Day 4-8 Severe Weather Outlook Issued on Sep 13, 2020
Updated: Sun Sep 13 08:33:02 UTC 2020
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
No Risk Areas Forecast
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
Wed, Sep 16, 2020 - Thu, Sep 17, 2020
D7
Sat, Sep 19, 2020 - Sun, Sep 20, 2020
D5
Thu, Sep 17, 2020 - Fri, Sep 18, 2020
D8
Sun, Sep 20, 2020 - Mon, Sep 21, 2020
D6
Fri, Sep 18, 2020 - Sat, Sep 19, 2020
(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 130831
SPC AC 130831
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0331 AM CDT Sun Sep 13 2020
Valid 161200Z - 211200Z
...DISCUSSION...
...Southeast States...
Some severe/tropical cyclone-related tornado threat could exist
across parts of MS/AL on Day 4-5/Wed-Thu. The National Hurricane
Center has current Tropical Storm Sally tracking slow north across
southern MS through Wednesday evening and across central/northern AL
on Thursday. Current guidance suggests low-level wind fields may
become more favorable as the system tracks more northerly and then
northeasterly. However, instability is forecast to be very weak and
prolific rainfall may be more likely than severe
thunderstorm/tornado threats. Trends will continue to be monitored,
but uncertainty will preclude severe probs at this time.
...Northern/Central Plains into the Upper Midwest...
Medium range guidance is in fairly good agreement with respect to
the overall large-scale pattern through the period. A mean upper
trough will persist east of the Mississippi River through about Day
6/Fri. A more progressive pattern is then expected during the
weekend as a western shortwave trough moves east across the Pacific
Northwest and northern Rockies on Friday, and emerges over the
northern Plains around Day 8/Sun. This should result in surface low
pressure developing over the northern/central High Plains and
tracking east/northeast toward the Upper Midwest by the end of the
period. As this occurs, a cold front is likely to move across
portions of the Plains/Upper Midwest. Modest moisture return ahead
of this feature could provide enough instability for thunderstorm
activity late in the period, but timing of these features at this
time frame is uncertain, and trends will be monitored for any
increasing severe potential with time.
..Leitman.. 09/13/2020
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