705
ACUS01 KWNS 171627
SWODY1
SPC AC 171625

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1125 AM CDT Thu Jul 17 2025

Valid 171630Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN
NEW ENGLAND AND THE NORTHERN HIGH PLAINS...

...SUMMARY...
Scattered damaging winds and a tornado are possible across northern
New England this afternoon.  A confined corridor of large hail and
severe gusts appears possible from north-central Montana to
southwest North Dakota this evening.

...Northeast...
Midday visible-satellite imagery shows cloud breaks and surface
observations show warming temperatures which imply a destabilizing
airmass.  A lead, convectively enhanced disturbance evident in
radar/satellite imagery, is moving east across southern Quebec,
while an upstream larger-scale mid-level trough continues eastward
across Ontario and into Quebec later today.  A cyclone will develop
northeast from eastern Ontario into eastern Quebec while a cold
front pushes through the Lower Great Lakes and through much of the
Northeast through mid evening.  The deep moisture through much of
the troposphere and weak lapse rate profiles, which were sampled by
the 12 UTC Buffalo and Albany, NY raobs, will undergo moderate
destabilization by early to mid afternoon.  Although forcing for
ascent will favor Quebec into northern New England, scattered
thunderstorms will likely develop from Maine southward into southern
New England.  The greatest potential for some organized storms will
favor northern New England where stronger effective shear (30-40 kt)
and adequate buoyancy will promote a wind-damage threat with the
stronger storms.  Forecast sounding over northern Maine show
enlarged hodographs for a few hours, which may aid in low-level
mesocyclone development and perhaps a risk for a tornado.  Lower
coverage of severe is forecast farther south where weaker shear will
tend to limit storm intensity.  The severe activity will likely
diminish by the early to mid evening.

...Northern High Plains...
Model guidance continues to show a focused corridor of supercell
thunderstorm potential from north-central MT to southwest ND, mainly
this evening.  Water-vapor imagery shows a mid-level shortwave
trough rotating southeastward across the southern part of the
Canadian Rockies moving towards the northern High Plains.  Forecast
soundings this afternoon show elongated hodographs amidst modest
buoyancy, which would support the development of a supercell or two
during the evening.  Large hail is the primary hazard with this
activity but severe gusts may occur on a localized basis.  An
isolated hail/wind risk may persist along the ND/SD border vicinity
overnight.

...Mid-Atlantic to the Southern High Plains...
A surface front draped over the south-central Plains
east-northeastward into the mid MS/OH Valleys will focus scattered
thunderstorm activity this afternoon.  The eastern part of this
broader region over the Mid-Atlantic into the OH Valley will be
displaced from the mid-level trough over influencing storm activity
over the Northeast.  A remnant MCV and outflow from overnight storms
in the MO/KS/OK vicinity will aid in developing storms and perhaps
localized threats for sporadic hail/wind mainly this afternoon.
Isolated damaging winds may also occur with thunderstorms that
develop east of the central Appalachians this afternoon, even though
coverage should be somewhat less.

..Smith/Lyons.. 07/17/2025

$$