3/26/11 Deep South Severe Weather Outbreak ?

[ROLLTIDE]

From James Spann

Quote:SEVERE WEATHER THREAT: Parameters continue to look more impressive for severe weather across Alabama Saturday afternoon into Saturday night with very good instability, strong wind fields, and a degree of helicity. While a shower is possible Saturday morning, it looks like the prime severe weather threat will come from 2:00 p.m. through the late night hours. Watch the Weather Xtreme video and you will see that the forecast STP values from the NAM (significant tornado parameter) are over 7 units, which is extremely significant. SPC maintains the standard slight risk of severe weather for the northern half of Alabama; don’t be surprised if that is upgraded to a moderate risk at some point. If the sun peeks out, we might be close to 80 in spots Saturday afternoon, adding to the instability.

[ROLLTIDE]

We will be out chasing Saturday and streaming live so you can ride along with us

[ROLLTIDE]

SPC thoughts day 3

Quote:

Mar 24, 2011 0730 UTC Day 3 Severe Thunderstorm Outlook

Updated: Thu Mar 24 07:28:57 UTC 2011 (Print Version)

Probabilistic to Categorical Outlook Conversion Table

Categorical Probabilistic (more info)

Probability of severe weather within 25 miles of a point. Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.

Forecast Discussion

SPC AC 240726

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0226 AM CDT THU MAR 24 2011

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS SATURDAY ACROSS THE NORTHERN
GULF STATES INTO PARTS OF THE TENNESSEE AND LOWER MISSISSIPPI
VALLEYS...

...SYNOPSIS...
MODELS INDICATE LITTLE CHANGE TO THE GENERAL LARGE-SCALE PATTERN
THROUGH THIS FORECAST PERIOD. SHORT WAVE IMPULSES EMANATING FROM A
STRONG MID LATITUDE PACIFIC JET...WHICH MAY BE GRADUALLY NOSING
TOWARD THE PACIFIC COAST...CONTINUE TO DIG WITHIN A STRONGER BELT OF
FLOW DIVERTED SOUTH OF AN UPPER RIDGE OVER CENTRAL CANADA... INTO A
CONFLUENT REGIME ACROSS THE MIDDLE MISSISSIPPI VALLEY THROUGH THE
MID ATLANTIC COAST. ONE OF THESE FEATURES MAY BE ACCELERATING INTO
THIS LATTER REGIME EARLY SATURDAY. WHILE AN UPSTREAM IMPULSE DIGS
THROUGH THE GREAT BASIN...A STRONG UPPER JET WITHIN THE CREST OF
BROAD SUBTROPICAL RIDGING BUILDING OVER THE MEXICAN PLATEAU AND GULF
OF MEXICO...IS PROGGED TO NOSE EASTWARD THROUGH THE REMAINDER OF THE
GULF COAST REGION.

IN LOWER LEVELS...A WAVE ALONG A SLOWLY RETREATING FRONTAL ZONE OVER
THE RED RIVER VALLEY AT 12Z SATURDAY PROBABLY WILL WEAKEN... WHILE
MIGRATING TOWARD THE NORTHERN GULF STATES. BUT...30 TO 40 KT
SOUTHWESTERLY LOW-LEVEL FLOW IS EXPECTED TO MAINTAIN AN INLAND
RETURN FLOW OF GULF MOISTURE...WITH LOWER/MID 60S SURFACE DEW POINTS
BECOMING COMMON THROUGH THE DAY SATURDAY...FROM THE WESTERN GULF
COAST THROUGH MUCH OF THE CENTRAL AND EASTERN GULF COAST STATES.
COUPLED WITH AT LEAST MODEST STEEPENING OF MID-LEVEL LAPSE RATES ON
MODERATELY STRONG WEST SOUTHWESTERLY TO WESTERLY MID-LEVEL
FLOW...THIS IS EXPECTED TO CONTRIBUTE TO CONSIDERABLE
DESTABILIZATION AND THUNDERSTORM ACTIVITY ACROSS THE MID SOUTH AND
SOUTHEAST STATES.

...GULF/SOUTH ATLANTIC COAST STATES INTO MID SOUTH...
LOWER/MID TROPOSPHERIC WARM ADVECTION ALONG AND NORTH OF THE FRONTAL
ZONE IS EXPECTED TO SUPPORT CLUSTERS OF STORMS THROUGH THE PERIOD.
HOWEVER...MID-LEVEL INHIBITION MAY REMAIN WEAK ENOUGH...WITHIN A
CORRIDOR ALONG AND JUST SOUTH OF THE FRONT...TO ALLOW THE
DEVELOPMENT OF BOUNDARY LAYER BASED STORMS DURING THE AFTERNOON AND
EVENING HOURS. HIGHEST PROBABILITIES FOR THIS APPEAR FROM PARTS OF
SOUTHEAST ARKANSAS EASTWARD THROUGH FAR SOUTHERN TENNESSEE AND
ADJACENT NORTHERN MISSISSIPPI/ALABAMA AND GEORGIA. DETAILS REMAIN
UNCLEAR...BUT GIVEN THE FAVORABLE THERMODYNAMIC ENVIRONMENT...A
SHEARED AND MODERATELY STRONG /30-40+ KT/ DEEP LAYER MEAN FLOW IS
EXPECTED TO BE SUPPORTIVE OF ORGANIZED STORMS CLUSTERS...AS WELL AS
SUPERCELLS. A FEW TORNADOES MAY BE POSSIBLE...IN ADDITION TO THE
RISK FOR LARGE HAIL AND DAMAGING WIND GUSTS.

..KERR.. 03/24/2011

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[ROLLTIDE]

...

Quote:

< Day 1 Outlook

Day 3 Outlook >

Mar 25, 2011 0600 UTC Day 2 Convective Outlook

Updated: Fri Mar 25 06:13:54 UTC 2011 (Print Version)

Probabilistic to Categorical Outlook Conversion Table

Categorical Probabilistic (more info)

Probability of severe weather within 25 miles of a point. Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.

Forecast Discussion

SPC AC 250612

DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0112 AM CDT FRI MAR 25 2011

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF THE LOWER MS
VALLEY INTO THE SERN STATES...

CORRECTED FOR INCLUSION OF SIG AREA

...SYNOPSIS...

BELT OF PROGRESSIVE QUASI-ZONAL WLYS WILL PERSIST THROUGH SATURDAY
ACROSS SRN TWO THIRDS OF THE U.S. AND SOUTH OF HIGHER LATITUDE
BLOCKING PATTERN. ANOTHER IN A SERIES OF IMPULSES EMANATING FROM
UPPER LOW ALONG PACIFIC NW COAST WILL LIKELY DEAMPLIFY AS IT MOVES
INTO CONFLUENT FLOW REGIME OVER THE MID MS VALLEY SATURDAY EVENING.
WARM FRONT WILL LIFT NWD AND LIKELY EXTEND FROM A WEAK SURFACE LOW
OVER THE SRN PLAINS EWD INTO THE SERN STATES EARLY SATURDAY. NWD
PROGRESSION OF FRONT SHOULD BE LIMITED BY LARGE HIGH PRESSURE AREA
CENTERED OVER ONTARIO AND EXTENDING SWD INTO THE OH VALLEY REGION.
AS THE IMPULSE ADVANCES EWD THROUGH THE MID-MS VALLEY INTO THE OH
VALLEY SURFACE LOW WILL DEVELOP EWD ALONG WARM FRONT INTO THE SERN
STATES WHILE COLD FRONT ADVANCES SWD THROUGH TX AND THE LOWER MS
VALLEY.

...ERN TX THROUGH LOWER MS VALLEY AND SERN STATES...

SWLY LLJ WILL STRENGTHEN FRIDAY NIGHT INTO SATURDAY FROM THE LOWER
MS VALLEY INTO SERN STATES AND ADVECT MODIFIED CP AIR WITH LOW 60S
DEWPOINTS NEWD THROUGH EXPANDING WARM SECTOR. WLY FLOW ALOFT WILL
TRANSPORT EML PLUME EWD ABOVE MOISTENING BOUNDARY LAYER WHICH IN
CONJUNCTION WITH DIABATIC WARMING SHOULD CONTRIBUTE TO 1000-1500
J/KG MLCAPE SATURDAY AFTERNOON. ELEVATED STORMS SHOULD BE ONGOING
FROM PORTIONS OF AR INTO THE TN VALLEY AT START OF PERIOD. SOME OF
THIS ACTIVITY COULD POSE A THREAT FOR ISOLATED HAIL. ADDITIONAL
STORMS MAY DEVELOP AS THE BOUNDARY LAYER DESTABILIZES...PRIMARILY IN
VICINITY OF CONVECTIVELY REINFORCED WARM FRONT OR RESIDUAL OUTFLOW
BOUNDARIES. EFFECTIVE SHEAR FROM 40-50 KT WILL SUPPORT SUPERCELLS
AND BOWING SEGMENTS WITH LARGE HAIL...DAMAGING WIND AND ISOLATED
TORNADOES POSSIBLE.

DEVELOPMENT SWWD TOWARD TX IN WARM SECTOR IS MORE UNCERTAIN DUE TO
POTENTIAL FOR STRONGER CAP AND WEAKER FORCING AS THE LLJ VEERS AND
WEAKENS AHEAD OF THE COLD FRONT. HAVE KEPT ERN TX THROUGH THE GULF
COASTAL AREA IN 5% SEVERE PROBABILITIES GIVEN THE POTENTIAL FOR MORE
ISOLATED COVERAGE.

..DIAL.. 03/25/2011

CLICK TO GET WUUS02 PTSDY2 PRODUCT

NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
CURRENT UTC TIME: 1159Z (6:59AM), RELOAD THIS PAGE TO UPDATE THE TIME

[Joe-Nathan]

[SIZE="3"]FOR TODAY MARCH 25th:[/SIZE]









DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1243 AM CDT FRI MAR 25 2011

VALID 251200Z - 261200Z

PHP Code:

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS ARKLATEX REGION TO
   LOWER MS VALLEY...
   
   ...SYNOPSIS...
   IN MIDDLE-UPPER LEVELS...SPLIT-FLOW PATTERN FCST TO PERSIST WELL
   BEYOND THIS PERIOD.  RIDGING WILL EXTEND SWD ACROSS ND FROM
   ANTICYCLONE CENTERED OVER NERN SK...WHILE CONTINUOUS/QUASI-ZONAL
   CURRENT COVERS MUCH OF CONUS FROM MIDDLE-SRN ATLANTIC COAST WWD
   ACROSS CENTRAL/SRN ROCKIES.  WELL-DEFINED CYCLONE -- NOW EVIDENT IN
   MOISTURE CHANNEL IMAGERY OFFSHORE ORE -- IS FCST TO MOVE INLAND
   EARLY THIS PERIOD.  THIS FEATURE THEN SHOULD QUICKLY DEAMPLIFY INTO
   WEAKENING OPEN-WAVE TROUGH OVER NRN ROCKIES...WHILE SECOND CYCLONE
   DEVELOPS OFFSHORE PAC NW.  SHORTWAVE TROUGH -- NOW MOVING INLAND
   CENTRAL/NRN CA -- IS FCST TO MOVE EWD ACROSS GREAT BASIN AND CENTRAL
   ROCKIES TO CENTRAL HIGH PLAINS BY 26/12Z.  MEANWHILE...DOWNSTREAM
   SHORTWAVE OVER CENTRAL PLAINS WILL MOVE EWD AND WEAKEN CONSIDERABLY
   ACROSS CENTRAL APPALACHIANS TODAY...AMIDST CONFLUENT FLOW ALOFT
   ASSOCIATED WITH CYCLONE OVER LOWER ST LAWRENCE VALLEY REGION.
   
   AT SFC...WEAK NW TX/SWRN OK LOW IS EXPECTED ALONG WARM FRONTAL ZONE
   EARLY IN PERIOD...WITH FRONT ESEWD ACROSS ARKLATEX TO CENTRAL/SRN
   LA.  FRONT SHOULD LIFT NWD INTO SERN OK AND SRN AR BY
   26/00Z...EXTENDING WNWWD ACROSS SRN TX PANHANDLE REGION.  BY THAT
   TIME...DRYLINE SHOULD EXTEND FROM SERN OK SWWD ACROSS N-CENTRAL TX
   TO SRN HILL COUNTRY...THEN RETREAT SLIGHTLY WWD DURING EVENING. 
   ANOTHER SFC LOW MAY DEVELOP OVERNIGHT ALONG FRONT INVOF SWRN OK/NW
   TX AND MOVE EWD...WITH RELATED VEERING OF SFC WINDS TO ITS S AND SW
   RESULTING IN EWD OSCILLATION OF DRYLINE AGAIN BEFORE 26/12Z.
   
   ...ARKLATEX REGION TO LOWER MS VALLEY...
   AREA OF STG-SVR TSTMS IS EXPECTED TO DEVELOP...EXPAND AND MOVE EWD
   FROM NE TX/SERN OK/SWRN AR AREA DURING EVENING...AMIDST INCREASING
   LOW-LEVEL MOISTURE AND FAVORABLE DEEP-LAYER SHEAR PROFILES TO
   SUPPORT SVR RISK.  SUPERCELLS WITH LARGE HAIL AND SVR GUSTS ARE
   POSSIBLE...AND THREAT FOR TORNADOES ALSO MAY EXIST INVOF
   WARM-FRONTAL ZONE.
   
   PROGS ARE IN VERY STG AGREEMENT REGARDING GENERAL EVOLUTION/LOCATION
   OF SCENARIO...HOWEVER TIMING OF INITIATION REMAINS QUITE
   UNCERTAIN...ESPECIALLY POTENTIAL FOR DIURNAL/SFC-BASED DEVELOPMENT
   BEFORE 00Z.  THIS IS BECAUSE OF STG CAPPING RELATED TO
   ANTECEDENT/ELEVATED MIXED LAYER...COMBINED WITH ONLY SUBTLE/SHALLOW
   WARM-FRONTAL LIFT AND LACK OF SIGNIFICANT MID-UPPER PERTURBATION
   NEARBY.  THIS REGION WILL BE TOO REMOVED FROM GREAT BASIN/CENTRAL
   ROCKIES SHORTWAVE TROUGH TO EXPERIENCE DIRECT EFFECTS. 
   HOWEVER...BROAD/LOW-LEVEL WAA REGIME ALREADY IN PLACE OUGHT TO
   STRENGTHEN OVERNIGHT ACROSS LOWER MS VALLEY REGION...RESULTING IN
   INCREASING THETAE WITH TIME FOR INFLOW PARCELS IN AND N OF SFC
   WARM-FRONTAL ZONE.  TIME WINDOW FOR SFC-BASED CONVECTION SHOULD
   EXIST DURING EVENING NEAR WARM FRONT BEFORE SUBSTANTIAL SFC
   COOLING...AS LOW-LEVEL HODOGRAPH EXPANDS BENEATH STRENGTHENING LLJ. 
   THIS WILL BOOST SRH AND TORNADO POTENTIAL FOR SEVERAL HOURS...BEFORE
   ACTIVITY MOVES EWD INTO MORE STABLE AIR MASS.  ADDITIONAL
   DEVELOPMENT MAY OCCUR OVERNIGHT IN EARLIER STORM GENESIS REGION OF
   SERN OK/NE TX...MAINTAINING SVR THREAT BEHIND INITIAL ACTIVITY.
   
   ...WRN OZARKS REGION...
   CLUSTER OF SCATTERED/ELEVATED TSTMS MAY BE ONGOING EARLY IN PERIOD
   OVER PORTIONS NERN OK/SERN KS...ROOTED IN 750-850 MB LAYER BASED ON
   RUC/ETA-KF FCST SOUNDINGS.  ALTHOUGH BUOYANCY IS EXPECTED TO BE
   RATHER UNSPECTACULAR...WITH MUCAPE 400-800 J/KG...40-50 KT EFFECTIVE
   SHEAR INDICATES CONVECTION MAY BE ORGANIZED ENOUGH FOR MRGL HAIL
   POTENTIAL.  THIS ACTIVITY SHOULD WEAKEN THROUGH MID-LATE MORNING AS
   IT MOVES EWD OVER AR/MO OZARKS AND INITIALLY SUPPORTIVE LLJ
   DIMINISHES.
   
   ..EDWARDS/DEAN.. 03/25/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT 


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[Joe-Nathan]

ROLLTIDE Wrote:

Looks like Terry's will get some storm action.

[ROLLTIDE]

Day 2

Quote:

Mar 25, 2011 1730 UTC Day 2 Convective Outlook

Updated: Fri Mar 25 17:19:53 UTC 2011 (Print Version)

Probabilistic to Categorical Outlook Conversion Table

Categorical Probabilistic (more info)

Probability of severe weather within 25 miles of a point. Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.

Forecast Discussion

SPC AC 251717

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1217 PM CDT FRI MAR 25 2011

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER MS
VALLEY AND GULF COAST STATES...

...GULF COAST STATES...
A SUBTLE SHORTWAVE TROUGH OVER THE ROCKIES TONIGHT WILL MOVE INTO
THE SRN PLAINS SATURDAY MORNING. AHEAD OF THE SYSTEM...A BROAD
LOW-LEVEL JET WILL BE IN PLACE ACROSS THE LOWER MS VALLEY AND CNTRL
GULF COAST STATES. ON THE NRN EDGE OF THE JET...SEVERAL CLUSTERS OF
ELEVATED THUNDERSTORMS SHOULD BE ONGOING SATURDAY MORNING FROM THE
SRN PLAINS EWD ACROSS ARKANSAS AND INTO THE TN VALLEY. THIS
CONVECTION COULD HAVE AN ISOLATED HAIL THREAT. AT THE SFC...A COLD
FRONT IS FORECAST TO MOVE SWD INTO TN VALLEY AND ERN GULF COAST
STATES BY LATE AFTERNOON. AS INSTABILITY INCREASES DURING THE
DAY...SFC-BASED THUNDERSTORM SHOULD INITIATE ALONG THE BOUNDARY AND
MOVE ESEWD ACROSS THE REGION.

MODEL CONSENSUS SUGGESTS THE GREATEST COVERAGE OF THUNDERSTORM
ACTIVITY WILL BE ALONG THE BOUNDARY FROM NRN MS ESEWD ACROSS NCNTRL
AL INTO CNTRL GA. THIS CORRIDOR IS ALONG THE NRN EDGE OF MODERATE
INSTABILITY AND ON THE SRN EDGE OF BROAD BAND OF STRONG MID-LEVEL
FLOW. FORECAST SOUNDINGS ACROSS NRN MS AND NRN AL AT 21Z SATURDAY
SHOW MLCAPE CAPE AROUND 2000 J/KG WITH 50 KT OF DEEP LAYER SHEAR AND
STEEP MID-LEVEL LAPSE RATES. THIS ENVIRONMENT SHOULD BE SUPPORTIVE
OF SUPERCELL DEVELOPMENT WITH LARGE HAIL ACCOMPANYING THE MORE
DOMINANT STORMS. IN ADDITION...TORNADOES MAY OCCUR AS SUPERCELLS
MATURE AND THE LOW-LEVEL JET STRENGTHENS SATURDAY EVENING. THE
BIRMINGHAM FORECAST SOUNDING EARLY SATURDAY EVENING SHOWS 0-3 KM
STORM RELATIVE HELICITIES AROUND 400 M2/S2 SUGGESTING A THREAT FOR
STRONG TORNADOES WILL BE POSSIBLE. A CLUSTERING OF TORNADOES MAY
OCCUR ACROSS NRN MS AND NCNTRL AL WHERE INSTABILITY...SHEAR AND LIFT
IS FORECAST TO BE MAXIMIZED.

FURTHER EAST SOUTHEAST ALONG THE BOUNDARY IN CNTRL GA...MODEL
FORECASTS ARE ALSO IN AGREEMENT WITH THUNDERSTORM DEVELOPMENT
SATURDAY AFTERNOON. FORECAST SOUNDINGS AROUND MACON AT 21Z SATURDAY
SHOW MLCAPE VALUES OF 1000 J/KG WITH 50 KT OF DEEP LAYER SHEAR. THIS
SHOULD BE SUFFICIENT FOR A SEVERE THREAT WITH SUPERCELL DEVELOPMENT
POSSIBLE. LARGE HAIL AND AN ISOLATED TORNADO THREAT MAY ACCOMPANY
THE STRONGER CELLS ESPECIALLY IF STORMS REMAIN DISCRETE.
HOWEVER...THERE IS A POSSIBILITY THAT A LINEAR MCS COULD DEVELOP
WHICH WOULD MAKE WIND DAMAGE THE PRIMARY THREAT.

...LOWER MS VALLEY/ARKLATEX...
A SHORTWAVE TROUGH WILL APPROACH THE ARKLATEX SATURDAY AS A COLD
FRONT ADVANCES SEWD INTO THE SRN PLAINS AND SRN OZARKS. AS SFC TEMPS
WARM AHEAD OF THE BOUNDARY...MODERATE INSTABILITY IS FORECAST TO
DEVELOP BY MIDDAY. FORECAST SOUNDINGS SHOW A STRONG CAPPING
INVERSION IN PLACE UNTIL MID-AFTERNOON WHEN INCREASING CONVERGENCE
ALONG THE BOUNDARY COULD RESULT IN THUNDERSTORM INITIATION ACROSS
SRN AR...NRN LA AND EAST TX. THE MODELS DISAGREE ON HOW MUCH
CONVECTION WILL FORM BUT THE GFS IS MORE AGGRESSIVE...DEVELOPING
SCATTERED STORMS BY EARLY SATURDAY EVENING. FORECAST SOUNDINGS
AROUND GREENVILLE AR AT 03Z SUNDAY SHOW MLCAPE VALUES OF 1200 TO
1500 J/KG WITH 0-6 KM SHEAR IN THE 40 TO 50 KT RANGE. THIS COMBINED
WITH STEEP MID-LEVEL LAPSE RATES SHOULD RESULT IN AN ISOLATED LARGE
HAIL THREAT. A FEW DAMAGING WIND GUSTS WILL ALSO BE POSSIBLE. THE
SEVERE THREAT SHOULD BE INCREASINGLY ISOLATED WITH SWWD EXTENT WITH
JUST A MINIMAL THREAT ACROSS SE TX.

..BROYLES.. 03/25/2011

CLICK TO GET WUUS02 PTSDY2 PRODUCT

[ROLLTIDE]

..

Quote:Dr. Greg Forbes
TORCON forecasts for today and tomorrow are posted. If moisture begins to show more of an increase, I might have to increase the Saturday values.

...

Quote:For Saturday March 26:

Severe Thunderstorm Area - TORCON Forecast
------------------------ ---------------
east OK - 2
west AR - 2
extreme northeast TX - 2
southeast AR - 3
north LA - 3
extreme east TX - 3 evening
north half MS - 4
north and central AL - 4
south AL - 3
northwest GA - 3
central GA - 3
southwest GA - 3
other areas - 2 or less


Brief synopsis:
Enough moisture returns by Friday evening to allow a chance of a tornado or
two near the warm front and surface low near the TX/OK border. A larger
threat in the warm frontal zone on Saturday, with lack of upper-air forcing
holding down TORCON values at this time.