SPC Aug 20, 2019 0600 UTC Day 1 Convective Outlook
(Di, 20 Aug 2019)
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0102 AM CDT Tue Aug 20 2019
Valid 201200Z - 211200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE MIDDLE MS VALLEY...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN
An organized cluster of thunderstorms capable of severe wind gusts
and hail will overspread portions of the middle Mississippi and
lower Ohio Valleys today. Hail and isolated strong winds are also
possible across portions of Minnesota this morning.
...Mid MS Valley eastward across the OH Valley...
An organized MCS will likely be moving through
south-central/southeast IA early this morning. Expectation is for
this MCS to be near its mature phase at this point with a
well-developed rear-inflow jet and strong cold pool resulting in
strong wind gusts. A few of these gusts could be greater than 75
mph. As the MCS continues southeastward through northwest MO and
central IL later this morning and into the early afternoon, it is
expected to gradually lose intensity as its cold pool accelerates
and loses depth. By the time the MCS reaches IN and western KY, it
is expected to be characterized by weakly organized multicells along
the cold pool. Even with this anticipated weakening, strong wind
gusts are still possible.
...Central High Plains/Central Plains...
A cold front is expected to push into the Upper Midwest and central
Plains, likely extending from western WI southwestward into
northeastern CO during the late afternoon. Moist upslope flow is
anticipated into eastern WY/northeast CO behind this front, with the
resulting convergence along the lee trough expected to result in
thunderstorm initiation. Downstream environment characterized by
strong buoyancy and at least moderate vertical shear will support
supercell storm structures capable of very large hail and strong
wind gusts. These storms are expected to continue eastward into NE
during the evening. A strengthening low-level jet will lead to a
reinvigoration of any ongoing storms and/or development of new
storms, primarily across central and eastern NE. Given the presence
of ample low-level moisture and steep mid-level lapse rates, large
hail is probable with these storms. Isolated very large hail (i.e.
greater than 2" in diameter) is possible. Dry mid-levels could also
contribute to strong wind gusts.
Ample low-level moisture and steep mid-level lapse rates will result
in strong buoyancy ahead of the approaching cold front this morning
across northern/central MN. Stable low-levels (below 850 mb) will
likely limit storm strength but large hail and occasional strong
gusts through the stable layer are possible.
Showers and thunderstorms will likely develop during the afternoon
within the moist and diurnally destabilized air mass across the
region. Vertical shear will be weak, leading to predominately
disorganized, outflow-dominant multicells. Even so, the very moist
air mass and steep low-level lapse rates support water-loaded
downbursts capable of damaging wind gusts.
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SPC Aug 20, 2019 0600 UTC Day 2 Convective Outlook
(Tue, 20 Aug 2019)
SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1254 AM CDT Tue Aug 20 2019
Valid 211200Z - 221200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
Scattered storms, some severe, are possible Wednesday over parts of
the Northeast, and over much of the central Plains into the mid
Mississippi Valley. Damaging wind gusts and marginal hail are
possible in both regions.
An upper low will move from Ontario into Quebec, with a leading
shortwave trough moving across the Great Lakes during the day and
New England overnight. A cold front will stretch from southwest
Ontario to IL by late afternoon, with mid to upper 60s F dewpoints
spreading into the Northeast. Aiding moisture advection as well as
low-level shear will be southwesterly 850 mb winds increasing to
25-30 kt, while mid to upper level winds increase throughout the
To the west, a convectively reinforced boundary is expected across
northern MO, KS, and into eastern CO, with a very moist and unstable
air mass to the south. Bouts of thunderstorms are likely throughout
the period near this boundary, with the greatest concentration over
MO, closer to the Great Lakes trough influence.
Heating will lead to numerous thunderstorms across the moist sector
by 18Z over much of NY and northeast PA, expanding across New
England during the afternoon. Around 30-35 kt of deep-layer shear
and 100-150 m2/s2 effective SRH will be sufficient to sustain severe
storms, including isolated supercells capable of marginal hail, a
brief/weak tornado, or damaging wind. Due to the expected large
number of storms, mergers are likely, and a few line segments may
form as well. Storms may persist well into the evening and overnight
into northern New England when the stronger height falls occur.
...Central Plains into the Mid MS and lower OH Valley...
Storms are expected to be ongoing from NE across MO and into IL
Wednesday morning along an east-west oriented front, and where
substantial instability will exist. This outflow-reinforced front
will likely translate south during the day, with continuous areas of
storms over KS, MO, and IL. Winds aloft will generally be westerly
and below 20 kt, thus disorganized storms are most likely. However,
a few small bows are possible, with localized areas of wind damage.
Given such strong instability, the strongest storms may produce
To the west, east/northeast surface winds will bring a moist air
mass into east-central WY and CO, where capping will be a concern.
Storms are likely to form over the higher terrain, with a narrow
north-south zone of hail or wind threat. Other storms are likely
farther south in the well-mixed and hot air, from northeast NM
across northern OK and AR, with localized downbursts possible.
...MAXIMUM RISK BY HAZARD...
Tornado: 2% - Marginal
Wind: 15% - Slight
Hail: 5% - Marginal
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