ACUS01 KWNS 161207
SWODY1
SPC AC 161205

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0705 AM CDT Thu Jul 16 2026

Valid 161300Z - 171200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
WESTERN MONTANA AND NORTHERN NEW ENGLAND...

...SUMMARY...
Severe thunderstorms capable of producing large hail and gusty winds
will be possible across parts of the northern Rockies this afternoon
and evening. Isolated to scattered damaging winds may also occur
over portions of northern New England, the Upper Midwest, and
Mid-Atlantic. A brief tornado or two remains possible across a small
part of south-central Texas this morning.

...Northern Rockies...
A closed upper low will move slowly northward along the coast of
WA/OR through the period. Upper ridging will persist across much of
the Rockies to the Plains. Between these features, a belt of
modestly enhanced south/southwesterly deep-layer flow will
overspread the northern Rockies. Modest easterly low-level winds
will transport generally 50s to low 60s surface dewpoints across
this region beneath steep mid-level lapse rates. As daytime heating
occurs, moderate instability should develop. Scattered thunderstorms
are forecast to initially form over the higher terrain during the
afternoon. Veering wind profiles with height through mid/upper
levels and gradually strengthening flow aloft will support around
30-40 kt of effective bulk shear. Organized cells will pose a risk
for gusty winds and severe hail across much of the region. The
greatest risk for 1+ inch hail still appears to be across parts of
western MT.

...Northern New England...
A vigorous mid-level shortwave trough will move quickly
southeastward from southern Ontario/Quebec across New England
through the day. Strong west/northwest deep-layer flow is evident in
recent NAM/RAP forecast soundings. Boundary layer moisture will be
somewhat limited compared to prior days, with surface dewpoints
generally in the 50s. Still, somewhat greater daytime heating is
expected to the north of the more prominent smoke plume across
southern New England, which should help steepening low-level lapse
rates by late morning/early afternoon. While MLCAPE will remain
modest (around 250-500 J/kg), the strong low/mid-level westerly flow
and steepened low-level lapse rates should support scattered
damaging winds as low-topped convection spreads southeast from
Quebec and across portions of northern New England through the
afternoon. Confidence in this scenario occurring has increased
enough to add greater severe wind probabilities and a corresponding
Slight Risk to parts of northeast VT/northern NH and ME.

...Mid-Atlantic...
Enhanced west-northwesterly mid/upper-level winds will overspread
the Mid-Atlantic today on the southern periphery of the mid-level
shortwave trough moving across New England. A surface front is
expected to sag southward through the day, approaching the PA/MD
border vicinity by late afternoon. Rich low-level moisture will be
in place ahead of the surface front and beneath steepening mid-level
lapse rates spreading in from the OH Valley. This, along with
diurnal heating, will foster a corridor of moderate to locally
strong instability this afternoon. Furthermore, various NAM/RAP
forecast soundings show 30-40 kt of effective bulk shear and steep
low-level lapse rates present south of the front. This environment
would generally support organized cells/line segments. However,
overall thunderstorm coverage remains uncertain given that stronger
forcing for ascent should remain mostly north of the warm sector.
Additionally, it is uncertain if smoke will continue to have a
negative impact on an otherwise favorable environment for severe
thunderstorms. Given the conditional potential for at least locally
damaging winds, have maintained the Marginal Risk with minor
expansions.

...Northeast North Dakota/Northern Minnesota...
A series of convectively enhanced vorticity maxima will migrate
across the Canadian Prairies north of the prominent upper ridge over
the Plains/Rockies, and through northwesterly flow aloft into parts
of ND and northern MN this afternoon into tonight. At the surface, a
weak low and surface front will move across ND into northern MN
during the evening and overnight hours. South/southeasterly
low-level flow will maintain a moisture-rich boundary layer,
supporting a narrow corridor of instability. NAM/RAP forecast
soundings show supercell wind profiles, but also increasing capping
through the late afternoon/evening. Even so, most high-resolution
guidance develops convection across southern Manitoba into northern
ND during the evening, spreading east/southeast across northern MN
overnight. Isolated severe hail and damaging winds may occur with
this activity.

...South-Central Texas...
Low-level rotation has occasionally been noted with cells occurring
early this morning across parts of south-central TX in a very moist
and weakly unstable environment, aided by a 30-35 kt southerly
low-level jet. A brief tornado or two still appears possible with
this activity through the morning, as low-level shear will remain
sufficient for continued updraft rotation. With time, a gradual
weakening of the low-level jet and related shear should result in a
lessening risk for tornadoes. See Mesoscale Discussion 1631 for more
details on the near-term threat across this area.

...Arizona...
Thunderstorms will develop over the higher terrain of the Mogollon
Rim and southeast AZ this afternoon/evening, and subsequently spread
westward across portions of central/southern AZ. Mid-level winds are
expected to be weaker compared to previous days, but modest
instability and steep lapse rates amid strong heating could support
sporadic strong gusts.

..Gleason/Thornton.. 07/16/2026

$$
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