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Severe weather Aug 27-28th


janetjanet998
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This look rather interesting...latest SPC outlook sums it up


 
.THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS PARTS OF THE  
UPPER MIDWEST...  
   
..SUMMARY  
  
NUMEROUS SEVERE STORMS WITH DAMAGING WINDS AS THE PRIMARY HAZARD ARE  
EXPECTED DURING THE LATE AFTERNOON AND EVENING ACROSS PARTS OF THE  
UPPER MIDWEST.  
   
..UPPER MIDWEST  
  
AN ACTIVE SEVERE WEATHER PERIOD MAY UNFOLD DURING THE LATE AFTERNOON  
AND EVENING, WITH POTENTIAL FOR A DERECHO AND/OR SIGNIFICANT SEVERE.  
FURTHER UPGRADES IN PROBABILITIES/RISK ARE POSSIBLE IN LATER  
OUTLOOKS.  
  
LARGE-SCALE MID-LEVEL HEIGHT FALLS WILL SPREAD ACROSS THE UPPER  
MIDWEST THIS AFTERNOON AND EVENING AS A SIGNIFICANT PIECE OF THE  
NORTHERN ROCKIES TROUGH EJECTS TOWARDS THE RED RIVER VALLEY. THIS  
FEATURE IS EXPECTED TO MAINTAIN A SOUTHWESTERLY LOW-LEVEL JET INTO  
SOUTHEAST MN AND SOUTHERN WI WITH AMPLE BOUNDARY-LAYER MOISTURE  
CHARACTERIZED BY LOWER 70S SURFACE DEW POINTS. ROBUST SURFACE  
HEATING IS ANTICIPATED IN THE WAKE OF MORNING ELEVATED CONVECTION  
OVER EASTERN IA/WI TO A SLOW-MOVING COLD FRONT THAT BISECTS MN TO A  
SURFACE CYCLONE OVER SOUTHEAST SD. THE PRESENCE OF A STOUT ELEVATED  
MIXED LAYER WILL YIELD A STRONGLY UNSTABLE AIR MASS BY PEAK HEATING  
WITH MLCAPE OF 2500-3500 J/KG ACROSS IA, SOUTHERN MN AND MOST OF WI.  
  
CONVERGENCE NEAR THE SURFACE CYCLONE IN CONJUNCTION WITH INCREASING  
MID-LEVEL ASCENT THROUGH A MINOR PERTURBATION APPROACHING FROM THE  
NE PANHANDLE AND LARGER-SCALE HEIGHT FALLS SHOULD RESULT IN  
DEEPENING CONVECTION BY 20-21Z ACROSS THE SIOUXLAND REGION. GIVEN  
VERY STEEP MID-LEVEL LAPSE RATES AND STRONG SPEED SHEAR THROUGH THE  
CLOUD-BEARING LAYER, INITIAL SUPERCELLS PRODUCING LARGE HAIL WILL BE  
POSSIBLE. HOWEVER, WITH WEAKNESS IN THE LOW-LEVEL HODOGRAPH WITHIN  
THE INITIATING CORRIDOR AND DEEP-LAYER FLOW MORE PARALLEL THAN  
ORTHOGONAL TO THE FRONT, UPSCALE GROWTH MAY RAPIDLY OCCUR AND IS  
CONSISTENTLY DEPICTED ACROSS CAMS. A FORWARD-PROPAGATING, BOWING MCS  
MAY EVOLVE ACROSS MAINLY SOUTHERN MN AND INTO NORTHERN/CENTRAL WI  
AND UPPER MI BEFORE EVENTUALLY WEAKENING OVER PARTS OF LAKES  
SUPERIOR/MICHIGAN.  
  
GUIDANCE IS CONSISTENT IN DEPICTING STRENGTHENING 700-MB  
SOUTHWESTERLIES IN THE WARM SECTOR COINCIDENT WITH THE EVOLVING MCS.  
THE NAM IS THE STRONGEST OF GUIDANCE WITH CONVECTIVE FEEDBACK OF THE  
MCS SUGGESTING 700-MB WINDS WOULD APPROACH 80 KT BY LATE EVENING  
NEAR THE WI/MI BORDER. THE LARGE BUOYANCY, STEEPNESS OF MID-LEVEL  
LAPSE RATES, AMPLIFYING FLOW REGIME, AND CONSISTENT CAM SIGNAL ALL  
SUGGEST THAT A DERECHO IS POSSIBLE DURING THE LATE AFTERNOON AND  
EVENING. DAMAGING WINDS COULD BECOME WIDESPREAD WITH SCATTERED  
SEVERE GUSTS. HAVE UPGRADED TO ENH RISK FOR THIS POSSIBILITY AND A  
FURTHER UPGRADE MAY BE NECESSARY IN LATER OUTLOOKS IF THIS SCENARIO  
APPEARS LIKELY. THE LINEAR/CLUSTER MODE SHOULD MITIGATE A GREATER  
TORNADO AND HAIL RISK. BUT GIVEN THE DEGREE OF INSTABILITY, BRIEF  
TORNADOES FROM EMBEDDED SUPERCELLS OR MESOVORTICIES WITHIN THE LINE  
ARE POSSIBLE.   
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PDS wording in the Severe Thunderstorm Warning associated with the incoming derecho.  Good luck to any resident AmWx cheeseheads, and stay safe.

Severe Thunderstorm Warning
WIC017-033-035-091-280015-
/O.NEW.KMPX.SV.W.0140.180827T2320Z-180828T0015Z/

BULLETIN - EAS ACTIVATION REQUESTED
Severe Thunderstorm Warning
National Weather Service Twin Cities/Chanhassen MN
620 PM CDT MON AUG 27 2018

The National Weather Service in The Twin Cities has issued a

* Severe Thunderstorm Warning for...
Northeastern Pepin County in west central Wisconsin...
Dunn County in west central Wisconsin...
Chippewa County in west central Wisconsin...
Eau Claire County in west central Wisconsin...

* Until 715 PM CDT.

* At 619 PM CDT, severe thunderstorms were located along a line
extending from Glenwood City to near Menomonie to Rattlesnake
Ridge, moving northeast at 80 mph.

These are very dangerous storms.

HAZARD...80 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Flying debris will be dangerous to those caught without
shelter. Mobile homes will be heavily damaged. Expect
considerable damage to roofs, windows, and vehicles.
Extensive tree damage and power outages are likely.

* Severe thunderstorms will be near...
Menomonie, Boyceville and Wheeler around 625 PM CDT.
Colfax around 630 PM CDT.
Ridgeland around 635 PM CDT.
Bloomer and New Auburn around 640 PM CDT.
Cornell around 655 PM CDT.
Augusta around 700 PM CDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This is an EXTREMELY DANGEROUS SITUATION. These storms are producing
widespread wind damage. SEEK SHELTER NOW inside a sturdy structure
and stay away from windows!

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1 hour ago, RyanDe680 said:

3 replies on a decent opportunity for weather today...  shows how much we've all given up

I would be excited if I was in Wisconsin, but here it is going to do another overnight two step and jump SEMI again for the 100th time this season.

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The southern crap in Iowa probably ruined it for my area today.  Light showers and thick clouds put the kibosh on our instability.  HRRR runs all day have kept the heavy stuff mostly north and south.  The sun is poking out ahead of the sw IA broken line, so perhaps that can surge into this area later.

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Quite a nice synoptic wave moving through for late August.  Looks like southern Iowa is starting to recover quite rapidly now as the WAA stuff has lifted out quite quickly.  Nice plume of steep mid lapse rates upstream coming in from the Plains should quickly re-destabilize central and southeast IA by later on today.  Definitely expect a nice round of convection or two after the current one overhead moves out.  Could be quite an active night.  DVN has gone with a FFW for the whole CWA, which is prob a good idea.  If there's some training of storms like what was seen last night in WI someone in the DVN  or LOT CWA may be in for a rough night lol.

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Confirmed tornado near Green Lake WI.

Quote

BULLETIN - EAS ACTIVATION REQUESTED Tornado Warning National Weather Service Milwaukee/Sullivan WI 338 PM CDT TUE AUG 28 2018 The National Weather Service in Milwaukee/Sullivan has issued a * Tornado Warning for... Southeastern Green Lake County in south central Wisconsin... Northwestern Fond du Lac County in east central Wisconsin... * Until 415 PM CDT. * At 337 PM CDT, a confirmed tornado was located near Green Lake, or 8 miles southwest of Ripon, moving east at 35 mph. HAZARD...Damaging tornado and quarter size hail. SOURCE...Public confirmed tornado. A tornado was reported near Green Lake. There has been considerable wind damage reported with this storm. IMPACT...Flying debris will be dangerous to those caught without shelter. Mobile homes will be damaged or destroyed. Damage to roofs, windows, and vehicles will occur. Tree damage is likely. * Locations impacted include... Ripon, North Fond Du Lac, Markesan, Rosendale, Green Lake, Brandon, Lamartine, Alto, Manchester, Fairwater, West Rosendale and Lagoda.

 

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That eastern IA line does look formidable.  Also concerned about discrete cells popping up ahead of it as shear and helicity move eastward into Illinois.  Derecho composite up to 8 and meso discussion out for strong winds for the next few hours from that line,.  Warning update for 80 mph gusts with that line near Iowa City eastward now.

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MESOSCALE DISCUSSION 1383  
NWS STORM PREDICTION CENTER NORMAN OK  
0607 PM CDT TUE AUG 28 2018  
  
AREAS AFFECTED...EAST CENTRAL IOWA FROM JOHNSON THROUGH SCOTT AND  
CLINTON COUNTIES.  
  
CONCERNING...SEVERE THUNDERSTORM WATCH 357...  
  
VALID 282307Z - 290000Z  
  
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 357  
CONTINUES.  
  
SUMMARY...A NARROW CORRIDOR OF STRONG DAMAGING WINDS AND POTENTIAL  
LINE EMBEDDED TORNADOES EXISTS FOR THE NEXT HOUR ACROSS JOHNSON AND  
WASHINGTON COUNTIES IN IOWA.  
  
DISCUSSION...A STRONG BOWING SEGMENT HAS DEVELOPED IN EAST CENTRAL  
IOWA WHERE THE LINE HAS INTERACTED WITH THE OUTFLOW BOUNDARY FROM  
EARLIER CONVECTION AND IS MOVING TOWARD IOWA CITY. A SHARP  
REFLECTIVITY GRADIENT AND A DEVELOPING REAR INFLOW JET SUGGEST THIS  
BOWING SEGMENT MAY BE PRODUCING SIGNIFICANTLY STRONG WIND GUSTS.  
CURRENT LOWEST TILT WIND SPEEDS IN THE APEX OF THIS BOW ARE MEASURED  
AROUND 85 KNOTS PER BOTH THE DMX AND DVN 88D. THESE WIND SPEEDS ARE  
BEING MEASURED AROUND 6000 FEET IN THE STORM, BUT STILL REPRESENT  
THE AREA OF GREATEST WIND SPEED. WIND GUSTS WERE MEASURED AT 68 MPH  
SOUTH OF THE APEX OF THIS BOW WHERE MEASURED WIND SPEEDS ARE MUCH  
LESS AND THE REFLECTIVITY STRUCTURE IS NOT AS ORGANIZED. THEREFORE,  
WOULD EXPECT THAT SURFACE WIND SPEEDS MAY BE IN EXCESS OF 80 MPH ON  
THE APEX OF THIS BOW. IN ADDITION, A LARGE MESOVORTEX HAS FORMED ON  
THE NORTHERN EDGE OF THIS BOWING SEGMENT. THIS VORTEX WILL LEAD TO  
THE POSSIBILITY OF A NARROW SWATH OF EVEN STRONGER WINDS AND EVEN A  
FEW TORNADOES.  SIGNIFICANT WIND DAMAGE MAY BE POSSIBLE ACROSS  
JOHNSON COUNTY, IOWA AND COULD PERSIST AS FAR EAST AS QUAD CITIES.  

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40 minutes ago, Indystorm said:

Look out Cyclone.  Tor warning just across the river from you in IA moving ne.  Radar confirmed near Grand Mound

That was the best storm here in quite a long time.  Incredible multi-tiered gust front, with the lower clouds practically scraping the earth as it marched in very quickly.  Had a period of 50-60mph winds and blinding rain.  Rain gauge says we got a little under a half inch, but I'm guessing quite a bit of it blew over the rain funnel lol.  

The growing concern now is the convection in southern IA/northern MO.  The LLJ is going to feed those puppies all night, so where the storms eventually align is going to be in for a lot of rain.  Still too early to tell where that will set up exactly, but it looks like southeast IA up towards the 80 corridor east of the QC.

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