SPC AC 100601

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0101 AM CDT Sun May 10 2020

   Valid 101200Z - 111200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
   THE OHIO VALLEY...THE FLORIDA KEYS...AND PORTIONS OF THE SOUTHERN
   HIGH PLAINS...

   ...SUMMARY...
   A few strong to severe thunderstorms are possible across a portion
   of the Ohio Valley, the Florida Keys, and portions of the southern
   High Plains today.

   ...Synopsis...
   A compact surface low will be near southern Lake Michigan at 12Z
   this morning and move to somewhere near central New York by 12Z
   Monday. A cold front will extend southwest from this surface low and
   will cross the Appalachians tonight. A mid-level shortwave currently
   over the central Gulf will cross southern Florida this
   afternoon/evening. A large upper low will approach the West Coast
   today which will deamplify the upper ridge extending from the
   Pacific Northwest southward to AZ/NM.

   ...Portions of the Ohio Valley...
   Low-to-mid 40s dewpoints will advect northward ahead of a
   fast-moving cold front in Indiana and Ohio this morning. Very cold
   air aloft (likely around -27 to -28C at 500mb) will lead to steep
   lapse rates in the mid-troposphere. These steep low-level lapse
   rates will extend to the surface by mid-day as temperatures warm
   into the 50s yielding MLCAPE around 250 to 500 J/kg. Modest heating
   coupled with increased forcing for ascent will promote storm
   development by early afternoon across Indiana. Updraft strength will
   likely be limited due to marginal instability, however, strong
   forcing for ascent should aid in storm intensification with a few
   strong to severe storms possible along the front. These storms may
   initially pose a threat for both marginally severe hail and damaging
   winds. Wind damage will become the primary threat as storms congeal
   into a broken linear mode, and low-level lapse rates continue to
   steepen ahead of the front.

   ...The Florida Keys...
   Scattered storms are expected today along and south of a stalled
   boundary near the Florida Keys as a mid-level shortwave trough
   approaches the area from the central Gulf. Instability and lapse
   rates are forecast to be quite weak across the Keys, with the better
   instability across the Florida Straits. Effective shear is expected
   to increase to around 45 knots throughout the day which should be
   sufficient for some storm organization with any stronger updrafts.
   An isolated strong wind gust is possible with this activity.

   ...Portions of the Southern High Plains...
   Southeasterly surface flow will strengthen today across Texas with
   low-level moisture gradually increasing through the day. The poor
   moisture quality per 5/10 00Z RAOBs will be the primary limiting
   factor for greater destabilization. Storm initiation will favor the
   higher terrain of the Sacramento Mountains and the Raton Mesa, but
   isolated storm coverage will be possible in the upslope regime
   across the entire region. 00Z CAMS show a consistent signal for some
   of the best storm organization in northeast New Mexico as storms
   initially form over the Raton Mesa. Steep lapse rates and effective
   shear around 25 to 30 knots will support multicell clusters with the
   threat for isolated severe winds and hail.  

   ...Southwest Oregon...
   An isolated storm or two is possible in southwest Oregon late this
   afternoon and into the evening. MLCAPE is forecast to be 1000 to
   1500 J/kg over the higher terrain with mid-level lapse rates around
   8 C/km. Despite the favorable thermodynamic environment, storm
   coverage should be limited due to terrain circulations, as the
   primary forcing mechanism with only weak influence from a passing
   upper-level shortwave. In addition, flow will be on the weaker side
   with effective shear around 20 to 25 knots. However, an isolated
   strong storm or two are possible late this afternoon and into the
   evening.

   ..Bentley/Smith.. 05/10/2020

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