Day 4-8 Severe Weather Outlook Issued on Jul 28, 2020
Updated: Tue Jul 28 08:52:03 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, Jul 31, 2020 - Sat, Aug 01, 2020
D7
Mon, Aug 03, 2020 - Tue, Aug 04, 2020
D5
Sat, Aug 01, 2020 - Sun, Aug 02, 2020
D8
Tue, Aug 04, 2020 - Wed, Aug 05, 2020
D6
Sun, Aug 02, 2020 - Mon, Aug 03, 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 280850
SPC AC 280850
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0350 AM CDT Tue Jul 28 2020
Valid 311200Z - 051200Z
...DISCUSSION...
Medium-range models suggest that the remnant perturbation from an
initially significant northeastern Pacific mid-level low will weaken
considerably as it pivots northward and northeastward, inland of the
British Columbia coast and across the Canadian Rockies. While the
downstream mid-level ridge axis (to the north of a prominent
subtropical high over the Southwest) may be shunted eastward across
the northern U.S. Rockies and Canadian Prairies, it appears likely
to remain amplified, until the next significant upstream
perturbation, on the nose of a more zonal regime, accelerates across
the Canadian Rockies into the Canadian Prairies early next week.
Downstream of this ridging, latest guidance appears increasingly
suggestive that there may be some consolidation of troughing within
initially split branch of westerlies by late this coming weekend,
along a positively tilted axis across eastern Canada and the Great
Lakes into the lower Mississippi Valley. This may include the
northeastward acceleration of a convectively enhanced perturbation
emerging from the southern branch, across Ohio Valley and lower
Great Lakes region into the St. Lawrence Valley.
It appears that this impulse may be accompanied by a developing
surface cyclone, and a broadening area of strengthening winds
(30-40+ kt) in the 850-500 mb layer, across the lower Ohio Valley
into the northern Mid Atlantic Coast states Saturday into Sunday.
While warm mid-levels may limit the degree of destabilization, warm
sector boundary-layer dew points in the upper 60s to near 70f may
still contribute to an environment conducive to low-topped
convection with the potential to produce organized damaging surface
gusts, and perhaps a few tornadoes.
At this point, the predictability of the synoptic and sub-synoptic
features still appears relatively low, resulting in the maintenance
of less than 15 percent severe probabilities. However, particularly
as developments become better resolved, this could change in later
outlooks for this time period.
..Kerr.. 07/28/2020
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