RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0251 PM CDT Thu Jul 16 2026
Valid 162000Z - 171200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
WESTERN MONTANA...
...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 could occur across a small part of
south-central/southwest Texas later today or tonight.
...20z Update...
The primary adjustment was to reduce wind probabilities across
portions of the Northeast behind a leading line of convection
attendant to a weak surface front. Falling temperatures and more
stable conditions in the wake of this front should preclude
additional thunderstorm development through the evening, though some
lingering threat persists across parts of New England as convection
continues to push east towards the Atlantic coast.
...Mid-Atlantic...
GOES visible imagery shows building cumulus across parts of
southeast PA within a favorable environment for organized
convection. Although guidance continues to suggest much of this
activity will mature along and off the coast, some potential for
severe wind, as well as large hail, is apparent based on latest RAP
mesoanalyses and forecast guidance.
...North Dakota...
The 2% tornado risk probability line was expanded eastward along a
surface warm front evident in visible imagery and surface
observations. Warm and moist conditions and ambient low-level
vorticity along this boundary may support some potential for brief
tornadoes as thunderstorms begin to develop later this evening.
Elsewhere, the previous forecast remains on track. See the previous
discussion below for additional details.
..Moore.. 07/16/2026
.PREV DISCUSSION... /ISSUED 1134 AM CDT Thu Jul 16 2026/
...Northern Rockies...
A closed upper low will move slowly northward along the coastal
Pacific Northwest through tonight. 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 F 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 appears to be across parts of western
Montana.
...Northern New England...
A vigorous mid-level shortwave trough will move quickly
southeastward from southern Ontario/Quebec across New England today
with strong west/northwest deep-layer flow. Boundary layer moisture
will be somewhat limited compared to prior days, with surface
dewpoints generally in the 50s F. 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 near a secondary/weak front.
...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
Pennsylvania/Maryland 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 Ohio
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 to what extent that
smoke may continue to have a negative impact on an otherwise
favorable environment for severe thunderstorms.
...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 North Dakota and northern Minnesota this afternoon into tonight.
At the surface, a weak low and surface front will move across North
Dakota into northern Minnesota 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 North Dakota
during the evening, spreading east/southeast across northern
Minnesota overnight. Isolated severe hail and damaging winds may
occur with this activity, and a tornado risk cannot be ruled out.
...South-Central Texas...
While low-level shear/SRH has weakened since last night, and ongoing
convection remains extensive/repetitive, a northward drift of the
MCV and potential re-establishment of stronger low-level winds later
today into tonight could account for non-zero/brief tornado
potential.
...Arizona...
Thunderstorms will develop over the higher terrain of the Mogollon
Rim and southeast Arizona this afternoon/evening, and subsequently
spread westward across portions of central/southern Arizona. Modest
instability and steep lapse rates amid strong heating could support
sporadic strong gusts.
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SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0227 PM CDT Thu Jul 16 2026
Valid 181200Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
OHIO VALLEY AND LOWER GREAT LAKES INTO THE MID-ATLANTIC...
...SUMMARY...
Strong to severe thunderstorms are expected across portions of the
Ohio Valley and lower Great Lakes into the Mid-Atlantic, mainly
Saturday afternoon into the evening. Some threat may linger into
late Saturday night.
...Ohio Valley into the Mid Atlantic and vicinity...
Some amplification of a mid/upper-level trough is expected over the
northeastern CONUS on Saturday, as multiple shortwaves move through
the base of the trough. The primary surface low is expected to
deepen as it moves across southern Quebec toward northern Maine. A
trailing cold front will move through parts of the Ohio Valley and
Northeast. A remnant surface front initially draped from western PA
toward the Delmarva region is forecast to lift northeastward as a
warm front through the period.
As deep-layer flow strengthens atop a richly moist and destabilizing
warm sector, organized severe potential is expected to develop
across a relatively broad region from the Ohio Valley into the Mid
Atlantic, with at least an isolated threat potentially reaching
parts of New England. Uncertainties include the influence of
early-day convection and potential persistent smoke on the
northeastward extent of substantial surface-based destabilization.
Along the cold front, the greatest relative threat is currently
expected from the lower Great Lakes into eastern parts of the Ohio
Valley, where stronger 850-700 mb flow (around 25-40 kt) is
forecast. Organized cells/clusters capable of damaging wind and
isolated hail may evolve along/ahead of the front and spread
eastward. Rich boundary-layer moisture and modest enhancement to
low-level SRH may also result in some tornado threat, depending on
storm-mode evolution. Favorable moisture/buoyancy will also extend
westward along/ahead of the front into parts of the Midwest and
lower Ohio Valley, but there may be more of a tendency for
convection to be undercut by the front with westward extent.
Farther south/east, organized convection may evolve or reintensify
near the effective warm front by afternoon into parts of PA/NJ, and
also develop into parts of MD/VA along/east of a surface trough.
Very warm temperatures and steepening low-level lapse rates will
become supportive of damaging-wind potential, and isolated hail may
also occur. Some tornado threat could also evolve in closer
proximity to the warm frontal zone.
An extensive frontal QLCS may develop by evening, and continue to
pose some wind-damage threat for as long as it persists into
Saturday night.
...Northern Rockies vicinity...
Compared to previous days, some drying from the west is expected
across parts of MT on Saturday, as a mid/upper-level shortwave
trough moves across parts of BC/AB through the day. High-based
convection is still expected from ID into southwest MT and vicinity,
though relatively weak buoyancy and deep-layer shear should limit
storm organization. Some overlap of stronger deep-layer shear and
moderate buoyancy is forecast to occur across parts of northern MT,
but storm coverage within this regime is uncertain, with stronger
large-scale ascent currently expected to remain north of the
international border.
..Dean.. 07/16/2026
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