SPC AC 031730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Mon Aug 03 2020

   Valid 041200Z - 051200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE COASTAL MID-ATLANTIC INTO SOUTHERN NEW ENGLAND...AND
   NORTHERN/CENTRAL PLAINS...

   ...SUMMARY...
   A few tornadoes will be possible from the Virginia Tidewater into
   New England Tuesday into Tuesday night, in association with Isaias.
   Scattered severe thunderstorms capable of producing large hail and
   damaging winds may also occur across portions of the northern and
   central Plains.

   ...Eastern North Carolina to New England...
   Latest forecast from the National Hurricane Center indicates that
   Isaias should be located over far northeastern NC and southeastern
   VA at the start of the period Tuesday morning. Isaias should
   accelerate northeastward along the Mid-Atlantic Coast and into New
   England through the period as it becomes absorbed within an
   upper-level trough over the eastern CONUS. A rather strong low-level
   flow field (60-70+ kt at 850 mb) will be present in the eastern half
   of Isaias' circulation, which will aid in substantial low-level
   hodograph curvature/enhancement.

   The best prospect for weak destabilization (MLCAPE 250-1000 J/kg)
   should exist along/near the Mid-Atlantic to southern New England
   Coast, where surface dewpoints should increase into the low to
   perhaps mid 70s through Tuesday evening. Given the very favorable
   low-level shear, primary concern will be a few tornadoes with any
   low-topped cells in outer rain bands along/east of the center of
   Isaias' circulation. Confidence has increased enough in the Isaias'
   track and potential for modest diurnal destabilization along/near
   the coast to include 5% tornado probabilities and a Slight Risk from
   the VA Tidewater region northeastward into southern New England.
   Eventually, the strong low-level shear should become displaced to
   the north of even weak inland destabilization across NH and ME by
   late Tuesday night. This should result in a gradual lessening of the
   isolated tornado threat with northward extent across New England.

   ...Northern/Central Plains...
   A weak shortwave trough is expected to continue moving eastward
   across the northern/central Plains on Tuesday while suppressing
   upper ridging over the western CONUS. Modest southeasterly low-level
   flow should transport generally mid 50s to low 60s surface dewpoints
   northward across the northern/central High Plains by peak afternoon
   heating. With steep mid-level lapse rates forecast to be present
   over this region, 1000-2000 J/kg of MLCAPE should develop by Tuesday
   afternoon. Current expectations are for storms to initially develop
   over the higher terrain and spread southeastward, with some
   potential for additional development along a weak front over the
   western Dakotas. Effective bulk shear of 30-40 kt should promote
   storm organization, with a mix of multicells and supercells
   possible. Both large hail and severe wind gusts may occur Tuesday
   afternoon and evening, before eventually weakening with eastward
   extent Tuesday night. There is some signal in guidance for upscale
   growth/clustering across parts of western into central NE Tuesday
   afternoon/evening, and the Marginal/Slight Risk areas have been
   expanded eastward to account for this possibility.

   ..Gleason.. 08/03/2020

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