SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0229 PM CDT Wed Oct 07 2020

Valid 072000Z - 081200Z


Strong to locally severe wind gusts are possible this afternoon and
perhaps persisting into the early evening from parts of the Hudson
Valley into southern New England.

Have upgraded to 15-percent wind probabilities for parts of
east-central NY eastward into southern New England ahead of a squall
line quickly moving east across NY.  Several NY Mesonet sites in
Chenango, Montgomery, and Herkimer counties have observed gusts in
the 50-56 mph range during the past hour.  

Water-vapor imagery shows a potent mid-level shortwave trough moving
into the Northeast.  The flow associated with this disturbance is
quite strong (50 kt at 1.5 km ARL) as sampled by the KENX (Albany,
NY) and KBOX (Boston, MA) 88D VADs.  Although the earlier rain
shield has progressed across southern New England, cloud breaks and
peak heating in wake of these showers will enable at least some
steepening of the low-level lapse rates and a few hundred J/kg
SBCAPE to develop.  Given the strongly forced squall line with
adequate instability developing ahead/downstream of the convective
line, it seems plausible strong to locally severe gusts (50-60 mph)
via horizontal momentum transport, will continue or possibly
increase in coverage over the next few hours and result in widely
scattered wind damage.

..Smith.. 10/07/2020

.PREV DISCUSSION... /ISSUED 1101 AM CDT Wed Oct 07 2020/

The current forecast area appears to be on track, with no changes
made.  A band of showers and thunderstorms is organizing from lake
Ontario northeastward along the St Lawrence Valley.  This activity
will move quickly eastward across much of NY early this afternoon,
and across much of New England through early evening.  Widespread
clouds are present ahead of the convection, which will limit
low-level lapse rates and CAPE.  It is likely that these fast-moving
showers and storms will produce gusty and marginally damaging winds,
but it is uncertain how prevalent the risk of 50 knot winds will be.
 Given the overall marginal thermodynamic environment, will maintain
the ongoing MRGL risk area.  Activity should move off the New
England coast by mid-evening, ending the threat of gusty winds.

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