SPC 1730Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1112 AM CST Thu Nov 19 2020

Valid 201200Z - 211200Z


The risk for thunderstorms currently appears negligible across much
of the U.S. Friday through Friday night.

Models indicate that the westerlies will remain split, roughly along
120-140W longitude, with broadly confluent downstream flow centered
across the northern tier of the U.S. and adjacent southern Canada. 
As one of the more significant perturbations embedded within this
regime continues accelerating eastward, from northwest Ontario and
the upper Great Lakes region through the Canadian Maritimes by 12Z
Saturday, the center of broad cold surface ridging is forecast to
build southeastward across/east of the middle Missouri Valley.  This
will tend to contribute to the reinforcement of generally dry and
stable conditions in the wake of a prior cold intrusion; however, it
will be preceded by at least some further boundary-layer recovery
and inland return flow around the southern/western periphery of
remnant surface ridging centered over the Southeast.

Models indicate increasing potential instability within moistening
easterly low-level flow across the southwestern Atlantic/Bahamas
vicinity into the Florida Peninsula.  This could contribute to
potential for deepening convective development and scattered showers
Friday into Friday night, particularly along the Atlantic coastal
areas.  However, it appears that relatively warm mid-levels and
generally weak forcing for ascent will preclude intensification of
convection into thunderstorms.

...Ozark Plateau vicinity...
Models indicate that weak to modest low-level moistening on
southerly return flow will contribute to weak CAPE above the leading
edge of the southward advancing reinforcing cold intrusion.  It
appears that this may become focused along the Interstate 44
corridor of southwestern through south central Missouri, where
mid-level cooling may also weaken inhibition sufficiently to allow
for deepening convective development by 12Z Saturday.  While
forecast soundings appear to suggest some risk for lightning with
this activity, the extent of this potential remains unclear, and
thunderstorm probabilities are being maintained at less than 10
percent for now.

Models also indicate weak destabilization will occur across the Four
Corners region Friday night, in response to low-level moisture
return and cooling aloft associated with a low-amplitude wave
emerging from the subtropical eastern Pacific.  While at least some
output suggests that this could be accompanied by convection capable
of producing lightning, it remains unclear whether the risk reaches
the minimum 10 percent probability for a categorical thunderstorm

..Kerr.. 11/19/2020

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