SPC 0600Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1246 AM CDT Fri Oct 09 2020

Valid 101200Z - 111200Z


Tropical Cyclone Delta should continue to pose a risk for a couple
of tornadoes and strong wind gusts across parts of the central Gulf
Coast states on Saturday. Thunderstorms may also impact Upstate New
York into portions of New England, posing an isolated risk for
damaging wind gusts.

The latest forecast from the National Hurricane Center regarding
Delta indicates that the tropical cyclone will continue to move
northeastward over the lower MS Valley on Saturday while steadily
weakening. Still, strong low-level south-southeasterly flow of
40-50+ kt will likely persist over parts of MS/AL and vicinity to
the east of Delta's circulation through the day. Related strong
low-level shear and curved hodographs suggest rotating updrafts will
be a possibility. However, widespread cloudiness, poor low/mid-level
lapse rates, and modest diurnal heating will tend to limit
destabilization Saturday afternoon, with MLCAPE around 250-750 J/kg
possible. Dry mid-level air is also forecast to overspread parts of
the warm sector through the period, which may further temper updraft

Even so, most guidance suggests that an outer rain band will be
ongoing Saturday morning from parts of coastal MS/AL northward into
central MS. This band of low-topped storms should shift
east-northeastward across central/eastern MS into AL and the western
FL Panhandle through Saturday evening, while posing a threat for
isolated strong straight-line wind gusts and perhaps a couple
tornadoes. Have opted to expand the Marginal Risk to include more of
southern AL and the western FL Panhandle based on trends in latest
guidance. An upgrade to Slight Risk remains possible across some
part of the central Gulf Coast states in a later outlook update.
However, confidence would need to increase that stronger diurnal
heating and related instability will be realized.

An upper trough is forecast to amplify across Quebec, with strong
low to mid-level west-southwesterly flow overspreading much of the
Northeast by Saturday afternoon. At the surface, a cold front should
shift east-southeastward across New England and Upstate NY by early
Saturday evening. Limited low-level moisture is forecast to advance
northeastward ahead of the cold front, with most guidance suggesting
surface dewpoints will reach only into the 50s. MLCAPE may modestly
increase to around 250-500 J/kg with diurnal heating and cooling
mid-level temperatures with the amplifying upper trough. A broken
line of low-topped storms may develop along/ahead of the cold front
from parts of western NY to ME, and subsequently move eastward in
tandem with the cold front. The forecast combination of weak
instability and enhanced low/mid-level winds suggest some potential
for isolated strong to damaging winds to reach the surface through
boundary-layer mixing and downdraft accelerations. At this point,
confidence remains too low regarding the degree of instability to
include greater severe wind probabilities.

..Gleason.. 10/09/2020

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