07/19/2025
.THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SUNDAY ACROSS
PARTS OF SOUTHERN MAINE...CENTRAL AND SOUTHERN NEW
HAMPSHIRE...SOUTHERN VERMONT...MASSACHUSETTS...RHODE
ISALAND...CONNECTICUT...SOUTHEASTERN NEW YORK STATE...LONG
ISLAND...NORTHERN NEW JERSEY AND PARTS OF NORTHEASTERN
PENNSYLVANIA...
...SUMMARY...
Severe thunderstorms accompanied by potentially damaging wind gusts
and some hail are possible Sunday across parts of New England into
the northern Mid Atlantic.
...Discussion...
Models suggest that the westerlies will remain modestly amplified
across the northern mid-latitudes through this period. While one
notable short wave perturbation may accelerate northeastward out of
the Pacific Northwest into the eastern Canadian provinces, another
is forecast to dig inland across the Pacific Northwest, maintaining
larger-scale troughing there. Downstream, broadly anticyclonic flow
is forecast across the northern Rockies through the Upper Midwest,
around the northern periphery of fairly prominent mid/upper ridging
centered over the northern Gulf/Gulf coast vicinity. Farther east,
it appears that a significant mid-level trough emerging from the
Hudson Bay vicinity will continue to dig across the St. Lawrence
Valley and lower Great Lakes vicinity, before turning eastward
across the northern Atlantic Seaboard.
The eastern trough will be accompanied by a reinforcing intrusion of
cooler, drier air southeast of the Great Lakes region and across the
northern and middle Atlantic Seaboard by Sunday night. The trailing
flank of this front is forecast to generally stall across the lower
Ohio into middle Missouri Valleys and adjacent portions of the Great
Plains, beneath the northern periphery of the subtropical ridge.
...New England into northern Mid Atlantic...
Based on latest model output, confidence is increasing in the
likelihood of appreciable (CAPE in excess of 1000 J/kg) pre-frontal
boundary-layer destabilization ahead of the southward advancing
front, as far north as the southern tier of New York through
portions of northern Vermont/New Hampshire into central Maine by
around 18-19Z Sunday afternoon. Forcing for ascent along/ahead of
the front, aided by the approaching upstream mid-level trough, is
expected to support the initiation of strong thunderstorm
development, in the presence of west-southwesterly deep-layer mean
flow on the order of 30 kt. Forecast soundings indicate moistening
thermodynamic profiles, including surface dew points in the mid 60s
to near 70F, but with sufficient sub-saturation to allow for
evaporative cooling, in addition to heavy precipitation loading, to
enhance downdrafts and downward momentum transfer.
Initial activity probably will be accompanied by potentially
damaging downbursts, and perhaps some hail, before perhaps
consolidating into a line with a continuing risk for strong to
severe gusts while spreading southeastward into and across coastal
areas.
...Lower Missouri into Lower Ohio Valleys...
East of the warmer and more strongly capping mid-level air across
the Great Plains, convection allowing guidance suggests that one or
two east-southeastward propagating clusters of storms could evolve
along the frontal zone across the region Sunday into Sunday night.
Seasonably moist boundary-layer air may support moderate to large
potential instability along and south of the front, near the
southern periphery of west-northwesterly mid-level flow supportive
of modest shear. However, with no low-level jet to focus convective
development, except perhaps across parts of northwestern Missouri
late Sunday evening, and mid/upper support still unclear, confidence
in depicting areas of higher severe probabilities, which may
eventually be needed, remains low at this time.
...Northern/Central Great Plains...
Thermodynamic profiles characterized by steep lapse rates and
sizable CAPE are likely to persist across much of the region through
this period, in the presence of modest to weak deep-layer shear.
However, mid/upper support for convective development remains
unclear, and warming mid-level temperatures downstream of the
Pacific Northwest trough may strengthen inhibition, contributing to
more sparse thunderstorm coverage than prior days.
