SPC AC 190539
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1239 AM CDT Tue Jun 19 2018
Valid 191200Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
Severe thunderstorms are expected across the central Plains Tuesday
afternoon and evening while marginally severe thunderstorms are
expected from the Midwest into Virginia.
Late evening model guidance suggests a significant short-wave trough
will eject across the Great Basin into western CO by 18z then into
the High Plains of KS/TX Panhandle by 20/12z. A corridor of stronger
mid-high level flow will translate across NV/UT into the central
High Plains by peak heating which should enhance convection that
evolves over the higher terrain from southeast WY to south of the
Palmer Divide by mid afternoon. CAM guidance supports this scenario
with scattered supercells evolving over the Plains within a
strengthening shear regime. This activity will be supported by
large-scale height falls and moist upslope flow that should
encourage east-southeast propagation toward western KS during the
Latest thinking is pre-dawn convection across the central Plains
should gradually wane as it drifts into south-central NE by the
start of the period. If convective outflow from this activity is not
too disruptive, the strongest corridor of boundary-layer heating is
expected to develop from southern CO into extreme southeast NE.
Forecast soundings strongly favor supercells across southeast WY/CO
into western KS. Aside from large hail a few tornadoes can be
expected across this region.
Thunderstorms that develop downstream along the frontal zone from
the northern TX Panhandle into southeast NE will do so within a
weaker-sheared environment and more clustering is expected. As a
result, hail/wind will be the primary threats.
...Midwest to VA...
Upper ridge is expected to be shunted a bit east Tuesday with
anticyclonic flow forecast across the Midwest/OH Valley into the
Middle Atlantic. High PW air mass will necessarily extend along this
corridor which will coincide with a frontal zone draped from VA into
IL. Boundary-layer heating will be instrumental in convective
development along/south of this wind shift but environmental shear
is not expected to support more than pulse/multi-cell updrafts.
Locally damaging winds are the primary threat with this diurnally
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