RSS Mesoscale Discussions from Storm Prediction Center

SPC Jun 19, 2018 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook
      
Day 1 Outlook Image
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
PLAINS...

...SUMMARY...
Severe thunderstorms are expected across the central Plains Tuesday
afternoon and evening while marginally severe thunderstorms are
expected from the Midwest into Virginia.

...Central Plains...

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
evening.

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
driven convection.

..Darrow/Squitieri.. 06/19/2018

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SPC Jun 19, 2018 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook
      
Day 2 Outlook Image
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1257 AM CDT Tue Jun 19 2018

Valid 201200Z - 211200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE PLAINS...THE MID ATLANTIC...AND OREGON...

...SUMMARY...
A few severe thunderstorms are possible on Wednesday across the
central and southern Plains, over parts of eastern Virginia, and
over parts of Oregon.

...Synopsis...
A shortwave trough will move slowly across the central Plains toward
the mid MS Valley, providing cool temperatures aloft along with a
belt of enhanced northwesterly midlevel flow. A weak low pressure
trough will extend roughly from IL to southwest TX, with a moist air
mass south of this boundary.  To the east, a large upper trough will
stretch from eastern Canada into the Northeast, with modest westerly
flow aloft over the Mid Atlantic where low pressure is forecast
during the day. To the west, low pressure will deepen over central
WA and OR during the day as a low-amplitude shortwave trough moves
across northern CA into OR.

...Central and southern Plains...
Areas of rain and storms may be ongoing Wednesday morning across the
central Plains beneath the upper trough. Given a weak surface focus,
any outflow boundaries will play a role in diurnal development.
Marginal wind and hail will be possible with scattered storm
clusters, with modest instability and marginal shear profiles for
any organized severe threat.

...Mid Atlantic...
Instability will build during the day over eastern VA into NC, with
weakly veering winds with height as the surface trough deepens.
Scattered storms are expected near this trough during the afternoon,
with marginal hail or wind possible.

...Central Oregon...
MUCAPE of 500-1000 J/kg will develop during the day with surface
heating and cooling aloft. Westerly surface winds may aid in upslope
and scattered storm development, with locally strong wind gusts or
marginal hail possible.

...MAXIMUM RISK BY HAZARD...
Tornado:   2%     - Marginal
Wind:      5%     - Marginal
Hail:      5%     - Marginal

..Jewell.. 06/19/2018

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