FOUS11 KWBC 060710
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
310 AM EDT Mon Apr 6 2026

Valid 12Z Mon Apr 06 2026 - 12Z Thu Apr 09 2026

...Missouri Valley/Corn Belt... Day 1...

An interesting evolution during the second half of Day 1 (00Z -
12Z Tuesday) could result in a very narrow corridor of heavy
snowfall from eastern Nebraska into southwest Iowa and far
northern Missouri. A modest shortwave dropping across the Central
Rockies will cause weak height falls and broad divergence across
the region Monday night into Tuesday morning. At the same time, a
potent NW to SE oriented jet streak will arc southward on the
upwind side of a trough moving over the Great Lakes/Northeast,
leaving favorable RRQ diffluence overlapping the best mid-level
divergence. This mid- level pattern will push a cold front through
the region today, but it is likely that this front will begin to
kink and return northward with warm advection Tuesday morning as
850mb flow returns to the S/SW creating a narrow corridor of
impressive fgen as moist isentropic upglide ascends the boundary.

The overlap of this moist isentropic ascent with the RRQ of the jet
streak aloft will create a narrow stripe of intense 850-600mb fgen,
creating a streak of heavy precipitation. With the most intense
ascent expected to lift into the deepening DGZ (50% chance of at
least 50mb of DGZ depth according to the SREF), dynamic cooling
should overcome the generally marginal thermal structure during the
overnight hours and absent of the April sun-angle, leading to a
stripe of heavy snow with snowfall rates potentially reaching
1"/hr. There remains some uncertainty into the placement of this
band due to its very narrow nature, as well as the intensity of
any of the snow. WPC probabilities have increased, and now feature
a 30-60% chance of at least 4" by Tuesday morning from east-
central NE through southwest IA, potentially leading to a hazardous
morning commute.

...Great Lakes & Northeast... Days 1-2...

Compact shortwave digging out of Manitoba will race southeast,
crossing the Upper Midwest and Great Lakes today before becoming
embedded into the more synoptic cyclonic flow across the Northeast
by Tuesday. This will help spawn a weak wave of low pressure along
an inverted surface trough, with locally enhanced moist advection
in the vicinity of this low leading to a swath of light to moderate
snowfall. The heaviest synoptic snow should be generally north of
the international border, but CAA in the wake of this impulse will
push 850mb temps down to around -15C, producing a favorable
environment for lake effect snow (LES) in the favored NW snow belts
downstream of the Great Lakes. The duration and intensity of this
LES may be somewhat modest, but significant accumulations exceeding
4" are still possible (30-70% chance) across the Huron Mts of the
MI U.P. on D1, and 10-20% along the Chautauqua Ridge east of Lake
Erie on D2 on north through the favored upslope regions of the
Adirondacks and Green Mts.

Snell/Weiss

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