SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1229 PM CDT Mon Sep 01 2025
Valid 021200Z - 031200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY
AFTERNOON AND EVENING ACROSS PARTS OF SOUTHEASTERN NORTH
DAKOTA...EASTERN SOUTH DAKOTA...SOUTHWESTERN INTO CENTRAL
MINNESOTA...
...SUMMARY...
Widely scattered to scattered strong thunderstorm development is
possible across parts of the eastern Dakotas into Minnesota, as well
as portions of the Southwest into Great Basin, late Tuesday
afternoon and evening. The risk for severe weather still appears
generally low, but a couple of storms could produce marginally
severe hail and localized strong surface gusts.
...Discussion...
In the mean, models indicate that mid/upper heights will remain
relatively high across much of the eastern Pacific into western
North America. However, an embedded blocking high across the
northeastern Pacific is forecast to become at least a bit less
prominent, and lower heights to its southeast and south may
consolidate. This latter regime includes a notable low, which may
undergo deepening while retrograding offshore of the Pacific
Northwest coast Tuesday through Tuesday night. At the same time, a
couple of weaker perturbations appear likely to slowly shift
north-northeastward, inland of California and northern Baja
California coastal areas.
Downstream of this regime, large-scale mid/upper troughing will be
maintained to the east of the Rockies, as far south as the Gulf
Basin, and reinforced by a vigorous short wave trough emerging from
the high latitudes. By Tuesday evening, this perturbation is
forecast to begin digging across the international border into the
northern Great Plains/Upper Midwest, accompanied by another cold
front.
Seasonably high moisture content, on the southern periphery of the
larger-scale cyclonic regime, has already become largely confined to
the subtropical latitudes, with further southward suppression
forecast across southern Texas and the Florida Peninsula through
this period. However, a tongue of more modest moisture lingers
inland across much of the Gulf Coast states and eastern Great
Plains, along the southwestern through western flank of the
troughing.
Weak to modest destabilization, with insolation, and forcing for
ascent associated with short wave perturbations embedded within the
evolving pattern are likely to support a number of areas of
scattered thunderstorm activity Tuesday through Tuesday night.
However, the risk for severe weather appears generally low across
most areas.
...Northern Great Plains...
The mid-level cold core of the approaching vigorous short wave
trough will remain post-frontal, but models suggest that a plume of
modestly steep lower/mid-tropospheric lapse rates ahead of the front
may contribute to destabilization sufficient for vigorous
thunderstorm development by late Tuesday afternoon. It appears that
this may become focused across parts of the eastern Dakotas into
western Minnesota, where a residual pocket of boundary-layer dew
points as high as the lower/mid 60s may contribute to CAPE on the
order of 1000-2000+ J/kg. Forecast soundings suggest that
deep-layer shear will remain generally weak, but mid/upper forcing
for ascent might contribute to scattered upscale growing clusters
with potential to produce marginally severe hail and wind.
...Southwestern Deserts into Great Basin...
Areas of thunderstorm development will likely be rooted above a warm
and deeply mixed boundary layer, with thermodynamic profiles
conducive to at least isolated to widely scattered microbursts.
However, the extent to which convection may be able to grow upscale
into consolidating clusters, with outflow enhanced by downward
transfer of momentum associated with southeasterly to southerly
mid-level flow, remains unclear. Forecast ambient flow appears
generally on the order 15-25 kts, but perhaps with embedded stronger
speed maxima. It is possible that severe wind probabilities at or
above 5 percent may still be needed, if/when potential corridors
become more confidently evident.
..Kerr.. 09/01/2025
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