SPC AC 101300

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0800 AM CDT Wed Jul 10 2024

   Valid 101300Z - 111200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS
   OF WESTERN AND CENTRAL NEW YORK...

   ...SUMMARY...
   Tornadoes and damaging winds are possible over parts of
   western/central New York.

   ...Synopsis...
   In mid/upper levels, the pattern will continue to be characterized
   by mean troughing over the Great Lakes and ridging in the west.  An
   anchoring anticyclone -- centered near LAS -- should remain
   quasistationary over the Great Basin, lower Colorado River Valley,
   Southeastern CA and much of AZ.  In the Great Lakes regime, a
   leading/strong shortwave trough is apparent in moisture-channel
   imagery from Lake Michigan to the Mid-South, containing an
   intermittently closed 700-500-mb circulation on the north end, over
   Lake Michigan.

   Associated cyclonic flow includes the increasingly diffuse midlevel
   remains of Beryl, with a warm axis aloft still apparent in 700-
   500-mb charts east/southeast of the shortwave perturbation's thermal
   trough.  This complex feature is forecast to eject northeastward by
   00Z to the neck of ON, Lake Huron, southeastern Lower MI, and the
   MIE area.  Overnight, the trough should lose amplitude while
   reaching southwestern QC and the Lower Great Lakes.  Upstream, a
   fairly prominent, compact, shortwave trough and PV anomaly were
   located over MN and eastern SD.  This feature should pivot
   southeastward to IA by 00Z, then parts of northwestern IL and
   northeastern MO by 12Z tomorrow.

   At the surface, 11Z analysis showed a low over northwestern OH, with
   cold front across eastern parts of KY/TN, to southern AL, becoming
   quasistationary near the LA coastline.  A slow-moving warm front was
   drawn from the low across the western NY/PA line to near ALB, then
   over central New England.  By 00Z, the cold front should extend from
   an occlusion triple point over (or just south of) Lake Ontario,
   across west-central NY, central parts of PA/VA/NC, to southern GA,
   becoming quasistationary and frontolytic over southern parts of
   AL/MS/LA.  The warm front should move slowly northward over western,
   central and northern NY today, decelerating/stalling across the
   higher terrain from the Adirondacks eastward across VT/NH/western
   ME.  The cold front also should decelerate as it shifts eastward
   over the Atlantic Seaboard, extending by 12Z from a triple point
   over northern parts of VT or NH across western New England, the
   Mid-Atlantic Coast, and near-coastal NC, to a deepening low offshore
   from MYR.  A prefrontal trough should shift eastward today over
   parts of NY/PA, while a post-frontal trough (with some mass-response
   reinforcement by the northwest-flow shortwave trough) should move
   southward over parts of IA, NE and northern IL.

   ...Northeastern CONUS...
   Scattered thunderstorms are expected to develop along/ahead of the
   cold front , especially near the prefrontal trough (with that
   activity ultimately evolving upscale into a line.  All severe
   hazards will be possible from relatively discrete convection
   (including potential for several supercells) from the early-stage,
   pre-linear regime, and perhaps even in the warm sector to its east. 
   Tornado potential should be relatively maximized near the warm
   front, where backed near-surface winds will contribute to enlarged
   low-level hodographs and enhanced storm-relative flow in the
   boundary layer.  The corridor of greatest tornado probabilities is
   narrow, and may need to be shifted around today as mesoscale trends
   suggest (especially with regard to warm-frontal position).  However,
   at least marginally favorable low-level shear for embedded
   supercellular or QLCS mesovortex tornado potential is possible as
   far south as the western/upper Chesapeake Bay region.

   Ample low-level moisture is in place, and will continue over the
   area, with surface dewpoints commonly in the upper 60s to low 70s
   along and south of the warm front.  This will contribute to low LCL
   and, in concert with diurnal heating that satellite imagery suggests
   should be common, will yield peak/preconvective MLCAPE in the
   1500-2000 J/kg range ahead of the main convective band.  Activity
   should weaken in and near eastern parts of the "slight" to
   "marginal" probabilities this evening as it encounters a more-stable
   boundary layer.

   ...NM and west TX...
   Isolated to scattered thunderstorms should develop this afternoon --
   preferentially over higher elevations as diurnal heating removes
   MLCINH.  Activity then should move generally southward over deeper,
   straggly heated/mixed, yet favorably moist boundary layers to
   sustain convective potential, and also, to support isolated severe
   gusts from the most vigorous downdrafts.  Forecast soundings show
   mixed/subcloud layers extending well above 700 mb, yet still beneath
   300-800 J/kg MLCAPE.  Although strong veering with height is
   expected over much of this area, very weak low/middle-level wind
   speeds and lack of appreciable vertical shear will limit convective
   organization and coverage of the severe threat overall.

   ...IA and vicinity...
   Widely scattered to scattered thunderstorms are expected to develop
   this afternoon, with isolated severe hail and a few damaging to
   severe gusts possible.  Activity should form in a weak-MLCINH
   airmass near the surface trough, destabilizing through the
   lower/middle troposphere via a combination of diurnal surface
   heating, low-level warm/theta-e advection, and DCVA-forced cooling
   aloft that precedes the shortwave trough.  These factors, with
   surface dewpoints generally remaining in the upper 50s to mid 60s F
   through the boundary-layer heating/mixing cycle, should support a
   meso-alpha scale patch of 1000-2000 J/kg MLCAPE, atop a well-mixed
   subcloud layer.  With weak low/middle-level winds and shear, the
   main mode should be multicellular, with isolated pulse severe,
   before evening boundary-layer cooling reduces instability and
   convective coverage/intensity.

   ..Edwards/Bentley.. 07/10/2024

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