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.
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.)
Some Larger Population Centers in Risk Area
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...
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
...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.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z