Apr 20, 2020 1730 UTC Day 2 Convective Outlook
Updated: Mon Apr 20 17:30:21 UTC 2020 (20200420 1730Z Day 2 shapefile | 20200420 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20200420 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 78,879 35,421,502 New York, NY...Philadelphia, PA...Oklahoma City, OK...Newark, NJ...Jersey City, NJ...
MARGINAL 115,351 24,855,483 Baltimore, MD...Boston, MA...Washington, DC...Virginia Beach, VA...Tulsa, OK...
Probabilistic Tornado Graphic
20200420 1730 UTC Day 2 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 2 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
2 % 9,657 75,008 Dumas, TX...Borger, TX...
Probabilistic Damaging Wind Graphic
20200420 1730 UTC Day 2 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 2 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 32,043 33,612,670 New York, NY...Philadelphia, PA...Newark, NJ...Jersey City, NJ...Yonkers, NY...
5 % 86,645 23,782,267 Baltimore, MD...Boston, MA...Washington, DC...Virginia Beach, VA...Norfolk, VA...
Probabilistic Large Hail Graphic
20200420 1730 UTC Day 2 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 2 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 45,517 1,710,560 Oklahoma City, OK...Norman, OK...Edmond, OK...Midwest City, OK...Moore, OK...
5 % 50,835 1,639,843 Tulsa, OK...Amarillo, TX...Wichita Falls, TX...Lawton, OK...Stillwater, OK...
   SPC AC 201730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Mon Apr 20 2020

   Valid 211200Z - 221200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TUESDAY AFTERNOON
   INTO TUESDAY NIGHT ACROSS PARTS OF THE NORTHERN MID ATLANTIC COAST
   REGION...AS WELL AS ACROSS PARTS OF THE SOUTH CENTRAL PLAINS...

   ...SUMMARY...
   Strong thunderstorms may pose a risk for damaging wind gusts across
   parts of the northern Mid Atlantic Coast region Tuesday afternoon. 
   A few strong to severe thunderstorms are also possible across parts
   of the south central Plains late Tuesday afternoon into Tuesday
   night.

   ...Synopsis...
   Recent blocking regime over the mid-latitude eastern Pacific
   continues to break down, with mid-level ridging weakening while
   shifting southeastward, inland across British Columbia and the
   Pacific Northwest.  The remnants of a mid-level closed low will 
   progress inland of the central California coast, within a lingering
   southern branch of split westerlies, likely crossing the lower
   Colorado Valley by 12Z Tuesday, before continuing across and east of
   the southern Rockies by 12Z Wednesday.

   Downstream, the westerlies appear likely to remain largely in phase
   east of the Mississippi Valley, with large-scale troughing gradually
   shifting across the Atlantic Seaboard into the western Atlantic. 
   Within the more prominent northern branch, a significant short wave
   trough, with a couple of embedded mid-level perturbations, is
   forecast to dig through the lower Great Lakes region, before turning
   eastward across southern Quebec and much of the Northeast Tuesday
   through Tuesday night.  This will be accompanied by a deep surface
   cyclone over Quebec, with secondary surface cyclogenesis possible
   near the northern New England coast into the Canadian Maritimes by
   late Tuesday night.

   A reinforcing cold front, in the wake of the cyclone, appears likely
   to overspread most areas east of the Mississippi Valley, as far
   south as northern Florida, by the end of the period.  This will be
   preceded by a stalling/weakening frontal zone across southern
   Florida and the north central Gulf of Mexico, into the upper Texas
   coast, central Texas and the Texas South Plains.  In response to the
   approaching southern branch impulse, models suggest that the frontal
   zone may retreat north of the Red River Valley by late Tuesday
   night, in response to a developing surface wave across the south
   central high Plains.

   ...Northern Mid Atlantic Coast...
   Early period pre-frontal cloud cover and precipitation still seem
   likely to limit daytime heating and boundary-layer destabilization
   along and ahead of the southeastward advancing cold front.  However,
   even with surface dew points in the 40s to near 50F, considerable
   model output (including latest convection allowing guidance),
   suggests that strong mid-level cooling and forcing for ascent along
   the front will promote the evolution of at least a narrow squall
   line across parts of eastern New York into the lee of the Allegheny
   Mountains by early Tuesday afternoon.  As this line advances
   southeastward, in the presence of 40-50 kt lower/mid-tropospheric
   ambient westerly mean flow, the downward transport of momentum in
   stronger downdrafts will contribute to the risk for potentially
   damaging wind gusts across much of the northern Mid Atlantic Coast
   region by early Tuesday evening.

   ...South central Plains...
   Capping associated with warm elevated mixed-layer air seems likely
   to inhibit thunderstorm development south of the developing warm
   frontal zone, as northward moisture advection contributes to
   boundary-layer destabilization across much of central and northern
   Texas.  One exception may be within lee surface troughing, aided by
   orography, near and east of the Raton Mesa vicinity, where forcing
   for ascent may be aided by a 50-70 kt 500 mb speed maximum by late
   Tuesday afternoon.  With steep lapse rates contributing to
   moderately large CAPE (in excess of 1000 J/kg) in the presence of
   strong deep-layer shear, organized convective development, including
   isolated supercells, may develop off the higher terrain into the
   Oklahoma/Texas Panhandle vicinity through Tuesday evening. 
   Thereafter, developments are more unclear, but a zone of enhanced
   lower/mid tropospheric warm advection, on the nose of the capping
   elevated mixed-layer air, may become the focus for vigorous elevated
   storm development posing a risk for severe hail, mainly across
   northwestern Oklahoma overnight.

   ..Kerr.. 04/20/2020

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