SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK
0100 AM CDT Thu Jul 09 2020 Valid 101200Z - 111200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL
SD AND NORTH-CENTRAL NE... ...SUMMARY...
Severe thunderstorms are expected across portions of the northern
and central Plains Friday. Greatest severe weather risk is currently
forecast from central South Dakota into central Nebraska Friday
evening/night. An isolated strong storm or two is also possible
across coastal portions of the northern Mid-Atlantic States and
southern New England. ...Synopsis...
Upper ridging is expected to build across the Southwest while a belt
of enhanced flow aloft extends along its northern periphery from
northern CA/Pacific Northwest eastward in the Mid/Upper MS Valley. A
shortwave trough is expected to progress through this belt of
enhanced flow, reaching the northern High Plains by Friday afternoon
and the Upper Midwest by early Saturday morning. Weak cyclonic flow aloft is anticipated over most of the eastern
CONUS. The only exception is in the vicinity of a tropical low,
which is forecast to begin the period just off the Delmarva
Peninsula. This low is expected to move northward along the
Mid-Atlantic coast throughout the day, reaching the Hudson Valley by
early Saturday morning. ...Great Plains...
A decaying convective line may be moving into the Ozark Plateau and
adjacent portions of eastern OK early Friday morning. Some severe
risk is possible downstream as this line continues southeastward.
However, significant variability exists within the guidance
regarding the presence and/or location of this line, resulting in
low predictability and preclude any severe probabilities in this
area with this outlook. Farther north, surface cyclogenesis is expected over the northern
High Plains ahead of the approaching shortwave trough. The surface
pressure gradient will tighten as a result of this cyclogenesis,
contributing to northwestward low-level moisture advection. By
Friday afternoon, 60 deg F surface dewpoints will likely reach into
far eastern MT, with mid 60s dewpoints into southern NE.
Consequently, moderate to strong instability will develop east of
the surface trough, which will combine with low-level convergence
and increasing large-scale ascent to support convective initiation. Initially, storms will likely be discrete, with long, straight
hodographs suggest splitting supercells capable of large hail
(isolated very large) and strong wind gusts. Eventual upscale growth
into an organized convective line appears probable, with a risk for strong wind gusts then continuing downstream across
portions of SD and NE. ...Northern Mid-Atlantic into Southern New England...
Increased low to mid level flow throughout the eastern and northern
periphery of the tropical low mentioned in the synopsis will result
in the potential for a few stronger storms within the convective
band surrounding the system. Damaging wind gusts and/or a brief
tornado or two are possible with any more persistent updrafts. Poor
lapse rates and warm temperature profiles will limit instability,
reducing the overall severe potential. ..Mosier.. 07/09/2020