Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk
Area (sq. mi.)
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
SPC AC 071958
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Sat Oct 07 2017
Valid 072000Z - 081200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE CENTRAL
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE CENTRAL
GULF COAST REGION...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE GREAT
LAKES AND OHIO VALLEY...
A couple of tornadoes are possible across the central Gulf Coast
States in association with hurricane Nate. A brief tornado or two
and isolated damaging winds are possible over parts of the Ohio
Valley and Great Lakes late afternoon and evening.
...Central Gulf Coast...
Minor northward adjustment was made to the outlook area over
southwest Alabama based on current trends. Hurricane Nate continues
to move rapidly northward toward the central Gulf coast, with a
primary outer convective band arcing from southeast Louisiana into
the Gulf of Mexico to the south of far northwest Florida. Radar
also shows small discrete cells north of the convective band over
from southeast Mississippi into southern Alabama, with MRMS
low-level rotational track data and single site radars exhibiting
transient weak rotational couplets in a few cells. As stronger
low-level winds and attendant shear/SRH located to the northeast of
the TC center spread northward, potential for a couple of tornadoes
will continue through the overnight hours over southeast parts of
Louisiana and Mississippi into southern Alabama and northwest
...Ohio Valley/Great Lakes...
No change has been made to this area. Weak lapse rates and minimal
CAPE remain evident over the warm sector in advance of a
precipitation band extending from eastern Wisconsin southward into
southwest Illinois. Radar also indicates a few smaller clusters of
weak convection downstream from the aforementioned band over the
lower Ohio Valley. However, no CG lightning is detected apparent at
this time likely reflecting insufficient CAPE in the charge
separation region. There remains potential for a low-topped line of
convection to develop, most likely on the leading edge of the
Wisconsin/Illinois convective band, which will advance eastward with
a threat for isolated damaging wind gusts into the evening hours. A
brief tornado will also be possible, especially in the Ohio Valley,
where marginally favorable low-level shear and SRH are present.
.PREV DISCUSSION... /ISSUED 1128 AM CDT Sat Oct 07 2017/
...Central Gulf Coast..
Expanded low tornado probabilities slightly farther north per latest
track of TC Nate.
An influx of tropical moisture and increasing low/mid-level
winds/shear will occur this afternoon and evening, as far north as
parts of southern AL/MS. Transient supercell structures should
develop to the east-northeast of the inner core of Nate with a risk
for a couple tornadoes.
...OH Valley/Great Lakes...
Added low tornado probabilities and considered a Slight risk, but
will defer on a possible upgrade to the 20Z update.
A pronounced midlevel shortwave trough over the central Plains will
accelerate east-northeast to the Lower Great Lakes through tonight.
Surface cyclone over central IA will decay over the central Great
Lakes, but a cold front will continue eastward. A swath of robust
insolation is underway across parts of IL/IN/OH/Lower MI between the
warm conveyor attendant to the front and a tropical moisture plume
preceding hurricane Nate across KY/TN. This diabatic heating should
compensate for poor mid-level lapse rates and yield meager buoyancy
with MLCAPE generally below 500 J/kg.
Ascent along the front will support a band of low-topped convection
late afternoon into evening across IN/Lower MI. Downward transport
of strong low-level flow should result in isolated damaging gusts,
but the lack of a strong surface pressure rise/fall couplet may
mitigate a greater severe wind risk. Scattered storms should form
within the deeper moisture plume over the OH Valley late
afternoon/early evening. Comparatively richer boundary-layer
moisture should aid in a couple supercells/multicell clusters
forming with risks of a brief tornado and locally damaging winds.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z