June 1-7 Severe Threat

[Stebo]

And the NAM starts to cave (Re: SLP track) for Wednesday...

NAM suffering from some convective feedback at 700mb tomorrow, so take what it shows after tomorrow with a grain of salt.

[Hoosier]

Anyone have any thoughts on where the greatest tornado threat may lay out on Wednesday?  What I mean is will areas in immediate proximity to the sfc low/frontal boundary be a bit more favored vs. farther south or is the entire zone pretty much under a similar threat level?  I've kinda been thinking the latter but would like to get some opinions.    

[andyhb]

I-70 corridor might be an early guess, but with the model differences, it probably won't stay that way by any means.

 

Also, judging by the wind fields throughout the warm sector, it doesn't look to be a solely warm front modulated threat.

[The_Doctor]

Any bets on what the top wind gust will be with the MCS tomorrow evening?

[Central Illinois]

Any bets on what the top wind gust will be with the MCS tomorrow evening?

I wouldn't be surprised if we saw close to a 85-90 mph gust with the MCS

Sent from my SM-G900V

[Thundersnow12]

3z RAP/HRRR are blowing the warm front well north to the SD border now.

Interesting solutions and would have implications on the track of the eventual MCS

[Hoosier]

Day 2 outlook just came out and mentions a possible upgrade to moderate risk once uncertainties are resolved.

[andyhb]

Day 2 outlook just came out and mentions a possible upgrade to moderate risk once uncertainties are resolved.

 

Large 30% hatched region, all severe hazards highlighted.

[Hoosier]

Large 30% hatched region, all severe hazards highlighted.

 

 

Looks like they are still hedging toward the southern placement to the point where my area is on the northern fringe of the slight risk.

[snowlover2]

New Day 1

 

 

 

 

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0104 AM CDT TUE JUN 03 2014

VALID 031200Z - 041200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS MUCH OF NEBRASKA AND INTO
SOUTHERN IOWA AND ADJACENT NORTHERN MISSOURI...

...THERE IS A SLGT RISK OF SVR TSTMS EXTENDING FROM THE NRN HIGH
PLAINS SEWD ACROSS THE CENTRAL PLAINS/MID MO VALLEY TO THE MID
MS/LOWER OH VALLEYS...

...SUMMARY...
AN OUTBREAK OF SEVERE STORMS IS FORECAST TUESDAY FROM THE NORTHERN
HIGH PLAINS REGION EAST-SOUTHEASTWARD ACROSS NEBRASKA...NORTHERN
KANSAS...IOWA...NORTHERN MISSOURI AND INTO ILLINOIS. LARGE HAIL AND
WIDESPREAD DAMAGING WINDS ARE LIKELY. IN ADDITION -- TORNADOES...A
FEW STRONG...WILL ALSO BE POSSIBLE.

...SYNOPSIS...
A STRONG SHORT-WAVE TROUGH FORECAST TO CREST THE S CENTRAL U.S.
RIDGE AND SHIFT INTO THE NRN AND CENTRAL PLAINS IS FORECAST TO BE
THE MAIN FEATURE ALOFT WITH RESPECT THE SEVERE CONVECTIVE FORECAST
THIS PERIOD. THIS FEATURE WILL DRIVE CENTRAL HIGH PLAINS SURFACE
CYCLOGENESIS DURING THE AFTERNOON...WITH THE LOW THEN SHIFTING EWD
TO THE MID MO VALLEY BY THE END OF THE PERIOD. A WARM FRONT
EXTENDING ESEWD FROM THIS LOW IS EXPECTED TO FOCUS WIDESPREAD
STRONG/SEVERE STORMS THROUGH THE PERIOD.

...NRN HIGH PLAINS ESEWD ACROSS THE MID MO/MID MS VALLEYS...
A SUBSTANTIAL/WIDESRPEAD SEVERE WEATHER EVENT IS FORECAST THIS
PERIOD...WITH INITIAL STORMS EXPECTED EARLY ACROSS THE SWRN SD
VICINITY WITHIN A ZONE OF STRONG QG FORCING AHEAD OF THE APPROACHING
UPPER SYSTEM. HAIL AND PERHAPS A STRONG GUST OR TWO WILL BE
POSSIBLE WITH THIS CONVECTION THROUGH EARLY AFTERNOON.

HEATING/DESTABILIZATION OF THE AIRMASS NEAR AND S OF THE SURFACE
WARM FRONT ACROSS NEB WILL CONTINUE THROUGH THE AFTERNOON...WITH
MIXED-LAYER CAPE OF 1500 TO 3000 J/KG EXPECTED TO EVOLVE.
CONVECTIVE DEVELOPMENT IS EXPECTED DURING THE MID TO LATE AFTERNOON
-- INCLUDING MORE ISOLATED/HIGH-BASED STORMS ACROSS THE HIGH PLAINS
FROM ERN MT TO WRN KS...AND MORE SUBSTANTIAL/WIDESPREAD STORMS
ACROSS SRN SD AND NEB INVOF THE SURFACE WARM FRONT. IN ADDITION TO
THE FAVORABLE THERMODYNAMIC ENVIRONMENT INVOF THE SURFACE
BOUNDARY...VERY STRONG SHEAR IS FORECAST ACROSS THIS ZONE -- WHERE
LOW-LEVEL SLY/SELY WINDS WILL INCREASE RAPIDLY WITH HEIGHT AND VEER
TO WLY THROUGH MID LEVELS WHERE 50-60 KT FLOW IS EXPECTED.

WHILE THIS KINEMATIC ENVIRONMENT WILL BE STRONGLY SUPPORTIVE OF
ROTATING STORMS -- AND THUS INITIAL STORM DEVELOPMENT ACROSS THE NEB
VICINITY IS LIKELY TO RAPIDLY BECOME SUPERCELLULAR...A WIDE ARRAY OF
MODEL DATA FROM VARIOUS RUNS REMAINS STRONGLY SUGGESTIVE OF RAPID
UPSCALE GROWTH INTO ONE OR MORE FAST-MOVING/BOWING-TYPE MCS/S.
THUS...WHILE THE RISK FOR TORNADOES WILL EXIST -- INCLUDING A FEW
STRONG TORNADOES...WIDESPREAD DAMAGING WINDS WILL LIKELY BECOME THE
PRIMARY SEVERE RISK THROUGH THE AFTERNOON AND INTO THE EVENING AS
STORMS CROSS NEB AND SHIFT INTO IA/NRN MO. VERY LARGE HAIL WILL
ALSO BE LIKELY ACROSS THIS REGION INTO THE EVENING.
OVERNIGHT...DAMAGING WIND RISK WILL CONTINUE AS STORMS MOVE RAPIDLY
EWD...POSSIBLY CROSSING THE MS VALLEY AND SHIFTING INTO CENTRAL IL
OVERNIGHT.

..GOSS/MOSIER.. 06/03/2014

[snowlover2]

New day 2

 

 

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT TUE JUN 03 2014

VALID 041200Z - 051200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER A LARGE PART OF THE OH
VALLEY INTO THE TN VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE HIGH
PLAINS...

...SUMMARY...
STRONG TO SEVERE STORMS ARE EXPECTED TO DEVELOP PRIMARILY THROUGH
THE OHIO VALLEY REGION WEDNESDAY WITH A THREAT FOR MAINLY DAMAGING
WIND AND LARGE HAIL. OTHER MORE ISOLATED STRONG TO SEVERE STORMS
WILL BE POSSIBLE FROM SOUTHERN KANSAS INTO NORTHERN OKLAHOMA AND THE
NORTHERN...CENTRAL...AND SOUTHERN HIGH PLAINS.

...SYNOPSIS...

PROGRESSIVE UPPER PATTERN WILL PERSIST OVER THE NRN HALF OF THE
COUNTRY WEDNESDAY. A FAST MOVING LOW AMPLITUDE SHORTWAVE TROUGH WILL
CONTINUE THROUGH THE OH VALLEY...DEAMPLIFYING AS IT BECOMES ABSORBED
IN A BROADER SCALE UPPER TROUGH CENTERED OVER SERN CANADA. COLD
FRONT THAT WILL MOVE SOUTH THROUGH THE OH VALLEY TUESDAY NIGHT OWING
TO CIRCULATION AROUND LOW PRESSURE IN SERN CANADA SHOULD LIFT BACK
NWD AS A WARM FRONT WEDNESDAY WITH THE APPROACH OF THE LOW AMPLITUDE
IMPULSE AND ITS ATTENDANT LLJ. THE SWRN EXTENSION OF THIS FRONT WILL
ACCELERATE SWD THROUGH THE MID MS VALLEY AND CNTRL PLAINS WITH
PASSAGE OF THE SHORTWAVE TROUGH BEFORE LIKELY BECOMING STATIONARY
FROM THE TX PANHANDLE INTO ARKANSAS WEDNESDAY NIGHT.


...OH VALLEY THROUGH CNTRL APPALACHIAN REGION...

RICH GULF MOISTURE WILL RESIDE IN THE OH VALLEY WARM SECTOR SOUTH OF
THE WARM FRONT SUPPORTING MODERATE INSTABILITY AS THE SFC LAYER
WARMS. AN MCS WILL LIKELY BE IN PROGRESS NORTH OF THIS BOUNDARY OVER
THE MID-UPPER MS VALLEY REGION. SOME UNCERTAINTY EXITS REGARDING
WHERE THE EFFECTIVE BOUNDARY WILL BE AND HOW FAR NORTH IT WILL
ADVANCE. ASCENT ACCOMPANYING THE PROGRESSIVE SHORTWAVE TROUGH AND
ATTENDANT LLJ WILL SUPPORT REDEVELOPMENT AND INTENSIFICATION OF
STORMS AS WARM SECTOR DESTABILIZES...POSSIBLY ALONG SRN FRINGE OF
THE MCS AS WELL AS ADDITIONAL DEVELOPMENT ALONG AND AHEAD OF THE
FRONT. STRONG VERTICAL SHEAR AND LARGE 0-2 KM HODOGRAPHS WILL
SUPPORT SUPERCELLS AND BOWING SEGMENTS. ALL SEVERE TYPES WILL BE
POSSIBLE INCLUDING DAMAGING WIND...LARGE HAIL AND TORNADOES.
UNCERTAINTY REGARDING PLACEMENT OF BOUNDARY AND IMPACT OF MORNING
CONVECTION AND OUTFLOW BOUNDARIES PRECLUDES A MODERATE RISK UPGRADE
AT THIS TIME. HOWEVER...A PORTION OF THE OH VALLEY MAY NEED TO BE
INCLUDED IN A MODERATE RISK IN LATER OUTLOOKS.

..DIAL.. 06/03/2014

 

 

[cyclone77]

SPC pretty much removed all of northern IL of the severe risk between the two days.  QC went from 45% hatched to a vanilla slight, Chicago sub-severe.  Global models look to have smashed the NAM to **** once again.

[Hoosier]

SPC pretty much removed all of northern IL of the severe risk between the two days.  QC went from 45% hatched to a vanilla slight, Chicago sub-severe.  Global models look to have smashed the NAM to **** once again.

 

 

Interestingly the 00z RGEM is still farther north and would offer better severe potential around there.  Almost feels like winter with the NAM/RGEM in one camp. 

[snowlover2]

SPC pretty much removed all of northern IL of the severe risk between the two days.  QC went from 45% hatched to a vanilla slight, Chicago sub-severe.  Global models look to have smashed the NAM to **** once again.

If i understand the text right, they don't discount possibly shifting the risk area north some.

[snowlover2]

ILN AFD not totally ruling out the NAM and talking MCS and supercells.

 

 

 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
413 AM EDT TUE JUN 3 2014

.SYNOPSIS...
A WEAK SURFACE BOUNDARY WILL PASS SOUTH OF OHIO AND LAY OUT OVER
KENTUCKY THIS EVENING. THIS BOUNDARY WILL BE A FOCUS FOR SHOWERS
AND THUNDERSTORMS INTO TONIGHT...BUT THEN SHIFT NORTHWARD AS A
WARM FRONT EARLY ON WEDNESDAY. A STRONG SURFACE LOW WILL THEN
TRACK EAST ALONG THE WARM FRONT LATER WEDNESDAY...WITH STRONG
THUNDERSTORMS POSSIBLE AS IT PASSES.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
CONVERGENT BOUNDARY IS IN EASTERN CWA AND MOVING AWAY THIS
MORNING. UPSTREAM...A SECOND W-E ORIENTED CONVERGENT BOUNDARY WILL
BE THE KICKER FOR ANY SHOWERS OR THUNDERSTORMS THAT BECOME ACTIVE
TODAY OUTSIDE OF THE MORNING BOUNDARY THAT IS MOVING EAST AND
SOUTH OUT OF OUR CWA INTO WV AND KY. THE EARLIER RUNS OF THE SHORTER
RANGE MODELS THAT ALLOW CONVECTIVE PROCESSES WERE A LITTLE MORE
PERMISSIVE OF THIS SECONDARY BOUNDARY BECOMING ACTIVE THIS
MORNING. LATEST RUNS ARE NOT SO FAVORABLE BUT ONLY LOW CHANCE POPS
WERE INCLUDED TODAY AND THE FEW STORMS CURRENTLY FIRING OVER NW OH
AND NRN IND TELL ME TO KEEP THIS POTENTIAL FOR CONTINUED
DEVELOPMENT IN THE FORECAST FOR TODAY.

OTHERWISE...HIGH PRESSURE BUILDING IN BEHIND THE CONVERGENT
BOUNDARY WILL INHIBIT STORMS LATER TODAY AS THEY GET SHUNTED E AND
S OF THE AREA. LOWER 80S WILL BE A PRETTY UNIFORM HIGH TODAY UNDER
CLOUDY SKIES THAT EXHIBIT A FAIRLY CONTINUOUS EROSION TOWARDS
PARTLY SUNNY SKIES LATER IN THE DAY.


&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
BOUNDARY IN KY WILL LIFT NORTHWARD THROUGH THE AREA EARLY
WEDNESDAY AFTER CLEARING SKIES TONIGHT LETS MOST OF THE REGION
DROP TO THE UPPER 50S OT LOWER 60S. EXTENDED PERIOD OF CLOUD COVER
IN KY AND FAR SE IN WITH SUBSEQUENT DEVELOPMENT OF THE WARM FRONT
WILL HOLD LOWS IN THESE AREAS TO THE UPPER 60S.

AS THE FRONT LIFTS NORTHWARD...IT IS PROGGED TO STALL OUT SOUTH OF
THE I-70 CORRIDOR. A MID LEVEL SHORTWAVE IN FAIRLY QUICK ZONAL
FLOW AT H5 WILL PRECEDE THE SURFACE LOW AND INITIATE CONVECTION
ALONG A LEADING LINE. SPC IS NOTING THE ABUNDANT MOISTURE IN PLACE
SOUTH OF THE WARM FRONT WITH A MCS MOVING EAST ALONG THE BOUNDARY.
ENOUGH WARM AND UNSTABLE AIR MAY OCCUR WITH DAYTIME HEATING SOUTH
OF THE FRONT TO SPAWN MORE THUNDERSTORM DEVELOPMENT ON THE FRINGES
OF THE EXPECTED MCS...SIMILAR TO POPUP STORMS ON AN OUTFLOW
BOUNDARY ONLY IN A SLIGHTLY LARGER SCALE.

THE ONLY REASON WHY POPS WERE NOT UPGRADED TO CATEGORICAL OVER CWA
WAS THE SLOWER TIMING OF THE NAM. NAM IS LAGGING SIGNIFICANTLY AT
H48 THAN THE CANADIEN...GFS...AND EUROPEAN MODELS. ENOUGH OF A
DISCREPANCY TO HEDGE A POSSIBLE DIFFERENCE IN TIMING TOWARDS.

WITH THE PRESENCE OF THE SURFACE LOW AND ITS ASSOCIATED
SHEAR...STORMS THAT DO DEVELOP ON WEDNESDAY HAVE A HIGHER
POTENTIAL FOR SUPERCELLULAR ACTIVITY AND SEVERE WEATHER.

ONCE STORMS PASS TO THE OHIO RIVER WEDNESDAY EVENING...UNLESS
SLOWER NAM IS CORRECT...NORTH WINDS IN THE WAKE OF THE LOW WILL
PUSH DRIER AND COOLER AIR TO THE REGION SO THAT HIGHS THURSDAY
WILL BE IN THE LOWER 70S AND READINGS ON FRIDAY WILL STILL BE HARD
PRESSED TO REACH 80 IN THE FAR SOUTH. OVERNIGHT LOWS IN THE 50S
WILL ALSO BE QUITE WELCOME.

[A-L-E-K]

SPC pretty much removed all of northern IL of the severe risk between the two days.  QC went from 45% hatched to a vanilla slight, Chicago sub-severe.  Global models look to have smashed the NAM to **** once again.

 

the writing has been on the wall for days now

 

6z NAM jumped way south

[yoda]

From the 1300z SPC OTLK... since it mentioned Illinois

BY THIS EVENING...CONVECTION-ALLOWING MODEL GUIDANCE REMAINS IN GOOD   AGREEMENT IN SUGGESTING THAT STORMS WILL GROW UPSCALE INTO AN MCS   COMPOSED OF HP SUPERCELLS AND BOWING STRUCTURES. GIVEN THE   SYNOPTIC-SCALE SETUP AND THE VOLATILE COMBINATION OF VERTICAL SHEAR   AND INSTABILITY...THE POTENTIAL WILL EXIST FOR A PROGRESSIVE DERECHO   EVENT FROM ERN NEB THROUGH SRN IA...NRN MO INTO W-CNTRL IL THIS   EVENING THROUGH TONIGHT. 

[Chicago WX]

NAM not backing down. 12z run looks a touch farther north than its 0z run even...through 12z Wednesday. Scoring the coup? Mind you I don't really know if its biases/errors are the same in the warm season, as they are in the cold season.

[A-L-E-K]

hi-res NAM essentially barfs convection over IA tonight, like 80% of the state under one massive 45+ dbz cluster

[tornadotony]

hi-res NAM essentially barfs convection over IA tonight, like 80% of the state under one massive 45+ dbz cluster

It overestimates extent of high reflectivity.

[A-L-E-K]

It overestimates extent of high reflectivity.

 

 

i mean, obviously the state isn't going to be covered in a single massive cell

[Central Illinois]

Anyone think a PDS Severe Thunderstorm watch is likely later this evening for the possible Derecho?

Sent from my SM-G900V using Tapatalk

[andyhb]

Anyone think a PDS Severe Thunderstorm watch is likely later this evening for the possible Derecho?

Sent from my SM-G900V

 

Tornado threat will probably exist with the MCS as well, would suspect a tornado watch with very elevated wind probs.

[A-L-E-K]

GFS looks to have taken a respectable jump north with MCS trajectory

[Hoosier]

Not sure what to think here regarding tomorrow.  A plausible scenario is that the morning activity focuses most of the afternoon redevelopment farther south.  Assuming we can recover as progged, parameters would certainly support chances for severe. 

[andyhb]

Not sure what to think here regarding tomorrow.  A plausible scenario is that the morning activity focuses most of the afternoon redevelopment farther south.  Assuming we can recover as progged, parameters would certainly support chances for severe. 

 

Not going to be surprised if there is a D2 mod hoisted in the next outlook, since there does appear to be some agreement over the highest risk corridor finally (possibly the I-70 corridor southward to the Ohio River if I had to guess although there still is potential further north), parameters would certainly support a significant damaging wind event and also a notable tornado threat with strong deep layer shear oriented favorably for at least a few supercells.

[Central Illinois]

Looks like they expanded both the slight risk and moderate risk more south in to MO

Sent from my SM-G900V

[snowlover2]

They mention in the text that a high risk area may be needed in next outlook update.

 

 

 

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 AM CDT TUE JUN 03 2014

VALID 031630Z - 041200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF NORTHERN AND
EASTERN NEBRASKA...WESTERN/SOUTHERN IOWA...NORTHERN MISSOURI AND
WESTERN ILLINOIS...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA
FROM THE NRN HIGH PLAINS TO MID MS VALLEY/MIDWEST...

...SUMMARY...
AN OUTBREAK OF SEVERE STORMS IS FORECAST THIS AFTERNOON THROUGH
TONIGHT FROM PARTS OF NEBRASKA THROUGH IOWA...NORTHERN
MISSOURI...AND INTO ILLINOIS. DESTRUCTIVE WINDS...VERY LARGE
HAIL...AND A COUPLE OF STRONG TORNADOES ARE EXPECTED.

...SYNOPSIS...
FAST-MOVING SHORTWAVE TROUGH AND ASSOCIATED 70KT MID-LEVEL SPEED MAX
CURRENTLY CROSSING THE GREAT BASIN/INTERMOUNTAIN WEST WILL CREST A
STRONG SUB-TROPICAL RIDGE AND PRODUCE MODEST MID-LEVEL HEIGHT FALLS
ACROSS THE CENTRAL PLAINS THROUGH THIS EVENING. IN ADDITION TO
SPURRING LEE-SIDE CYCLOGENESIS ACROSS THE CENTRAL HIGH
PLAINS...LARGE SCALE ASCENT ASSOCIATED WITH THE MID/UPPER
DISTURBANCE WILL BE FOCUSED ALONG AND NORTH OF A WARM FRONT SITUATED
FROM NEB PANHANDLE ESEWD TO NEAR THE IA/MO BORDER.

A BROAD ZONE OF SFC LOW PRESSURE OVER ERN WY/CO WILL CONSOLIDATE
INTO LEE-CYCLONE AND TRACK TO WRN NEB BY THIS EVENING. ADDITIONAL
MESO-LOWS/FRONTAL WAVES MAY FORM AND TRACK EAST ALONG THE WARM
FRONT...AIDED BY LATENT HEATING/DEEP CONVECTION...INTO LATE EVENING.
SOUTH OF THE LOW/WARM FRONT...A DRYLINE/THERMAL TROUGH WILL
STRENGTHEN THROUGH THE AFTERNOON AND EXTEND FROM WRN NEB SSWWD
THROUGH WRN KS TO FAR ERN NM.

IN THE EAST...COLD FRONT ASSOCIATED WITH DEEP LOW PRESSURE NEAR
JAMES BAY WILL CONTINUE EAST FROM ERN GREAT LAKES TO NEW ENGLAND.

...SD/NEB TO IA/MO THROUGH LATE EVENING...
INTENSE STORMS POSING PRIMARILY A THREAT FOR LARGE HAIL ARE ALREADY
UNDERWAY NORTH OF SFC WARM FRONT AND NEAR THE SD/NE BORDER THIS
MORNING /REF WW 206/. THIS CONVECTION WAS LIKELY ROOTED ABOVE THE
850MB LEVEL IN AN ENVIRONMENT CHARACTERIZED BY STEEPENING MID-LEVEL
LAPSE RATES AND STRONG VERTICAL SHEAR. EXPECT THESE ELEVATED STORMS
TO PERSIST GIVEN MASS AND MOISTURE FLUXES NOW UNDERWAY IN RESPONSE
TO LARGE SCALE ASCENT AND DIABATIC PROCESSES.

BY MID-AFTERNOON...ELEVATED STORMS WILL CONTRIBUTE TO... 1) A
REINFORCEMENT OF THE EXISTING LOW LEVEL BAROCLINIC ZONE/WARM
FRONT...AND 2) A DEEPENING COLD POOL ALONG AND NORTH OF THE FRONT.
MODEST TO LOCALLY STRONG WARM SECTOR SFC HEATING WILL CONTRIBUTE TO
WEAKENING INHIBITION AND AN INCREASING POTENTIAL FOR CONVECTION TO
BECOME ROOTED IN A VERY UNSTABLE BOUNDARY LAYER NEAR THE FRONT BY
LATE AFTERNOON. ADDITIONAL STORMS ARE EXPECTED TO INCREASE WITHIN
THE LOW-LEVEL UPSLOPE FLOW REGIME OVER PARTS OF SD/NEB.

A FEW MODELS SUPPORT AT LEAST ISOLATED WARM SECTOR DISCRETE STORMS
BY LATE AFTERNOON/EARLY EVENING ACROSS CNTRL/ERN NEB. ANY DISCRETE
STORMS INITIATING NEAR THE WARM FRONT WILL EXIST IN AN IDEAL
ENVIRONMENT FOR TORNADIC SUPERCELLS WITH EFFECTIVE SRH IN EXCESS OF
200 M2/S2 AND RELATIVELY LOW LFC. AWAY FROM THE FRONT AND NEAR THE
DRYLINE...HEATING AND DEEPER MIXING MAY OFFSET THE TORNADO POTENTIAL
SOMEWHAT AND RESULT IN MORE OUTFLOW-DOMINANT STORMS WITH HIGH WIND
AND VERY LARGE HAIL POTENTIAL.

WHILE ABOVE SCENARIO HAS LOW TO MODEST CONFIDENCE...GREATER
CONFIDENCE EXISTS IN THE CONTINUATION AND GRADUAL UPSCALE GROWTH OF
ONGOING CONVECTION INTO AN COMPLEX OF EVEN MORE INTENSE
STORMS...INCLUDING EMBEDDED SUPERCELLS...MOVING ESEWD TO ERN NEB AND
THEN TO SRN IA/NRN MO THROUGH THE LATE EVENING. THIS CONVECTION WILL
DEVELOP INTO AN AXIS OF STRONG INSTABILITY /SBCAPE TO 3000-4000 J
PER KG/ COINCIDENT WITH INTENSIFICATION OF A WLY 60-70KT MID-LEVEL
JET. BOTH PARALLEL ARW/NMMB HIRES WINDOWS DEPICT THIS SCENARIO QUITE
WELL BUT STILL OFFER DIFFERING OUTCOMES IN TIME/INTENSITY AND
PLACEMENT OF GREATEST HIGH WIND POTENTIAL.

THUS...WILL MAINTAIN A RELATIVELY HIGH CONFIDENCE FORECAST IN
DERECHO EVOLUTION ACROSS NEB/IA/MO AREA THROUGH THE LATE EVENING.
EXPECT AN INCREASING CHANCE FOR WIDESPREAD DAMAGING WINDS...LARGE
HAIL...AND A COUPLE OF POTENTIALLY STRONG TORNADOES IN THESE AREAS.
IF CONFIDENCE CONTINUES TO INCREASE IN THIS WIDESPREAD SEVERE WIND
SCENARIO...A HIGH RISK AREA MAY BE ADDED IN THE AFTERNOON SWODY1
UPDATE.

...ACROSS THE MS RIVER TO IL/IND BEFORE DAYBREAK WED...
MCS/DERECHO SHOULD MAINTAIN DAMAGING WIND AND SOME HAIL POTENTIAL
EAST ACROSS THE MS RIVER AND INTO IL/IND...ESPECIALLY AFTER MIDNIGHT
CDT. WHILE BOUNDARY LAYER STABILIZATION MAY ACT TO OFFSET MORE
SUBSTANTIAL WIND THREAT WITH TIME...UPSCALE STORM ORGANIZATION AND
CONTINUING LARGE SCALE SUPPORT FOR ASCENT SUGGESTS AT LEAST MODEST
SEVERE WIND PROBABILITIES/SLGT RISK AREA IS WARRANTED AS FAR EAST AS
CENTRAL IND THROUGH DAYBREAK WED.

...LOWER GREAT LAKES/OH VALLEY NEWD TO CHAMPLAIN VALLEY...
DIURNAL HEATING OF MIDDLE 60S-LOWER 70S PRE-FRONTAL SFC
DEWPOINTS WILL SUPPORT POCKETS OF MLCAPE FROM 1000 TO 2000 J/KG THIS
AFTERNOON. THE STRONGEST INSTABILITY IS FORECAST TO OCCUR ACROSS THE
OHIO VALLEY -- I.E. IN THE WAKE OF A BAND OF WEAK H85-H7 WARM
ADVECTION AND ASSOCIATED CLOUDS/PRECIPITATION CROSSING THE CNTRL
APPALACHIANS. LOW-LEVEL ASCENT ALONG AND AHEAD OF A COLD FRONT
CROSSING THE GREAT LAKES WILL BE WEAK...BUT SHOULD BE SUFFICIENT FOR
ISOLATED TO WIDELY SCATTERED THUNDERSTORMS. THIS ASCENT WILL BE
LOCALLY AUGMENTED BY DIFFERENTIAL-HEATING-INDUCED BAROCLINICITY
AHEAD OF THE ZONE OF WARM ADVECTION -- I.E. ACROSS NRN NY TO THE
CHAMPLAIN VALLEY. HOWEVER...GIVEN THE MAGNITUDE OF THE
AFOREMENTIONED BUOYANCY AND 30-40 KT OF MID-LEVEL FLOW...SPORADIC
INSTANCES OF DMGG WINDS AND MARGINALLY SVR HAIL WILL BE POSSIBLE
WITH CONVECTION PRIMARILY ORGANIZED IN MULTICELL CLUSTERS.

..CARBIN/COHEN/KERR.. 06/03/2014

[snowlover2]

New day 2 stayed at slight risk.

[snowlover2]

New day 2 stayed at slight risk.

 

 

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1240 PM CDT TUE JUN 03 2014

VALID 041200Z - 051200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER A LARGE PART OF THE OH

VALLEY INTO THE TN VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE HIGH

PLAINS INTO CENTRAL KS...

...SUMMARY...

STRONG TO SEVERE STORMS ARE EXPECTED TO DEVELOP PRIMARILY THROUGH

THE OHIO VALLEY REGION WEDNESDAY WITH A THREAT FOR MAINLY DAMAGING

WIND AND LARGE HAIL...THOUGH A TORNADO THREAT CANNOT BE RULED OUT.

OTHER MORE ISOLATED STRONG TO SEVERE STORMS WILL BE POSSIBLE FROM

SOUTHERN MISSOURI...SOUTHERN KANSAS INTO NORTHERN OKLAHOMA...AND THE

NORTHERN...CENTRAL...AND SOUTHERN HIGH PLAINS.

...SYNOPSIS...

A PROGRESSIVE UPPER PATTERN WILL PERSIST OVER THE NRN HALF OF THE

COUNTRY WEDNESDAY. A FAST MOVING LOW AMPLITUDE SHORTWAVE TROUGH WILL

CONTINUE THROUGH THE OH VALLEY...DEAMPLIFYING AS IT BECOMES ABSORBED

IN A BROADER SCALE UPPER TROUGH CENTERED OVER SERN CANADA. THE ERN

PORTION OF A COLD FRONT MOVING SOUTH THROUGH THE OH VALLEY AND

CENTRAL APPALACHIANS DURING DAY 1...SHOULD EXTEND WWD FROM DELMARVA

THROUGH NRN VA INTO WV AND ALONG THE OH RIVER IN SWRN OH/NRN KY.

THE WRN EXTENT OF THIS COLD FRONT SHOULD ALREADY BE LIFTING BACK NWD

AS A WARM FRONT THROUGH CENTRAL IL...SRN IND AND ADJACENT KY AT 12Z

WEDNESDAY. THE N/NEWD MOVEMENT OF THIS BOUNDARY WILL PERSIST THROUGH

DAY 2 ACROSS THE OH VALLEY...GIVEN THE APPROACH OF THE LOW AMPLITUDE

IMPULSE AND ITS ATTENDANT LLJ. MEANWHILE...A SWRN EXTENSION OF THIS

FRONT WILL ACCELERATE SWD THROUGH THE MID MS VALLEY AND CNTRL PLAINS

WITH PASSAGE OF THE SHORTWAVE TROUGH BEFORE LIKELY BECOMING

STATIONARY FROM THE TX PANHANDLE INTO ARKANSAS WEDNESDAY NIGHT. THE

PASSAGE OF THE SHORTWAVE TROUGH DURING THE SECOND HALF OF DAY 2

ACROSS THE OH VALLEY AND CENTRAL APPALACHIANS WILL SUPPORT THE SWD

MOVEMENT OF THE FRONT AND SHOULD EXTEND FROM ERN PA SWWD THROUGH NRN

VA TO PERHAPS THE KY/TN BORDER.

...OH VALLEY THROUGH CNTRL APPALACHIAN REGION...

AN ENHANCED SLIGHT RISK AREA WILL BE MAINTAINED FOR THE DAY 2

OUTLOOK WITH DAMAGING WINDS AND HAIL BEING THE PRIMARY

THREATS...THOUGH ISOLATED TORNADOES CANNOT BE RULED OUT. THE

COMBINATION OF LATE DAY 1 MCS THAT SHOULD BE LOCATED IN PARTS OF IL

AND PERHAPS CENTRAL IND AT 12Z WEDNESDAY...AND ONGOING EARLY DAY 2

CONVECTION ALONG THE RETREATING WARM FRONT PROVIDE UNCERTAINTY WITH

REGARDS TO 1/ THE NWD ADVANCEMENT OF THE WARM FRONT AND 2/ ANY

ATTENDANT OUTFLOW BOUNDARIES THAT WOULD BE A FOCUS FOR TSTMS. RICH

GULF MOISTURE WILL RESIDE IN THE OH VALLEY WARM SECTOR SUPPORTING

MODERATE-STRONG INSTABILITY AS THE SFC LAYER WARMS. SOME STABILIZING

EFFECTS FROM EARLY DAY 2 CONVECTION IN THE LOWER OH VALLEY AND A CAP

ROOTED AROUND 700 MB MAY LIMIT NEW TSTM DEVELOPMENT UNTIL THE

AFTERNOON. ASCENT ACCOMPANYING THE PROGRESSIVE SHORTWAVE TROUGH AND

ATTENDANT LLJ WILL SUPPORT REDEVELOPMENT AND INTENSIFICATION OF

STORMS AS WARM SECTOR DESTABILIZES...POSSIBLY ALONG SRN FRINGE OF

THE MCS AS WELL AS ADDITIONAL DEVELOPMENT ALONG AND AHEAD OF THE

WARM FRONT. STRONG VERTICAL SHEAR AND LARGE 0-2 KM HODOGRAPHS WILL

SUPPORT SUPERCELLS AND BOWING SEGMENTS. ALL SEVERE TYPES WILL BE

POSSIBLE INCLUDING DAMAGING WIND...LARGE HAIL AND TORNADOES.

UNCERTAINTY REGARDING PLACEMENT OF BOUNDARY AND IMPACT OF MORNING

CONVECTION AND OUTFLOW BOUNDARIES CONTINUES TO PRECLUDE A MODERATE

RISK UPGRADE AT THIS TIME. HOWEVER...A PORTION OF THE OH VALLEY MAY

NEED TO BE INCLUDED IN A MODERATE RISK IN LATER OUTLOOKS.