Severe Storm Outlook Narrative (AC)
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000
ACUS03 KWNS 290722
SWODY3
SPC AC 290721

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0221 AM CDT Mon May 29 2017

Valid 311200Z - 011200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHEAST...SOUTHERN AND CENTRAL APPALACHIANS...MID MISSISSIPPI
VALLEY AND CENTRAL PLAINS...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTH-CENTRAL TEXAS...

...SUMMARY...
Marginally severe thunderstorms with strong wind gusts and hail will
be possible across parts of the Northeast, central Appalachians, mid
Mississippi Valley and central Plains on Wednesday. A marginal
wind-damage and hail threat will also be possible in south-central
Texas.

...Northeast...
An upper-level trough is forecast to move eastward across the Great
Lakes and Ohio Valley on Wednesday. At the surface, a cold front is
forecast to move east-southeastward across the Northeast. Surface
dewpoints should be in the lower to mid 50s F across much of New
York and Pennsylvania which should contribute to a corridor of weak
instability by midday. A band of large-scale ascent associated with
the upper-level system in the Great Lakes along with low-level
convergence along the front will likely result in the development of
thunderstorms during the afternoon. Forecast soundings from central
Pennsylvania northeastward into central New York at 21Z on Wednesday
show 0-6 km shear in the 50 to 60 kt range. This strong deep-layer
shear should be enough for a marginal wind-damage threat especially
if a line can organize along the front. Hail could also occur with
the stronger updrafts.

...Central Plains/Mid Mississippi Valley/Central Appalachians...
An upper-level trough is forecast to move across the Great Lakes and
Ohio Valley on Wednesday. A front is forecast to be located from the
lower Missouri Valley eastward into the Ohio Valley by midday.
Surface dewpoints south of the boundary should be in the lower to
mid 60s F with pockets of moderate instability developing in the
afternoon. Thunderstorms appear likely to initiate along the front
in areas that heat up the most. The greatest thunderstorm coverage
should be in the Ohio Valley where large-scale ascent is forecast to
be stronger. Moderate deep-layer shear is forecast along most of the
front which should enable the stronger thunderstorms to produce
marginally severe wind gusts and hail.

...South-central Texas...
An upper-level trough is forecast to move across the Rio Grande
Valley on Wednesday. At low levels, a moist airmass should be in
place with surface dewpoints generally in the lower to mid 60s F
across the lower Rio Grande Valley. Model forecasts suggest that
scattered thunderstorms will develop in the higher terrain of
northern Mexico and move eastward into southern and central Texas
during the late afternoon and early evening. Moderate deep-layer
shear associated with gradually veering winds with height, along
with steep low-level lapse rates, should be sufficient for a
marginal wind damage threat. Hail will also be possible.

..Broyles.. 05/29/2017

$$



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