Day 4-8 Severe Weather Outlook Issued on Jul 17, 2020
Updated: Fri Jul 17 08:47:02 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
Mon, Jul 20, 2020 - Tue, Jul 21, 2020
D7
Thu, Jul 23, 2020 - Fri, Jul 24, 2020
D5
Tue, Jul 21, 2020 - Wed, Jul 22, 2020
D8
Fri, Jul 24, 2020 - Sat, Jul 25, 2020
D6
Wed, Jul 22, 2020 - Thu, Jul 23, 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 170845
SPC AC 170845
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0345 AM CDT Fri Jul 17 2020
Valid 201200Z - 251200Z
...DISCUSSION...
As an upper trough continues moving across eastern Canada on Day
4/Monday, a lingering/marginal severe threat may exist ahead of a
surface cold front across parts of New England and the Mid-Atlantic.
Some low-level moisture in the vicinity of a weak front and modestly
enhanced west-northwesterly mid-level winds may also promote
occasional storm organization across parts of the central Plains on
Day 4/Monday. However, this potential is highly uncertain given
nebulous large-scale ascent.
A more pronounced shortwave trough may advance eastward from the
northern/central Plains across the Upper Midwest/Great Lakes and
eventually the Northeast in the Day 5/Tuesday - Day 6/Wednesday time
frame. An organized severe risk may ultimately evolve across parts
of these regions given a favorable combination of instability and
shear. However, confidence in the placement of relevant surface
features and timing of the shortwave trough remains too low to
include 15% severe probabilities at this time.
Large-scale upper ridging should build over the central CONUS late
next week, with an upper trough/low moving over the western CONUS.
Small-scale perturbations may rotate around the upper ridge, and
could promote robust convection across parts of the northern Plains
and Upper Midwest on Day 7/Thursday into Day 8/Friday. Far too much
uncertainty exists in the timing/placement of these disturbances to
highlight areas of greater severe potential at this extended time
frame.
..Gleason.. 07/17/2020
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