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May 31st Mississippi Valley/Great Lakes Severe Weather


wisconsinwx

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I think it's time to have a thread for May 31st, since it looks like we will have a cold front sweeping through the Upper Mississippi Valley and Western Great Lakes region. Whatever happens with this, happens. Might also be our warmest day of the year so far here along the western shore of Lake Michigan.

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Well, the NAM has at least sped up things enough to make Tuesday interesting for my area. And with the high CAPE/good shear/steep low-level lapse rate environment, I fully expect to see a rather substantial damaging wind potential to my north/west on Tuesday.

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I wouldn't mind adding another event to my sig... :guitar:

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1213 AM CDT MON MAY 30 2011

VALID 311200Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE GREAT LAKES INTO A

PORTION OF THE MID MS VALLEY...

..SYNOPSIS

LARGE UPPER TROUGH OVER THE INTERMOUNTAIN AND GREAT BASIN REGIONS

WILL EJECT INTO THE CNTRL/NRN PLAINS AND UPPER MS VALLEY MONDAY

BEFORE TURNING EWD THROUGH SERN CANADA AND GREAT LAKES TUESDAY

RESULTING IN DEAMPLIFICATION OF UPPER RIDGE. ATTENDANT SURFACE LOW

WILL DEVELOP THROUGH SRN ONTARIO WHILE TRAILING COLD FRONT ADVANCES

THROUGH THE GREAT LAKES. SRN PORTIONS OF THIS BOUNDARY WILL STALL

ACROSS THE MID MS VALLEY AND SRN PLAINS. WARM FRONT WILL LIFT

THROUGH THE NERN STATES AND NEW ENGLAND.

..GREAT LAKES AREA INTO A PORTION OF THE MID MS VALLEY

MOIST WARM SECTOR WITH DEWPOINTS IN THE MID 60S WILL HAVE ADVECTED

INTO THE GREAT LAKES WARM SECTOR WHERE STEEP MID LEVEL LAPSE RATES

WILL EXIST. MODERATE /1500-2000 J/KG/ MLCAPE WILL LIKELY DEVELOP AS

THE BOUNDARY LAYER WARMS. REMNANT EML COULD POTENTIALLY RESULT IN AT

LEAST A MODERATELY STRONG CAP...BUT DEEPER FORCING WITH EJECTING

SHORTWAVE TROUGH WILL OCCUR ALONG GREAT LAKES PORTION OF FRONT AS IT

ADVANCES THROUGH WI...UPPER AND NRN LOWER MI. THIS FORCING SHOULD BE

SUFFICIENT FOR STORMS TO DEVELOP ALONG AND EAST OF COLD FRONT. 0-6

KM SHEAR OF 40-50 KT WILL SUPPORT ORGANIZED STORMS INCLUDING A FEW

SUPERCELLS. HOWEVER...MODEST HIGH LEVEL WINDS IN WARM SECTOR

SUGGESTS ACTIVITY MAY TREND TOWARD OUTFLOW DOMINANCE WITH BOWING

LINE SEGMENTS CAPABLE OF SIGNIFICANT WIND DAMAGE AND LARGE

HAIL...BUT ISOLATED TORNADOES WILL ALSO BE POSSIBLE.

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This potential screams damaging wind event, good 0-6km unidirectional shear along a cold front plowing right into an area with >3000 J/kg of SB cape.

So are you thinking something similar to today, but a little further north? That seems in line with what is expected, although given the 30% probs and hatched area, an upgrade to mod risk seems likely.

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So are you thinking something similar to today, but a little further north? That seems in line with what is expected, although given the 30% probs and hatched area, an upgrade to mod risk seems likely.

the event yesterday had nothing to do with a frontal passage, different animal altogether.

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...GREAT LAKES AREA INTO A PORTION OF THE MID MS VALLEY...

MOIST WARM SECTOR WITH DEWPOINTS IN THE MID 60S WILL HAVE ADVECTED INTO THE GREAT LAKES WARM SECTOR WHERE STEEP MID LEVEL LAPSE RATES WILL EXIST. MODERATE /1500-2000 J/KG/ MLCAPE WILL LIKELY DEVELOP AS THE BOUNDARY LAYER WARMS. REMNANT EML COULD POTENTIALLY RESULT IN AT LEAST A MODERATELY STRONG CAP...BUT DEEPER FORCING WITH EJECTING SHORTWAVE TROUGH WILL OCCUR ALONG GREAT LAKES PORTION OF FRONT AS IT ADVANCES THROUGH WI...UPPER AND NRN LOWER MI. THIS FORCING SHOULD BE SUFFICIENT FOR STORMS TO DEVELOP ALONG AND EAST OF COLD FRONT. 0-6 KM SHEAR OF 40-50 KT WILL SUPPORT ORGANIZED STORMS INCLUDING A FEW SUPERCELLS. HOWEVER...MODEST HIGH LEVEL WINDS IN WARM SECTOR SUGGESTS ACTIVITY MAY TREND TOWARD OUTFLOW DOMINANCE WITH BOWING LINE SEGMENTS CAPABLE OF SIGNIFICANT WIND DAMAGE AND LARGE HAIL...BUT ISOLATED TORNADOES WILL ALSO BE POSSIBLE.

SPC...

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Good mid level forcing tomorrow and what appears to be a weaker cap than today.

post-525-0-56401200-1306808019.png

post-525-0-01952300-1306808070.png

There will be over 40 knots of bulk shear moving over the warm sector by afternoon, but it will be unidirectional. In addition, a large MCS appears to be developing over the High Plains right now which may limit destabilization in some areas, depending on how east it makes it overnight.

post-525-0-04797000-1306808281.jpg

So, with a weaker cap and shear that may even be more unidirectional than today destructive interference will likely reign supreme and storms will likely quickly grow upscale into a forward propigating MCS/squall line. Lapse rates will be moderatly steep, which along with moderate to strong instability (should clearing occur, which it likely will for at least a few hours late morning into the early afternoon over the upper MS Valley/western lakes), a likely linear storm mode, and an 80 knot mid-upper level flow should contribute to a nice wind threat. I'd expect a moderate risk upgrade perhaps over eastern WI/northern lower MI/upper MI should things destabilize properly. The tornado threat will probably be low, I can see the SPC not going higher than 5% on the tornado probabilities for tomorrow.

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Good mid level forcing tomorrow and what appears to be a weaker cap than today.

post-525-0-56401200-1306808019.png

post-525-0-01952300-1306808070.png

There will be over 40 knots of bulk shear moving over the warm sector by afternoon, but it will be unidirectional. In addition, a large MCS appears to be developing over the High Plains right now which may limit destabilization in some areas, depending on how east it makes it overnight.

post-525-0-04797000-1306808281.jpg

So, with a weaker cap and shear that may even be more unidirectional than today destructive interference will likely reign supreme and storms will likely quickly grow upscale into a forward propigating MCS/squall line. Lapse rates will be moderatly steep, which along with moderate to strong instability (should clearing occur, which it likely will for at least a few hours late morning into the early afternoon over the upper MS Valley/western lakes), a likely linear storm mode, and an 80 knot mid-upper level flow should contribute to a nice wind threat. I'd expect a moderate risk upgrade perhaps over eastern WI/northern lower MI/upper MI should things destabilize properly. The tornado threat will probably be low, I can see the SPC not going higher than 5% on the tornado probabilities for tomorrow.

You know, it might be worth mentioning what happened on the morning of May 31st, 1998. That was when a powerful derecho plowed through much of the Northern Tier of the country, bringing up to 100 mph winds or greater along with it. Coincidence?

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You know, it might be worth mentioning what happened on the morning of May 31st, 1998. That was when a powerful derecho plowed through much of the Northern Tier of the country, bringing up to 100 mph winds or greater along with it. Coincidence?

meh, not even close to the same setup.

As far as cloud cover limiting sun, i doubt it, its 6 1/2 hours til sunshine again across most of the risk area tomorrow and the storms and clouds are still in western MN with a more NE movement then anything, plus the cap in place across the area. This is one of the few times across the area, upper great lakes, then i feel safe saying clouds SHOULD NOT be a factor.

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You know, it might be worth mentioning what happened on the morning of May 31st, 1998. That was when a powerful derecho plowed through much of the Northern Tier of the country, bringing up to 100 mph winds or greater along with it. Coincidence?

Hmm, the derecho ongoing right now certainly has a very strong pressure rise/fall associated with it, and is moving through some moderate to strong instability for the next few hours with a 50 knot 850mb flow ahead of it.

post-525-0-78818700-1306809552.jpg

Some sub 60f dew points mixed down over SE MN, NE IA and far western WI this afternoon probably due to the strong cap. That might slow it down some in several hours, although there is some strong instability pretty far east near the warm front where the capping was weaker.

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Hmm, the derecho ongoing right now certainly has a very strong pressure rise/fall associated with it, and is moving through some moderate to strong instability for the next few hours with a 50 knot 850mb flow ahead of it.

post-525-0-78818700-1306809552.jpg

Some sub 60f dew points mixed down over SE MN, NE IA and far western WI this afternoon probably due to the strong cap. That might slow it down some in several hours, although there is some strong instability pretty far east near the warm front where the capping was weaker.

I just wanted to stir up the dramatic element. In no way am I expecting something similar, but if it happened, it would be very fitting.

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DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1259 AM CDT TUE MAY 31 2011

VALID 311200Z - 011200Z

...THERE IS A MDT RISK OF SVR TSTMS OVER MUCH OF LOWER MI AS WELL AS

ERN UPPER MI...

...THERE IS A SLGT RISK OF SVR TSTMS FROM NRN IL/WI EWD INTO

MI...NRN IND AND NWRN OH...

..SYNOPSIS

AN UPPER LOW AND SHORTWAVE TROUGH WILL TAKE ON A NEGATIVE TILT AS IT

EJECTS NEWD ACROSS THE UPPER MS VALLEY/UPPER GREAT LAKES REGION

TODAY WITH AN 80-90 KT MID LEVEL SPEED MAX. AT THE SURFACE...LOW

PRESSURE WILL MOVE FROM SRN MANITOBA INTO WRN ONTARIO WITH A

RELATIVELY SHARP LOW PRESSURE TROUGH/COLD FRONT EXTENDING SWD ACROSS

MN INTO NRN MO DURING THE MORNING...WEAKENING A BIT AS IT LIFTS NEWD

ACROSS THE GREAT LAKES. TO THE W...A LARGE UPPER LOW WILL BE NEARLY

STATIONARY JUST OFF THE PACIFIC COAST...WITH A BROAD AREA OF SWLY

FLOW FROM CA INTO THE GREAT BASIN. IN ASSOCIATION WITH THIS TROUGH

AND WITH DAYTIME HEATING...A WEAK LOW PRESSURE TROUGH WILL LIE

ROUGHLY FROM ERN WA INTO NRN NV.

..WI/MI AND NRN IL/IND/OH

WIND PROFILES WILL BECOME INCREASINGLY UNIDIRECTIONAL ACROSS THE

WARM SECTOR DUE TO MIXING AND ALSO A SLIGHT WEAKENING/LIFTING OUT OF

THE SURFACE LOW TO THE N. DESPITE THIS...DEEP LAYER FLOW FIELDS WILL

BE STRONG AND FAVOR ORGANIZED SEVERE THUNDERSTORMS CAPABLE OF

DAMAGING WINDS AND HAIL. INDICATIONS ARE THAT STORMS WILL INCREASE

IN COVERAGE ALONG THE COLD FRONT ACROSS WRN UPPER MI AND CNTRL WI BY

MIDDAY AND INCREASE IN INTENSITY AND ORGANIZATION AS THEY MOVE

ACROSS NRN IL...NRN IND...AND EWD ACROSS LOWER MI BY LATE AFTERNOON.

MIXED STORM MODES MAY OCCUR...WITH FAST MOVING LINE SEGMENTS/BOWS

AND A FEW SUPERCELLS EARLY. WITH TIME...THE DOMINANT STORM MODE

SHOULD BE QUASI-LINEAR WITH THE POSSIBILITY OF WIDESPREAD SEVERE

WINDS. TORNADO THREAT WILL BE LIMITED BY VEERED LOW LEVEL FLOW AND

WEAK EFFECTIVE SRH...AS WELL AS LINEAR STORM MODE WITH TIME.

..MO/OK/TX

A WEAK FRONTAL BOUNDARY WILL STRETCH ROUGHLY FROM CNTRL MO INTO OK

AND NWRN TX THIS AFTERNOON...WITH AMPLE INSTABILITY PRESENT BY LATE

AFTERNOON. ALTHOUGH CIN WILL ERODE DURING THE DAY...OVERALL FORCING

FOR ASCENT WILL BE WEAK...ESPECIALLY OVER TX WHERE UPPER HEIGHT

RISES WILL OCCUR. STILL...STRONG HEATING SHOULD LEAD TO AT LEAST

ISOLATED THUNDERSTORM ACTIVITY ALONG THE ENTIRE ZONE. PULSE TO

MULTICELL STORMS CAPABLE MARGINAL HAIL/WIND ARE MOST LIKELY. AFTER

00Z...A SLY LOW LEVEL JET IS FORECAST TO INCREASE OVER THE SRN

PLAINS...WHICH WILL BRING MOISTURE AND INSTABILITY NWD. THIS MAY

HELP FORCE SOME WEAK ACTIVITY INTO SRN KS...BUT CONCERNS ABOUT CIN

AND DEGREE OF FORCING CURRENT LIMIT SEVERE PROBABILITIES.

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Looking at the most recent RUC runs, they all seem to form a line of t'storms with the cold front just as it approaches Lake Michigan. Cutting it close, but we should be getting the storms if the RUC is correct.

looking forward to some nice shots of the towers over the lake. Few things more photogenic than tower to the east over the lake with a low sitting sun to the west.

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looking forward to some nice shots of the towers over the lake. Few things more photogenic than tower to the east over the lake with a low sitting sun to the west.

Yeah, it's nice that this should be coming through mid to late afternoon, unlike most events around here that come around or after sunset.

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Yeah, it's nice that this should be coming through mid to late afternoon, unlike most events around here that come around or after sunset.

Don't get too jacked, timing is looking less than ideal for this side of the lake, visible shows clouds moving in pretty soon, so passage will be well before peak heating.

http://www.ssec.wisc.edu/~tomw/wisgifloop.html

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