Day 4-8 Severe Weather Outlook Issued on Apr 9, 2018
Updated: Mon Apr 9 08:41:03 UTC 2018
Day 4 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 5 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
15 %
137,279
7,246,538
Shreveport, LA...Little Rock, AR...Springfield, MO...Tyler, TX...Fort Smith, AR...
Day 6 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 7 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 8 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4
Thu, Apr 12, 2018 - Fri, Apr 13, 2018
D7
Sun, Apr 15, 2018 - Mon, Apr 16, 2018
D5
Fri, Apr 13, 2018 - Sat, Apr 14, 2018
D8
Mon, Apr 16, 2018 - Tue, Apr 17, 2018
D6
Sat, Apr 14, 2018 - Sun, Apr 15, 2018
(All days are valid from 12 UTC - 12 UTC the following day)
Note: A severe weather area depicted in the Day 4-8 period indicates 15%, 30% or higher probability for severe thunderstorms within 25 miles of any point.
PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears unlikely (i.e., less than 15%) for the forecast day.
Forecast Discussion
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 090839
SPC AC 090839
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0339 AM CDT Mon Apr 09 2018
Valid 121200Z - 171200Z
...DISCUSSION...
The main focus of the extended period continues to be the impressive
amplification of a mid/upper trough over the central US late this
week into the weekend. Along the base of the trough, an approximate
100-kt west/southwesterly 500-mb jet will overspread the
southern/central Plains on D5/Fri, transporting a broad area of
relatively steep lapse rates across the region. Concurrently, a
deepening low over the central US will encourage a narrow corridor
of enhanced poleward moisture return (generally characterized by
surface dew points in the 60s) from eastern Texas to the lower
Missouri Valley. Attendant to this low, a dry line and cold front
will accelerate eastward from the Plains towards the Mississippi
Valley through Friday night, promoting thunderstorm activity from
the western Gulf Coast to the Midwest.
While still exhibiting diversity in the timing of the eastward
evolution of the trough, medium-range guidance continues to
highlight areas from eastern Texas to the Mid-South for the highest
probability of severe weather late Friday into the overnight. Here,
deterministic/ensemble guidance indicates robust wind fields will
overlap adequate surface-based buoyancy for the development of
severe thunderstorms. Considering the magnitude of forcing for
ascent and the forecast meridional nature of deep-layer flow,
upscale growth into larger convective complexes appears probable.
Such evolution should enhance the ability of severe convection to
spread east overnight; therefore, the ongoing 15-percent area has
been expanded slightly towards the Mississippi Valley.
Farther north towards the lower Missouri and mid Mississippi
Valleys, guidance also indicates a possibility for severe
convection. However, a narrowing moist/warm sector towards the
primary surface low yields greater uncertainty with the spatial
placement of such convection during the afternoon/evening. In turn,
15-percent probabilities have not been expanded northward with this
cycle, but could be in later updates.
Beyond D5/Fri, timing of the eastward progression of the trough and
associated convection remains quite uncertain. Furthermore,
lessening buoyancy with eastward extent suggests stronger convection
will likely remain focused near the corridor of greatest deep
ascent, magnifying concerns regarding temporal uncertainty.
Subsequently, predictability too low is maintained through the
remainder of the extended period.
..Picca.. 04/09/2018
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