Severe Weather possible May 10 - MDT risk issued

[CrazyC83]

Risk levels jumped to a hatched 45% for a large area. I smell a big outbreak tomorrow - and I think it will go MUCH farther north as well, perhaps well into the Great Lakes.

[CrazyC83]

SPC AC 091744

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1244 PM CDT TUE MAY 09 2006

VALID 101200Z - 111200Z

...THERE IS A MDT RISK OF SVR TSTMS FROM THE CONFLUENCE OF THE OH/MS
RIVERS SWD ACROSS THE LOWER MS VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM
SERN TX TO LOWER MI TO GA AND NRN FL...

...WIDESPREAD AND POTENTIALLY SIGNIFICANT SEVERE WEATHER EPISODE
APPEARS INCREASINGLY LIKELY OVER PARTS OF THE MS/TN VALLEYS AND
LOWER OH VALLEY DURING WEDNESDAY...

...SYNOPSIS...
MID/UPPER LEVEL FLOW OVER THE CNTRL U.S. WILL CONTINUE TO UNDERGO
STRONG AMPLIFICATION THROUGH MIDWEEK AS LARGE SCALE PHASING BETWEEN
MIDDLE AND NRN BRANCH FLOW PRODUCES AN ANOMALOUSLY DEEP CYCLONE
ACROSS THE MIDWEST. THIS LARGE SCALE EVOLUTION WILL UNFOLD AS STRONG
MIDDLE STREAM SHORT WAVE TROUGH DEVELOPS EAST ACROSS THE SRN PLAINS
THROUGH LATE TUESDAY EVENING. THIS IMPULSE IS EXPECTED TO INDUCE
STRONG MCS DEVELOPMENT ACROSS OK THROUGH TUESDAY NIGHT. SRN PLAINS
SURFACE LOW IS FORECAST TO STRENGTHEN COINCIDENT WITH THE MCS AND
SPREAD EAST TO NEAR THE MO BOOTHEEL AREA BY WEDNESDAY MORNING.
SLOWER MOVING NRN BRANCH SHORT WAVE TROUGH/LOW WILL DEVELOP ESEWD
FROM MT TOWARD THE UPPER MS VALLEY THROUGH WEDNESDAY AFTERNOON.
STRONG COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL SPREAD QUICKLY
SWD/SEWD ACROSS THE PLAINS AND MERGE WITH THE DEEPENING CYCLONE
ACROSS THE LOWER OH VALLEY DURING WEDNESDAY AFTERNOON. WHILE PRIMARY
DEEP LAYER CYCLONE ASSOCIATED WITH THE NRN BRANCH TROUGH UNDERGOES
OCCLUSION OVER LAKE MI...INTENSIFYING SECONDARY CYCLONE IS FORECAST
TO TRACK NNEWD ACROSS THE MIDWEST... AND INTO LOWER MI...THROUGH
WEDNESDAY EVENING. TRAILING COLD FRONT WILL SWEEP EWD ACROSS THE
MID/LOWER MS VALLEY...AND ACROSS MUCH OF THE DEEP SOUTH AND OFF THE
NCNTRL GULF COAST...THROUGH EARLY THURSDAY.

...SERN MO TO LOWER MI...
POTENTIAL EXISTS FOR WIDESPREAD CLOUDS AND PRECIPITATION TO SOMEWHAT
IMPEDE AIR MASS MODIFICATION ACROSS THE LOWER OH VALLEY DURING
WEDNESDAY GIVEN PRESENCE OF UPSTREAM MCS ACTIVITY AND STRONG OUTFLOW
BOUNDARIES. HOWEVER...GFS AND ENSEMBLE FORECASTS SUPPORT AT LEAST
MODEST RECOVERY IN THE WAKE OF MORNING CONVECTION AND AHEAD OF
APPROACHING MID LEVEL WIND MAX AND DEEPENING SURFACE LOW. GIVEN LOW
TO MID 60S SURFACE DEWPOINTS AND POCKETS OF MLCAPE AROUND 500 J/KG
/POSSIBLY HIGHER IF GFS FORECAST VERIFIES/ SHEAR AND FORCING APPEAR
MORE THAN ADEQUATE TO PROMOTE STORM ORGANIZATION INTO LINE SEGMENTS
AND LOW TOPPED SUPERCELLS. THIS ACTIVITY SHOULD SPREAD ENEWD ACROSS
THE LOWER OH VALLEY AND LOWER MI FROM AFTERNOON THROUGH EVENING WITH
AN INCREASING CHANCE FOR HAIL AND HIGH WINDS. TORNADO POTENTIAL
APPEARS GREATEST NEAR THE INTENSIFYING SURFACE LOW. IF MODEST TO
STRONG INSTABILITY CAN DEVELOP COINCIDENT WITH THIS FEATURE...A
COUPLE OF STRONG TORNADOES APPEAR POSSIBLE.

...LOWER MS VALLEY/TN VALLEY/DEEP SOUTH...
SOUTH OF THE SURFACE LOW...WIDESPREAD MOISTURE AND INCREASING
INSTABILITY SHOULD EXIST. OUTFLOW FROM POSSIBLE OK/AR MCS MAY SPREAD
SEWD INTO AND INHIBIT STRONGER AIR MASS DESTABILIZATION EARLY IN THE
DAY. HOWEVER...STRONG RECOVERY IS EXPECTED IN THE WAKE OF THIS
OUTFLOW...FROM TXK ACROSS THE LOWER MS VALLEY BY AFTERNOON.
DIFFLUENT AND INCREASINGLY STRONG WLY MID LEVEL FLOW WILL SPREAD
ACROSS THE RECOVERING WARM SECTOR AND FOSTER NEW CONVECTION AHEAD OF
THE COLD FRONT FROM AR ACROSS THE MS RIVER. THIS ACTIVITY WILL EXIST
WITHIN A STRONGLY SHEARED ENVIRONMENT AND NUMEROUS SUPERCELLS WITH
LARGE HAIL AND DAMAGING WINDS APPEAR POSSIBLE. IF THIS CONVECTION
CAN REMAIN DISCRETE THROUGH LATE AFTERNOON...STORMS WILL MOVE INTO
HIGH HELICITY REGIME EXISTING IN THE WAKE OF EARLIER MCS OUTFLOW.
TORNADIC STORMS APPEAR POSSIBLE BEFORE CONVECTION BECOMES
INCREASINGLY LINEAR AS INTENSIFYING COLD FRONT DEVELOPS INTO THE
REGION. WIND DAMAGE AND ISOLATED TORNADO THREAT MAY EXTEND BEYOND
SUNSET AS SEVERE SQUALL LINE DEVELOPS ESEWD ACROSS THE NRN GULF
COAST/DEEP SOUTH.

..CARBIN.. 05/09/2006

CLICK TO GET WUUS02 PTSDY2 PRODUCT

NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z
CURRENT UTC TIME: 1757Z (1:57PM), RELOAD THIS PAGE TO UPDATE THE TIME

[6SpeedTA95]

Tomorrow will be interesting indeed.

[CrazyC83]

I think that the southern end will be a major derecho, the northern end (which extends well beyond the SPC forecast) a tornado outbreak.

I wouldn't be surprised to see them go High Risk tomorrow, and to see PDS's issued...

[6SpeedTA95]

I think that the southern end will be a major derecho, the northern end (which extends well beyond the SPC forecast) a tornado outbreak.

I wouldn't be surprised to see them go High Risk tomorrow, and to see PDS's issued...

I think you probably have it backwards

...SERN MO TO LOWER MI...
POTENTIAL EXISTS FOR WIDESPREAD CLOUDS AND PRECIPITATION TO SOMEWHAT
IMPEDE AIR MASS MODIFICATION ACROSS THE LOWER OH VALLEY DURING
WEDNESDAY GIVEN PRESENCE OF UPSTREAM MCS ACTIVITY AND STRONG OUTFLOW
BOUNDARIES. HOWEVER...GFS AND ENSEMBLE FORECASTS SUPPORT AT LEAST
MODEST RECOVERY IN THE WAKE OF MORNING CONVECTION AND AHEAD OF
APPROACHING MID LEVEL WIND MAX AND DEEPENING SURFACE LOW. GIVEN LOW
TO MID 60S SURFACE DEWPOINTS AND POCKETS OF MLCAPE AROUND 500 J/KG
/POSSIBLY HIGHER IF GFS FORECAST VERIFIES/ SHEAR AND FORCING APPEAR
MORE THAN ADEQUATE TO PROMOTE STORM ORGANIZATION INTO LINE SEGMENTS
AND LOW TOPPED SUPERCELLS. THIS ACTIVITY SHOULD SPREAD ENEWD ACROSS
THE LOWER OH VALLEY AND LOWER MI FROM AFTERNOON THROUGH EVENING WITH
AN INCREASING CHANCE FOR HAIL AND HIGH WINDS. TORNADO POTENTIAL
APPEARS GREATEST NEAR THE INTENSIFYING SURFACE LOW. IF MODEST TO
STRONG INSTABILITY CAN DEVELOP COINCIDENT WITH THIS FEATURE...A
COUPLE OF STRONG TORNADOES APPEAR POSSIBLE.

Basically tornadoes are possible in the northern sections but appear much more probably downsouth where cape/LI/LFC/LCL's appear more conducive to discrete supercell/tornadic activity.

As with any severe weather system this time of year tornadoes will be possibly tomorrow just about everywhere in the risk area, however, I think the biggest risk for tornadic activity will be south of I70.

[6SpeedTA95]

NOT AN OFFICIAL FORCAST!

This is what I feel for tomorrow based on the data we have.



Purple = high, IF a high forcast materializes. At this point I dont know that it will. They dropped the MDT for us due to mixing and we could be into a similar situation east of us tomorrow. We should have new data between 8 and 10pm tonight and we'll know more about todays development and whether or not it will significantly affect tomorrows chances of svr weather.

[CrazyC83]

You're right, it is a difficult forecast at this point. There isn't great confidence, hence I am holding the risk (in my view) at Level 3 - but for an enormous area.

[CrazyC83]

NOT AN OFFICIAL FORECAST - just my prediction.

This is a new format. It is always for the 24 hour period ending 1200 UTC the next day.

[CrazyC83]

STILL a very difficult forecast. Could be a total bust or a major tornado outbreak.

[wxmann_91]

STILL a very difficult forecast. Could be a total bust or a major tornado outbreak.

So true. One of the more difficult events to forecast, I can recall, in the past few years. Sun will be key. More=outbreak, Less=bust.

[CrazyC83]

STILL a very difficult forecast. Could be a total bust or a major tornado outbreak.

So true. One of the more difficult events to forecast, I can recall, in the past few years. Sun will be key. More=outbreak, Less=bust.

That is why I am sticking with my map from earlier today with the Level 3 risk due to lack of confidence.

[6SpeedTA95]

STILL a very difficult forecast. Could be a total bust or a major tornado outbreak.

So true. One of the more difficult events to forecast, I can recall, in the past few years. Sun will be key. More=outbreak, Less=bust.

That is why I am sticking with my map from earlier today with the Level 3 risk due to lack of confidence.

What does your lvl3 entail? I do not see a significant tornado threat that far north, I just dont see it at all tomorrow. A few isolated tornadic cells maybe but I dont think we'll see anything significan't with reguards to tornadoes north of I64.

[CrazyC83]

Level 3 - Significant (i.e. SPC Moderate) risk of severe weather. My feeling is that the severe weather will stretch farther north than their prediction.

That is for all types of severe weather - wind, hail and tornadic.

I'm not going above that right now as I don't have the confidence, even though the potential is there for a major outbreak, I hate busting a Level 5.

[6SpeedTA95]

No high risk yet today, the MDT was shifted a bit south but was expanded in coverage area.

[CrazyC83]

Nope, it seems to be shifting south though which goes against my original prediction...

15-hatched for tornado, 45-hatched for wind and 45-hatched for hail. I wouldn't be surprised to see an upgrade to High Risk later.

This is still a dangerous situation. My prediction maps have increased the risk to Level 4.

[6SpeedTA95]

Nope, it seems to be shifting south though which goes against my original prediction...

15-hatched for tornado, 45-hatched for wind and 45-hatched for hail. I wouldn't be surprised to see an upgrade to High Risk later.

This is still a dangerous situation. My prediction maps have increased the risk to Level 4.

I could see them doing a high risk but I honestly dought it. I've pulled what upper air soundings I can find from potentially affected areas and there's been a fair amount of mixing due ot the MCS events. Now these MCS's will probably allow some outflow boundaries to form and that could be where we have our supercell development. Looks like the onset for discreet supercell development will be after 2pm.

Some areas are reporting high capes 5000+ and one area is reporting 7000+ cape values. So there is instability in the air the question is what kind of recovery can the atmosphere make with reguards to other indicators by afternoon.

[6SpeedTA95]

Here's my map
NOT AN OFFICIAL FORCAST

[CrazyC83]

NOT AN OFFICIAL FORECAST - just my prediction.

Confidence is higher that a major event will take place. However, it is not great enough to warrant a Level 5, even though the potential for violent tornadoes and extreme winds is there. Still, I do increase the threat to Level 4. The overall threat area is still somewhat north of the SPC prediction, but not as much as before.

[CrazyC83]

The main line seems to be farther back around the Arklatex right now. That is where I see the PDS's later.

The big question mark remains: tornado outbreak or long serial derecho?

[CrazyC83]

First Tornado Watch issued - not a PDS:

SEL2

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 332
NWS STORM PREDICTION CENTER NORMAN OK
1200 PM CDT WED MAY 10 2006

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

NORTHEAST LOUISIANA
CENTRAL MISSISSIPPI

EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM NOON UNTIL
900 PM CDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 50 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 110 MILES WEST OF JACKSON
MISSISSIPPI TO 20 MILES EAST OF MERIDIAN MISSISSIPPI. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU2).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION...CONTINUE...WW 328...WW 329...WW
330...WW 331...

DISCUSSION...THE LOW-LEVELS CONTINUE TO DESTABILIZE ALONG AND S OF A
COMPOSITE OUTFLOW BOUNDARY ACROSS CENTRAL MS...NEAR AND JUST N OF
I-20. MLCAPE VALUES IN EXCESS OF 3000 J/KG ARE EXPECTED THIS
AFTERNOON IN THE WARM SECTOR...WHILE THE CAP GRADUALLY WEAKENS.
ADDITIONAL THUNDERSTORM DEVELOPMENT APPEARS LIKELY BY EARLY
AFTERNOON ALONG THE OUTFLOW BOUNDARY...AND POTENTIALLY BY MID
AFTERNOON IN THE WARM SECTOR IMMEDIATELY S OF THE BOUNDARY. DEEP
LAYER VERTICAL SHEAR WILL BE SUFFICIENT FOR SUPERCELLS AND BOW
ECHOES CAPABLE OF PRODUCING TORNADOES AND DAMAGING WINDS...AND VERY
LARGE HAIL WILL BE POSSIBLE WITH THE MOST INTENSE STORMS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
550. MEAN STORM MOTION VECTOR 27030.


...THOMPSON