SPC Sep 13, 2019 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1229 PM CDT Fri Sep 13 2019

Valid 141200Z - 151200Z


Strong to severe storms may impact parts of the mid Missouri and
upper Mississippi Valleys Saturday afternoon and evening.  A few
thunderstorms associated with a tropical system may also pose a risk
for strong wind gusts and isolated tornadoes across parts of the
east central Florida peninsula. Strong wind gusts are also possible
across central and southern Arizona Saturday afternoon and evening.

Moderate, predominantly zonal upper flow is expected across the
northern tier of CONUS on Saturday with flattened ridging remaining
in place over the southern CONUS. A low-amplitude shortwave trough
embedded within the stronger westerly flow will move from its early
period position over the northern Plains eastward through the Upper
MS Valley and Upper Great Lakes. At the same time, a weak surface
low associated with this shortwave is expected to move from central
SD northeastward into southern MN. A cold front attendant to this
surface low will move across the northern Plains for much of the day
Saturday. However, the southern portion of this front is expected to
slow down and eventually stall late Saturday night/early Sunday

Farther south, a tropical cyclone will likely be centered over the
northern Bahamas early Saturday morning. This storm is expected to
move gradually northwestward throughout the period.

...Mid MO Valley into the Upper MS Valley...
Strong moisture advection is anticipated across the central and
southern Plains on Saturday, bringing upper 60s dewpoints in the Mid
MO and Upper MS Valleys by late Saturday afternoon. As a result, a
moist and moderately buoyant warm sector beneath moderate vertical
shear. The strongest forcing for ascent will likely remain north of
the region and convergence along the front will be limited by
pre-frontal veering of the surface winds. These factors are expected
to keep the overall storm coverage isolated. Even so, the few storms
that do develop will likely be capable of large hail and damaging
wind gusts. Additionally, any robust storms near the warm front may
also pose a risk for a tornado or two. Anticipated storm coverage
currently precludes higher severe probabilities but upgrades may be
needed in subsequent outlooks if higher storm coverage appears more

...Eastern FL Peninsula - Potential Tropical Cyclone Nine...
Recent intensity guidance from the National Hurricane Center
suggests the cyclone will have reached Tropical Storm intensity by
the beginning of the Day 2 period (i.e. 12Z Saturday). Latest
forecast track keeps the center about 60-70 mi off the east-central
FL coast, which keeps the strongest winds (and highest wind/tornado
risk) offshore. Best chance for any damaging wind gusts and/or a
tornado is currently along the immediate coastal areas of the
eastern FL Peninsula during the afternoon when thunderstorms are
most likely. However, any westward shift in the storm's path could
result in damaging wind gusts/tornado risk farther inland.

...Central/Southern AZ...
Scattered thunderstorm coverage is anticipated across central and
southern AZ as low-level moisture surges northward into the region
and a weak vorticity maximum approaches from northern Mexico.
Expectation is for thunderstorms to develop during the early
afternoon across the higher terrain, with some potential propagation
into the lower deserts thereafter. Mid-level flow will be very weak
but the deeply mixed boundary layer is still expected to support a
few strong wind gusts and low severe probabilities have been
introduced as a result.

Tornado:   2%     - Marginal
Wind:      5%     - Marginal
Hail:      5%     - Marginal

..Mosier.. 09/13/2019

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