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Labor Day Weekend Heavy Rain/Severe Thread


IWXwx

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model agreement on a large well defined outflow cutting SE across central IL is a classic punt signal north of I80…a lock, no but it's the right call

 

 

I agree in the sense that the greatest probs should be south of I-80...a case could probably be made for 30% wind probs in that area although forcing could be better. 

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meh, looks pretty much on schedule

 

LOT favoring I80 south as well

 

http://www.crh.noaa.gov/wxstory.php?site=lot

 

One forecast radar I just looked at (albeit, this forecast radar is pure crap) has it into IL/WI by Midnight ET.

 

Either way, as the cold pool continues to develops and the better jet dynamics kick in, a faster timing wouldn't surprise me...

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One forecast radar I just looked at (albeit, this forecast radar is pure crap) has it into IL/WI by Midnight ET.

 

Either way, as the cold pool continues to develops and the better jet dynamics kick in, a faster timing wouldn't surprise me...

 

 

i expect the remnant northern portion of complex to be moving along the IL/WI border near daybreak with the southern outflow lagging bit across central IL

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LOT backing off 

 

INTENSE THUNDERSTORMS DEVELOPING OVER EASTERN NEBRASKA/WESTERN
IOWA WILL LIKELY CONGEAL INTO A LARGE CLUSTER AND MOVE EAST ACROSS
IOWA TONIGHT...ARRIVING IN NORTHWEST ILLINOIS TOWARD DAWN. MODELS
SUGGEST THESE STORMS WILL WEAKEN OR COMPLETELY DISSIPATE AS THEY
MOVE ACROSS NORTHERN ILLINOIS MONDAY MORNING...HOWEVER CONFIDENCE
IN THAT SCENARIO IS NOT TERRIBLY HIGH AS CONVECTION COULD GROW
MORE ORGANIZED TONIGHT AND MAINTAIN ITSELF INTO THE MORNING
MONDAY. STORMS WILL EITHER RE-INTENSIFY OR RE-DEVELOP ALONG
REMNANT OUTFLOW BOUNDARY SUNDAY AFTERNOON...MAINLY SOUTHEAST OF
THE TERMINALS WITH STRONG-SEVERE THUNDERSTORMS POSSIBLY EXTENDING
FROM SOUTHEAST KANSAS NORTHEAST INTO NORTHERN INDIANA BY LATE
MONDAY AFTERNOON. BEST CHANCE OF SHRA/TSRA AT RFD WILL BE WITH
WEAKENING STORM COMPLEX APPROACHING FROM WEST MONDAY MORNING.

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LOT backing off 

 

INTENSE THUNDERSTORMS DEVELOPING OVER EASTERN NEBRASKA/WESTERN

IOWA WILL LIKELY CONGEAL INTO A LARGE CLUSTER AND MOVE EAST ACROSS

IOWA TONIGHT...ARRIVING IN NORTHWEST ILLINOIS TOWARD DAWN. MODELS

SUGGEST THESE STORMS WILL WEAKEN OR COMPLETELY DISSIPATE AS THEY

MOVE ACROSS NORTHERN ILLINOIS MONDAY MORNING...HOWEVER CONFIDENCE

IN THAT SCENARIO IS NOT TERRIBLY HIGH AS CONVECTION COULD GROW

MORE ORGANIZED TONIGHT AND MAINTAIN ITSELF INTO THE MORNING

MONDAY. STORMS WILL EITHER RE-INTENSIFY OR RE-DEVELOP ALONG

REMNANT OUTFLOW BOUNDARY SUNDAY AFTERNOON...MAINLY SOUTHEAST OF

THE TERMINALS WITH STRONG-SEVERE THUNDERSTORMS POSSIBLY EXTENDING

FROM SOUTHEAST KANSAS NORTHEAST INTO NORTHERN INDIANA BY LATE

MONDAY AFTERNOON. BEST CHANCE OF SHRA/TSRA AT RFD WILL BE WITH

WEAKENING STORM COMPLEX APPROACHING FROM WEST MONDAY MORNING.

 

Wasn't that Izzi's aviation forecast?

 

BTW, NAM sped things up some. Brings an initial (severe) squall line through here around 18z-21z.

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Seeing reports of gusts near 60 with the line moving into eastern Iowa.  The line is moving in sooner than the models predicted, so it's holding together pretty well.

 

Looks like you're gonna get a nice dumping finally tonight. 

 

SPC will likely be making a major shift southeast with the risk for tomorrow.  Looks like they are about 200 miles too far northwest with the risk area in the last few day 2 outlooks.  Amazing how the large scale system setups usually skip over this area.  The Plains really seems to act as sort of a barrier reef for the larger scale severe setups for this area. 

 

Looking pretty good for the LAF boys tomorrow.

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Looks like you're gonna get a nice dumping finally tonight. 

 

SPC will likely be making a major shift southeast with the risk for tomorrow.  Looks like they are about 200 miles too far northwest with the risk area in the last few day 2 outlooks.  Amazing how the large scale system setups usually skip over this area.  The Plains really seems to act as sort of a barrier reef for the larger scale severe setups for this area. 

 

Looking pretty good for the LAF boys tomorrow.

 

It's definitely a messy setup for sure...

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Looks like the storms are hitting a brick wall at the Iowa/Wisconsin and Minnesota/Wisconsin borders.  Probably is a good thing for our prospects tomorrow.

Rough estimation using Radarscope's distance tool puts them moving ~11 miles east over the past half hour or so of radar scans, though the severe warning over Iowa City calls for 50MPH movement.

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Here is today's Day 1 Outlook from SPC

 

post-2790-0-72117900-1409574203_thumb.gi

SPC AC 010554   DAY 1 CONVECTIVE OUTLOOK     NWS STORM PREDICTION CENTER NORMAN OK   1254 AM CDT MON SEP 01 2014   VALID 011200Z - 021200Z   ...THERE IS A SLGT RISK OF SVR TSTMS FROM LOWER MI AND SERN WI   THROUGH THE MIDWEST...MID MS VALLEY TO ERN KS AND FAR NERN OK...   ...SUMMARY...   ISOLATED TO SCATTERED SEVERE THUNDERSTORMS SHOULD DEVELOP ALONG AND   AHEAD OF A WEAK COLD FRONT FROM PARTS OF THE SOUTHERN GREAT LAKES   REGION SOUTHWESTWARD ACROSS INDIANA...ILLINOIS...MISSOURI INTO   EASTERN KANSAS AND FAR NORTHEAST OKLAHOMA.  DAMAGING WINDS AND LARGE   HAIL WILL BE POSSIBLE WITH THE STRONGEST STORMS...WHILE A TORNADO   CANNOT BE RULED OUT ACROSS THE SOUTHWESTERN EXTENT OF THE SLIGHT   RISK AREA. A FEW STRONG WIND GUSTS WILL BE POSSIBLE THIS AFTERNOON   ACROSS FAR EASTERN WYOMING INTO PARTS OF SOUTHERN SOUTH DAKOTA AND   NORTHERN NEBRASKA.   ...LOWER MI/SERN WI TO MID MS VALLEY TO SERN KS/NERN OK...    A PROGRESSIVE SHORTWAVE TROUGH IS EXPECTED TO TRACK NEWD FROM THE   UPPER MS VALLEY THROUGH THE UPPER GREAT LAKES EARLY IN THE FORECAST   PERIOD...REACHING ONTARIO AND WRN QUEBEC BY LATE AFTERNOON/EARLY   EVENING.  ALTHOUGH THE STRONGEST 500-MB HEIGHT FALLS /60-90 M/ ARE   FORECAST TO SPREAD THROUGH THE NRN EXTENT OF THE UPPER GREAT   LAKES...30-60 METER FALLS SHOULD OCCUR ACROSS THE ERN WI AND LOWER   MI PORTION OF THE SLIGHT RISK AREA.  MEANWHILE...AN UPSTREAM   SHORTWAVE TROUGH AND ATTENDANT SPEED MAX ARE EXPECTED TO MOVE FROM   THE CENTRAL ROCKIES THROUGH THE CENTRAL PLAINS THIS AFTERNOON TO THE   MIDWEST AND SRN GREAT LAKES LATER MONDAY NIGHT.   A COLD FRONT ASSOCIATED WITH THE LEAD SHORTWAVE TROUGH IS EXPECTED   TO EXTEND FROM WRN LAKE SUPERIOR SSWWD THROUGH CENTRAL IA INTO   CENTRAL KS AT 12Z.  THIS BOUNDARY WILL ADVANCE TO A POSITION FROM   ERN UPPER MI THROUGH SERN IA INTO SERN KS AND NORTH CENTRAL OK TO   THE TX PANHANDLE BY LATE AFTERNOON.  FRONTAL CONVECTION WILL LIKELY   BE ONGOING AT THE BEGINNING OF THE PERIOD...ENHANCED PRIMARILY BY   ASCENT AHEAD OF THE UPPER MS VALLEY SHORTWAVE TROUGH.  ADDITIONAL   STORMS MAY ALSO BE ONGOING AT DAYBREAK ACROSS ERN KS INTO CENTRAL/   SRN MO WITHIN A LOW-LEVEL WAA REGIME. GUSTY WINDS AND ISOLATED HAIL   MAY OCCUR WITH THE EARLY MORNING ACTIVITY...THOUGH GREATER TSTM   COVERAGE AND SEVERE WEATHER THREAT WILL BE POSSIBLE ACROSS THE   SLIGHT RISK AREA LATER TODAY.   STRONGEST BOUNDARY-LAYER HEATING SHOULD OCCUR ACROSS SERN KS/SWRN MO   AND OK WHERE SURFACE TEMPERATURES WILL WARM INTO THE 90S.  AS A   RESULT...INSTABILITY IS EXPECTED TO BE GREATEST ALONG THE TRAILING   PORTIONS OF THE FRONT WHERE THE ERN EXTENT OF STEEP LAPSE RATES WILL   CONTRIBUTE TO MODERATE-STRONG INSTABILITY /MLCAPE 2000-3000 J PER   KG/.  DESPITE WEAKER MIDLEVEL LAPSE RATES AND SOME UNCERTAINTY IN   DEGREE OF SURFACE HEATING...DUE IN PART TO EARLY DAY CONVECTIVE   DEBRIS...MODERATE INSTABILITY SHOULD ALSO DEVELOP ENEWD FROM MO TO   LOWER MI.   NEW TSTM DEVELOPMENT SHOULD OCCUR FROM SERN WI INTO LOWER MI AND ERN   IA TO INDIANA FROM LATE MORNING INTO THE AFTERNOON IN VICINITY OF   THE COLD FRONT AND ANY DIFFERENTIAL HEATING BOUNDARIES ATTENDANT TO   EARLY MORNING CONVECTION.  A 50-60 KT SWLY MIDLEVEL JET ACCOMPANYING   THE LEAD TROUGH WILL RESULT IN STRENGTHENING BULK SHEAR FOR THE   POTENTIAL FOR ORGANIZED STORMS PRODUCING DAMAGING WINDS AND HAIL.    MEANWHILE...TSTMS ARE EXPECTED TO BACK-BUILD SWWD THROUGH MO TO SERN   KS DURING THE MID-LATE AFTERNOON AS THE CAP WEAKENS.  LOW-LEVEL   WINDS WILL REMAIN BACKED TO SLY INTO SERN KS...NERN OK AND SWRN MO   ENHANCING CONVERGENCE INTO THE COLD FRONT AND POTENTIAL OUTFLOW   BOUNDARY FROM EARLY MORNING STORMS.  STRENGTHENING WLY MIDLEVEL   WINDS ACROSS KS/MO BY LATE AFTERNOON WILL RESULT IN STRONG BULK   SHEAR FOR ORGANIZED STORMS INCLUDING SUPERCELLS WITH THE STRONG   INSTABILITY SUPPORTING THE POTENTIAL FOR VERY LARGE HAIL AND STRONG   WIND GUSTS.  THE AFOREMENTIONED ZONE OF BACKED LOW-LEVEL WINDS WILL   ENHANCE LOW-LEVEL SHEAR FOR A TORNADO THREAT INTO THE EARLY EVENING.   ...ERN WY/SWRN SD AND WRN/CENTRAL NEB...   A FAST-MOVING MIDLEVEL IMPULSE IS EXPECTED TO TRACK ESEWD FROM THE   NRN ROCKIES TO THIS DISCUSSION AREA BY LATE THIS AFTERNOON.  DESPITE   SURFACE DEW POINTS IN THE 40S...STEEP LAPSE RATES...WITH 500-MB   TEMPERATURES AROUND -15 C ACCOMPANYING THE IMPULSE...WILL RESULT IN   MARGINAL INSTABILITY /MLCAPE 500-1000 J PER KG/ THIS AFTERNOON.    TSTMS ARE EXPECTED TO DEVELOP WITHIN THIS NORTHWEST FLOW REGIME WITH   LOCALLY STRONG WIND GUSTS BEING THE PRIMARY THREAT.   ..PETERS/DEAN.. 09/01/2014   CLICK TO GET WUUS01 PTSDY1 PRODUCT   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z   CURRENT UTC TIME: 1214Z (7:14AM), RELOAD THIS PAGE TO UPDATE THE TIME
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Updated SPC day 1 outlook:

 

day1otlk_1300.gif?1409576284531

 

 

 

SPC AC 011252

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0752 AM CDT MON SEP 01 2014

VALID 011300Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
FROM LOWER MI TO THE NE OK/SE KS BORDER REGION...

...SUMMARY...
A FEW SEVERE STORMS WITH DAMAGING WINDS AND LARGE HAIL ARE EXPECTED
LATER TODAY FROM PARTS OF ILLINOIS INTO LOWER MICHIGAN. A SOMEWHAT
LONGER-DURATION SEVERE STORM THREAT IS EXPECTED THIS AFTERNOON INTO
TONIGHT FROM THE KANSAS/OKLAHOMA BORDER REGION INTO SOUTHERN
MISSOURI...WHERE A COUPLE TORNADOES WILL ALSO BE POSSIBLE.
OTHERWISE...ISOLATED STORMS WITH STRONG WINDS ARE POSSIBLE ACROSS
THE CENTRAL HIGH PLAINS THIS AFTERNOON.

...SE KS/NE OK BORDER TO LOWER MI TODAY INTO TONIGHT...
A LEAD SHORTWAVE TROUGH OVER THE UPPER MS VALLEY THIS MORNING WILL
MOVE NEWD OVER UPPER MI BY THIS AFTERNOON...WHILE AN UPSTREAM WAVE
OVER ID/WY PROGRESSES EWD TO THE CENTRAL HIGH PLAINS THIS AFTERNOON
AND THE MID MS VALLEY BY SUNRISE TUESDAY. AT THE SURFACE...AN
ASSOCIATED COLD FRONT WILL MOVE EWD ACROSS IA/WI TODAY TO WRN LOWER
MI AND NW IL BY THIS EVENING...WHILE THE SW EXTENT OF THE FRONT WILL
BECOME QUASI-STATIONARY NEAR THE KS/OK BORDER.

OUTFLOW FROM OVERNIGHT CONVECTION HAS PROGRESSED WELL AHEAD OF THE
SURFACE COLD FRONT...AND THE POTENTIAL FOR ADDITIONAL SEVERE STORM
DEVELOPMENT TODAY FROM NRN MO TO SE WI APPEARS TO BE DIMINISHING AS
A RESULT OF THE STABILIZING INFLUENCE OF THIS OUTFLOW...AS WELL AS
EARLY DAY PASSAGE OF THE LEAD SHORTWAVE TROUGH. FARTHER E...A
BROKEN BAND OF PRE-FRONTAL CONVECTION WILL BE POSSIBLE THIS
AFTERNOON FROM NRN INDIANA INTO LOWER MI. HERE...A FEW DAMAGING
GUSTS WILL BE POSSIBLE AS BOUNDARY LAYER DEWPOINTS NEAR 70 F AND
DAYTIME HEATING CONTRIBUTE TO MLCAPE AROUND 2000 J/KG...IN AN
ENVIRONMENT WITH SOME ENHANCEMENT TO DEEP-LAYER VERTICAL SHEAR WITH
THE LEAD SHORTWAVE TROUGH.

THE MORE FOCUSED SEVERE WEATHER THREAT AREA WILL BE FARTHER S FROM
THE OK/KS BORDER INTO SRN MO...ALONG THE RESIDUAL OUTFLOW BOUNDARY
FROM THE ONGOING STORMS IN MO/KS. CONTINUED MOISTURE INFLUX INTO
THE BOUNDARY FROM THE S...IN CONJUNCTION WITH STRONG DAYTIME
HEATING...WILL MAINTAIN MLCAPE OF 2500-3000 J/KG ALONG THE SRN
FRINGE OF THE STRONGER WLYS...AND THE NRN FRINGE OF THE WARMER
ELEVATED MIXED LAYER/CAP. DESTABILIZATION IN THE WARM SECTOR AND
CONTINUED WAA/ASCENT OVER THE REMNANT OUTFLOW/EFFECTIVE FRONT WILL
SUPPORT ADDITIONAL THUNDERSTORM DEVELOPMENT FROM N CENTRAL/NE OK AND
SE KS INTO SRN MO THIS AFTERNOON INTO TONIGHT. THE MODERATE-STRONG
BUOYANCY AND EFFECTIVE BULK SHEAR OF 30-40 KT WILL SUPPORT A WSW-ENE
ORIENTED BAND OF STORMS WITH SOME EMBEDDED SUPERCELLS CAPABLE OF
PRODUCING LARGE HAIL/DAMAGING WINDS. LOW-LEVEL SHEAR AND MOISTURE
WILL BE SUFFICIENT FOR SOME TORNADO RISK WITH STORMS ON THE
IMMEDIATE COOL SIDE OF THE BOUNDARY...AS SWD MOTION OF THE BOUNDARY
ENDS AND THE OUTFLOW AIR MASS MODIFIES BY THIS AFTERNOON.
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