Jul 28, 2017 1630 UTC Day 1 Convective Outlook
Updated: Fri Jul 28 16:30:45 UTC 2017 (20170728 1630Z Day 1 shapefile | 20170728 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170728 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 471,569 59,952,875 Dallas, TX...Baltimore, MD...Charlotte, NC...Washington, DC...Nashville, TN...
Probabilistic Tornado Graphic
20170728 1630 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 % 27,704 7,572,975 Baltimore, MD...Raleigh, NC...Norfolk, VA...Chesapeake, VA...Richmond, VA...
Probabilistic Damaging Wind Graphic
20170728 1630 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 % 471,450 59,831,560 Dallas, TX...Baltimore, MD...Charlotte, NC...Washington, DC...Nashville, TN...
Probabilistic Large Hail Graphic
20170728 1630 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 % 72,241 431,488 Rapid City, SD...Scottsbluff, NE...Sterling, CO...Fort Morgan, CO...Spearfish, SD...
   SPC AC 281630

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 AM CDT Fri Jul 28 2017

   Valid 281630Z - 291200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   INTO TONIGHT FOR THE MID ATLANTIC TO THE GULF STATES AND RED RIVER
   VALLEY OF TX/OK...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS
   AFTERNOON/EVENING FOR PARTS OF THE HIGH PLAINS...

   ...SUMMARY...
   Thunderstorms associated with marginally severe wind gusts will be
   possible today from the Ohio and Tennessee Valleys eastward into the
   Mid-Atlantic, and westward to the Red River Valley of Texas and
   Oklahoma. A few storms with marginally severe hail and strong wind
   gusts will also be possible across parts of the central and northern
   High Plains.

   ...Mid Atlantic to Gulf states and Red River Valley of TX/OK...
   A midlevel shortwave trough over MI this morning will dig
   southeastward to the Appalachians by tonight, with downstream
   cyclogenesis expected in the vicinity of the VA Tidewater region by
   early Saturday.  An associated surface cold front will progress
   southward across the OH/TN Valleys and the southern Plains in
   response to anticyclogenesis in the wake of the MI midlevel trough.

   Relatively widespread/thick cloud cover will tend to limit surface
   heating from the northern Gulf coast states to the Mid Atlantic in
   advance of the front, and regional 12z soundings revealed poor
   midlevel lapse rates of only 5.5-6 C/km within this broad band of
   clouds.  Thus, both buoyancy and downdraft potential will tend to be
   limited ahead of the front (other than within smaller-scale cloud
   breaks), and only isolated strong outflow winds are expected.  There
   will be some increase in deep-layer vertical shear across VA/NC with
   the approach of the midlevel trough by this evening, and perhaps a
   modest increase in low-level hodograph curvature in conjunction with
   cyclogenesis.  This combined with moist profiles could support a
   low-end threat for a tornado, but the overall severe-storm risk
   should remain marginal.

   Stronger surface heating is expected this afternoon from the central
   Gulf coast states into the Carolinas, along and south-southeast of
   the thicker cloud band.  Here, isolated strong downburst winds will
   be possible with largely diurnal storms along the differential
   heating zone and/or a pre-frontal trough into the Carolinas.  The 5%
   wind/MRGL area has also been extended westward to the Red River
   Valley of TX/OK to reflect the potential for isolated strong
   downburst winds this afternoon, where hot afternoon
   temperatures/steep low-level lapse rates impinge on the differential
   heating zone/surface cold front.

   ...High Plains this afternoon/evening...
   A series of embedded speed maxima will eject east-southeastward over
   the High Plains, around the northern periphery of the lingering
   southern Rockies ridge.  Lapse rates have been reduced within the
   persistent monsoonal convective plume, though surface heating and
   boundary layer dewpoints in the 60s in southeasterly low-level flow
   will contribute to weak-moderate buoyancy this afternoon.  A few
   storms will likely form this afternoon and move southeastward
   through the evening, and the mesoscale environment should favor some
   supercell structures with a marginal hail/wind threat.

   ..Thompson/Dial.. 07/28/2017

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