SPC AC 290535

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1135 PM CST Tue Jan 28 2020

   Valid 291200Z - 301200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   The risk for severe thunderstorms appears negligible across the
   U.S., today through tonight.

   ...Synopsis...
   Models indicate that positively tilted mid-level troughing over the
   eastern Pacific will undergo significant amplification across the
   northeastern Pacific into British Columbia and the Pacific Northwest
   during this period.  As this occurs, a vigorous short wave trough,
   now approaching the British Columbia coast, is forecast to turn
   eastward, inland around the crest of the ridge, and become
   increasing fragmented in splitting flow across and east of the
   Canadian Rockies.

   At the same time, one of several perturbations emerging from a
   preceding inland advancing short wave trough, and now beginning to
   dig into the U.S. Great Basin, is forecast to continue sharply
   southward to the east of the ridging.  As it approaches and crosses
   the Southwestern international border area, it may provide support
   for a developing frontal wave to the west of the Texas Big Bend by
   12Z Thursday.

   Downstream, models indicate that large-scale mid-level ridging will
   build from the lee of the southern Rockies through much of the
   remainder of the southern tier of the U.S., today through tonight. 
   As it does, a significant short wave trough, initially crossing the
   lower Mississippi Valley, is forecast to gradually lose amplitude
   while accelerating across the Southeast, and east of the south
   Atlantic Coast.  But, it does appear that associated forcing for
   ascent will remain sufficient to provide continuing support for weak
   to modest surface wave development, along a frontal zone across the
   northeastern Gulf of Mexico through the Atlantic waters north of the
   Bahamas by 12Z Thursday.

   ...Southeast...
   Latest model output continues to suggest that potential for the
   inland advection of weakly unstable, warm sector boundary layer air
   across north central/northeast Gulf coastal areas is low.  If this
   air mass does advect inland, low-level and deep-layer shear will
   probably be strong and supportive of organized severe convection. 
   However, at most, it currently seems that this may only potentially
   impact southeast Louisiana coastal areas near Boothville around
   11-13Z this morning, with enough uncertainties lingering to maintain
   severe probabilities at less than 5 percent.

   Otherwise, while there may be considerable mid to lower tropospheric
   moistening ahead of the wave across the Florida Peninsula during the
   day today, forecast soundings (particularly across the interior
   peninsula) suggest that substantive moistening  closer to the
   surface may not take place until the 30/00-06Z time frame.  The
   extent to which this contributes to boundary-layer destabilization
   (mainly across the southwestern and southeastern portions of the
   peninsula) remains unclear, but the risk for severe weather
   currently appears negligible.

   ...Southwest...
   Beneath cold mid-level (500 mb temps -24 to -28 C) air accompanying
   the digging short wave trough, daytime heating and orographic
   forcing may contribute to some convection capable of producing
   lightning, mainly late this afternoon.

   ..Kerr/Squitieri.. 01/29/2020

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