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Minnesota_storms

July 15-20 Severe weather

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Some scattered severe storms yesterday and today across the upper midwest. Tomorrow could be huge in Minnesota if morning convection doesn't interfere and the cap breaks. So far the SPC only has a slight risk. The models are going crazy.

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Tomorrow looks to be a tornado outbreak in Minnesota and Wisconsin.

day1probotlk_1200_torn.gif.3dd2ed1b6368c2dd16bb3bdad91eeb41.gif

Quote
 ...Upper Midwest...Upper Great Lakes...
   Showers and isolated thunderstorms will likely be ongoing at the
   beginning of the period over portions of the Upper Great Lakes,
   supported by a modest low-level jet. These showers and thunderstorms
   are expected to dissipate by the early morning as the low-level jet
   weakens. 

   A very moist air mass is currently in place over the Upper
   Midwest/Upper Great Lakes, with even better moisture upstream across
   the Middle MS Valley. This air mass will remain over the region
   today with some modest moist advection possible. As a result,
   dewpoints are expected to be mid to upper 70s across a large portion
   of the Upper Midwest and Upper Great Lakes. Dewpoints around 80 may
   be realized across southern MN near a weak surface low. Surface
   temperatures are also expected to climb into the 90s as the boundary
   layer mixes. These very warm and moist conditions will exist beneath
   relatively cool mid-level temperatures, resulting in very steep
   (i.e. 8-8.5 deg C per km) mid-level lapse rates. As a result, an
   extremely buoyant thermodynamic environment (i.e. 4000+ J/kg of
   MLCAPE) will be in place. Highest buoyancy will likely occur across
   northern IA, southern MN, and west-central WI. In these areas MLCAPE
   could exceed 6000 J/kg this afternoon and evening. 

   In addition to this extreme buoyancy, seasonally strong westerly
   flow aloft will extend from the northern High Plains through Upper
   MI. Generally southerly low-level flow beneath these westerlies
   results in effective bulk shear values of 45-55 kt across much of MN
   and northern WI today afternoon and evening. 

 

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47 minutes ago, mob1 said:

Upgraded to Moderate and they introduced a 15 percent TOR contour. 

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0736 AM CDT Fri Jul 19 2019

   Valid 191300Z - 201200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS EAST-CENTRAL MN
   AND NORTHERN WI...

   ...SUMMARY...
   A regional outbreak of severe thunderstorms with strong tornadoes
   and potentially widespread significant wind damage may occur from
   central Minnesota across northern Wisconsin during the mid-afternoon
   to evening.

   ...Upper Midwest/Great Lakes...
   Upgrading to Moderate Risk this outlook for the potential threats of
   multiple strong tornadoes and a derecho later this afternoon and
   evening. CAPE/shear/SRH parameter space in this region is forecast
   to be exceptionally rare for mid July amid a predominately zonal
   flow regime across the northern states.

   A convective cluster is ongoing across north-central SD aided by
   warm/moist advection around 700 mb along a pronounced baroclinic
   zone. 00Z CAM guidance had a decent handle on this activity earlier
   this morning and are consistent with a decaying trend through late
   morning as advection shifts east amid pronounced MLCIN as sampled by
   the 12Z Aberdeen sounding. There is a low confidence scenario that a
   strong enough cold pool is becoming established with this early-day
   cluster such that total decay does not occur. If this occurs, robust
   boundary-layer heating downstream may be sufficient for an
   increasing threat during the afternoon of strong to severe wind
   gusts. This could still yield a scattered to widespread damaging
   wind scenario, albeit in an earlier time frame than progged by
   guidance.

   The more probable scenario is for an extremely unstable air mass
   (MLCAPE > 4000 J/kg) to become established to from southeast SD
   through central/southern WI as the elevated mixed-layer overspreads
   surface dew points rising into the mid to upper 70s. A surface
   cyclone over central SD should track towards the Twin Cities through
   early evening. Strong low-level convergence near/northeast of this
   cyclone along the warm front should sustain surface-based storm
   development across central into east-central MN. Once initiation
   occurs, intense supercells will develop rapidly, with an attendant
   threat for all severe hazards including strong tornadoes amid 50-60
   kt effective shear and 0-3 km SRH > 300 m2/s2. The very warm/moist
   thermodynamic profiles will also support generation of strong cold
   pools which should eventually yield a bowing, forward-propagating
   MCS across northern WI into parts of northern Lower and Upper MI.
   Strength of the vertical shear suggests the potential for intense
   bowing segments capable of yielding a derecho with significant
   severe wind gusts.

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Amazing soundings for any time of year, let alone mid July.  Going to be a dangerous situation for MN and WI later today if that first complex this morning decays as expected and these parameters verify this afternoon and evening.

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