SPC Aug 4, 2020 1300 UTC Day 1 Convective Outlook
(Di, 04 Aug 2020)
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0704 AM CDT Tue Aug 04 2020
Valid 041300Z - 051200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTRAL HIGH
Tornadoes will be most likely through this afternoon from Delaware
into southern New England, with a lingering threat for a couple
tornadoes across northern New England this evening. Scattered large
hail and severe wind gusts will be possible across the central High
Plains from mid-afternoon to mid-evening.
...DE to New England...
As T.C. Isaias rapidly shifts northeastward today, an accompanying
very moist low-level environment will permit maintenance of weak
buoyancy across the coastal plain of the Northeast into southern New
England. Clusters and cells of shallow convection to the north and
east of the circulation center will continue to pose a risk for
tornadoes. The greatest risk will be where mid 70s surface dew
points can become coincident with immense low-level hodograph
curvature from DE to the NYC tri-state area. Most guidance is
consistent in suggesting the very rich surface moisture will become
pinched off across parts of southern New England later today. This
suggests the overall tornado risk should decrease this evening as it
spreads into northern New England.
...Central High to Northern Great Plains...
A broad plume of 50s surface dew points is prevalent ahead of a lee
surface trough, a low-amplitude shortwave impulse near the MT/SK
border, and an MCV near the SD/MT border. The greatest buoyancy this
afternoon should develop along the central High Plains portion of
the lee trough amid very steep low to mid-level lapse rates, with
relatively weaker mid-level lapse rates in the Dakotas.
Scattered thunderstorms should initiate near the Front Range during
the mid-afternoon and spread east within moderate mid-level
west-northwesterlies. The setup should yield supercells initially
producing large hail, some of which may be significant, from eastern
CO into the NE Panhandle. Conglomerating cold pools should tend to
foster multiple clusters as activity spreads towards the KS/CO
border longitude. A dearth of surface-based instability with eastern
extent in KS/OK suggests waning severe potential during the evening
even though an elevated MCS should persist to the southeast.
Farther north, scattered thunderstorms are expected as well, mainly
across western to central ND in closer proximity to ascent tied to
the approaching shortwave trough. Weak mid-level lapse rates should
be a limiting factor and may result in only isolated coverage of
severe hail and wind. Have expanded Marginal Risk northward for this
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