SPC Jul 9, 2020 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook
Day 3 Outlook Image

Day 3 Convective Outlook NWS Storm Prediction Center Norman OK
0230 AM CDT Thu Jul 09 2020 Valid 111200Z - 121200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE SOUTHERN PLAINS AND OZARK PLATEAU...AND OVER THE COASTAL
MID-ATLANTIC AND NEW ENGLAND... ...SUMMARY...
Isolated severe thunderstorms are possible across portions of the
southern Plains and Ozark Plateau on Saturday. A few strong storms
are also possible over the coastal Mid-Atlantic and New England. ...Synopsis...
Upper ridging will remain in place over the Southwest, with some
westward expansion into the Great Basin and southern/central CA
anticipated. Farther north, a shortwave trough is forecast to move
from the Upper Midwest and into the Upper Great Lakes/Mid MS Valley while another shortwave trough moves through the Pacific
Northwest/British Columbia late. Over the eastern CONUS, broad upper
troughing will likely extend from the Upper Great Lakes into the
southern Appalachians at the beginning of the period. This upper
trough is then forecast to gradually move eastward throughout the
day. Additionally, a surface low (and attendant mid-level cyclone)
will be over and approaching southern New England early Saturday
morning, with a generally northward track expected during the
period. ...Southern Plains/Ozark Plateau...
Decaying MCS may be ongoing over eastern KS/southwest MO/northeast
OK at the beginning of the period, with at least some downstream
severe potential possible. Greater severe potential is anticipated
later in the day along any residual outflow from this MCS. Air mass
over the region will be very warm and moist, contributing to strong
instability. This region is expected to be on the edge of the
stronger northwesterly flow aloft but enough vertical shear will
likely be in place to support severe storms. This severe potential
will rely on the existence of a mesoscale boundary, which has
limited predictability at this forecast range. The overall parameter
space looks very favorable for severe but the limited predictability
merits only introducing a 5% probability with this outlook. ...Northern Mid-Atlantic into New England...
Position of the surface low (and related mid-level cyclone) will
critical for determined the areas of greatest severe risk across the
region Saturday. Overall expectation is for enhanced low to
mid-level winds to be in place east of the surface low, coincident
with modest instability. Unfortunately, model guidance does not
currently have a good consensus on the location of this low, which
limits predictability and precludes anything higher than 5% severe
probabilities. With that being said, a large 5% area was delineated
from NJ northeastward into southern ME where at least some severe
threat is currently indicated by the guidance. Refinements to this
area are likely in later outlooks as position and track of the
surface low become more predictable. ...Mid-Atlantic...
Widespread thunderstorms are expected over the Mid-Atlantic ahead of
the broad upper trough (and its attendant surface trough). Moderate
instability will likely be in place but weak vertical shear is
expected to limit storm organization/updraft persistence, tempering
the overall severe potential. ..Mosier.. 07/09/2020 

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