Jul 27, 2017 1630 UTC Day 1 Convective Outlook
Updated: Thu Jul 27 16:25:39 UTC 2017 (20170727 1630Z Day 1 shapefile | 20170727 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170727 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 24,970 197,125 Cheyenne, WY...Gillette, WY...Torrington, WY...Douglas, WY...
MARGINAL 164,314 28,112,431 Philadelphia, PA...Baltimore, MD...Denver, CO...Washington, DC...Colorado Springs, CO...
Probabilistic Tornado Graphic
20170727 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 % 29,576 372,178 Greeley, CO...Cheyenne, WY...Gillette, WY...Evans, CO...Windsor, CO...
Probabilistic Damaging Wind Graphic
20170727 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 % 177,734 27,961,483 Philadelphia, PA...Baltimore, MD...Denver, CO...Washington, DC...Colorado Springs, CO...
Probabilistic Large Hail Graphic
20170727 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
15 % 24,970 197,125 Cheyenne, WY...Gillette, WY...Torrington, WY...Douglas, WY...
5 % 76,014 4,044,931 Denver, CO...Colorado Springs, CO...Aurora, CO...Lakewood, CO...Fort Collins, CO...
   SPC AC 271625

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1125 AM CDT Thu Jul 27 2017

   Valid 271630Z - 281200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EASTERN WY
   VICINITY...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS NORTHERN/CENTRAL
   HIGH PLAINS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SOUTHERN
   APPALACHIANS TO MID-ATLANTIC...

   ...SUMMARY...
   Scattered large hail and isolated severe wind gusts are expected
   late afternoon into this evening in the eastern Wyoming vicinity.
   Locally damaging winds are possible this afternoon over the southern
   Appalachians and Mid-Atlantic States.

   ...Northern/central High Plains...
   Isolated to scattered storms will develop off the Front Range and
   Big Horns late this afternoon with a few supercells likely evolving
   in a north/south corridor across the eastern WY vicinity. In this
   corridor, surface dew points in the upper 50s to lower 60s are
   prevalent with robust insolation underway. This should result in
   MLCAPE reaching 1000-1500 J/kg. With approach of a decaying
   mid-level impulse from ID maintaining a belt of enhanced high-level
   westerlies, effective shear of 30-40 kt will support updraft
   rotation. While mid/upper-level lapse rates will not be particularly
   steep, they should still be sufficient for a risk of large hail and
   locally severe winds.

   ...Southern Appalachians to Mid-Atlantic States...
   Non-severe multicell clusters are ongoing across parts of the
   Cumberland to Allegheny Plateau of KY/WV. As pockets of moderate
   diabatic heating occur from NC to Delmarva, this activity along with
   additional widely scattered storm development may become weakly
   organized amid 20-25 kt effective shear. The marginal mid-level
   lapse rate environment suggests buoyancy should remain modest.
   Primary hazard will be isolated strong wind gusts producing tree
   damage.

   ...OK to OH Valley...
   Extensive cloud cover and areas of stratiform rain are ongoing
   along/ahead of a frontal boundary extending from northern OK to the
   Midwest. This will limit destabilization near the front with
   diabatic heating more pronounced farther south within a weak
   mid-level lapse rate and shear environment. Sporadic downbursts are
   possible where widely scattered pulse storms form late afternoon
   into evening, but the risk for organized severe storms appears
   minimal.

   ..Grams/Dial.. 07/27/2017

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