Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 211600
SWOMCD
SPC MCD 211600
MEZ000-211830-

Mesoscale Discussion 1378
NWS Storm Prediction Center Norman OK
1100 AM CDT Fri Jul 21 2017

Areas affected...Portions of Maine

Concerning...Severe potential...Watch unlikely

Valid 211600Z - 211830Z

Probability of Watch Issuance...20 percent

SUMMARY...Some risk for isolated severe thunderstorms will develop
through the mid-day hours and continue into the late afternoon.
Watch issuance is unlikely.

DISCUSSION...Beneath broadly cyclonic flow aloft -- embedded with
low-amplitude impulses -- isolated thunderstorm development is
expected during the next few hours. This activity will likely
initiate along subtle, fragmented baroclinic troughs along which
initially swelling cumulus fields are noted over southern Quebec,
along a differential-heating zone peripheral to persistent mid-level
clouds over northern Maine, and amid diurnally deepening
boundary-layer circulations augmented by orographic effects. A
modestly moist boundary layer characterized by lower 60s dewpoints
will offer sufficient -- albeit marginal -- buoyancy (MLCAPE around
500-1000 J/kg) amid minimal convective inhibition for convection to
be sustained throughout the afternoon. Long mid/high-level
hodographs supporting around 35-40 kt of effective shear may support
sustained cells and small convective clusters capable of isolated
severe hail and wind. However, without stronger buoyancy, and given
the lack of stronger ascent, greater severe coverage is not
expected.

..Cohen/Coniglio/Dial.. 07/21/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...CAR...GYX...

LAT...LON   45377074 46247023 47086942 47056817 46416778 45356759
            44666821 44456961 44847064 45377074




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