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July 15-20 Severe weather


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

day1probotlk_1200_torn.gif.3dd2ed1b6368c2dd16bb3bdad91eeb41.gif

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 ...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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