Jul 27, 2017 0600 UTC Day 1 Convective Outlook
Updated: Thu Jul 27 05:45:18 UTC 2017 (20170727 1200Z Day 1 shapefile | 20170727 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170727 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 468,922 91,117,363 New York, NY...Philadelphia, PA...Indianapolis, IN...Columbus, OH...Baltimore, MD...
Probabilistic Tornado Graphic
20170727 1200 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
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20170727 1200 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
5 % 468,714 91,212,271 New York, NY...Philadelphia, PA...Indianapolis, IN...Columbus, OH...Baltimore, MD...
Probabilistic Large Hail Graphic
20170727 1200 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
5 % 77,120 4,454,421 Denver, CO...Colorado Springs, CO...Aurora, CO...Lakewood, CO...Fort Collins, CO...
   SPC AC 270545

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1245 AM CDT Thu Jul 27 2017

   Valid 271200Z - 281200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE CENTRAL AND EASTERN U.S....

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE CENTRAL AND NORTHERN HIGH PLAINS...

   ...SUMMARY...
   Scattered thunderstorms will develop today from parts of the
   southern Plains east-northeastward into parts of the Northeast.
   Marginally severe wind gusts will be possible with a few of the
   stronger thunderstorms. Thunderstorms associated with hail and
   isolated strong wind gusts will also be possible across parts of the
   central and northern High Plains.

   ...Eastern U.S...
   West to northwest mid-level flow will be in place across much of the
   northern and eastern U.S. today as a shortwave trough moves across
   the Northeast. At the surface, a cold front will advance
   southeastward into the Ohio Valley and central to northern
   Appalachians as a moist airmass remains from the Carolinas to the
   Mid-Atlantic. Surface dewpoints should be in the upper 60s and lower
   70s F along this corridor resulting in pockets of moderate
   instability by afternoon. Scattered thunderstorms will develop
   during the afternoon along pre-existing boundaries and in areas that
   heat up the most.  Steep low-level lapse rates and adequate
   deep-layer shear may be enough for a marginal wind-damage threat
   mainly during the late afternoon.

   ...Southern Plains/Ozarks/Mid Mississippi Valley...
   West to northwest mid-level flow will be in place across the central
   U.S. today as a cold front advances southward into the southern
   Plains and Ozarks. Surface dewpoints along the front should be in
   the lower to mid 70s F. As surface heating takes place, a corridor
   of moderate instability should develop along the front with isolated
   thunderstorms forming during the afternoon. Although deep-layer
   shear will be on the low end, steep low-level lapse rates and
   moderate instability may be enough for a few strong wind gusts.

   ...Central and Northern High Plains...
   An upper-level ridge will be in place today across the central and
   northern High Plains. At the surface, a narrow corridor of maximized
   low-level moisture will be located from eastern Colorado to eastern
   Montana, along which the development of moderate instability will be
   possible this afternoon. Despite weak large-scale ascent, isolated
   thunderstorms may initiate along the instability axis due to
   low-level convergence and surface heating late this afternoon.
   Directional shear in the low to mid levels along with steep low to
   mid-level lapse rates may be enough for hail and marginally severe
   wind gusts with the strongest of cells.

   ..Broyles/Dean.. 07/27/2017

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z