(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.
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 080859
SPC AC 080859
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Wed Apr 08 2020
Valid 111200Z - 161200Z
While considerable uncertainties remain, a substantial severe
episode appears possible this weekend, from Texas into portions of
the lower MS Valley on Saturday, and especially from the lower MS
Valley into portions of the Southeast on Sunday.
...D4/Saturday: Southern Plains into the Arklatex/Lower MS Valley...
Extended-range guidance continues to vary regarding the timing of
the ejecting cutoff low over the Southwest, though all solutions are
in generally good agreement in the development of a deep surface low
over the central/southern High Plains on Saturday as the upper low
ejects eastward. As low-level moisture streams northward, moderate
destabilization appears possible as far north as the Red River, as
deep-layer shear increases in advance of the ejecting trough. Severe
thunderstorm development will be possible during the
afternoon/evening across much of TX. Late Saturday night, an
increasing low-level jet may help to advect very rich low-level
moisture inland and potentially provide an additional focus for an
overnight severe thunderstorm threat from the TX Gulf Coast into the
lower MS Valley.
...D5/Sunday: Arklatex/Lower MS Valley into the Southeast...
Timing differences continue among the extended-range guidance into
D5/Sunday, with the GFS notably faster, while the 08/00Z ECMWF has
trended slower compared to other guidance as well as its own
previous cycles. Regardless of timing, most guidance depicts the
ejecting trough as taking on a neutral to negative tilt, with a
deepening surface low moving into portions of the MS/TN Valleys.
While the northward extent of substantial destabilization remains
uncertain due to the potential for widespread convection, sufficient
instability and increasing low-level and deep-layer shear will
support a severe thunderstorm threat across much of the Southeast
throughout the day into Sunday night. If very rich low-level
moisture (low 70s dewpoints) over the Gulf can spread inland in
advance of this dynamic system, as depicted by recent ECMWF/UKMET
runs, then a substantial severe thunderstorm event could evolve,
with all hazards possible. Higher probabilities will be required if
guidance continues to trend in that direction.
The severe threat could spread into portions of the Carolinas and
mid Atlantic on Sunday night, though too much uncertainty remains
regarding the northward extent of surface-based destabilization to
include probabilities for those areas at this time.
...D6/Monday: Mid Atlantic southward to Florida...
If the slower guidance verifies regarding the eastward movement of
the surface low and attendant cold front, some severe threat will
persist into D6/Monday from the Mid Atlantic southward along the
Southeast coast. Predictability is too low to delineate any
probabilities for D6/Monday at this time.
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