Tornado Alley Forecasts, Nowcasting and Reports

**debris74** · 28/02/2007, 20:51

VALID 011200Z - 021200Z

...THERE IS A MDT RISK OF SVR TSTMS PORTIONS
LA...AR...MO...IL...SWRN INDIANA...WRN KY...WRN/MID
TN...MS...AL...GA...SC...

OUTBREAK OF SVR TSTMS -- INCLUDING CONDITIONAL POTENTIAL FOR
STRONG-VIOLENT TORNADOES -- WILL AFFECT PORTIONS E-CENTRAL/SERN
CONUS. UNCERTAINTIES REGARDING INSTABILITY AND CONVECTIVE MODE
REMAIN ATTM...PRECLUDING HIGH PROBABILITIES THIS SOON. HOWEVER...AN
UPGRADE OF SOME PORTION OF CATEGORICAL MDT RISK AREA IS POSSIBLE IN
FUTURE OUTLOOKS VALID FOR THIS PERIOD.

**Stormchaser** · 28/02/2007, 20:53

ecco comunque tutte le previsioni

Day1 Outlook!

SPC AC 281620

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1020 AM CST WED FEB 28 2007

VALID 281630Z - 011200Z

...THERE IS A MDT RISK OF SVR TSTMS TONIGHT OVER PARTS OF SOUTHERN
AND CENTRAL MO... NRN AR AND SMALL PART OF NORTHEAST OK AND
SOUTHEAST KS...

...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON AND
OVERNIGHT OVER PARTS OF THE CENTRAL PLAINS AND MID MS VALLEY......

...SYNOPSIS...
DEEPENING COLD UPPER TROUGH MOVING EWD ACROSS WRN U.S. AS ADVERTISED
BY LAST SEVERAL MODEL RUNS WITH A POWERFUL 150KT POLAR JET MAX
CURRENTLY ACROSS AZ/NM DRIVING ACROSS SRN PLAINS TONIGHT. RAPID
DEEPENING OF SURFACE LOW TX/OK PANHANDLE BY LATER THIS AFTERNOON
WITH LOW THEN TRACKING ENEWD INTO WRN MO AHEAD OF INTENSIFYING UPPER
TROUGH BY 12Z THU.

STRENGTHENING LOW LEVEL JET SRN PLAINS INTO MID MS VALLEY THRU THE
PERIOD WILL RAPIDLY SPREAD GULF MOISTURE NEWD. BY LATER THIS
AFTERNOON 60F DEWPOINTS SHOULD BE AS FAR N AS ERN OK/WRN AR WITH MID
50S TO SERN KS/SWRN MO. ELEVATED MIX LAYER HAS OVERSPREAD PLAINS
WHICH WILL DELAY INITIATION OF SURFACE CONVECTION UNTIL LATE
AFTERNOON OR EARLY EVENING WHEN LARGE SCALE ASCENT AND MID LEVEL
COOLING ARRIVE WITH APPROACH OF TROUGH AND EXIT REGION OF JET MAX.

...KS/OK LATE THIS AFTERNOON AND EVENING...
DRY LINE WILL SHARPEN UP ACROSS CENTRAL OK INTO SERN KS DURING
AFTERNOON WITH MLCAPE INCREASING TO 1000-1500 J/KG ERN OK. BY LATE
THIS AFTERNOON OR EARLY EVENING SEVERE THUNDERSTORMS SHOULD RAPIDLY
DEVELOP AS CAP WEAKENS SUFFICIENTLY. INITIAL DEVELOPMENT MOST LIKELY
VICINITY KS/OK BORDER WITH STORMS THEN RAPIDLY EXPANDING ACROSS ERN
KS INTO SWRN MO. STORMS EXPECTED TO EVOLVE FAIRLY QUICKLY INTO
SUPERCELLS GIVEN THE STRONG SHEAR BOTH SPEED AND DIRECTIONAL. IN
ADDITION TO LARGE HAIL AND DAMAGING WINDS... TORNADOS WILL BE
POSSIBLE. SWD EXTENSION OF DEVELOPMENT ALONG DRY LINE THRU ERN OK
SHOULD OCCUR BUT IT COULD BE WELL AFTER DARK WHEN THE CAP WEAKENS
SUFFICIENTLY.

...ERN OK/MO/AR OVERNIGHT...
OVERNIGHT MID LEVEL CAP WILL ERODE MUCH OF THIS AREA E OF DRY LINE
AND AHEAD OF DEEPENING SURFACE LOW AS LARGE SCALE ASCENT CONTINUES
TO INCREASE AND SPREAD EWD. EVEN WITH SOME QUESTION AS TO AMOUNT OF
INSTABILITY ...THE STRENGTH OF THE KINEMATICS AND VERY STRONG SHEAR
PROFILES SUPPORT TORNADO POTENTIAL ALONG WITH LARGE HAIL AND
DAMAGING WINDS. THE IMPRESSIVE STRENGTH OF THIS SYSTEM SUPPORTS
POSSIBILITY OF STRONG TORNADOS OVERNIGHT.

...IL/KY/IN AFTER MIDNIGHT...
STRONG LOW LEVEL JET WILL EXPAND RAPIDLY EWD ACROSS MID MS VALLEY
OVERNIGHT WITH GULF MOISTURE SURGING NEWD. MODEL SOUNDINGS AFTER
06Z SHOW SUFFICIENT ELEVATED CAPE TO SUPPORT A RISK OF AT LEAST
LARGE HAIL ACROSS MID MS RIVER REGION. RISK COULD REACH TO WESTERN
IL/KY AND SWD TO WRN TN AND NRN MS BY 12Z

..HALES.. 02/28/2007

CLICK TO GET WUUS01 PTSDY1 PRODUCT

NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
CURRENT UTC TIME: 1950Z (8:50PM), RELOAD THIS PAGE TO UPDATE THE TIME

**debris74** · 28/02/2007, 20:54

cioè significa HIGH RISK probabile x domani...

**Stormchaser** · 28/02/2007, 21:02

Day2 Outlook

SPC AC 281739

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1139 AM CST WED FEB 28 2007

VALID 011200Z - 021200Z

...THERE IS A MDT RISK OF SVR TSTMS PORTIONS
LA...AR...MO...IL...SWRN INDIANA...WRN KY...WRN/MID
TN...MS...AL...GA...SC...

...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM MID MS VALLEY TO
CENTRAL GULF COAST TO SRN ATLANTIC COAST...

OUTBREAK OF SVR TSTMS -- INCLUDING CONDITIONAL POTENTIAL FOR
STRONG-VIOLENT TORNADOES -- WILL AFFECT PORTIONS E-CENTRAL/SERN
CONUS. UNCERTAINTIES REGARDING INSTABILITY AND CONVECTIVE MODE
REMAIN ATTM...PRECLUDING HIGH PROBABILITIES THIS SOON. HOWEVER...AN
UPGRADE OF SOME PORTION OF CATEGORICAL MDT RISK AREA IS POSSIBLE IN
FUTURE OUTLOOKS VALID FOR THIS PERIOD.

...SYNOPSIS...
IN MID/UPPER LEVELS...HEIGHTS ARE FCST TO FALL ACROSS MOST OF
CENTRAL CONUS...WITH EWD ADVANCEMENT OF TROUGHING NOW AMPLIFYING
FROM NRN ROCKIES SWD ACROSS WRN GREAT BASIN AND SRN CA. PRIMARY
SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER SRN
NV...SERN CA AND EXTREME WRN AZ -- IS FCST TO EVOLVE INTO CLOSED
MIDLEVEL LOW EARLY IN PERIOD INVOF NERN KS/NWRN MO...THEN MOVE NEWD
OVER WI AS OCCLUDING DEEP-LAYER CYCLONE BY 2/12Z. ASSOCIATED SFC
LOW WILL STRENGTHEN AND LIFT NEWD ACROSS MO/IA EARLY IN
PERIOD...BECOMING VERTICALLY STACKED WITH UPPER LOW BY END OF
PERIOD. ASSOCIATED COLD FRONT WILL CATCH FOREGOING DRYLINE EARLY IN
PERIOD...THEN COMBINED BOUNDARY WILL SWEEP EWD OVER OH/TN VALLEY
REGIONS AND GULF COAST STATES.

SFC/925/850 MB ANALYSES AND VIS IMAGERY INDICATES ROBUST LOW LEVEL
MOISTURE FROM CENTRAL GULF SWD...BOUNDED ON N SIDE BY BAND OF LOW
CLOUDS EVIDENT IN VIS IMAGERY FROM S FL WNWWD TO ABOUT 120 NM S OF
CENTRAL/WRN COAST OF LA. ASSOCIATED MARINE/WARM FRONT IS FCST TO
MOVE INLAND LATE DAY-1 PERIOD THEM BECOME INCREASINGLY DIFFUSE AS
INTENSE LOW LEVEL THETAE ADVECTION REGIME SHIFTS NWD THROUGH
THIS AIR MASS...PARTLY SAMPLED BY 28/12Z RAOBS FROM MONTERREY
MEX...BRO...CRP...MERIDA MEX...AND EYW...APPEARS CHARACTERIZED BY
BOUNDARY LAYER THAT BECOMES MORE SHALLOW WWD AND SWD AND DEEPEST
INVOF MARINE FRONT.

...AR/MO/IL...LOWER OH VALLEY REGION...
PRIOR-OVERNIGHT SVR POTENTIAL DESCRIBED IN DAY-1 OUTLOOK IS EXPECTED
TO CONTINUE UNABATED THROUGH EARLY DAY-2 PERIOD...WITH DAMAGING WIND
AND TORNADOES BEING MAIN CONCERNS. ONE OR MORE LINES OF SVR TSTMS
ARE EXPECTED TO SWEEP NEWD ACROSS OZARKS AND ADJACENT PORTIONS
MO/AR...THEN INTO WRN/SRN IL THROUGH MIDDAY. DEEP-LAYER VERTICAL
SHEAR PROFILES ARE STRONGLY FAVORABLE FOR BOWS AND SUPERCELLS.
BUOYANCY WILL BE MRGL...WITH MLCAPES GENERALLY UNDER 500
J/KG...HOWEVER MODIFIED FCST SOUNDINGS SUGGEST SFC-BASED INFLOW IS
POSSIBLE AS FAR N AS PORTIONS IL/INDIANA. FAST STORM MOTIONS
EXCEEDING 45 KT ARE LIKELY...WHICH WOULD ENHANCE THREAT OF
LONG-TRACK TORNADOES FOR ANY RELATIVELY DISCRETE/SUSTAINED
SUPERCELLS THAT CAN DEVELOP IN THIS ENVIRONMENT.

...MID SOUTH...MS/AL...
MAXIMIZED SFC HEATING WILL COINCIDE WITH OPTIMAL VERTICAL SHEAR AND
INCREASING LOW LEVEL MOISTURE TO MAXIMIZE RISK FOR SVR
HAIL...WIND...AND IN PARTICULAR...SIGNIFICANT TORNADOES. ALTHOUGH
MIDLEVEL LAPSE RATES MAY REMAIN AOB 7 DEG C/KM...SFC DEW POINTS
SHOULD INCREASE INTO 60S F ALONG AND S OF MARINE FRONT. THIS WILL
SUPPORT POCKETS OF MLCAPES 500-1000 J/KG...WHERE BREAKS IN CLOUD
COVER OCCUR BEHIND EARLY-PERIOD PRECIP ASSOCIATED WITH STRONG WAA
REGIME. THIS WILL BE SUITABLE FOR TORNADIC SUPERCELLS AND BOWING
LINE SEGMENTS IN ENVIRONMENT CHARACTERIZED BY LARGE LOW LEVEL
HODOGRAPHS -- 0-1 KM SRH AOA 300 J/KG -- AND 0-6 KM SHEAR EXCEEDING
60 KT. A FEW LONG-LIVED AND LONG-TRACK SUPERCELLS ARE POSSIBLE
GIVEN STRENGTH OF DEEP-LAYER KINEMATIC PROFILES AND RAPID NEWD
SPREAD OF FAVORABLE INFLOW-LAYER MOISTURE.

...CAROLINAS/GA...SRN PIEDMONT AND COASTAL PLAIN...
FAVORABLE ENVIRONMENT FOR SVR OUTBREAK IS EXPECTED TO SHIFT/EXTEND
EWD FROM MS/AL INTO THIS REGION DURING EVENING AND OVERNIGHT HOURS.
RAPID BOUNDARY LAYER MOISTURE RECOVERY IS FCST DURING DAY AND
THROUGHOUT EVENING...FROM SW-NE...LEADING TO SFC DEW POINTS UPPER
50S TO MID 60S AS FAR NE AS ERN NC. SWLY LLJ OFF GULF IS PROGGED TO
INCREASE TO 55-70 KT RANGE BY 2/06Z AHEAD OF COLD FRONT. MOIST
ADVECTION WILL OFFSET DIABATIC NOCTURNAL COOLING...RENDERING INFLOW
LAYER SFC BASED OR VERY NEARLY SO. AS INCREASINGLY FAVORABLE
BOUNDARY LAYER THETAE SPREADS UNDERNEATH STRENGTHENING DEEP-LAYER
WIND FIELDS...ENVIRONMENT WILL BECOME FAVORABLE FOR SUPERCELLS AND
BOWS...WITH ATTENDANT RISKS FOR TORNADOES AND DAMAGING WIND.

...FL PENINSULA...AFTERNOON...
TSTMS MAY DEVELOP OVER PORTIONS FL PENINSULA -- PRIMARILY DURING
AFTERNOON INVOF SEABREEZE BOUNDARIES...WHEN DIURNAL HEATING
MINIMIZES CINH. SRN PERIPHERY OF STRONGEST MID-UPPER WINDS SHOULD
EXTEND OVER PORTIONS CENTRAL/NRN FL...WITH SLY WINDS AT SFC
ENHANCING DEEP-LAYER SHEAR AND SUPPORTING POTENTIAL FOR A FEW
SUPERCELLS. 0-6 KM SHEAR AOA 50 KT MAY EXTEND AS FAR S AS LAKE
OKEECHOBEE AREA BY 1/21Z. INSOLATION AND SFC DEW POINTS UPPER 60S
TO LOW 70S SHOULD OFFSET MODEST LAPSE RATES ALOFT TO LEAD TO MLCAPES
500-1000 J/KG.

..EDWARDS.. 02/28/2007

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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z
CURRENT UTC TIME: 1958Z (8:58PM), RELOAD THIS PAGE TO UPDATE THE TIME