SPC AC 271938

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0238 PM CDT Mon Jul 27 2020

   Valid 272000Z - 281200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER NORTHERN
   NEW ENGLAND AND THE OHIO VALLEY...

   ...SUMMARY...
   Isolated to scattered strong thunderstorms are expected across
   northern New England and portions of the Ohio Valley this afternoon
   and evening, accompanied by a local risk for gusty/potentially
   damaging winds.

   ...20Z Update...

   ...OH Valley...
   Line of thunderstorms moving through western IN has produced several
   strong wind gusts over the past hour, including 42 kt at AOH and 40
   kt at HUF. The downstream convective line across northwest OH has
   also produced a gust of 38 kt at LWV. This overall trend for strong,
   but sub-severe, gusts is expected to continue this afternoon and
   evening, with the lack of stronger vertical shear precluding more
   robust storm organization. 

   ...Elsewhere...
   Overall forecast remains on track elsewhere across the CONUS. A few
   strong to severe storms are still possible across northern New
   England this afternoon and evening. Scattered to widespread
   thunderstorm activity is still anticipated along the front extending
   from central IL into central OK and ahead of a broad shortwave
   trough moving through central CA into the Great Basin.

   ..Mosier.. 07/27/2020

   .PREV DISCUSSION... /ISSUED 1129 AM CDT Mon Jul 27 2020/

   ...Northern New England...
   Thunderstorms are expected to develop across Quebec Province this
   afternoon as an upper-level trough approaches from the west, and
   move east across northern New England through this evening.
   Mid-level flow averaging 40 kts will contribute to sufficient
   deep-layer shear to support updraft organization. Substantial cloud
   cover is present over northern portions of the risk area, however
   pockets of heating in the presence of upper 60s/lower 70s dew points
   will contribute to MLCAPE locally 1000-1500 J/kg. Strong/locally
   damaging wind gusts will be the primary severe threat. 

   ...Ohio Valley...
   Substantial heating is taking place this morning in advance of the
   southeast-moving cold front, and despite poor mid-level lapse rates
   the presence of lower-mid 70s surface dew points will contribute to
   moderate-strong MLCAPE by early afternoon.  Although the region will
   generally be south of stronger mid-level flow, numerous storms are
   expected to develop, occasionally merging into clusters/short line
   segments with a risk for damaging gusts.  The Marginal Risk was
   adjusted slightly southwest over southeast/east-central IL. 

   ...Kansas/Oklahoma/Texas Panhandle...
   Thunderstorm coverage is expected to increase in association with a
   remnant MCV located near the KS/OK border and an outflow
   boundary/effective cold front across southeast KS/northwest OK and
   west into the TX panhandle. Strong instability will be in place, and
   there is some potential for strong/gusty winds with the more intense
   storms, however the overall severe risk is expected to remain too
   low for introduction of severe probabilities with this outlook, and
   heavy rain appears to be the greater threat.  

   ...Great Basin/northern California...
   Large-scale ascent associated with an upper trough over California 
   will support an increase in thunderstorm coverage today.
   Precipitable water values around 0.75 inches and strong diurnal
   heating should yield MLCAPE values between 500-1000 J/kg during the
   afternoon. A dry sub-cloud layer and steep low-level lapse rates
   (approaching 9 C/km) will support a few dry microbursts.

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