Jul 23, 2018 0600 UTC Day 1 Convective Outlook
Updated: Mon Jul 23 05:59:22 UTC 2018 (20180723 1200Z Day 1 shapefile | 20180723 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180723 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 7,202 466,051 Marrero, LA...Houma, LA...Estelle, LA...Westwego, LA...Waggaman, LA...
MARGINAL 139,621 33,825,816 Baltimore, MD...Denver, CO...Washington, DC...New Orleans, LA...Colorado Springs, CO...
Probabilistic Tornado Graphic
20180723 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
2 % 14,675 1,666,336 New Orleans, LA...Metairie, LA...Kenner, LA...Marrero, LA...Houma, LA...
Probabilistic Damaging Wind Graphic
20180723 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
15 % 7,152 464,842 Marrero, LA...Houma, LA...Estelle, LA...Westwego, LA...Waggaman, LA...
5 % 139,748 33,889,858 Baltimore, MD...Denver, CO...Washington, DC...New Orleans, LA...Colorado Springs, CO...
Probabilistic Large Hail Graphic
20180723 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 % 54,269 6,543,825 Denver, CO...New Orleans, LA...Colorado Springs, CO...Aurora, CO...Baton Rouge, LA...
   SPC AC 230559

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1259 AM CDT Mon Jul 23 2018

   Valid 231200Z - 241200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS
   SOUTHEASTERN LOUISIANA...

   ...SUMMARY...
   A few severe storms will be possible across southern Louisiana and
   vicinity today. Elsewhere, strong to marginally severe storms will
   be possible across the Florida Peninsula, Mid-Atlantic, and eastern
   Colorado, primarily this afternoon and evening.

   ...Synopsis...
   A rather persistent mid-level pattern will feature an amplified
   trough across most of the eastern half of the US today. Around its
   periphery, a series of vorticity maxima will transit from the
   central Gulf Coast southeast to the Florida Peninsula and then
   northward across the Mid-Atlantic. To the west, an expansive ridge
   will remain anchored over New Mexico, relegating stronger westerly
   flow to areas from the Pacific Northwest to the northern Plains.

   ...Louisiana...
   Along the southwestern fringe of the aforementioned 500mb trough,
   confluence from the surface through 850 mb is forecast to support
   increasing convective coverage in a northwest/southeast-oriented
   band over southern Louisiana and adjacent coastal waters today.
   Although 700-500mb lapse rates will not be particularly impressive,
   rich boundary-layer theta-e ahead of the surface front will
   contribute to at least 2500-3000 J/kg of MLCAPE by afternoon.
   Additionally, continued anomalously strong north/northwesterly flow
   will offer substantial effective shear for updraft organization,
   further bolstering vertical accelerations. Storm coverage along the
   initiating boundary, combined with motion somewhat parallel to the
   boundary, should favor clusters of multicells/supercells that slowly
   advance southward. Damaging winds will likely evolve as the primary
   threat due to this cluster mode, but isolated large hail and perhaps
   even a brief tornado may be possible, given ample boundary-layer
   moisture.

   ...Florida Peninsula...
   Any severe potential today will be largely regulated by ongoing
   convection and an adjoining outflow boundary near Tampa Bay as of
   06Z. The ongoing southward progression of this outflow over the
   Peninsula may shunt the potential for strong convection farther
   south today, as areas farther north remain relatively more stable
   and new initiation is focused along the outflow boundary. Although
   mid-level flow and resultant shear will weaken with southward extent
   (where convection is more likely considering the current evolution),
   damaging downburst winds may be possible given favorably high PWs
   and sufficient surface-based buoyancy.

   ...Mid-Atlantic...
   A channel of enhanced southerly 500mb flow will remain situated over
   much of the region today, continuing to transport plentiful
   tropospheric moisture northward across parts of the East Coast.
   Although mid-level lapse rates will likely remain weak across much
   of the region, diurnal heating amidst a moist/confluent regime will
   support clusters/bands of strong convection from the Carolinas
   northward to Pennsylvania. Downward momentum transfer of 25-35kt
   850-700mb flow could support a few stronger/damaging gusts in the
   strongest cores this afternoon and evening.

   ...Colorado...
   Despite a lack of stronger forcing for ascent, convection is still
   expected to develop along the higher terrain and foothills of
   Colorado today, aided by easterly upslope flow and surface dew
   points in the upper 50s to lower 60s. Prior convection across the
   region will further dampen mid-level lapse rates, but sufficient
   heating should yield at least modest surface-based buoyancy over
   eastern Colorado by afternoon. Veering flow with height will likely
   support primarily multicellular convection, although a few embedded
   supercells may materialize as well. Storms will pose a threat of
   isolated damaging gusts and large hail as they propagate
   south/southeastward through the evening.

   ..Picca/Bentley.. 07/23/2018

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