SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1254 AM CDT Mon Jun 09 2025
Valid 091200Z - 101200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY ACROSS PARTS
OF THE OHIO AND LOWER MISSISSIPPI VALLEYS INTO THE APPALACHIANS AND
SOUTH ATLANTIC SEABOARD,...AS WELL PARTS OF NORTHEASTERN NEW
MEXICO...
...SUMMARY...
Scattered strong to severe thunderstorm development appears probable
today, particularly across parts of the Ohio Valley into
Appalachians, and east of the lower Mississippi Valley into eastern
Gulf Coast states.
...Discussion...
It appears that mid/upper ridging inland of the Pacific coast
through the western Canadian Prairies and northern U.S. Rockies is
beginning to become suppressed by a short wave perturbation. As
this continues, a seasonably deep downstream trough, currently still
digging through the northern Great Plains/Upper Midwest vicinity, is
forecast to pivot east-northeastward across the Great Lakes and Ohio
Valley, gradually taking on a negative tilt as it does. An
initially broad, modest associated surface cyclone may deepen some,
mainly across northern Ontario into the James Bay vicinity, with at
least a couple of reinforcing surges of cooler air overspreading the
Great Lakes region, Ohio and Mississippi Valleys.
Within a belt of more modest cyclonic mid/upper flow in latitudes to
the east of the southern Rockies, at least one notable meso-beta to
meso-alpha scale cyclonic circulation appears to be in the process
of developing near the Ark-La-Tex vicinity. It appears that this
circulation will tend to migrate east-northeastward across and to
the east of the lower Mississippi Valley during the day. However,
the extent to which it is maintained or becomes sheared, as
larger-scale troughing within the two branches of westerlies tends
to come in phase, remains unclear based on latest model output.
Upstream, weak mid-level troughing is forecast to dig inland of the
southern California coast, through the Southwest, around the
northeastern periphery of a prominent mid-level high over the
subtropical eastern Pacific.
Seasonably moist air appears likely to remain largely confined to a
remnant frontal zone across the southern tier of the U.S.,
associated with the modest southern mid- and subtropical westerlies.
However, a narrow plume of southerly return flow is ongoing ahead of
the lead reinforcing cold front now advancing southeast of the upper
Great Lakes and Midwest.
...Lower Mississippi Valley into south Atlantic Seaboard...
Potential convective evolution remains unclear, but guidance remains
suggestive that ongoing convective development propagating across
northeastern and north central Texas will be in the process of
weakening while spreading into Louisiana and upper Texas coastal
areas early in the period. Additional convection is also likely to
be ongoing downstream of the emerging mesoscale vortex, aided by
low-level warm advection, as it migrates east of the Mississippi
Valley.
The impact of this convection on boundary-layer destabilization
remains unclear. However, while mid-level lapse rates may be weak,
with at least some insolation, boundary-layer dew points in excess
of 70 F across the Gulf Coast region may contribute to sufficient
destabilization to support at least scattered intensifying
thunderstorm development, both upstream and downstream of the
convective vortex. Some of this activity may pose a risk for,
mainly, strong surface gusts. A brief tornado also might be
possible, particularly near the convective vortex as long as it
remains relatively well-defined. This severe risk may continue into
the south Atlantic Seaboard tonight, but this remains more unclear.
...Ohio Valley into Appalachians...
Moderate boundary-layer destabilization ahead of the lead cold front
might provide support for scattered strong to severe thunderstorm
development, including supercells, in the presence of strong
deep-layer shear beneath 40-60+ kt southwesterly mid/upper flow.
Toward mid to late afternoon, it is possible that modestly deepening
surface troughing across the upper Ohio Valley into the lee of the
Allegheny front may provide a better defined focus for this threat.
...Great Lakes vicinity...
Convection-allowing model output and associated guidance suggest
that destabilization and shear may become supportive of convection
capable of producing severe hail and wind in a narrow corridor ahead
of a secondary surface cold front (closer to the mid-level cold core
overspreading the Great Lakes), as it advances across and
east-southeast of Lake Michigan this afternoon.
...Southern Rockies through northwestern Gulf coast...
Extensive convective outflow appears likely to be progressing into
and through the upper Texas coastal plain by the beginning of the
period, and perhaps gradually stalling across parts of south central
Texas into the Pecos Valley. The gust front might still be a focus
for widely scattered strong thunderstorm development early in the
day, otherwise the extent of the outflow's stabilizing influence
remains unclear, particularly later in period to the lee of the
southern Rockies.
Downstream of the Southwestern mid-level tough, models suggest that
destabilizing, moist upslope flow into the Raton Mesa/eastern slopes
of the Sangre de Cristo Mountains might become supportive of a
couple of supercells and one or two small upscale growing
thunderstorm clusters. Beneath modest to weak northwest mid-level
flow, this activity may pose a risk for severe hail and wind while
propagating off the higher terrain through this evening. Continuing
development into portions of west Texas overnight is more unclear.
..Kerr/Squitieri.. 06/09/2025
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