SPC 1730Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1230 PM CDT Mon Jul 26 2021

Valid 271200Z - 281200Z


Isolated thunderstorms are possible late Tuesday across the upper
Mississippi Valley.  A conditional risk for large hail and damaging
gusts will accompany the stronger storms.  Strong to locally severe
gusts will be possible mainly Tuesday afternoon and evening for
parts of the Northeast.

A mid-level anticyclone will be centered over the central High
Plains on Tuesday while a mid-level low will reside over central
Quebec.  A belt of strong northwesterly mid-level flow will extend
from south-central Canada into the upper Great Lakes and into the
Northeast.  Model guidance indicates a disturbance will move from
the western Great Lakes eastward into NY during the day.  

...Upper MS Valley...
A reservoir of low-level moisture will reside over the region
Tuesday to the south of a residual frontal zone draped
northwest-southeast.  The airmass is forecast to become very
unstable by late afternoon as a cap weakens due to strong heating. 
However, the lack of appreciable large-scale forcing for ascent will
likely limit convective coverage with a weak cap remaining through
the early evening.  However, weak 850 mb theta-e advection near the
boundary may aid in isolated storm development by early evening in a
corridor from eastern SD to central WI.  Strong shear/large CAPE
would conditionally support a hail risk with any sustained storm.  

Broad cyclonic mid-level flow will encompass the Northeast to the
south of a primary disturbance over Canada.  Models show strong
westerly mid-level flow moving through the base of the large-scale
trough.  Strong heating through midday and into the afternoon will
result in steepened low-level lapse rates.  The arrival of the
aforementioned disturbance into the lower Great Lakes by mid
afternoon will probably aid in storm development across NY with
activity spreading/developing east into southern New England.  As a
few clusters develop during peak heating, a gradual intensification
is expected as storms move through an environment characterized with
upper 50-lower 60s surface dewpoints.  Strong to locally severe
gusts capable of damaging gusts are possible with the stronger
clusters before this activity weakens during the evening as it
approaches the coast.

..Smith.. 07/26/2021

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