Day 4-8 Severe Weather Outlook Issued on Oct 6, 2020
Updated: Tue Oct 6 08:35:03 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
Fri, Oct 09, 2020 - Sat, Oct 10, 2020
D7
Mon, Oct 12, 2020 - Tue, Oct 13, 2020
D5
Sat, Oct 10, 2020 - Sun, Oct 11, 2020
D8
Tue, Oct 13, 2020 - Wed, Oct 14, 2020
D6
Sun, Oct 11, 2020 - Mon, Oct 12, 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 060833
SPC AC 060833
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0333 AM CDT Tue Oct 06 2020
Valid 091200Z - 141200Z
...DISCUSSION...
Medium-range models continue to indicate substantial amplification
within a belt of westerlies emanating from the mid-latitude Pacific
this coming weekend into early next week. This still appears likely
to include the evolution of large-scale mid/upper troughing across
and east of the Canadian and U.S Rockies by Sunday. This likely
will be accompanied by deepening surface troughing and embedded
cyclogenesis across the Canadian Prairies and U.S. Great Plains,
before shifting northeastward and eastward, toward Hudson Bay and
across the Mississippi Valley by late Monday.
This is expected to be preceded by the inland migration of Hurricane
Delta Friday night, which will pose the most substantive initial
potential for severe weather (in the form of tornadoes) during this
period. However, as is typically the case with features the scale
and nature of tropical cyclones, the extent of this risk, at this
extended range, remains unclear due to a number of uncertainties.
One in particular concerns relatively dry/potentially cool low-level
air associated with surface high pressure, which appears likely to
encompass much of the East and Gulf Coast states prior to landfall
of Delta. An elevated influx of moisture and associated rain
falling into this air mass may further reinforce stable
boundary-layer conditions preceding Delta. And this could mitigate
the risk for tornadoes inland of perhaps a small corridor near
coastal areas, before Delta weakens.
Thereafter, the most appreciable severe weather potential associated
with the extratropical cyclogenesis is probably Sunday into Monday,
before diminishing by Tuesday. The high latitude nature of the
stronger cyclogenesis (i.e. across the northern Great
Plains/Canadian Prairies into the west of Hudson Bay), and the
likely dependence on substantive moisture return from the Gulf of
Mexico for appreciable destabilization, contribute to uncertainty
which remains sizable concerning the extent of this risk.
..Kerr.. 10/06/2020
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