janetjanet998 Posted August 27, 2018 Share Posted August 27, 2018 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. Link to comment Share on other sites More sharing options...
Chinook Posted August 27, 2018 Share Posted August 27, 2018 This is one of the nastier squall lines I've seen on convection-allowing models in a while. The SPC has an enhanced risk today, which seems appropriate. On the other hand, yesterday's enhanced risk didn't verify. Link to comment Share on other sites More sharing options...
Santa Claus Posted August 27, 2018 Share Posted August 27, 2018 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! Link to comment Share on other sites More sharing options...
wisconsinwx Posted August 28, 2018 Share Posted August 28, 2018 The southern part of that line from La Crosse to Ottumwa looks like it is wanting to turn right; if so, many of the same areas that got thrashed with heavy rain and some severe last night may get clipped again. Link to comment Share on other sites More sharing options...
RyanDe680 Posted August 28, 2018 Share Posted August 28, 2018 3 replies on a decent opportunity for weather today... shows how much we've all given up Link to comment Share on other sites More sharing options...
Stebo Posted August 28, 2018 Share Posted August 28, 2018 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. Link to comment Share on other sites More sharing options...
RyanDe680 Posted August 28, 2018 Share Posted August 28, 2018 That and I think there's convection too far south already in IA/IL thats going to dampen the whole thing. Link to comment Share on other sites More sharing options...
snowlover2 Posted August 28, 2018 Share Posted August 28, 2018 Watch up for NE IA and southern WI. Link to comment Share on other sites More sharing options...
hawkeye_wx Posted August 28, 2018 Share Posted August 28, 2018 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. Link to comment Share on other sites More sharing options...
cyclone77 Posted August 28, 2018 Share Posted August 28, 2018 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. Link to comment Share on other sites More sharing options...
hawkeye_wx Posted August 28, 2018 Share Posted August 28, 2018 Cyclone is back! Link to comment Share on other sites More sharing options...
wisconsinwx Posted August 28, 2018 Share Posted August 28, 2018 Saukville is probably getting tired of all this storm action, not sure his plants are loving it either. That bow could do some damage north of 94. Link to comment Share on other sites More sharing options...
snowlover2 Posted August 28, 2018 Share Posted August 28, 2018 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. Link to comment Share on other sites More sharing options...
Hoosier Posted August 28, 2018 Share Posted August 28, 2018 Nice line in Iowa... looks like the worst will pass south of Cedar Rapids. Link to comment Share on other sites More sharing options...
Jackstraw Posted August 28, 2018 Share Posted August 28, 2018 Starting to get some notches on that IA line, one of them warned now. Link to comment Share on other sites More sharing options...
snowlover2 Posted August 28, 2018 Share Posted August 28, 2018 Tornado warning west of Iowa City IA. Link to comment Share on other sites More sharing options...
Santa Clause Posted August 28, 2018 Share Posted August 28, 2018 Iowa line looking very favorable for brief tornadoes. Link to comment Share on other sites More sharing options...
Jackstraw Posted August 28, 2018 Share Posted August 28, 2018 Looking a little "Derechoish" on radar. Link to comment Share on other sites More sharing options...
Indystorm Posted August 28, 2018 Share Posted August 28, 2018 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. Link to comment Share on other sites More sharing options...
janetjanet998 Posted August 28, 2018 Author Share Posted August 28, 2018 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. Link to comment Share on other sites More sharing options...
janetjanet998 Posted August 28, 2018 Author Share Posted August 28, 2018 AN 83 MPH WIND GUST WAS MEASURED AT THE IOWA CITY AIRPORT AT 628 PM. Link to comment Share on other sites More sharing options...
Chinook Posted August 28, 2018 Share Posted August 28, 2018 This radar frame definitely shows a strong, distinguishable rotation (22:50z) Link to comment Share on other sites More sharing options...
Stebo Posted August 29, 2018 Share Posted August 29, 2018 Iowa City's ASOS measured 83mph earlier when the storm passed through. Link to comment Share on other sites More sharing options...
Indystorm Posted August 29, 2018 Share Posted August 29, 2018 Look out Cyclone. Tor warning just across the river from you in IA moving ne. Radar confirmed near Grand Mound Link to comment Share on other sites More sharing options...
Stebo Posted August 29, 2018 Share Posted August 29, 2018 Was a confirmed tornado west of Gaylord as well. Warning just ended. Link to comment Share on other sites More sharing options...
snowlover2 Posted August 29, 2018 Share Posted August 29, 2018 MD out for a likely watch for the rest of northern IL. Link to comment Share on other sites More sharing options...
cyclone77 Posted August 29, 2018 Share Posted August 29, 2018 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. Link to comment Share on other sites More sharing options...
snowlover2 Posted August 29, 2018 Share Posted August 29, 2018 Tornado warning in NW IL south of Freeport. Link to comment Share on other sites More sharing options...
Stebo Posted August 29, 2018 Share Posted August 29, 2018 TW west of Alpena as well. Link to comment Share on other sites More sharing options...
Chinook Posted August 29, 2018 Share Posted August 29, 2018 KDVN radar shows 66 kt of wind along the line, above the surface. It showed similar values near Cyclone77. Link to comment Share on other sites More sharing options...
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