SPC 0730Z Day 3 Outlook

Day 3 Outlook Image

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0230 AM CDT Thu Oct 08 2020

Valid 101200Z - 111200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SATURDAY ACROSS
MUCH OF NORTHERN AND CENTRAL MISSISSIPPI AND ALABAMA...AND ADJACENT
PORTIONS OF SOUTHERN TENNESSEE...AS WELL AS ACROSS MUCH OF UPSTATE
NEW YORK INTO NORTHERN NEW ENGLAND...

...SUMMARY...
The weakening remnants of Delta may continue to contribute to a risk
for a couple of tornadoes and strong wind gusts across parts of the
central Gulf Coast states on Saturday.  Strong thunderstorms may
also impact Upstate New York into portions of northern New England,
posing at least some risk for severe wind and hail.

...Synopsis...
A belt of westerlies emanating from the mid-latitude Pacific appears
likely to become increasingly amplified across Canada and the
northern tier of the U.S. through this period.  This appears likely
to include a digging mid-level trough inland of the Pacific coast
and across the northern intermountain region, accompanied by surface
cyclogenesis within deepening surface troughing to the lee of the
Canadian/northern U.S. Rockies by late Saturday night.

Downstream troughing is also forecast to amplify to the east and
southeast of Hudson Bay, with a lead embedded short wave trough
digging across southern Quebec into the Canadian Maritimes.  This is
forecast to be accompanied by a deep surface cyclone, with another
cold front advancing across New York state and New England by the
end of the period.

Within a weaker branch of westerlies across the southern tier of the
U.S., mid-level troughing, including the remnants of Delta, likely
will continue to slowly shift east-northeast of the lower
Mississippi Valley.  Most guidance indicates substantial rapid
weakening of the associated surface cyclone as it migrates
northeastward out of northeastern Louisiana through northwestern
Mississippi.

...Lower Mississippi to Tennessee Valley vicinity...
An initially narrow plume of lower 70s surface dew points, wrapping
into the low-level circulation center of Delta, may broaden
northeastward across much of Mississippi and Alabama through the
day.  This is where the strongest southerly 850 mb flow will
contribute to large clockwise-curved low-level hodographs most
conducive to tornado potential.  However, the extent of this
potential Saturday remains unclear, as the peak wind fields weaken,
and warm mid-levels limit boundary-layer destabilization.  Still,
there may be a window of opportunity for sufficient warming to
destabilize the boundary layer before low-level wind fields weaken
and hodographs shrink too much, to allow the environment to become
conducive to a few low-topped supercells capable of producing
tornadoes and locally strong surface gusts.

...Upstate New York into northern New England...
To the south of the digging short wave impulse, models suggest that
a narrow plume of warm elevated mixed-layer air may advect into the
region by the beginning of the period, as boundary-layer moistening
proceeds ahead of a southeastward advancing cold front.  The NAM
appears most aggressive with this moistening, and it may be too
moist.  However, there appears potential for sufficient pre-frontal
boundary-layer destabilization, with daytime heating, to support at
least scattered thunderstorm development by Saturday afternoon. 
Near the southeastern periphery of the digging mid-level trough,
30-50+ kt flow in the 850-500 mb layer may contribute to the risk
for organized storms capable of producing potentially damaging wind
gusts and marginally severe hail.

..Kerr.. 10/08/2020

Read more
There’s more click here.

Comments are closed.