NOAA Storm Prediction Center

Convective Outlooks

Convective Outlooks
The convective outlooks serve as guidance to the local NWS forecast offices and are used by emergency managers, private sector meteorologists, media, and other weather customers concerned with public safety. Three separate risk areas (slight, moderate, and high) are used to describe the expected coverage and intensity for the categorical severe weather threat on days 1-3 along with severe weather probabilities for the potential threat.

Day 1 Outlook Day 2 Outlook Day 3 Outlook Days 4-8 Outlook

Day 1 Outlook Convective Tornado
Hail Wind
Categorical Day1 1200Z Outlook
Images courtesy of the NWS Storm Prediction Center
 Forecast Discussion

ACUS01 KWNS 230600
SPC AC 230559

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

Valid 231200Z - 241200Z


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.

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.

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

...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.

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.

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