
MORNING FROM SE MO SWWD ACROSS CNTRL AR. AHEAD OF THE LINE…SFC
DEWPOINTS ACROSS THE WARM SECTOR WILL BE IN THE MID TO UPPER 60S
F…ALLOWING FOR THE DEVELOPMENT OF MODERATE INSTABILITY ACROSS A
BROAD AREA. AS THE LINE MOVES SEWD…A GRADUAL INTENSIFICATION
SHOULD OCCUR AND CONVECTIVE COVERAGE SHOULD RAPIDLY INCREASE LATE
THIS MORNING. MODEL FORECASTS ARE CONSISTENT…ORGANIZING A NEARLY
CONTINUOUS SQUALL-LINE BEGINNING NEAR THE MS RIVER IN FAR ERN AR
LATE THIS MORNING AND DRIVING THE LINE ESEWD ACROSS WRN TO MIDDLE
TN…NRN TO CNTRL MS AND NW AL BY EARLY THIS AFTERNOON. THIS LINE
WILL BE ON THE SEWD SIDE OF A WELL-DEVELOPED MID-LEVEL JET WHICH
SHOULD PRODUCE STRONG DEEP LAYER SHEAR TO SUPPORT SEVERE
THUNDERSTORM DEVELOPMENT ACROSS A WIDESPREAD AREA THROUGH
MID-AFTERNOON. THE WIND DAMAGE THREAT SHOULD BE ENHANCED ACROSS WRN
TN…NRN TO CNTRL MS…NW AL…FAR SE AR AND FAR NE LA WHERE A
MODERATE RISK HAS BEEN OUTLOOKED. THIS CORRIDOR SHOULD HAVE THE MOST
FAVORABLE SHEAR PROFILES FOR SEVERE STORMS DUE TO THE CROSSOVER OF
THE LOW AND MID-LEVEL JETS. A TORNADO THREAT WILL ALSO EXIST WITH
ROTATING STORMS EMBEDDED IN THE LINE OR WITH ISOLATED SUPERCELLS
THAT INITIATE AHEAD OF THE LINE. A THREAT FOR HAIL WILL ALSO BE
LIKELY WITH THE MORE INTENSE CORES.

FURTHER TO THE SOUTH ACROSS THE LOWER MS VALLEY…MODERATE
INSTABILITY WILL BE IN PLACE AND THUNDERSTORMS ARE EXPECTED TO
DEVELOP ALONG THE FRONT BY EARLY AFTERNOON. AS A RESULT…A THREAT
FOR HAIL AND WIND DAMAGE SHOULD EXIST SWWD ACROSS LA INTO SE TX BY
EARLY THIS AFTERNOON WITH THIS POTENTIAL MOVING EWD INTO CNTRL AND
SRN MS BY LATE AFTERNOON. ALTHOUGH THE LINE COULD CONTINUE EWD INTO
SRN AL AND THE FL PANHANDLE THIS EVENING…INSTABILITY IS FORECAST
TO WEAKEN SUGGESTING THE SEVERE THREAT SHOULD BECOME INCREASINGLY
ISOLATED.

….OH VALLEY/CNTRL APPALACHIAN MTNS…
AN AXIS OF LOW-LEVEL MOISTURE WILL MOVE EWD ACROSS THE OH VALLEY
THIS MORNING AND INTO THE CNTRL APPALACHIAN MTNS THIS AFTERNOON AS A
COLD FRONT ADVANCES QUICKLY EWD ACROSS THE REGION. THUNDERSTORMS
SHOULD DEVELOP ALONG THE FRONT AS SFC HEATING TAKES PLACE THIS
MORNING WITH A LINE OF STORMS ORGANIZING IN ERN IND AND CNTRL KY
AROUND MIDDAY. STRONG DEEP LAYER SHEAR PROFILES WITH 40 TO 50 KT OF
LOW-LEVEL FLOW SHOULD BE SUFFICIENT FOR A WIND DAMAGE THREAT WITH
THE MORE INTENSE CELLS EMBEDDED IN THE LINE. IN ADDITION…THE
STRONG DEEP LAYER SHEAR AND 500 MB TEMPS OF -14 TO 16C SHOULD BE
SUFFICIENT FOR ISOLATED HAIL THREAT. THIS THREAT SHOULD MOVE EWD
ACROSS OH…ERN KY INTO WV BY EARLY EVENING.

..BROYLES/GARNER.. 04/04/2011

Category: Alabama's Weather, Severe Weather