4/15/11 Alabama severe weather threat

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Apr 13, 2011 0730 UTC Day 3 Severe Thunderstorm Outlook

Updated: Wed Apr 13 07:30:58 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 130728

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0228 AM CDT WED APR 13 2011

VALID 151200Z - 161200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER TO
MID-MS VALLEY...CNTRL GULF COAST...TN VALLEY AND OH VALLEY...

...LOWER TO MID-MS VALLEY/CNTRL GULF COAST/TN VALLEY/OH VALLEY...
A STRONG NEGATIVELY-TILED UPPER-LEVEL LOW IS FORECAST TO MOVE FROM
THE CNTRL PLAINS EWD INTO THE OZARKS ON FRIDAY. THE EXIT REGION OF A
WELL-DEVELOPED 80 TO 100 KT MID-LEVEL JET IS FORECAST TO SPREAD
ACROSS THE CNTRL GULF COAST STATES DURING THE DAY CREATING STRONG
DEEP LAYER SHEAR PROFILES FAVORABLE FOR SEVERE STORMS. THE
GFS...ECMWF AND NAM BEGIN THE DAY 3 PERIOD WITH AN MCS LOCATED IN
THE MID-MS VALLEY DRIVING THIS FEATURE EWD INTO WRN KY AND WRN TN BY
MIDDAY. SOUTH ACROSS THE WARM SECTOR...THE MODELS DEVELOP MODERATE
INSTABILITY ACROSS MUCH OF THE CNTRL GULF COAST STATES AND INITIATE
NUMEROUS THUNDERSTORMS FROM MIDDLE TN SWWD INTO NCNTRL AL...MS AND
SE LA DURING THE AFTERNOON. THE DEVELOPMENT OF A SEVERE MCS SEEMS
PROBABLE ACROSS THE CNTRL AND SRN PARTS OF THE SLIGHT RISK AREA
FRIDAY AFTERNOON AND EVENING.

FORECAST SOUNDINGS IN CNTRL MS AND WRN AL AT 21Z ON FRIDAY SHOW
IMPRESSIVE WIND SHEAR PROFILES WITH 50 TO 60 KT OF 0-6 KM SHEAR AND
0-3 KM STORM RELATIVE HELICITIES AROUND 400 M2/S2. THIS ENVIRONMENT
SHOULD SUPPORT SUPERCELL DEVELOPMENT WITH A THREAT FOR STRONG
TORNADOES POSSIBLE. HOWEVER...THE MAGNITUDE OF THE TORNADO THREAT
WILL BE CONDITIONAL UPON STORM MODE. IF A SQUALL-LINE WERE TO
DEVELOP INSTEAD OF MORE DISCRETE CONVECTION....THEN WIND DAMAGE
COULD BE THE GREATER THREAT. THE UPPER-LEVEL SYSTEM IS QUITE
IMPRESSIVE WITH A WELL-DEVELOPED LOW-LEVEL JET IN PLACE ACROSS THE
ECNTRL STATES. THE GFS AND NAM SOLUTIONS FOCUS THE LOW-LEVEL JET
FURTHER NORTH IN TN AND KY BY LATE AFTERNOON WHILE THE ECMWF SHOWS A
STRONG COMPONENT OF THE JET IN THE TN VALLEY AND CNTRL GULF COAST
STATES. IF THE ECMWF SOLUTION IS CORRECT AND MOISTURE RETURN ENDS UP
BEING STRONGER THAN FORECAST...THEN A TORNADO OUTBREAK COULD OCCUR
IN PARTS OF WRN TO MIDDLE TN...MS AND AL FRIDAY AFTERNOON. AT THIS
POINT...THE POTENTIAL FOR AN OUTBREAK REMAINS CONDITIONAL AND
DIFFERENCES IN THE MODEL SOLUTIONS RAISE UNCERTAINTIES CONCERNING
THE EXACT SCENARIO.

FURTHER NORTH ACROSS THE OH VALLEY...SEVERE STORMS WILL ALSO BE
POSSIBLE FRIDAY AFTERNOON AS THE UPPER-LEVEL LOW APPROACHES FROM THE
WEST. IN SPITE OF WEAKER INSTABILITY...A STRONG WIND FIELD IS
FORECAST WITH COLD TEMPS ALOFT. THIS WOULD RESULT IN A POTENTIAL FOR
HAIL AND WIND DAMAGE WITH THE MORE ORGANIZED CONVECTIVE CLUSTERS. A
TORNADO THREAT WILL ALSO BE POSSIBLE IN THE OH VALLEY DUE TO THE
STRONG LOW-LEVEL SHEAR FORECAST BUT THIS POTENTIAL SHOULD BE
DEPENDENT UPON MOISTURE RETURN.

..BROYLES.. 04/13/2011

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BMX

azardous Weather Outlook

Important Note:
Calling All Skywarn Spotters...Calling All Skywarn Spotters

Click here for a description/definition of hazardous weather.

000 FLUS44 KBMX 131101 HWOBMX HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE BIRMINGHAM AL 600 AM CDT WED APR 13 2011 ALZ011>015-017>050-141130- AUTAUGA-BARBOUR-BIBB-BLOUNT-BULLOCK-CALHOUN-CHAMBERS-CHEROKEE- CHILTON-CLAY-CLEBURNE-COOSA-DALLAS-ELMORE-ETOWAH-FAYETTE-GREENE-HALE- JEFFERSON-LAMAR-LEE-LOWNDES-MACON-MARENGO-MARION-MONTGOMERY-PERRY- PICKENS-PIKE-RANDOLPH-RUSSELL-SHELBY-ST CLAIR-SUMTER-TALLADEGA- TALLAPOOSA-TUSCALOOSA-WALKER-WINSTON- 600 AM CDT WED APR 13 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE COUNTIES SERVED BY THE NATIONAL WEATHER SERVICE OFFICE IN BIRMINGHAM. .DAY ONE...TODAY AND TONIGHT. NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY. SEVERE THUNDERSTORMS APPEAR LIKELY ON FRIDAY AHEAD OF AN APPROACHING COLD FRONT. AT THIS TIME...THE HAZARDOUS THREATS INCLUDE...DAMAGING WINDS...LARGE HAIL...TORNADOES AND LOCALLY HEAVY RAIN. THERE ARE SOME DIFFERENCES IN MODEL OUTPUT THAT WOULD AFFECT WHICH THREAT BECOMES THE DOMINANT THREAT AND THE OVERALL TIMING AND PLACEMENT OF THE GREATEST THREAT. AT THIS TIME...IT APPEARS THE THREAT MAY BE LENGTHY AND COVER ALL OF CENTRAL ALABAMA...BEGINNING IN THE WEST BY AROUND NOON FRIDAY AND LASTING UNTIL AFTER MIDNIGHT FRIDAY NIGHT SOUTHEAST. STAY TUNED TO FURTHER UPDATES ON THIS DEVELOPING SEVERE WEATHER EPISODE. WINDY CONDITIONS ARE POSSIBLE BOTH AHEAD AND BEHIND THE COLD FRONT FRIDAY AND SATURDAY. SOUTHERLY WINDS ARE EXPECTED AHEAD OF THE FRONT WHILE WESTERLY WINDS ARE ANTICIPATED BEHIND THE FRONT. THESE WINDS ARE EXPECTED BETWEEN 15 AND 20 MPH WITH HIGHER GUSTS. .SPOTTER INFORMATION STATEMENT... ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT PERSONNEL MAY BECOME NECESSARY FRIDAY. $$ 75

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James Spann

FRIDAY: A vigorous stacked low (from the surface to 20,000 feet) will be near Kansas City by midday, and widespread convection will break out in the warm sector to the south during the morning hours over Arkansas, Mississippi, and Louisiana. This will move into our state later in the day Friday into Friday night… it still looks like the main window for severe weather here will be from about 3:00 p.m. until 12:00 midnight. Watch the Weather Xtreme video for all of the graphics associated with this system.
SPC has all of Alabama in a severe weather risk for Friday afternoon and Friday night, and a significant severe weather risk is defined for West Alabama and East Mississippi.
Here are some severe weather parameters for Friday evening for Birmingham from the 00Z NAM…
Surface based CAPE 450 j/kg
Lifted index -3.4
0-3 storm relative helicity 223 m2/s2
850 mb wind speed 45 knots
500 mb wind speed 74 knots
Clearly the potential limiting factor is the surface based instability; you really want to see SBCAPE values over 1,500 j/kg this time of the year. Timing will be important; if the dynamics arrive later Friday night after the sun is down, then more than likely it will be another squall line situation with the main threat being straight line winds. But, if it happens earlier during the peak of the daytime heating process, and if we can get some sun breaking through the clouds during the midday hours, that would really increase the tornado potential assuming the cap breaks.
So, still lots of questions, but no doubt there is a chance there could be a significant severe weather event in our state Friday afternoon and Friday night, so keep an eye on these discussions as we get closer to the event. Remember also this is race weekend at Talladega, so thousands of campers will be out on the grounds at the Superspeedway that will need to really keep up with weather developments.
COOLER WEEKEND: Saturday will feature a clearing sky in the wake of the storms, and we turn cooler. The high Saturday will be in the mid to upper 60s with a cool breeze. Sunday looks picture perfect, with blue sky and sunshine along with low humidity. The high Sunday will be in the low to mid 70s following a morning low around 40. Doesn’t get much better for the running of the Aarons 499 at the Talladega Superspeedway.
NEXT WEEK: The 00Z GFS continues the idea of dry weather on Monday and Tuesday, followed by a cold front Wednesday along with a good chance of showers and storms. See the Weather Xtreme video for more long range ideas.

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Jan

SEVERE THUNDERSTORMS CAPABLE OF DAMAGING WINDS...HAIL AND TORNADOES
WILL BE POSSIBLE OVER THE WHOLE OUTLOOK AREA FRIDAY...WITH THE EAST
EXPERIENCING A GREATER CHANCE OCCURRENCE. THIS ACTIVITY IS WILL BE
POSSIBLE ALONG AND AHEAD OF A COLD FRONT THAT WILL NOT MOVE THROUGH
SOUTHEAST MISSISSIPPI UNTIL FRIDAY EVENING. EVERYONE IS URGED TO KEEP
UP WITH THE LATEST OUTLOOKS CONCERNING THIS POTENTIAL SEVERE WEATHER
EVENT.

.SPOTTER CALL TO ACTION STATEMENT...
THE ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS...AND
EMERGENCY MANAGEMENT PERSONNEL IN SUPPORT OF SEVERE WEATHER
OPERATIONS MAY BE NEEDED THURSDAY NIGHT WITH ACTIVATION LIKELY ON
FRIDAY.

$$

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James Spann

Significant Severe Weather Threat By Friday Afternoon

James Spann | 3:25 pm April 13, 2011 | Comments (0)
An all new edition of the ABC 33/40 Weather Xtreme video is available in the player on the right sidebar of the blog. You can subscribe to the Weather Xtreme video on iTunes by clicking here.
THIS AFTERNOON: Doesn’t get much better than this. A bright sunny sky, low humidity, and temperatures in the 70s. One of the warmest spots at 2:00 was Alexander City with 77 degrees.
We will squeeze out one more nice day tomorrow with a good supply of sunshine and a high close to 80. To the west, a severe weather/tornado outbreak will likely begin across the nation’s heartland, where SPC has a moderate risk out for places like Tulsa and Wichita.
SEVERE WEATHER THREAT FRIDAY: All of Alabama is in the SPC severe weather risk Friday, with an enhanced risk over the western half of the state into East Mississippi. We still believe the main risk will begin at mid-afternoon around 3:00 over West Alabama, then spreading east during the evening and nighttime hours.
Watch the Weather Xtreme video for all of the graphics… here are some severe weather parameters valid at 7:00 p.m. local time Friday from the 12Z NAM…
Surface based CAPE: 820 j/kg
Lifted index: -1.9
0-3 km storm relative helicity: 402 m2/s2
850 mb wind speed: 50 knots
500 mb wind speed: 72 knots
Seems like the NAM instability values are fairly low, otherwise everything seems in place for a significant severe weather outbreak for Alabama. Discreet thunderstorms should form during the peak of the afternoon heating process in the 3-8 p.m. time frame; those storms could be severe with potential for high wind, hail, and a few tornadoes. Then, the squall line will move through a little later, exiting the state around 2:00 a.m. Damaging winds will be the main threat along this line.
Alabamians will need to be a in a place to hear severe weather watches and warnings Friday afternoon and Friday night, and all of the campers around the Talledega Superspeedway will need to be very aware of the weather, and have a plan of action ready in case a tornado warning is issued for that part of Talladega County.

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My targeted zone :)

CONVECTIVE INHIBITION IS FORECAST TO GIVE WAY TOTALLY FRIDAY...
ALLOWING THE DEVELOPMENT OF INTENSE CONVECTIVE UPDRAFTS AND
SUPERCELL DEVELOPMENT ACROSS THE REGION. WIDESPREAD DESTABILIZATION
WILL OCCUR. CAPE VALUES ABOVE 1000-1500 ARE FORECAST ACROSS THE
ENTIRE FORECAST AREA...PAINTED AS HIGH AS 2-3K BY THE GFS ACROSS THE
BULK OF THE REGION FRIDAY AFTERNOON. GFS BUFR SOUNDINGS SHOW VERY
HEALTHY LAPSE RATES WITH THE EURO GOING HEAVIEST WITH FORECAST LAPSE
RATE VALUES AT OR ABOVE 7 DEGREES OVER MANY NRN AND ERN AREAS.
SYNOPTIC LIFT IS ENHANCED WHEN THE DEEPENING UPPER TROUGH PIVOTS
INTO THE AREA FRIDAY AFTERNOON...MAINTAINING ITS NEGATIVELY TILTED
ORIENTATION AS A SECONDARY WAVE PIVOTS AROUND THE LOW CENTER.
HEALTHY UPPER DIVERGENCE DEVELOPS ACROSS THE ENTIRE AREA EARLY IN
THE DAY AND IS FORECAST TO PERSIST IF NOT STRENGTHEN OVER ERN ZONES
DURING THE AFTERNOON...AS DOES LOW LEVEL HELICITY AND SHEAR. INTENSE
0-1KM HELICITIES AND IMPRESSIVE VGP VALUES HIGHLIGHT THE HIGH
POTENTIAL FOR TORNADIC DEVELOPMENT FOR MUCH OF THE AREA...
PARTICULARLY OVER ERN ZONES DURING THE AFTERNOON AS THE LOW LEVEL
JET INTENSIFIES.

INTENSE UPDRAFTS AND PW VALUES AROUND 1.5 INCHES FRIDAY ALSO SUGGEST
THE POTENTIAL FOR PERIODS OF HIGH RAINFALL RATES WHICH INTRODUCE A
POTENTIAL FOR PONDING WATER ISSUES DURING THE DAY.

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Day 2 SPC: "TORNADO OUTBREAK BECOMING INCREASINGLY POSSIBLE ACROSS THE CNTRL GULF COAST STATES ON FRIDAY INTO FRIDAY NIGHT"

[Joe-Nathan]

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT THU APR 14 2011

   VALID 151200Z - 161200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL GULF
   COAST STATES AND TN VALLEY...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER TO
   MID-MS VALLEY...CNTRL TO ERN GULF COAST STATES...SRN APPALACHIAN
   MTNS AND OH VALLEY...
   
   ...TORNADO OUTBREAK BECOMING INCREASINGLY POSSIBLE ACROSS THE CNTRL
   GULF COAST STATES ON FRIDAY INTO FRIDAY NIGHT...
   
   ...CNTRL GULF COAST STATES/SRN APPALACHIAN MTNS...
   AN IMPRESSIVE NEGATIVELY-TILTED UPPER-LEVEL LOW IS FORECAST TO MOVE
   FROM THE CNTRL PLAINS EWD INTO THE OZARKS. THE EXIT REGION OF A 75
   TO 90 KT MID-LEVEL JET ROUNDING THE BASE OF THE UPPER-LEVEL TROUGH
   WILL OVERSPREAD THE CNTRL GULF STATES FRIDAY AFTERNOON CREATING VERY
   FAVORABLE DEEP LAYER SHEAR PROFILES FOR SEVERE STORMS OVER A BROAD
   AREA. AT THE SFC...A LOW WILL DEEPEN AND MOVE NEWD ACROSS THE OH
   VALLEY AS A TRAILING COLD FRONT ADVANCES EWD ACROSS THE MS VALLEY.
   ELEVATED THUNDERSTORM ACTIVITY MAY BE ONGOING ACROSS THE WARM SECTOR
   FRIDAY MORNING IN AL AND MIDDLE TN WITH THIS CONVECTION BEING
   SHUNTED EWD AWAY FROM THE MODERATE RISK AREA AROUND MIDDAY. AS THIS
   OCCURS...MODEL FORECASTS ARE CONSISTENT WITH DEVELOPING NUMEROUS
   THUNDERSTORMS ALONG THE WRN EDGE OF AN AXIS OF MODERATE TO STRONG
   INSTABILITY FROM WRN TN SWD ACROSS NRN AND CNTRL MS. THIS ACTIVITY
   SHOULD SPREAD EWD ACROSS THE MODERATE RISK AREA LATE FRIDAY
   AFTERNOON INTO THE EVENING.
   
   FORECAST SOUNDINGS ALONG THE INSTABILITY AXIS SHOW MLCAPE VALUES
   FROM 2000 TO 3000 J/KG IN CNTRL MS TO 1500 TO 2000 J/KG ACROSS WRN
   KY AND WRN TN. THIS IS COMBINED WITH 55 TO 70 KT OF DEEP LAYER SHEAR
   AND STRONG LOW-LEVEL SHEAR SHOULD RESULT IN SUPERCELL DEVELOPMENT
   WITH TORNADOES ACROSS THE MODERATE RISK AREA. 0-3 KM STORM RELATIVE
   HELICITIES ARE FORECAST TO BE 400 TO 500 M2/S2 WITH LOOPING
   HODOGRAPHS ACROSS MUCH OF ERN MS AND WRN AL SUGGESTING A POTENTIAL
   FOR LONG-TRACK STRONG TORNADOES WILL EXIST. 500 MB TEMPS ARE
   FORECAST TO BE FROM -12C IN SRN MS AND SRN AL TO -16C IN WRN TO
   MIDDLE TN. THIS ALONG WITH THE STRONG DEEP LAYER SHEAR SHOULD ALSO
   BE FAVORABLE FOR LARGE HAIL. VERY LARGE HAIL WILL BE POSSIBLE
   ESPECIALLY IN ERN MS AS SUPERCELLS DEVELOP DURING THE MID TO LATE
   AFTERNOON WHERE THE STRONGEST INSTABILITY IS FORECAST. ALTHOUGH
   DISCRETE CONVECTION IS ANTICIPATED EARLY IN THE EVENT...LINEAR
   DEVELOPMENT SHOULD INCREASE ALONG THE COLD FRONT BY EARLY EVENING
   WITH A SQUALL-LINE MOVING EWD ACROSS THE REGION. DISCRETE STORMS
   AHEAD OF THE LINE SHOULD CONTINUE TO HAVE TORNADO THREAT THROUGH THE
   EVENING.
   
   ONE CONCERN IS THAT THE LOW-LEVEL JET IS FORECAST TO BE MAXIMIZED
   OVER KY AND TN DURING THE EARLY EVENING. LOW-LEVEL SHEAR PROFILES
   WILL STILL BE VERY FAVORABLE FURTHER SOUTH IN MS AND AL BUT THE
   LOW-LEVEL JET RESPONSE MAY BE FOCUSED FURTHER TO THE NORTH. ANOTHER
   CONCERN IS FOR THE SRN EDGE OF THE MODERATE RISK. MODEL FORECASTS
   DIFFER ON CONVECTIVE COVERAGE WITH THE NAM ISOLATED BUT THE ECMWF
   DEVELOPS NUMEROUS STORMS. IN SPITE OF THE UNCERTAINTIES...WILL ISSUE
   A MODERATE RISK ACROSS MUCH OF THE CNTRL GULF COAST STATES DUE TO
   THE POTENTIAL FOR A HIGHER-END EVENT.
   
   ...MID-MS VALLEY/OH VALLEY...
   AN UPPER-LEVEL LOW WILL MOVE ACROSS THE OZARKS FRIDAY WITH A MOIST
   AXIS IN PLACE ACROSS KY...IL AND IND. THE DEVELOPMENT OF NUMEROUS
   SEVERE THUNDERSTORMS APPEARS LIKELY TO THE EAST OF THE UPPER-LEVEL
   LOW AS STRONG LARGE-SCALE ASCENT MOVES ACROSS THE REGION FRIDAY
   AFTERNOON. FORECAST SOUNDINGS ALONG THE MOIST AXIS SHOW SFC
   DEWPOINTS IN THE UPPER 50S F WITH DEEP LAYER SHEAR OF 40 TO 50 KT.
   THIS ENVIRONMENT ALONG WITH COLD TEMPS ALOFT SHOULD SUPPORT THE
   DEVELOPMENT OF SUPERCELLS WITH LARGE HAIL. BACKED SFC WINDS AND
   STRONG LOW-LEVEL SHEAR ALSO SHOULD BE FAVORABLE FOR A TORNADO THREAT
   WITH ROTATING STORMS. HOWEVER...STRONG LOW-LEVEL CONVERGENCE ALONG A
   COLD FRONT MAY FORCE A LINEAR MCS. THIS WOULD RESULT IN A WIDESPREAD
   WIND DAMAGE THREAT WITH THE LINE MOVING INTO IND...CNTRL KY AND
   ECNTRL TN DURING THE EVENING.
   
   ..BROYLES.. 04/14/2011
   
   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
   CURRENT UTC TIME: 1116Z (6:16AM), RELOAD THIS PAGE TO UPDATE THE TIME 

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Hazardous Weather Outlook

Important Note:
Calling All Skywarn Spotters...Calling All Skywarn Spotters

Click here for a description/definition of hazardous weather.

000
FLUS44 KBMX 141115
HWOBMX

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BIRMINGHAM AL
600 AM CDT THU APR 14 2011

ALZ011>015-017>050-151130-
AUTAUGA-BARBOUR-BIBB-BLOUNT-BULLOCK-CALHOUN-CHAMBERS-CHEROKEE-
CHILTON-CLAY-CLEBURNE-COOSA-DALLAS-ELMORE-ETOWAH-FAYETTE-GREENE-HALE-
JEFFERSON-LAMAR-LEE-LOWNDES-MACON-MARENGO-MARION-MONTGOMERY-PERRY-
PICKENS-PIKE-RANDOLPH-RUSSELL-SHELBY-ST CLAIR-SUMTER-TALLADEGA-
TALLAPOOSA-TUSCALOOSA-WALKER-WINSTON-
600 AM CDT THU APR 14 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE COUNTIES SERVED BY THE
NATIONAL WEATHER SERVICE OFFICE IN BIRMINGHAM.

.DAY ONE...TODAY AND TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

SEVERE THUNDERSTORMS ARE ANTICIPATED ON FRIDAY AHEAD OF AN
APPROACHING COLD FRONT. AT THIS TIME...THE HAZARDOUS THREATS
INCLUDE...DAMAGING WINDS...TORNADOES...LARGE HAIL...AND LOCALLY HEAVY
RAIN. THERE ARE SOME DIFFERENCES IN MODEL OUTPUT THAT WOULD AFFECT
WHICH THREAT BECOMES THE DOMINANT THREAT AND THE OVERALL TIMING AND
PLACEMENT OF THE GREATEST THREAT. AT THIS TIME...IT APPEARS THE
THREAT MAY BE LENGTHY AND COVER ALL OF CENTRAL ALABAMA...BEGINNING IN
THE WEST BY AROUND 10 AM FRIDAY AND LASTING UNTIL AROUND MIDNIGHT
FRIDAY NIGHT SOUTHEAST. ATMOSPHERIC PARAMETERS APPEAR FAVORABLE FOR
THE POSSIBILITY OF STRONG TORNADOES. STAY TUNED TO FURTHER UPDATES ON
THIS DEVELOPING SEVERE WEATHER OUTBREAK POTENTIAL.

WINDY CONDITIONS ARE POSSIBLE BOTH AHEAD AND BEHIND THE COLD FRONT
FRIDAY AND SATURDAY. SOUTHERLY WINDS ARE EXPECTED AHEAD OF THE FRONT
WHILE WESTERLY WINDS ARE ANTICIPATED BEHIND THE FRONT. THESE WINDS
ARE EXPECTED BETWEEN 10 AND 20 MPH WITH HIGHER GUSTS.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF STORM SPOTTERS, EMERGENCY MANAGEMENT PERSONNEL, AND HAM
RADIO OPERATORS IS ANTICIPATED FRIDAY.

$$

75

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James Spann

ROUGH DAY TOMORROW: SPC has the western two-thirds of Alabama in a moderate risk of severe weather tomorrow and tomorrow night, along with the eastern half of Mississippi. Severe weather parameters are coming together for the potential for a significant outbreak of severe thunderstorms, and it will be a day where everybody will need to be in a place to hear severe weather warnings as they are issued.
TIMING: Out of respect to our RPM model, which has trended toward a faster solution over the past few runs, we are going to adjust the timing now to indicate potential for severe thunderstorms in West Alabama as early as 10:00 a.m. The threat will slowly shift eastward, and may extend into far East Alabama as late as 10:00 p.m. So, the bottom line is that we have a 12 hour window with severe weather potential for our state, 10 a.m. to 10 p.m.
NUMBERS: For the weather folks, here are some severe weather parameters for Birmingham late tomorrow afternoon from the NAM…
Surface based CAPE: 870 j/kg
Lifted index -4.0
SRH (storm relative helicity, 0-3 km) 418 m2/s2
SWEAT Index: 487
850 mb wind: 50 knots
The instability values remain a little on the low side for a major outbreak, but the other models are showing higher CAPE values. And, with limited convective inhibition, the door is certainly open for discreet supercell storms to form ahead of the squall line that is likely along the dryline.
WHAT TO EXPECT: Initially, the the threat will be from those isolated storms that pop up during the late morning and afternoon hours. They will have the potential to produce large hail, perhaps the size of baseballs, damaging straight line winds, and a few tornadoes. We can’t rule out the chance of one or two long track tornadoes. Then, later in the day into the evening hours, the threat will be from high wind along the line of storms that will sweep through the state.

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[Joe-Nathan]

Looks like the on shore flow is setting off some lite showers here in LA.

Fuel for the fire...

[Alex]

We were completely bypassed by the storm system earlier this week. Local rain chances are at 40-50%, so I am not holding my breath on this one unless something changes...

[Joe-Nathan]

VIA NWS ALERT EMAIL:

PUBLIC SEVERE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1131 AM CDT THU APR 14 2011

...SEVERE THUNDERSTORMS EXPECTED OVER PARTS OF THE SOUTH-CENTRAL
PLAINS THIS AFTERNOON AND TONIGHT...

THE NWS STORM PREDICTION CENTER IN NORMAN OK IS FORECASTING THE
DEVELOPMENT OF A FEW STRONG TORNADOES...VERY LARGE HAIL AND DAMAGING
WINDS OVER PARTS OF THE SOUTH-CENTRAL PLAINS THIS AFTERNOON AND
TONIGHT.

THE AREAS MOST LIKELY TO EXPERIENCE THIS ACTIVITY INCLUDE

WESTERN ARKANSAS
SOUTHEAST KANSAS
EXTREME SOUTHWEST MISSOURI
EASTERN OKLAHOMA
EXTREME NORTHEAST TEXAS

ELSEWHERE...SEVERE STORMS ARE ALSO POSSIBLE FROM THE CENTRAL PLAINS
TO THE MID-SOUTH.

...KEY WEATHER PLAYERS...
A STRONG STORM SYSTEM OVER THE SOUTHERN ROCKIES AT MIDDAY WILL MOVE
EAST TO THE CENTRAL AND SOUTHERN PLAINS STATES BY LATE THIS
AFTERNOON AND TO THE MID AND LOWER-MISSISSIPPI RIVER VALLEY
OVERNIGHT. THE WEATHER DISTURBANCE WILL BE ACCOMPANIED BY STRONG
WINDS IN THE MIDDLE AND HIGH-LEVELS OF THE ATMOSPHERE ALONG WITH
RELATIVELY COLD UPPER AIR TEMPERATURES. COMBINING THESE INGREDIENTS
WITH MOISTURE FLOWING NORTH FROM THE GULF OF MEXICO WILL RESULT IN
CONDITIONS RIPE FOR SEVERE THUNDERSTORMS.

...TIMING...
SEVERE THUNDERSTORMS WILL FIRST DEVELOP BY 300 PM ACROSS CENTRAL
KANSAS AND MOVE INTO EASTERN KANSAS BY EARLY THIS EVENING.

Read more
• SPC - No watches are valid as of Thu Apr 14 16:34:02 UTC 2011
04/14/2011 12:33 PM EDT
No watches are valid as of Thu Apr 14 16:34:02 UTC 2011.

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Apr 14, 2011 1730 UTC Day 2 Convective Outlook

Updated: Thu Apr 14 17:26:56 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 141724

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1224 PM CDT THU APR 14 2011

VALID 151200Z - 161200Z

...THERE IS A MDT RISK OF SVR TSTMS OVER MUCH OF CNTRL AND NRN MS
AND AL INTO PORTIONS OF SRN TN...

...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF THE LOWER MS
VALLEY/GULF COAST REGION NWD INTO THE MID MO/OH VALLEYS...

...SYNOPSIS...
A VERTICALLY STACKED SFC AND UPPER LEVEL LOW WILL MOVE FROM THE
CNTRL PLAINS EWD INTO THE MID/LOWER MS VALLEY DURING THE DAY...WITH
A STRONGLY CYCLONIC UPPER SPEED MAX NOSING INTO NRN MS/WRN TN. SLY
SFC FLOW ACROSS THE WARM SECTOR WILL HELP TO TRANSPORT LOW TO MID
60S F DEWPOINTS NWD AHEAD OF A DRYLINE THAT WILL EXTEND SWD BE NEAR
THE MS RIVER AROUND 21Z. WITH STRONG WIND PROFILES OVERSPREADING AN
UNSTABLE AIR MASS...AREAS OF SIGNIFICANT SEVERE WEATHER ARE LIKELY
DURING THE DAY.

...MID/LOWER MS RIVER VALLEY EWD INTO THE OH/TN VALLEYS AND AL...
NUMEROUS SHOWERS AND STORMS SHOULD BE ONGOING FRIDAY MORNING FROM
CNTRL AR INTO SERN MO IN AN AREA OF STRONG WARM ADVECTION ASSOCIATED
WITH A 50+ KT LOW LEVEL JET...AND IN A REGION OF STRONG DCVA WITH
THE UPPER JET NOSING IN. WITH 60S DEWPOINTS IN PLACE...FORECAST
SOUNDINGS INDICATE EFFECTIVE SURFACE BASED PARCELS AND LARGE LOOPING
HODOGRAPHS FAVORABLE FOR ROTATING STORMS. THUS...IT APPEARS SOME OF
THIS ACTIVITY MAY BE SEVERE AT THE BEGINNING OF THE PERIOD INCLUDING
A THREAT OF TORNADOES.

THIS EARLY ACTIVITY MAY HAVE AN IMPACT ON SWD DEVELOPMENT
INITIALLY...BUT GIVEN LITTLE CONVECTIVE INHIBITION ACROSS THE WARM
SECTOR...AND STRONG SURFACE CONVERGENCE NEAR THE DRYLINE...MORE
STORMS SHOULD FORM BY LATE MORNING OR EARLY AFTERNOON OVER MUCH OF
NRN AND CNTRL MS. HERE...A TIGHT MID LEVEL THERMAL GRADIENT WILL BE
IN PLACE WHICH MAY HAMPER STORM COVERAGE OVER SERN LA/SRN MS AND AL.
HOWEVER...SHEAR PROFILES WOULD SUPPORT SUPERCELLS ALL THE WAY TO THE
GULF COAST WITH A HAIL/WIND/TORNADO THREAT.

POTENTIAL DESTABILIZATION FARTHER N WILL BE SOMEWHAT HAMPERED BY
EARLY DAY CONVECTION...BUT STRONG COOLING ALOFT AND STEEPENING LOW
LEVEL LAPSE RATES SHOULD RESULT IN A SECONDARY AREA OF SUPERCELL AND
TORNADO POTENTIAL OVER SERN MO INTO SRN IL/WRN KY BY AFTERNOON.
FORECAST HODOGRAPHS IN THIS AREA DEPICT SUFFICIENT LOW LEVEL
CURVATURE FOR SUPERCELLS...ALONG WITH SOMEWHAT MARGINAL HODOGRAPH
LENGTH DUE TO WEAKENING MID LEVEL FLOW CLOSER TO THE UPPER LOW.
REGARDLESS...A FEW TORNADOES AND LARGE HAIL APPEAR LIKELY IN THIS
REGION AS WELL.

ACTIVITY WILL CONTINUE EWD AFTER 00Z/DARK...WITH THE GREATEST
NOCTURNAL THREAT OVER AL IN CLOSER PROXIMITY TO MOISTURE AND
INSTABILITY...AND WHERE STRONGLY CURVED HODOGRAPHS WILL RESIDE.

..JEWELL.. 04/14/2011

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