SPC AC 041257

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0657 AM CST Sun Feb 04 2018

   Valid 041300Z - 051200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   Thunderstorms are expected across portions of the Southeast today.

   ...Synopsis...
   In mid/upper levels, a mean trough will remain over the eastern
   states, traversed by several shortwaves.  The most pronounced of
   those shortwaves will include a trough -- now evident in moisture-
   channel imagery over portions of MN/SD -- forecast to pivot
   southeastward/eastward over the Great Lakes, Ohio Valley, and
   northern/central Appalachians through the period.  Meanwhile,
   cyclonic flow is expected to extend across most of the contiguous
   U.S. as a strong shortwave trough -- now located offshore from BC --
   moves past the mean ridge position and southeastward over the
   Pacific Northwest. 

   At the surface, a synoptic cold front influenced by the northern-
   stream perturbation was analyzed from lower MI across MO to northern
   OK.  By 00Z, this front should reach central OH, western/mid TN,
   central TX and northeastern NM, before merging with or becoming
   indistinguishable in the building anticyclone behind the front
   described next.  A surface trough was analyzed from middle TN across
   MS to southeastern LA, with some baroclinicity evident closer to the
   Gulf.  Frontogenesis is forecast as a low forms over AL and moves
   northeastward toward the VA Tidewater region by 00Z, with the front
   extending southwestward across the Carolinas, GA and western/central
   FL Panhandle.  

   ...Southeast...
   Multiple bands of low-level convergence, both near and ahead of the
   eastern frontal zone, are expected to support thunderstorm potential
   shifting generally eastward across this region today.  Isolated to
   scattered thunderstorms are expected in a broad zone of elevated
   warm advection and moisture transport, as parcels are lifted
   isentropically to an LFC, with episodic banding and clustering of
   storm modes.  Activity largely will be elevated above relatively
   stable near-surface conditions, amidst modest midlevel lapse rates. 

   The greatest depth/coverage of thunderstorms should remain over the
   Gulf, as well as late in the period over the Atlantic's Gulf Stream
   waters.  So will the most consistent potential for surface-based
   convection -- especially across the northern Loop Current where
   ocean-air thermal fluxes will be maximized.  With eastward extent
   from there into the FL peninsula, expect cooling of the boundary
   layer -- gradual at first across cooler shelf waters then stronger
   amidst lower antecedent/overland boundary-layer theta-e.  That
   storm-relative thermal transition should be deleterious to
   maintenance of optimal inflow parcels inland, though a strong gust
   or two cannot be ruled out along the southernmost Panhandle coast
   near AAF or the northern part of the FL west coast.  Overall,
   convection will outrun near-surface inflow regimes and severe
   potential appears too isolated/conditional to warrant a categorical
   severe-risk area at this time.

   ..Edwards.. 02/04/2018

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