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 Forecast Discussion

  
000
ACUS01 KWNS 240601
SWODY1
SPC AC 240559

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1259 AM CDT Sat Jun 24 2017

Valid 241200Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS EARLY OVER
PORTIONS OF COASTAL SOUTHERN NEW ENGLAND...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE CAROLINAS AND NORTHEAST GEORGIA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
NEW MEXICO...

...SUMMARY...
Isolated severe thunderstorms with damaging winds will be possible
over portions of the Southeast on Saturday, with isolated severe
hail and strong winds over parts of New Mexico.  Isolated damaging
winds and perhaps a brief tornado will be possible across southern
New England Saturday morning.

...Synopsis...
Within a broad cyclonic mid-level flow regime from the
central/northern Plains east to the northeast U.S., a notable
embedded impulse will move southeast across the upper Midwest and
Great Lakes on Saturday.  In response, slight amplification of the
upper-level trough will occur and an increase in mid-level flow will
occur across the Carolinas/portions of the mid-Atlantic region. 
Farther west, an upper-level anticyclone will strengthen in the
vicinity of the Arizona/Mexico border.  A surface cold front will
extend near the New England coast southwest across the Carolinas,
and west through the lower Mississippi Valley/central Texas and then
curving north across the high terrain of New Mexico Saturday
afternoon.  A very moist (upper 60s/lower 70s surface dew points)
air mass will remain in place south of the frontal boundary.

...Carolinas...
Diurnal heating of a very moist air mass along and south of the
front will result in pockets of moderate MLCAPE by afternoon, and
moderate southwesterly flow aloft will result in 30-40 kts of
effective shear.  Despite generally weak low-level flow, updraft
water loading in the presence of PW values in excess of 2 inches
should result in isolated strong/damaging gusts with the strongest
storms during the afternoon and early evening hours.

...New Mexico...
Southeasterly low-level flow will continue to transport increasing
moisture into the high terrain Saturday, and areas of moderate
surface-based instability will develop during the afternoon. 
Thunderstorms developing near the Continental Divide in the presence
of 20-35 kts of northwest mid-level flow may become sufficiently
organized with mid-level rotation to pose a risk for isolated large
hail.  In addition, the presence of a well-mixed boundary layer will
promote a risk for damaging winds. 

...Coastal southern New England early...
Forecast soundings depict strong low-level wind fields and
unidirectional flow in advance of the front during the morning
hours, in part due to a notable southerly low-level jet from near
the mid-Atlantic coast into southern New England.  Although
instability will be meager, some high-res guidance continues to
suggest a potential for short line segments near the immediate
coast, and will introduce a focused area with low severe
probabilities for isolated damaging winds and perhaps a tornado. 

...Lower Mississippi Valley into central Texas...
Although mid-level flow and deep-layer shear will be generally weak
across this area, at least some potential for strong/severe storms
may exist during the afternoon as storms diurnally intensify in the
vicinity of the front or perhaps along remnant outflow from prior
convection.  With moderate instability expected to develop, severe
probabilities may be introduced in later outlooks where confidence
in greater storm coverage increases.

..Bunting/Mosier.. 06/24/2017

$$