Tim from Springfield (IL) Posted July 4, 2017 Share Posted July 4, 2017 SPC already has a Day 3 Enhanced for WI, with much of IA, MN, and NW IL under a Slight, on Thursday: http://www.spc.noaa.gov/products/outlook/day3otlk.html ...Upper Mississippi Valley into the Great Lakes... Richer low-level moisture with upper 60s to near 70 F dewpoints resulting from both evapotranspiration and advection will reside in pre-frontal warm sector. Meanwhile plume of steeper mid-level lapse rates will advect into this region, contributing to moderate to strong instability as the boundary layer destabilizes during the day with MLCAPE approaching 3000 J/kg. Winds aloft will strengthen with amplification of the northern stream trough. Southwesterly low-level winds veering to west and northwesterly with height will further augment vertical shear with 0-6 km magnitudes of 40-50 kt. Destabilization and forcing for ascent accompanying the southeast-advancing shortwave trough should contribute to thunderstorm initiation by early afternoon over the upper MS valley region, and this activity will subsequently develop southeastward into the evening and overnight. Organized storms including supercells and bowing line segments are likely with large hail and damaging wind the primary threats. Link to comment Share on other sites More sharing options...
Tim from Springfield (IL) Posted July 4, 2017 Author Share Posted July 4, 2017 SPC also not ruling out severe for Friday in the OV: http://www.spc.noaa.gov/products/exper/day4-8/ Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0414 AM CDT Tue Jul 04 2017 Valid 071200Z - 121200Z ...DISCUSSION... Model consensus is that the synoptic upper trough will amplify over the eastern U.S. with an upstream ridge persisting in the west at least through day 7. Several shortwave troughs embedded within the eastern U.S. trough will move through the Ohio Valley and Northeast States. The amplifying upper trough will be associated with a cold front that will move through the Northeast States and Ohio Valley day 4 (Friday) and the Mid Atlantic and Southeast States day 5 (Saturday) where it will stall. A moist, pre-frontal warm sector will support moderate instability, and some threat for severe storms will exist Friday from the Ohio Valley into the Northeast U.S., shifting into the Mid Atlantic and Southeast States Saturday. At this time too much uncertainty exists regarding timing of cold front and effects of any ongoing convection on warm-sector destabilization to introduce a categorical risk area. ..Dial.. 07/04/2017 And SPC isn't ruling out tomorrow's marginal in parts of the sub to go slight: http://www.spc.noaa.gov/products/outlook/day2otlk.html ...Northern Plains through upper Mississippi Valley and Great Lakes... Richer low-level moisture with mid to upper 60s F dewpoints will advect into this region, contributing to potential for moderate instability. A weak front or surface trough will advance through MN and Wi during the day in association with a weak, low-amplitude shortwave trough. Storms may redevelop along this boundary during the afternoon, primarily from IA into WI and the Upper Peninsula of MI. This region will reside along the southern fringe of modest winds aloft, and vertical shear will remain less than 35 KT supportive of multicells. A few of the storms may become capable of producing strong wind gusts from late afternoon through early evening. Farther upstream, some potential will exist for a few storms to develop within zone of deeper mixing in vicinity of a pre-frontal trough across western ND during the afternoon. Other storms may develop overnight within pre-frontal warm advection regime and spread into northern MN. Storms in these areas will be embedded within stronger winds aloft supporting some potential for organization. However, considerable uncertainty persists regarding storm coverage. Will maintain marginal risk category for now, but this region will continue to be monitored for a possible slight risk in later updates. Link to comment Share on other sites More sharing options...
bjc0303 Posted July 4, 2017 Share Posted July 4, 2017 Was shocked when SPC didn't include a risk area for Thursday on their 4-8 outlook. This looks like a mixed mode event. Strong supercells with very large hail, some tornadoes (possibly strong) mixed in with bowing segments, especially near the effective/warm front. Link to comment Share on other sites More sharing options...
snowlover2 Posted July 4, 2017 Share Posted July 4, 2017 42 minutes ago, bjc0303 said: Was shocked when SPC didn't include a risk area for Thursday on their 4-8 outlook. This looks like a mixed mode event. Strong supercells with very large hail, some tornadoes (possibly strong) mixed in with bowing segments, especially near the effective/warm front. Thursday would be the day 3 outlook. Link to comment Share on other sites More sharing options...
Hoosier Posted July 4, 2017 Share Posted July 4, 2017 Just now, snowlover2 said: Thursday would be the day 3 outlook. I think he was meaning yesterday's day 4-8 outlook, as Thursday would've been day 4 and there was no area outlined. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted July 5, 2017 Share Posted July 5, 2017 3KM is nasty for parts of MN, IA and west-central WI. Considering trying to get Friday off so my chase range isn't limited by having to be back by 3AM and then working on no sleep. Link to comment Share on other sites More sharing options...
Chinook Posted July 5, 2017 Share Posted July 5, 2017 This is the HRW-NMMB for Thursday evening. It's one of a few possible solutions that show severe thunderstorms generally in MN/WI, similar to the SPC day-3 enhanced risk, (issued 7/4.) Chance of thunderstorms/severe weather in Ohio may be of interest to a few people on this board, even though it isn't related to the MN/WI risk area. Link to comment Share on other sites More sharing options...
IllinoisWedges Posted July 5, 2017 Share Posted July 5, 2017 Am I one of the only ones not seeing an insane event for Thursday? If so, please do explain to me why it looks different than every other typical event so far this year. Link to comment Share on other sites More sharing options...
Quincy Posted July 5, 2017 Share Posted July 5, 2017 7 hours ago, IllinoisWedges said: Am I one of the only ones not seeing an insane event for Thursday? If so, please do explain to me why it looks different than every other typical event so far this year. It doesn't look like anything crazy. A cold front drops through from the northwest. Given rich boundary layer moisture and strong heating supporting upwards of 2000-3000 J/kg MLCAPE, veering winds with height (SW near the surface to NW at 500mb) and more than adequate deep layer shear magnitudes, large hail and damaging winds seem likely with initial discrete/semi-discrete supercells. Convective evolution with time is a bit unclear. While upscale growth into a linear system would "enhance" a damaging wind threat, most of the short range guidance seems to favor more of a broken band of storms. If this does happen, one couldn't rule out an isolated tornado threat by early evening. Still, if there is a tornado or two on a northwest flow day with large CAPE and ample shear in July in the upper Midwest, that's nothing unusual at all. Link to comment Share on other sites More sharing options...
Tim from Springfield (IL) Posted July 5, 2017 Author Share Posted July 5, 2017 So far SPC just has a marginal along the OV (including most of OH, SE 2/3 IN, and S IL) for Friday on their D3 outlook this morning. A slight could be forthcoming for Friday perhaps as early as tomorrow's first Day 2 outlook. http://www.spc.noaa.gov/products/outlook/day3otlk.html ...Ohio Valley area... A moist pre-frontal warm sector with dewpoints in the upper 60s to around 70F will reside across the OH Valley into a portion of the Northeast States. Destabilization of the boundary layer will result in moderate instability in the presence of modest mid-level lapse rates. At least a modest increase in deep-layer winds is expected with 30-40 kt unidirectional westerly between 2-6 km. A significant upper speed max is forecast to move southeast into the Great Lakes and Ohio Valley region, but this feature will remain post frontal. Nevertheless...storms should redevelop within the weakly capped warm sector and along the southeast advancing cold front during the afternoon. Vertical shear from 25-35 kt will support primarily multicells with storms evolving into clusters and line segments. A few strong to damaging wind gusts will be possible through early evening. Trends will continue to be monitored for a possible slight risk in later updates. Link to comment Share on other sites More sharing options...
Tim from Springfield (IL) Posted July 5, 2017 Author Share Posted July 5, 2017 BTW, the latest D1 just came out a half-hour ago--still has a small slight risk for central MN, and now a larger strip of NE ND. Brief tornadoes can't be ruled out: http://www.spc.noaa.gov/products/outlook/day1otlk.html ...ND/MN... The primary band of westerlies is across Canada today, with the southern fringe of stronger flow aloft over portions of ND/MN/WI. Full sunshine is occurring in this region, with dewpoints in the mid 60s to lower 70s yielding afternoon MLCAPE values over 3000 J/kg. Forcing for ascent is weak, and water vapor loop suggests only subtle upstream features that might aid in convective initiation. This suggests that overall coverage of storms will be low. Nevertheless, forecast soundings show thermodynamic and shear parameters favorable for organized/supercell storms later today. Large hail is likely the main threat, as storms may remain isolated and maintain discrete mode. However, damaging winds or a brief tornado cannot be ruled out. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted July 5, 2017 Share Posted July 5, 2017 4 hours ago, Quincy said: ...a tornado or two on a northwest flow day with large CAPE and ample shear in July in the upper Midwest, that's nothing unusual at all. This. These are also the kind of days where a higher-impact event can sneak up on you in this time of year/region of the country if everything pans out just right (or wrong, depending on your perspective). Here I'm thinking of days like Oakfield, Plainfield, Roanoke, June 23, 2004 (17 tornadoes in WI including two F3s, one of them killer), and August 18, 2005 (record-setting 27 tornadoes in WI including killer F3). Not saying something like that appears likely tomorrow based on current model progs, but history shows it's one of those days to keep an eye on. Link to comment Share on other sites More sharing options...
Jim Martin Posted July 6, 2017 Share Posted July 6, 2017 66 MPH wind tonight near Monticello, Iowa with severe thunderstorm moving through. Link to comment Share on other sites More sharing options...
Quincy Posted July 6, 2017 Share Posted July 6, 2017 11 hours ago, CheeselandSkies said: This. These are also the kind of days where a higher-impact event can sneak up on you in this time of year/region of the country if everything pans out just right (or wrong, depending on your perspective). Here I'm thinking of days like Oakfield, Plainfield, Roanoke, June 23, 2004 (17 tornadoes in WI including two F3s, one of them killer), and August 18, 2005 (record-setting 27 tornadoes in WI including killer F3). Not saying something like that appears likely tomorrow based on current model progs, but history shows it's one of those days to keep an eye on. Upon deeper investigation of today's threat, analogs feature quite a bit of severe events from southern MN/IA into WI. Along with about 1/3 of analogs producing one or more tornadoes in the northern IA vicinity, 7/6/14 can be identified as a close analog to the expected environment later today. General similarities can be seen in the upper levels, with fairly close matches in the sfc-3km layer, including capping, frontal placement and low level shear. That event produced numerous weak tornadoes in Iowa, along with a couple of longer-lived, destructive ones. The 00z 7/7/14 DVN sounding is very similar to forecast soundings across central IA around 00z Friday. Convective evolution looks similar to what is expected tomorrow as well. Isolated storm coverage with concerns about longevity of storms, given relatively warm 800-700mb temperatures. Even the SPC day 1 discussions from 7/6/14 sound similar to what's being said this time around. Iowa is a fickle state, but today's event could very well be a bit sneaky. Isolated storm coverage, favorable shear (speed, directional and orientation with respect to the cold front). Early day convection doesn't appear to be a big concern and even if there was any, it would probably be minimal and could locally enhance the severe threat, were outflow boundaries to be evident. While capping may delay convective initiation until after 22z, forecast soundings in the immediate prefrontal warm sector show little to no remaining MLCIN by 23-00z. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted July 6, 2017 Share Posted July 6, 2017 HRRR has been all over the place but latest run is not encouraging for central and southern WI (or IA/SE MN) seeing anything of significance. Satellite does show some outflow boundaries in the latter area so will continue to monitor. 12Z 3KM NAM meanwhile was much more bullish on convective coverage and intensity. Link to comment Share on other sites More sharing options...
Quincy Posted July 6, 2017 Share Posted July 6, 2017 57 minutes ago, CheeselandSkies said: HRRR has been all over the place but latest run is not encouraging for central and southern WI (or IA/SE MN) seeing anything of significance. Satellite does show some outflow boundaries in the latter area so will continue to monitor. 12Z 3KM NAM meanwhile was much more bullish on convective coverage and intensity. It's definitely an odd (or at least unclear) setup. All guidance has been highly variable, from NCAR ensembles to HopWRF, HRRR, 3km NAM, etc. The trend has been for already (progged) minimal large scale forcing to be even more nebulous. Forecast soundings don't show a significant cap, yet convective temperatures appear out of reach for most of the warm sector. The final evolution may very well include a few cells trying to go up in WI, while more robust activity is delayed until after 01-02z, but as nocturnal cooling takes place, the window for severe could be quite limited. An already conditional threat becomes even more unlikely with westward extent across Iowa, despite a seemingly favorable CAPE/shear overlay. Negligible forcing will likely be a large limiting factor. Link to comment Share on other sites More sharing options...
Indystorm Posted July 6, 2017 Share Posted July 6, 2017 Cell forming se of Stevens Point WI. Meso discussion out. Maybe the start of something. Link to comment Share on other sites More sharing options...
Indystorm Posted July 6, 2017 Share Posted July 6, 2017 Svr watch issued for ne WI and western UP. Bit farther north than I expected initially. Link to comment Share on other sites More sharing options...
Jim Martin Posted July 7, 2017 Share Posted July 7, 2017 Dangerous supercell thunderstorm tonight near Friendship, Wisconsin. Movement is southeast. Link to comment Share on other sites More sharing options...
Jim Martin Posted July 7, 2017 Share Posted July 7, 2017 Tonight's 0z NAM having all of the Lower Great Lakes in play for a severe weather risk on Friday. Attached sounding is for the Findlay area at 21z on Friday. Link to comment Share on other sites More sharing options...
Hoosier Posted July 7, 2017 Share Posted July 7, 2017 Still have a couple warned cells in WI but a bit of a lackluster day overall. Link to comment Share on other sites More sharing options...
Stebo Posted July 7, 2017 Share Posted July 7, 2017 A cell heading this way just went warned. Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted July 7, 2017 Share Posted July 7, 2017 New Day One has a substantial expansion of the Slight and Marginal Link to comment Share on other sites More sharing options...
Stebo Posted July 7, 2017 Share Posted July 7, 2017 Mesonet at the shore near Grand Haven measured 91mph. Now you are talking there. Link to comment Share on other sites More sharing options...
outflow Posted July 7, 2017 Share Posted July 7, 2017 C man station west of grand haven gusted to 91mph Link to comment Share on other sites More sharing options...
Stebo Posted July 7, 2017 Share Posted July 7, 2017 59 mph gust at GRR. Link to comment Share on other sites More sharing options...
snowlover2 Posted July 7, 2017 Share Posted July 7, 2017 Enhanced area added to SE IN/SW OH and a watch is already in place. Link to comment Share on other sites More sharing options...
Indystorm Posted July 7, 2017 Share Posted July 7, 2017 Looks like a possible mini bow could be forming and aiming for Wabash and Huntington counties this noon EDT. But as new SPC meso disc stated we may have to wait till later for increased svr wind potential. Link to comment Share on other sites More sharing options...
Indystorm Posted July 7, 2017 Share Posted July 7, 2017 I would anticipate a new watch being issued west and south of the current watch as outflow moves westward and current svr cells in nw In continue to strengthen. Link to comment Share on other sites More sharing options...
Hoosier Posted July 7, 2017 Share Posted July 7, 2017 23 minutes ago, Indystorm said: I would anticipate a new watch being issued west and south of the current watch as outflow moves westward and current svr cells in nw In continue to strengthen. Severe cell skirted just to my south with hail. From what I could tell, no hail where I am. Link to comment Share on other sites More sharing options...
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