Thursday, April 6, 2017

SPC Apr 6, 2017 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0743 AM CDT Thu Apr 06 2017

Valid 061300Z - 071200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THROUGH MIDDAY
TO EARLY AFTERNOON FOR PARTS OF THE MID-ATLANTIC...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
ENHANCED RISK AREA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
SLIGHT RISK AREA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS MORNING
ACROSS CENTRAL FLORIDA...

...SUMMARY...
Scattered severe storms with damaging winds, large hail, and a
couple of tornadoes will be possible through about midday to early
afternoon across the Mid-Atlantic.  A marginal wind and hail risk
will diminish slowly this morning across central Florida.

...Synopsis...
Secondary cyclogenesis is underway near the Blue Ridge in northwest
VA, where 3-6 mb pressure falls per two hours have been observed in
advance of a negative tilt shortwave trough accelerating
northeastward over the southern Appalachians.  The northwest VA
cyclone will deepen and move north-northeastward to eastern PA by
early-mid afternoon.  A trailing cold front will move off the NC
coast by 18z, and the remaining warm sector near the Delmarva will
be pinched off by 21z.

...Mid-Atlantic region through early afternoon...
Overnight convection has lingered near the NC coast, and anvil
cirrus has overspread eastern NC and southeastern VA this morning. 
Low-level moisture inflow across eastern NC/VA has been
disrupted/reduced by this convection, and the clouds will likely
slow surface heating prior to frontal passage.  However, strong
forcing for ascent and modest moisture recovery ahead of the front
will support a severe-storm risk until the cold front moves offshore
this afternoon.  Very strong deep-layer shear and conditionally
unstable midlevel lapse rates will support a risk for damaging winds
and marginally severe hail with embedded cells/line segments, and an
isolated tornado or two cannot be ruled out with fast-moving cells.

...Central FL this morning...
A pre-frontal band of thunderstorms moving across central FL this
morning is expected to weaken slowly as the strong midlevel
shortwave trough passes well to the north of this area.  Deep-layer
shear and buoyancy will be sufficient for a marginal damaging wind
risk this morning, prior to the storms weakening.

..Thompson/Cohen.. 04/06/2017

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