SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1200 AM CDT Sat Aug 03 2024
Valid 041200Z - 051200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY INTO
SUNDAY NIGHT ACROSS PARTS OF CENTRAL INTO NORTHEASTERN FLORIDA AND
ADJACENT SOUTHEASTERN GEORGIA...SOUTHERN MINNESOTA AND ADJACENT
PORTIONS OF EASTERN SOUTH DAKOTA...NORTHERN IOWA...AND SOUTHWESTERN
WISCONSIN...SOUTH CENTRAL INTO SOUTHEASTERN MONTANA AND ADJACENT
NORTHERN WYOMING...
...SUMMARY...
Widely scattered strong thunderstorms may pose at least some risk
for severe weather across parts of central into northeastern Florida
and adjacent southeastern Georgia, portions of the upper Mississippi
Valley and portions of the northern Rockies Sunday through Sunday
night.
...Synopsis...
Models indicate that mid-level flow across the northern
mid-latitudes will remain amplified, with a notable mid-level high
continuing to evolve over the Canadian Yukon Territory vicinity
Sunday through Sunday night. Downstream, seasonably strong cyclonic
flow likely will be maintained across the upper Great Lakes vicinity
through St. Lawrence Valley, to the south of a prominent cyclone
slowly migrating eastward across northern Quebec.
In lower latitudes, a prominent high is forecast to remain centered
across the Four Corners vicinity, while higher heights also begin to
elongate eastward across the southern Rockies into the central Great
Plains. Within modest westerly flow on the northern periphery of
this feature, low-amplitude troughing may progress across and
east-southeast of the northern Rockies into the Dakotas.
Seasonably high moisture content (including a plume of precipitable
water in excess of 2 inches) will remain largely confined to along
and east of a weakening mid-level trough/shear axis, between the
Western Ridging and ridging over the subtropical western Atlantic.
While this is forecast to shift offshore of the northern Atlantic
Seaboard, to the south of the Quebec cyclone, it likely will linger
near the southern Mid Atlantic coast through the Florida Peninsula,
and be reinforced by a surge of tropical moisture associated with a
developing tropical cyclone emerging from the Caribbean.
Beneath a lingering plume of warm-elevated mixed-layer air extending
east-southeast of the northern Rockies, toward the upper Mississippi
Valley, residual low-level moisture, enhanced by evapotranspiration,
may contribute to a corridor of moderate to strong potential
instability near a stalling surface frontal zone.
...Southeast...
The risk for severe weather Sunday through Sunday night still
appears largely conditional at the present time, due to the typical
uncertainties accompanying a developing landfalling tropical system
at this extended time frame. However, based on the current forecast
track of what is expected to be a developing tropical storm,
west-southwest of Tampa Bay early Sunday into the Big Bend vicinity
by early Monday, much of central through northeastern Florida may be
impacted by a period of enlarging clockwise-curved low-level
hodographs, coincident with a tropically moist and unstable
boundary-layer. This environment may become supportive of a risk
for tornadoes.
...Northern Rockies...
Model forecast soundings suggest that the boundary-layer may become
very warm, deeply mixed and characterized by at least weak
instability across much of southeastern into south central Montana
by late Sunday afternoon, before an evolving cluster of
thunderstorms begins to propagate east-southeast of the higher
terrain. It appears that this convective development will be aided
by forcing associated with the low-amplitude perturbation which may
include a 30-40+ kt westerly mid-level speed maximum. Downward
mixing of this momentum, coupled with the thermodynamic forcing,
probably will contribute to a few strong to severe surface gusts,
before the convection weakens Sunday evening.
...Northern Great Plains/Upper Mississippi Valley...
Convective potential remains unclear due to model variability and
uncertain forcing for thunderstorm development within the corridor
of strong potential instability near the stalled frontal zone.
However, models suggest that mid-level inhibition may become weaker
across the upper Mississippi Valley portion of the surface front,
relative to upstream across the northern Great Plains. Isolated
thunderstorm development may not be out of the question during the
peak late afternoon heating. Otherwise, forcing on the nose of a
nocturnally strengthening and veering low-level jet might support
thunderstorm development late Sunday evening and overnight.
..Kerr.. 08/03/2024
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