Jul 6, 2017 2000 UTC Day 1 Convective Outlook
Updated: Thu Jul 6 20:03:37 UTC 2017 (20170706 2000Z Day 1 shapefile | 20170706 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170706 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 52,709 3,151,662 Green Bay, WI...Appleton, WI...Oshkosh, WI...La Crosse, WI...Sheboygan, WI...
SLIGHT 140,167 15,369,981 Charlotte, NC...Milwaukee, WI...Raleigh, NC...Madison, WI...Grand Rapids, MI...
MARGINAL 414,766 53,903,861 Chicago, IL...Memphis, TN...Washington, DC...Nashville, TN...Virginia Beach, VA...
Probabilistic Tornado Graphic
20170706 2000 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
2 % 163,365 9,520,151 Milwaukee, WI...St. Paul, MN...Madison, WI...Rockford, IL...Cedar Rapids, IA...
Probabilistic Damaging Wind Graphic
20170706 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
30 % 52,759 3,249,067 Green Bay, WI...Appleton, WI...Oshkosh, WI...La Crosse, WI...Sheboygan, WI...
15 % 139,644 15,189,274 Charlotte, NC...Milwaukee, WI...Raleigh, NC...Madison, WI...Grand Rapids, MI...
5 % 415,630 53,800,129 Chicago, IL...Memphis, TN...Washington, DC...Nashville, TN...Virginia Beach, VA...
Probabilistic Large Hail Graphic
20170706 2000 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 27,775 1,993,455 Green Bay, WI...Appleton, WI...Oshkosh, WI...La Crosse, WI...Fond du Lac, WI...
30 % 30,231 2,240,944 Green Bay, WI...Appleton, WI...Oshkosh, WI...La Crosse, WI...Fond du Lac, WI...
15 % 102,756 5,537,386 Milwaukee, WI...Madison, WI...Rockford, IL...Rochester, MN...Racine, WI...
5 % 179,768 15,925,352 Chicago, IL...Minneapolis, MN...St. Paul, MN...Grand Rapids, MI...Des Moines, IA...
   SPC AC 062003

   Day 1 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0303 PM CDT Thu Jul 06 2017

   Valid 062000Z - 071200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
   WISCONSIN AND NORTHERN LOWER MICHIGAN...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENHANCED RISK ACROSS MUCH OF THE WESTERN AND CENTRAL GREAT LAKES
   REGION...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
   CAROLINAS PIEDMONT SOUTHWESTWARD INTO NORTHERN GEORGIA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK ACROSS MUCH OF THE WESTERN AND CENTRAL GREAT LAKES
   REGION...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
   ARKLAMISS NORTHEASTWARD TO THE CAROLINAS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS A PORTION
   OF THE ROCKIES AND INTO THE CENTRAL HIGH PLAINS...

   CORRECTED FOR NDFD GRID ERROR

   ...SUMMARY...
   Severe storms with a threat for large hail and damaging wind are
   expected from a portion of the upper Mississippi Valley into the
   Great Lakes today.  Other storms with locally damaging wind gusts
   are possible from the Tennessee Valley to North Carolina and
   Virginia Thursday afternoon.  An isolated severe hail/wind threat
   also extends from southern Nebraska to eastern Wyoming, northeastern
   Colorado, and southeast Montana.

   ...Synopsis...
   The overall forecast philosophy from the 1630Z outlook is generally
   on track, although with a few changes:

   1) A couple of linear segments have organized across northern
   Georgia, and at least one of these segments has produced localized
   wind damage.  This threat will persist into upstate South Carolina a
   bit south of areas indicated by previous guidance, and there are
   some indications that this threat will persist even farther
   downstream into central North Carolina through sunset.  5%/marginal
   probabilities have been expanded, and a slight risk has been
   introduced across the Carolinas Piedmont into northern Georgia with
   the expectation that scattered wind damage/severe wind gusts will
   occur in these areas.

   2) A cluster of storms has developed just northwest of the Arrowhead
   of Minnesota, and a cumulus field has increase in satellite to the
   southwest of these storms and very near a surface trough migrating
   through that region.  Latest high-resolution guidance suggests that
   storms may initiate in northeastern Minnesota and spread
   southeastward into a moderately unstable environment with 40+ knots
   of deep shear.  Given the latest trends, 5%/marginal probabilities
   for wind and hail have been added to northeastern Minnesota, and
   higher probabilities are retained downstream despite some concerns
   about eventual convective coverage through the evening.  2% tornado
   probabilities have also been expanded northwestward as an isolated
   tornado cannot be ruled out in areas downstream of initial
   development in northeastern Minnesota.

   ..Cook.. 07/06/2017

   .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Jul 06 2017/

   ...Upper MS Valley and western Great Lakes...
   This morning's water vapor loop shows a shortwave trough moving
   across the MN Arrowhead.  This feature will continue southwestward
   this afternoon and aid in the development of afternoon thunderstorms
   over parts of MN/WI/MI.  Surface dewpoints in the mid/upper 60s and
   strong heating will combine with steep mid level lapse rates to
   yield strong CAPE values this afternoon.  Forecast soundings also
   show strengthening wind fields through the day, with effective shear
   becoming favorable for supercell and bowing structures.  12z CAM
   solutions lack consistency in the location/timing of initiation, but
   generally agree that intense storms will affect the region later
   today.  Large (potentially very large) hail and damaging winds are
   the main threats, with some concern for upscale growth and more
   widespread wind damage this evening as storms move across the ENH
   area.

   ...Gulf Coast states into Mid Atlantic...
   Visible satellite imagery suggests strong heating will occur across
   a broad corridor from MS to VA today, with low and mid level wind
   fields slightly stronger than yesterday.  It appears likely that
   pockets of strong instability will develop, promoting scattered
   afternoon thunderstorms.  Larger-scale forcing mechanisms are hard
   to find, but eventually this region will likely see multiple
   clusters of storms capable of locally gusty/damaging wind gusts.  If
   these mesoscale areas of greater risk can be identified later today,
   portions of this corridor will be considered for an upgrade to SLGT
   risk.

   ...MT into NE...
   Widely scattered thunderstorms are expected this afternoon over the
   northern and central High Plains region, on the east side of a
   developing upper ridge.  The strongest cells in this area may
   produce hail and gusty winds for a few hours this evening.

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