SPC 1730Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1227 PM CDT Wed Apr 14 2021

Valid 151200Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM
WEST-CENTRAL TEXAS TO THE CENTRAL GULF COAST...

...SUMMARY...
Isolated strong to severe storms are possible from west-central
Texas eastward along the central Gulf Coast. Locally strong gusts
and hail will be the main hazards with this activity.

...Synopsis...
Satellite imagery currently shows two well-defined upper lows, one
over the western Great Basin and the other over the Upper Great
Lakes. Expectation is for these lows to gradually move eastward
today, beginning the Day 2 Period (i.e. 12Z Thursday) centered over
the central Great Basin and southwestern Quebec. Surface low
associated with the eastern upper low will likely be centered just
off the Mid-Atlantic coast early Thursday, with an associated cold
front extending southwestward from this low through another low off
the MS/AL coast and into South Texas. Central and eastern portions
of this front will likely remain progressive throughout the day
before stalling Thursday evening. In contrast, the western portion
of the front over the western Gulf and south TX will likely remain
stationary throughout the day before returning northward as a warm
front Thursday evening through Friday morning.

...Central Gulf Coast through FL Panhandle/Northern FL...
This is some uncertainty regarding the position of the cold front
early Thursday morning, particularly given the expectation for
augmentation of this boundary by storm outflow. Even so, modest
warm-air advection is anticipated across this boundary, contributing
to scattered thunderstorms from southern LA into the western FL
Panhandle early Thursday morning. Steep mid-level lapse rates will
exist over the region, as will moderate westerly flow aloft.
Resulting combination of vertical shear and buoyancy could result in
a few stronger storms capable of hail and/or damaging downburst
winds. Elevated storm character should preclude any tornado threat.

Surface-based storms are possible along the front Thursday afternoon
as it traverses the northern FL Peninsula. Warm temperatures aloft
and resulting convective inhibition will likely temper updraft
strength within most storms. However, vertical shear will remain
strong enough to support rotation/organization of a few updrafts,
with large hail and/or damaging gusts possible with these more
robust embedded storms.

...West-Central TX to the Middle/Upper TX Coast...
A stalled frontal boundary will likely be in place from just off the
southeast TX coast back westward through South TX, eventually
intersecting lee troughing off the higher terrain of the southern
High Plains and northeast Mexico. Deepening of this lee troughing is
anticipated throughout the day, with surface southeasterly winds
strengthening in tandem. More southerly low-level flow will also
increase at the same time. Resulting increase in isentropic ascent
will augment the ascent attendant to a subtle shortwave through
expected to move across TX. All of these factors will contribute to
showers and thunderstorms across much of the southern Plains. Given
the steep lapse rates and strong deep-layer vertical shear, a few
stronger storms are possible, with large hail as the primary severe
risk.

Guidance is beginning to hint at a corridor of modestly higher
severe potential, from central TX into southeast TX, where storms
may begin to encounter slightly higher dewpoints and the northward
moving warm front. However, uncertainty regarding frontal position
and storm timing remains too high to delineate higher probabilities
within this corridor with this forecast.

Lastly, conditional risk of supercells capable of large hail exists
near the Del Rio vicinity with any storms that can develop over the
higher terrain of northeast Mexico and then move eastward.

..Mosier.. 04/14/2021

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