SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0246 PM CDT Sat Oct 10 2020

Valid 102000Z - 111200Z


A few tornadoes are possible into this evening across parts of
Alabama, western Georgia, and the Florida Panhandle. Damaging
thunderstorm winds are possible across parts of northern New York
and northern New England from mid afternoon into this evening.

...20Z Update...

Tropical Depression Delta is currently centered over west-central
MS. A warm front currently extends eastward from this low along the
southern TN border, with modest instability south of this boundary
across much of AL and GA. Cloudiness closer to the center has
precluded much destabilization thus far across MS. Strong low to
mid-level wind fields remain in place around Delta, resulting in the
potential for damaging wind gusts and a few tornadoes this
afternoon. Greatest risk currently exists across eastern AL and
western GA, where Tornado Watch 498 is in place. Wind fields are
expected to gradually weakened throughout the afternoon and evening
but still remain stronger enough for some severe risk through this

...Upstate NY into northern New England this afternoon/evening...
Strong forcing for ascent and modest instability has resulted in the
development of fast-moving thunderstorms across northern NY.
Updrafts have struggled to maintain intensity thus far, but
additional storms are anticipated into east-central NY and eastward
into more of VT, NH, and ME. The threat for damaging wind gusts will
continue through the afternoon into the evening.

..Mosier.. 10/10/2020

.PREV DISCUSSION... /ISSUED 1124 AM CDT Sat Oct 10 2020/

...AL/FL Panhandle/western GA through late evening...
The weakening remnants of tropical cyclone Delta will move generally
eastward across northern MS today to northern AL tonight.  The
system has a more baroclinic structure now with a warm front
extending eastward from roughly Birmingham to Atlanta, and the
primary surface trough near the MS/AL border.  Most of the
convection is focused in a north-south band across central/southern
AL and the western FL Panhandle in the zone of strongest low-level
confluence/convergence.  Expect the main threat for embedded
rotating storms to be focused within this band this afternoon as the
stronger forcing for ascent spreads northeastward, and along the
warm front as more isolated storms form in response to daytime
heating in cloud breaks.  The combination of boundary-layer
dewpoints in the low-mid 70s, weak buoyancy (MLCAPE of 500-1000
J/kg), and sufficiently strong flow/shear east of the center of
Delta will support a threat for occasional supercells and tornadoes
this afternoon through late evening.

...Upstate NY into northern New England this afternoon/evening...
A midlevel shortwave trough over the upper Great Lakes and ON will
progress eastward over upstate NY and northern New England this
afternoon through early tonight.  The midlevel trough will be
accompanied by a surface cold front, with a narrow corridor of
low-level moistening and modest destabilization expected along and
just ahead of the front.  Though boundary-layer dewpoints will
remain in the 50s, daytime heating and midlevel lapse rates of 7-8
C/km will support MLCAPE of 500-1000 J/kg.  Deep-layer vertical
shear will increase in this same corridor this afternoon, with
effective bulk shear increasing to 50-60 kt with 50 kt flow within
1-2 km of the ground.  Scattered thunderstorm development is
expected along and just ahead of the front by mid afternoon across
upstate NY, and storms will subsequently spread eastward across
northern New England through this evening.  Storms will consist of a
mix of supercells and line segments, with the primary threat for
damaging winds.

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