STORM2K

Whilst its still quite early days the SPC earlier issued a severe weather outlook for day 5, which would be 7th May for area around the Great Lakes, due to a developing upper low that swings in from the west with a tight eastern gradient showing some decent winds aloft, here is the discussion:


ZCZC SPCSWOD48 ALL
ACUS48 KWNS 030814
SPC AC 030814

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0314 AM CDT MON MAY 03 2010

VALID 061200Z - 111200Z

...DISCUSSION...

THOUGH SLIGHT DIFFERENCES STILL EXIST...03/00Z ECMWF AND GFS
GUIDANCE IS NOW IN MUCH BETTER AGREEMENT IN THE EVOLUTION OF THE
NEXT SIGNIFICANT MIDLEVEL TROUGH AND ASSOCIATED FRONTAL SYSTEM WHICH
WILL IMPACT THE CNTRL AND ERN PARTS OF THE NATION ON DAYS 4 AND 5
/THU MAY 6TH AND FRI MAY 7TH/.

ON DAY 4...IT STILL APPEARS THAT BOUNDARY LAYER MOISTURE WILL REMAIN
QUITE MARGINAL RELATIVE TO THE CAP ASSOCIATED WITH AN EML FROM THE
SURFACE LOW SWD ALONG THE DRYLINE OVER THE CNTRL AND SRN PLAINS.
FARTHER E FROM THE OZARKS INTO THE OH VALLEY...THE PRESENCE OF A
MORE MOIST AND UNSTABLE BOUNDARY LAYER AND A WEAKER CAP MAY ALLOW
FOR THE DEVELOPMENT OF STORMS --A FEW OF WHICH COULD BE SEVERE--
ALONG THE WARM FRONT LIFTING NWD THROUGH THE REGION. HOWEVER...THE
POTENTIAL FOR A MORE WIDESPREAD SEVERE WEATHER EPISODE MAY BE
LIMITED BY WESTWARD DISPLACEMENT OF THE STRONGER DEEP LAYER WIND
FIELD AND FORCING FOR ASCENT FROM THE MORE UNSTABLE BOUNDARY LAYER.
AS SUCH...NO AREA WILL BE DELINEATED.

ON DAY 5...CONSIDERABLE DEEPENING OF THE MIDLEVEL TROUGH AND
ATTENDANT SURFACE LOW IS FORECAST AS THE SYNOPTIC SYSTEM ACCELERATES
NEWD INTO THE GREAT LAKES. WHILE THE GFS IS SLIGHTLY MORE
PROGRESSIVE THAN THE ECMWF WITH THE MOVEMENT OF THIS SYSTEM...IT
STILL APPEARS THAT A STRONG WIND FIELD WILL OVERSPREAD A MOIST AND
UNSTABLE WARM SECTOR IN PLACE OVER THE OH VALLEY INTO LOWER GREAT
LAKES. HERE...ENVIRONMENTAL PARAMETERS WILL BE QUITE OPTIMAL FOR
SUPERCELLS AND/OR A LARGE-SCALE LINEAR CONVECTIVE SYSTEM WITH THE
THREAT FOR WIDESPREAD SEVERE WEATHER.

THE NEXT MAJOR TROUGH IS EXPECTED TO BECOME ESTABLISHED OVER THE WRN
U.S. TOWARD THE END OF THE EXTENDED PERIOD WITH AN ASSOCIATED
INCREASE IN SEVERE WEATHER POTENTIAL OVER THE CNTRL AND SRN PLAINS
BY THE EARLY TO MIDDLE PART OF NEXT WEEK.


The GFS is also quite suggestive of an increase in severe risk for the 9th onwards as hinted by the SPC, though the ECM is much more sluggish with moving in the upper low and doesn't really ramp up the severe threat till the 11th.

Whilst the two possible rounds of severe weather will be caused by two seperate features, the first one will probably b short lived so there isn't much point in opening a thread jsut for that, so this is a general discussion on both these set-ups.

That looks like the first real good chance at severe weather for me this year. After a near-miss last night (the cells were lined up right at me and radar estimated 6 to 10 inches of rain between midnight and 7 am - only the first one hit at full strength but still got about 1.5 inches of rain in 30 minutes), I sure hope NEITHER the severe weather NOR the flooding affects anyone with this system.

I just hope the Mississippi and Ohio River valley is spared heavy rain. Moisture return looks a little meager to me.

Models still looking very interesting for the period between the 7-11th, the day 4 SPC still suggestive for the NE of the US:


ZCZC SPCSWOD48 ALL
ACUS48 KWNS 040843
SPC AC 040843

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0343 AM CDT TUE MAY 04 2010

VALID 071200Z - 121200Z

...DISCUSSION...

04/00Z RUNS OF THE ECMWF AND GFS REMAIN IN RELATIVELY GOOD AGREEMENT
IN THE EWD PROGRESSION OF AN INTENSE MIDLEVEL TROUGH AND ASSOCIATED
SURFACE LOW AND COLD FRONT FROM THE UPPER MIDWEST THROUGH THE GREAT
LAKES AND OH VALLEY ON DAY 4 /FRI MAY 7TH/. WHILE BOUNDARY LAYER
MOISTURE MAY REMAIN SOMEWHAT MARGINAL...THE PRESENCE OF STEEP LAPSE
RATES...STRONG VERTICAL SHEAR AND DYNAMIC FORCING FOR ASCENT SHOULD
CONTRIBUTE TO A FAST-MOVING...COLD FRONTAL BAND OF TSTMS CAPABLE OF
PRODUCING A SIZABLE SWATH OF SEVERE WEATHER.

THEREAFTER...MEDIUM-RANGE GUIDANCE CONTINUES TO SUGGEST THE
DEVELOPMENT OF ANOTHER SIGNIFICANT TROUGH OVER THE WRN STATES BY DAY
5 INTO DAY 6 /SAT MAY 8TH INTO SUN MAY 9TH/. AND THE LATEST RUNS OF
THE ECMWF AND GFS ARE IN GOOD AGREEMENT IN THE NEWD EJECTION OF A
STRONG SHORT WAVE TROUGH INTO THE GREAT PLAINS ON DAY 7 /MON MAY
10TH/. HOWEVER...THERE STILL REMAINS CONSIDERABLE RUN-TO-RUN
INTRA-MODEL VARIABILITY WITH RESPECT TO THE EVOLUTION OF THIS
FEATURE. THEREFORE...NO ADDITIONAL SEVERE WEATHER AREAS WILL BE
DELINEATED ATTM.


After that, the models are still keen on injecting another trough into the west of the states, with some really big heat coming up from the south with it, but there is still some timing uncertainties, but the models are still quite suggestive of another severe weather spell on the 9-12th....

It's quite interesting how all the severe weather events seem to occur during weekends since late March this year.

But yes, Tennessee and Mississippi really can't use any more rain at the moment.

Medium range models still seem to be indicating the threat for sustained severe weather over several days next week. We shall see if it pans out.

Dryline may become active on Sunday per LBK and Ama AFD with dewpoints possibly in the 60 of eastern Texas panhandle and rolling plains regions. Wonder if there will be a cap?

Many of the NWS offices across the Southern Plains are looking ahead to next week with great interest. Model data seems to fall in line with this, with the obvious discrepancies on where and when the minor details fall into place.

Looks like next week will be fairly active.

The last couple of weeks sure have made up for a quiet early season, haven't they?

I was on a short run last night at midnight. Single cell t-storm popped up along the leading edge of a cool front and decided to drop some hail on us up here, so what else could I do at midnight but go after it. No major damage, just a lot of leaf shredding but had a nice lightning show for an added attraction.

Haven't looked yet this morning, in fact haven't found the coffee yet...yeah been up that long...but I think SPC had us in the ohio river valley in a slight risk for friday night again...will check that out next. Now whose got the coffee pot?

Actually a slight risk for today now as well:

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1132 AM CDT THU MAY 06 2010

VALID 061630Z - 071200Z

...THERE IS A SLGT RISK OF SVR TSTMS NEB/KS BORDER ACROSS MO RIVER
VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS ERN FL...

...SYNOPSIS...
AS ONE STRONG/PROGRESSIVE UPPER TROUGH DEPARTS NEW ENGLAND COAST
LATER TODAY...THE NEXT DISTURBANCE OF NOTE WILL MOVE FROM THE NRN
ROCKIES INTO THE GREAT PLAINS. MEANWHILE...BROAD SUBTROPICAL RIDGE
AXIS WILL REMAIN IN PLACE FROM BAJA TO THE GOM.

...NEB/KS BORDER ACROSS MO RIVER VALLEY...
DESPITE STRONG DYNAMIC FORCING FOR ASCENT AND LEE CYCLOGENESIS
ALREADY UNDERWAY OVER CO AND THE ADJACENT HIGH PLAINS OF WRN
KS/NEB...MOISTURE REMAINS INADEQUATE TO SUPPORT DEEP CONVECTION.
THIS SITUATION IS EXPECTED TO CHANGE ONLY GRADUALLY THROUGH THE DAY
AS RESIDUAL LOW LEVEL MOISTURE PLUME ASSOCIATED WITH STALLED
DEEP-LAYER FRONTAL ZONE ACROSS OK AND OZARKS IS DRAWN NWD/NWWD
THROUGH ISALLOBARIC FORCING. EVAPOTRANSPIRATION MAY FURTHER AID
MOISTURE FLUX INVOF DEEPENING CYCLONE AND DEVELOPING WARM
FRONT...EXPECTED TO BE SITUATED FROM NWRN KS TO WRN MO BY THIS
EVENING.

EML PLUME/INVERSION EVIDENT IN AMA AND DDC MORNING SOUNDINGS SHOULD
KEEP WARM SECTOR EFFECTIVELY CAPPED AS HEATING AND LOW LEVEL
MOISTENING CONTRIBUTE TO INCREASING SBCAPE OF ABOUT 1000-1500 J/KG
AHEAD OF THE LOW/DRYLINE AND RETREATING WARM FRONT. STRONG CAP AND
LACK OF MORE SIGNIFICANT HEIGHT FALLS ACROSS THE WARM SECTOR SUGGEST
THAT CONVECTIVE INITIATION WILL MOST LIKELY BE DECOUPLED FROM
SURFACE LAYER...OR AT LEAST VERY HIGH-BASED...AND OCCUR IN AREAS OF
STRONGEST FORCED ASCENT NORTH OF THE SURFACE WARM FRONT AND
NEAR/NORTH OF THE LEE CYCLONE.

INITIAL STORM DEVELOPMENT THROUGH THIS EVENING IS FORECAST FROM NERN
CO TO NEB/KS BORDER AREA WITH ANOTHER AREA OF INITIATION POSSIBLE
NORTH OF THE WARM FRONT OVER MO. LAPSE RATES AND SHEAR IN THE
CLOUD-BEARING LAYER WILL BE MORE THAN ADEQUATE FOR PERSISTENT
UPDRAFTS AND HAIL PRODUCTION WITH THIS ACTIVITY. STRONG DOWNDRAFTS
MAY ALSO ACCOMPANY STORMS INITIATING IN HIGHER TERRAIN AND ATOP
DEEPLY MIXED BOUNDARY LAYER AIRMASS.

LARGE SCALE ASCENT ACCOMPANYING THE UPPER TROUGH...AND INTENSIFYING
LLJ /MOISTURE AND MASS FLUX/ THROUGH LATE EVENING SHOULD PROMOTE
UPSCALE DEVELOPMENT OF CONVECTION. MCS EVOLUTION APPEARS QUITE
POSSIBLE FROM NRN KS INTO NEB...AND EAST INTO MO THROUGH THE NIGHT.
THIS COMPLEX OF STORMS WILL HAVE ACCESS TO SUFFICIENT
ELEVATED/MLCAPE UP TO 2000 J/KG TO POSE A THREAT FOR LARGE HAIL. IT
IS ALSO POSSIBLE THAT MESOSCALE LIFT ALONG CONSOLIDATED COLD POOL
NEAR THE SURFACE LOW AND WARM FRONT COULD SUPPORT NEAR SURFACE-BASED
STORM DEVELOPMENT WITH AN INCREASING CHANCE FOR DAMAGING
WINDS...PERHAPS EVEN A TORNADO...THROUGH EARLY FRI FROM NERN KS INTO
WRN MO.

...FL...
WEAK WNWLY FLOW ALOFT AND RELATIVELY COLD MID-LEVEL TEMPS WILL AID
STORM DEVELOPMENT AND CELL MERGERS ALONG EAST COAST SEA-BREEZE
THROUGH LATER THIS AFTERNOON. GENERALLY WEAK INHIBITION AND STRONG
INSTABILITY SHOULD CONTRIBUTE TO PULSE/WEAKLY ORGANIZED MULTICELL
STORMS WITH SOME CHANCE FOR HAIL AND LOCALLY DAMAGING WINDS.

...NRN NEW ENGLAND...
STRONGEST FORCING FOR ASCENT WILL ACCOMPANY THE SHORT WAVE NOW
MOVING ACROSS NY/VT. A FEW LOW-TOPPED TSTMS MAY PRODUCE SMALL HAIL
AND GUSTY WINDS THIS AREA...EWD TO MAINE...THROUGH THE AFTERNOON.
HOWEVER...LIMITED INSTABILITY SHOULD PRECLUDE MORE SUBSTANTIAL
SEVERE WEATHER THIS AREA.

FARTHER SOUTH...LACK OF GREATER FORCING...AND POST-FRONTAL
REGIME...WOULD SUGGEST TSTM/SEVERE POTENTIAL EVEN MORE LIMITED THAN
FARTHER NORTH SO SLGT RISK PROBABILITIES HAVE BEEN REMOVED FROM SRN
NEW ENGLAND.

As for the longer term outlook, it seems very interesting indeed...Monday looks like it'll probably be at least a moderate risk event, to be talking about significant tornadoes at day-5 is very agressive!:


USA.gov is the U.S. Government's official Web portal to all Federal, state and local government Web resources and services.

< Day 3 Outlook
Day 4-8 Convective Outlook Issued on May 6, 2010
Updated: Thu May 6 08:23:10 UTC 2010
Day 4-8 Convective Outlook Graphics Issued on May 6, 2010
D4 Sun, May 09, 2010 - Mon, May 10, 2010 D7 Wed, May 12, 2010 - Thu, May 13, 2010
D5 Mon, May 10, 2010 - Tue, May 11, 2010 D8 Thu, May 13, 2010 - Fri, May 14, 2010
D6 Tue, May 11, 2010 - Wed, May 12, 2010 (All days are valid from 12 UTC - 12 UTC)

Note: A severe weather area depicted in the Day 4-8 period indicates a 30% or higher probability for severe thunderstorms within 25 miles of any point.

PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears highly unlikely during the entire period (e.g. less than a 30% probability for a regional severe storm area across the CONUS through the entire Day 4-8 period).

Forecast Discussion

ZCZC SPCSWOD48 ALL
ACUS48 KWNS 060822
SPC AC 060822

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0322 AM CDT THU MAY 06 2010

VALID 091200Z - 141200Z

...DISCUSSION...

06/00Z ECMWF...GFS AND MEDIUM-RANGE ENSEMBLE GUIDANCE ARE IN
GENERALLY GOOD AGREEMENT IN THE EVOLUTION OF THE LARGE-SCALE PATTERN
THROUGH THE EXTENDED FORECAST PERIOD. ON DAY 4 /SUN MAY 9TH/...THE
NWD RETURN OF A MOIST BOUNDARY LAYER BENEATH THE ERN EDGE OF AN EML
DEVELOPING OVER THE WRN STATES WILL CONTRIBUTE TO A MODERATELY
UNSTABLE AIR MASS OVER WRN TX. THERE IS SOME INDICATION THAT A
WEAK...LOW AMPLITUDE PERTURBATION MAY PROGRESS EWD INTO THE SRN HIGH
PLAINS BY LATE DAY...POSSIBLY SUPPORTING ISOLATED STORM FORMATION
ALONG THE DRY LINE...OR PERHAPS A RETREATING WARM FRONT. VERTICAL
SHEAR WILL BE SUFFICIENT FOR ORGANIZED STORMS INCLUDING SUPERCELLS
WITH THE THREATS FOR HAIL AND PERHAPS TORNADOES. DUE TO
UNCERTAINTIES IN STORM INITIATION AND POTENTIAL COVERAGE...NO SEVERE
WEATHER AREA WILL BE INCLUDED IN THIS FORECAST.

ON DAY 5 /MON MAY 10TH/...MODEL GUIDANCE REMAINS CONSISTENT IN THE
NEWD PROGRESSION OF AN INTENSE...NEGATIVELY-TILTED MIDLEVEL TROUGH
INTO THE CNTRL PLAINS. AN ASSOCIATED...RAPIDLY DEEPENING SURFACE
LOW OVER THE CNTRL HIGH PLAINS WILL DRAW A MOIST AIR MASS
NWD...SETTING THE STAGE FOR A POTENTIAL OUTBREAK OF SUPERCELLS
CAPABLE OF VERY LARGE HAIL AND SIGNIFICANT TORNADOES.

ON DAY 6 /TUE MAY 11TH/...THE SYNOPTIC SYSTEM IS FORECAST TO
DE-AMPLIFY/FILL AS IS PROGRESSES NEWD INTO THE UPPER GREAT LAKES.
SEVERE STORMS WILL REMAIN POSSIBLE ALONG THE COLD FRONT FROM THE
UPPER MIDWEST INTO OZARK PLATEAU. HOWEVER...GIVEN THE EXPECTED POOR
LAPSE RATES...WEAKENING SYSTEM AND POTENTIAL FOR ONGOING/WIDESPREAD
STORMS...THE POTENTIAL FOR A MORE WIDESPREAD SEVERE WEATHER EVENT
REMAINS IN QUESTION.

ON DAY 7 /WED MAY 12TH/...THE ECMWF AND GFS ARE IN RELATIVELY GOOD
AGREEMENT IN THE SLOW EWD PROGRESSION OF A LARGE-SCALE TROUGH OVER
THE WRN STATES. HOWEVER...DIFFERENCES DO EXIST IN THE LOCATION OF
NE-SW ORIENTED BAROCLINIC ZONE WHICH WILL STRETCH FROM WEAKENING LOW
PRESSURE OVER THE GREAT LAKES REGION INTO THE SRN PLAINS. THIS
FRONTAL LOCATION BECOMES EVEN MORE PROBLEMATIC WHEN FACTORING IN THE
POSSIBILITY THAT EPISODIC TSTM ACTIVITY FOR THE PREVIOUS TWO DAYS
COULD POTENTIALLY DISPLACE THE EFFECTIVE FRONT EVEN FARTHER S.
WHILE THE ENVIRONMENT ALONG AND TO THE S OF THIS BOUNDARY WILL BE
SUPPORTIVE OF SEVERE STORMS...UNCERTAINTY IN ITS LOCATION PRECLUDES
THE ISSUANCE OF AN ADDITIONAL SEVERE WEATHER AREA

Vortex II folks must be drooling all over that day 5 area

I know...looks like this year, Vortex II will be getting at least one good severe weather outbreak!

Not that I enjoy seeing tornadoes destroy property, but I hope that VORTEX 2 catches a couple strong tornadoes over farmland. The appreciable part of a VORTEX survey is that they could measure the winds even if the tornado does not produce damage and therefore provide accurate ratings for country twisters, which are otherwise rated as EF0 by default.

I don't intend to be an alarmist, but Greg Forbes is, as he was mentioning similarities in dynamics between tomorrow and the infamous May 31, 1985 tornado outbreak a minute ago on TWC. It would take many elements combining to produce another event of that magnitude, of course, but I also think there could be perhaps a small tornado event tomorrow in similar areas as effected by that outbreak, hopefully nothing of that severity.

Looks like a big rain/snow event as well in the upper Midwest...could be power problems this weekend with the heavy wet snow THEN major flooding?

Looks like the day 4 is showing significant outbreak possible in KS/OK pushing into Western MO where I am.

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0748 AM CDT FRI MAY 07 2010

VALID 071300Z - 081200Z

...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTERNOON/EVENING FOR
NE INDIANA AND NRN OH...

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO EARLY
TONIGHT FROM THE LOWER GREAT LAKES/OH VALLEY TO THE LOWER MS
VALLEY...

...SYNOPSIS...
A MIDLEVEL TROUGH OVER THE NRN PLAINS THIS MORNING WILL PROGRESS EWD
TO THE GREAT LAKES AND INTENSIFY THROUGH TONIGHT. THE MIDLEVEL
TROUGH WILL BE PRECEDED BY A DEEPENING SURFACE CYCLONE WHICH WILL
MOVE ENEWD ALONG A BAROCLINIC ZONE FROM NE MO THIS MORNING TO THE
LOWER GREAT LAKES OVERNIGHT. THE MOIST WARM SECTOR WILL SPREAD NEWD
IN ADVANCE OF THE SURFACE LOW...REACHING NRN INDIANA/OH THIS
AFTERNOON. TRAILING THE SURFACE LOW...A COLD FRONT WILL MOVE EWD
ACROSS THE OH VALLEY AND SEWD ACROSS THE MS VALLEY. THE PRIMARY
FOCUS FOR SEVERE STORM DEVELOPMENT TODAY INTO EARLY TONIGHT WILL BE
THE SURFACE LOW AND COLD FRONT ACROSS THE OH VALLEY.

...OH VALLEY AREA LATER THIS AFTERNOON INTO EARLY TONIGHT...
A SWATH OF BOUNDARY LAYER DEWPOINTS IN THE LOW 60S IS SPREADING
NWD/NEWD FROM THE LOWER MS VALLEY TO THE OH VALLEY...BENEATH A
REMNANT ELEVATED MIXED LAYER FROM THE SRN PLAINS. CONTINUED MOISTURE
ADVECTION THROUGH THE DAY AND STRONG SURFACE HEATING S OF THE WARM
FRONT WILL CONTRIBUTE TO THE DEVELOPMENT OF MODERATE INSTABILITY
/MLCAPE OF 1000-1500 J PER KG/ IN THE WARM SECTOR TODAY ACROSS THE
OH VALLEY. CONVECTIVE INHIBITION ASSOCIATED WITH THE REMNANT EML
WILL LIKELY DELAY CONVECTIVE INITIATION UNTIL MID-LATE AFTERNOON
NEAR THE SURFACE LOW...WHILE LATER STORM DEVELOPMENT IS EXPECTED IN
THE EVENING FARTHER S/SW ALONG THE COLD FRONT.

MEANWHILE...VERTICAL SHEAR WILL BE STRONG WITHIN THE NRN PORTION OF
THE WARM SECTOR IN CONJUNCTION WITH A 40-50 KT SSWLY LLJ...AND 60-70
KT WSWLY MIDLEVEL FLOW WITH THE APPROACHING TROUGH. THE NET RESULT
WILL BE AN ENVIRONMENT SUPPORTIVE OF BOTH SUPERCELLS AND SHORT
BOWING SEGMENTS. DAMAGING WINDS WILL BE THE MAIN SEVERE
THREAT...THOUGH A FEW TORNADOES AND LARGE HAIL CAN ALSO BE EXPECTED
GIVEN EFFECTIVE SRH OF 200-300 M2/S2 AND THE LIKELIHOOD OF A FEW
DISCRETE STORMS LATE THIS AFTERNOON/EVENING. OVERNIGHT...THE SEVERE
THREAT SHOULD DIMINISH AS THE BOUNDARY LAYER STABILIZES.
HOWEVER...SOME POTENTIAL FOR DAMAGING WINDS WILL PERSIST ACROSS PA
AND WRN NY NEAR AND IMMEDIATELY SE OF THE SURFACE LOW TRACK...IN
PROXIMITY TO THE STRONGER MEAN FLOW AND HEIGHT FALLS.

...TN/LOWER MS VALLEYS LATE THIS AFTERNOON/EVENING...
SCATTERED THUNDERSTORM DEVELOPMENT IS EXPECTED BY ABOUT 00Z ALONG
THE SEWD-MOVING COLD FRONT...WHERE LOW-LEVEL ASCENT AND DAYTIME
HEATING/MIXING WILL HAVE WEAKENED CONVECTIVE INHIBITION. BOUNDARY
LAYER DEWPOINTS INCREASING INTO THE MID-UPPER 60S AND AFTERNOON
TEMPERATURES OF 85-90 F WILL RESULT IN MLCAPE VALUES OF 2000-3000
J/KG IN A NARROW CORRIDOR E OF THE COLD FRONT. DEEP-LAYER VERTICAL
SHEAR WILL BE AT LEAST MARGINALLY FAVORABLE FOR SUPERCELLS AND
PERSISTENT STORM CLUSTERS FOR A FEW HOURS THIS EVENING...BEFORE
INSTABILITY WEAKENS. ISOLATED DAMAGING WINDS AND LARGE HAIL WILL BE
THE MAIN SEVERE STORM THREATS.

...INTERIOR CENTRAL/S FL THIS AFTERNOON...
LOCAL SEA BREEZE CIRCULATIONS WILL SUPPORT ISOLATED THUNDERSTORM
DEVELOPMENT THIS AFTERNOON...PRIMARILY ACROSS THE INTERIOR
CENTRAL/SRN PENINSULA WITH BOUNDARY COLLISIONS. STORM COVERAGE WILL
BE LIMITED BY THE DRYING ALOFT NOTED IN SATELLITE PW FIELDS AND 12Z
SOUNDINGS COMPARED TO YESTERDAY. STILL...SOMEWHAT ORGANIZED STORMS
WILL BE POSSIBLE IN THE WEAK NWLY FLOW ALOFT IN AN ENVIRONMENT OF
MODERATE INSTABILITY. THE STRONGEST STORMS MAY PRODUCE STRONG
DOWNBURST WINDS AND SOME HAIL.

000
FXUS63 KIND 071040
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
640 AM EDT FRI MAY 7 2010

.SHORT TERM.../TODAY THROUGH SUNDAY/.
THE MAIN FOCUS OF SHORT TERM CONTINUES TO BE THE SEVERE THREAT FOR
LATER TODAY. SPC HAS NOW PUT THE NORTHEAST QUADRANT OF WARNING
AREA UNDER A MODERATE RISK...AND WOULDN/T BE SURPRISED IF THIS
GETS EXTENDED INTO OTHER PORTIONS OF WARNING AREA AS DAY WEARS ON.

CURRENT RADAR MOSAIC IS SHOWING SHOWERS AND THUNDERSTORMS ACROSS
IOWA AND NORTHERN ILLINOIS...WITH A FEW POPPING UP OVER NORTHWEST
COUNTIES OF OUR WARNING AREA. IT APPEARS THAT MOST OF THE ACTIVITY
WILL STAY NORTH OF CENTRAL INDIANA THIS MORNING. SO FAR...STORMS
HAVE STAYED BELOW SEVERE LEVEL.

UPPER TROUGH PROGGED TO MOVE INTO WARNING AREA LATER TODAY STILL
LOOKS IMPRESSIVE. UPPER LEVEL JET STILL HOLDING AT 130 PLUS KTS.
LOW LEVEL JET IS AROUND 40-50 KTS. IN ADDITION...THE INSTABILITY
LOOKS IMPRESSIVE WITH INDIANA IN WARM SECTOR OF SYSTEM. A LARGE
PLUME OF GULF MOISTURE COMBINED WITH HIGHS IN THE MID 80S WILL
FALL INTO PLACE. LATEST MODELS ARE SHOWING SB CAPE AROUND 2000
J/KG UNTIL SAT 00Z. EARLIER RUNS HAD THE CAPE DECREASING BY THIS
TIME...BUT MODELS ARE NOW LEANING TOWARD AN UNSTABLE ENVIRONMENT
INTO THE EVENING HOURS. THIS COULD HAVE A HUGE IMPACT ON THE
SEVERITY OF EVENT BECAUSE THE BEST FORCING ISN/T UNTIL THE SAT
00-06Z TIME FRAME. THE ONLY CAVEAT IS A SURFACE COLD FRONT THAT
MAY TAP INTO THIS MOISTURE/WARM TEMPS BEFORE THE UPPER LOW GETS TO
CENTRAL INDIANA. FORECAST SOUNDINGS ARE STILL LEANING TOWARD MORE
OF A STRAIGHT LINE EVENT AS DIRECTIONAL SHEAR DECREASES BY MID
AFTERNOON. AGAIN...IT WILL ALL COME DOWN TO TIMING FOR ANY
POSSIBLE TORNADOES...BUT SUPERCELLS ARE LIKELY.

EVENT WILL END RATHER QUICKLY AS SYSTEM PUSHES OUT OF FORECAST
AREA BY SAT 06Z. DID ADD POPS TO GRIDS THROUGH SAT 00Z DUE TO AMPLE
ISENTROPIC LIFT THROUGH THE EVENING HOURS. MOISTURE WILL THEN CUT
OFF BY SAT 06Z.

Web briefing from NWS KIND:

http://www.crh.noaa.gov/ind/?n=webbriefing

And from my SW - Louisville KY NWS:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
705 AM EDT FRI MAY 7 2010

...UPDATED AVIATION DISCUSSION...

.SHORT TERM (TODAY AND TONIGHT)...

...WIND ADVISORY THIS AFTERNOON FOLLOWED BY SEVERE WEATHER POTENTIAL
THIS EVENING...

LOW PRESSURE IS NOW CENTERED OVER NRN OKLAHOMA...WITH ITS WARM FRONT
EXTENDING EASTWARD THROUGH OUR CWA. THE DEWPOINT SPREAD ACROSS THE
CWA MAKES THE WARM FRONT OBVIOUS...WITH CLOSE TO 60 DEGREE DEWPTS
NEAR TN BORDER DOWN TO THE LOW 40S OVER THE NERN CWA. TEMPS AND
DEWPTS WILL BE STEADY OR RISE TOWARD DAWN AS THE WARM FRONT MOVES
NORTHWARD. CLOUDS MAY SPILL SE FROM CENTRAL IL...AND WINDS SHOULD
START TO INCREASE JUST AFTER DAWN AND VEER AROUND TO THE SOUTH.

THE LOW WILL MOVE TO LAKE MICHIGAN TODAY AND BRIEFLY WEAKEN...TAKING
ITS WARM FRONT INTO NRN IN. WE WILL BE WELL EMBEDDED IN THE WARM
SECTOR WITH WARM SWRLY FLOW IN PLACE. BUFKIT SOUNDINGS MAINLY ACROSS
OUR NRN CWA INDICATE 35 KTS OF WIND GUST POTENTIAL WITH EVEN HIGHER
WINDS AT TOP OF WELL-MIXED LAYER EXPECTED LATE THIS AFTERNOON.
BECAUSE OF THE STEEP ML AND STRONG WINDS ALOFT...WILL GO WITH A WIND
ADVISORY FROM 18Z-00Z THIS AFTERNOON AND EARLY EVENING FOR ENTIRE
CWA. IT SHOULD BE NOTED THAT THE HIGHEST WIND GUSTS ARE EXPECTED
OVER SOUTH-CENTRAL IN AND N-CNTRL KY...WITH GUSTS OVER 40 MPH
POSSIBLE. DRIVING WILL BE DIFFICULT AT TIMES THIS AFTERNOON
ESPECIALLY ON WEST-TO-EAST ROADWAYS FOR HIGH-PROFILE VEHICLES.

LATE THIS AFTERNOON...A 500MB LOW NOW OVER THE NRN CONUS WILL MOVE
ESE AND HELP DEEPEN/INTENSIFY THE SFC LOW. AS THE LOW QUICKLY
STRENGTHENS...THE 850MB WINDS ARE PROGGED TO INCREASE QUICKLY JUST
AHEAD OF COLD FRONT...WHICH WILL INCREASE THE SHEAR. THE LOW`S COLD
FRONT WILL DRAG ACROSS THE CWA MAINLY FROM 23Z OVER THE FAR WNW TO
ROUGHLY 07Z OVER THE FAR ERN CWA. WITH TEMPS WELL INTO THE MID AND
UPPER 80S TODAY...DEWPTS IN THE UPPER 50S/LOW 60S...STEEP LAPSE
RATES WILL BE THE RULE ALOFT BUT WE WILL BE CAPPED MOST OF THE DAY
BETWEEN 800-600MB. ASSUMING THE CAP WILL BREAK...CONVECTION SHOULD
ERUPT ALONG THE COLD FRONT OVER IN/OH AND CONTINUE SW TO OUR CWA
THIS EVENING. 0-6KM BULK SHEAR AT 00Z JUST AHEAD OF PRECIP WILL BE
ABOUT 50 KTS FROM SW AT SFC TO WSW AT 500MB. BEST DIRECTIONAL SHEAR
IS WELL N NEAR THE LOW...BUT STRONG SPEED SHEAR AND SLIGHT TURNING
OF WINDS WILL SUPPORT SEVERE STORMS THIS FAR SOUTH. THINK SUPERCELLS
WILL FIRST FORM AND THEN COAGULATE INTO A SQUALL LINE OVER OUR ERN
CWA. SO INITIALLY OUR THREATS WILL BE HAIL...WIND AND POSSIBLY A
TORNADO OR TWO (MAINLY OVER OUR IN COUNTIES)...AND THEN THE MAIN
THREAT WILL EVENTUALLY BECOME STRAIGHT-LINE WINDS MOSTLY.

THE BEST CHANCE FOR SEVERE WEATHER WILL BE ACROSS OUR SOUTH-CENTRAL
INDIANA COUNTIES AND OUR FAR NRN KY COUNTIES AFTER 5PM UNTIL
MIDNIGHT...MAYBE 2AM. THINK BETWEEN 6-10PM OVER S-CNTRL IN WILL BE
THE PRIME TIME/LOCATION FOR SEVERE WEATHER. AGAIN ITS WORTH
MENTIONING THAT WE WILL BE CAPPED MOST OF THE DAY...SO THINK
CONVECTION WILL BE LATE TO FORM...BUT WILL EXPLODE WHEN IT DOES.

TONIGHT...SEVERE THREAT WILL WEAKEN AFTER MIDNIGHT AS COLD FRONT
PLOWS EASTWARD. WINDS WILL SHIFT AROUND TO THE WEST-NORTHWEST AND
WILL CONTINUE TO BE GUSTY. A FEW SHOWERS COULD LINGER BEHIND THE
MAIN LINE BUT THINK CONVECTION WILL BE EAST OF OUR CWA BY 08Z AT THE
LATEST AND IF NOT A FEW HOURS EARLIER. TEMPS WILL DROP SIGNIFICANTLY
BEHIND THE FRONT WITH UPPER 40S USHERING IN ACROSS THE NWRN CWA BY
DAWN SATURDAY.