SPC AC 221953

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0253 PM CDT Mon Jul 22 2019

   Valid 222000Z - 231200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
   NORTHEAST/MID-ATLANTIC STATES AND TENNESSEE VALLEY...

   ...SUMMARY...
   Scattered damaging winds are possible across portions of the
   Mid-Atlantic States into southern New England, as well as the
   Tennessee Valley, this afternoon to early evening.

   No changes were made to the previous outlook.

   ..Jewell.. 07/22/2019

   .PREV DISCUSSION... /ISSUED 1135 AM CDT Mon Jul 22 2019/

   ...Mid-Atlantic States to southern New England...
   Additional amplification of the large-scale trough over the eastern
   CONUS will contribute to a slight cooling of mid-level temperatures
   and strengthening southwesterly winds aloft coincident with a
   slow-southeastward-moving front across the central Appalachians
   toward parts of the Mid-Atlantic region. 

   The coverage of yesterday's storms across most of this region has
   impacted thermodynamic profiles, with surface temperatures/dewpoints
   running at least several degrees lower than this time (late
   morning/midday) yesterday. As noted in the prior Outlook discussion,
   12Z soundings from Sterling, Wallops, Upton, Pittsburgh, and
   Wilmington OH all sampled mean mixing ratios about 2-3 g/kg lower
   compared to 12Z yesterday and have weaker mid-level lapse rates.

   That said, moisture will steadily recover and ample insolation is
   noted at midday across the Mid-Atlantic in the lee of the
   Appalachians, with MLCAPE to 1500-2000 J/kg possible (highest near
   the coast). As compared to yesterday, somewhat stronger wind
   profiles between 2-6km AGL will also be a factor for individual
   storm longevity/organized storms. Multicells will be common and the
   possibility exists for a few transient supercells from far southern
   New York/northern New Jersey into southern New England. Damaging
   winds will be the most common risk through the afternoon into early
   evening.

   ...Mid-South and Tennessee Valley...
   A moist air mass (70-75F surface dewpoints) remains ahead of a
   southeastward-moving cold front. As morning cloud cover thins,
   increasing cumuliform/thunderstorm development are expected this
   afternoon, particularly downstream of a pair of residual MCVs. Wet
   microbursts yielding localized wind damage will be the main risk.

   While weak vertical shear will tend to limit overall organization
   and risk magnitude, a somewhat more focused/organized severe risk
   may exist this afternoon into early evening across western/middle
   Tennessee and nearby southern Kentucky and perhaps northern portions
   of Mississippi/Alabama. Enhanced winds are noted with the MCV near
   the Mississippi River, with 30-40 kt west-southwesterly winds
   between 4-6 km in recent (16Z) Paducah, KY WFO-88D VWP data.

   ...Central/southern Rockies and adjacent High Plains...
   Isolated thunderstorms will develop this afternoon and remain
   largely confined to the higher terrain of Wyoming/Colorado/New
   Mexico, although a few storms could drift into the immediately
   adjacent High Plains. A belt of modest mid-level north/northwesterly
   flow aloft will persist around the Four Corners/southern Rockies
   upper ridge, yielding some threat for marginally severe hail/wind.

   ...Southeast/south-central Arizona...
   On the southern periphery of the south-central Rockies-centered
   upper ridge, 15-20 kt mid-level easterlies may help loosely organize
   scattered thunderstorms that develop over the higher terrain during
   the late afternoon and move toward the desert floor. Hot/deeply
   mixed boundary layer will support vigorous downdrafts and the
   possibility of severe-caliber winds and blowing dust late this
   afternoon/early evening.

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