Skip Navigation Links 
NOAA logo-Select to go to the NOAA homepage NOAA's National Weather Service   Select to go to the NWS homepage
Storm Prediction Center
navigation bar left  
  navigation bar end cap is the U.S. Government's official Web portal to all Federal, state and local government Web resources and services.

Mesoscale Discussion 1339
< Previous MD         Next MD >
MD 1339 graphic

   Mesoscale Discussion 1339
   NWS Storm Prediction Center Norman OK
   0219 PM CDT Tue Jul 18 2017

   Areas affected...Far northern Iowa...southeastern Minnesota...much
   of Wisconsin...and the Upper Peninsula of Michigan

   Concerning...Severe potential...Watch possible 

   Valid 181919Z - 182115Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Convective coverage is increasing across the region, and
   is expected to continue to do so over the next two to three hours. 
   At least an isolated severe hail/wind threat will exist with this
   activity.  A WW may be considered for parts of the area pending
   convective trends.

   DISCUSSION...Convection continues to increase across the region, and
   this increase is likely aided by forcing for ascent associated with
   a mid-level shortwave approaching northern portions of the
   discussion area in conjunction with an approaching surface cold
   front.  Ahead of the front, surface temperatures have reached the
   upper 80s in a few areas amidst a broken mid-level cloud deck from
   Iowa into western Wisconsin - with a moderately unstable airmass in
   place (MUCAPE around 2000 J/kg).  Storms so far have been sub-severe
   and have struggled to organize especially across southeastern
   Minnesota where surface heating has been stunted some by the
   aforementioned cloud deck.  Storms in the U.P. of Michigan (west of
   Marquette) will pose a near-term threat for hail and gusty winds,
   although this activity is somewhat displaced from stronger
   instability to the southwest.

   Latest thinking is that storms will continue to gradually increase
   in intensity and coverage - especially across northern Wisconsin as
   that area resides nearer to mid/upper forcing attendant to the
   shortwave trough.  At least an isolated threat for severe wind and
   hail will exist with this activity, although there is considerable
   uncertainty regarding the extent of the severe threat and whether a
   severe thunderstorm watch will be needed.  Convective trends will
   continue to be monitored.

   ..Cook/Hart.. 07/18/2017

   ...Please see for graphic product...


   LAT...LON   46199023 46538960 46818859 46798746 46768683 46588576
               46248550 45728597 44988690 44898697 44308803 43628991
               43069213 42829417 42879460 43309456 43719384 44269256
               45079150 45779057 46199023 

Top/All Mesoscale Discussions/Forecast Products/Home
Weather Topics:
Watches, Mesoscale Discussions, Outlooks, Fire Weather, All Products, Contact Us

NOAA / National Weather Service
National Centers for Environmental Prediction
Storm Prediction Center
120 David L. Boren Blvd.
Norman, OK 73072 U.S.A.
Page last modified: July 18, 2017
Information Quality
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities