spc ac 180559
day 1 convective outlook
nws storm prediction center norman ok
1259 am cdt tue jun 18 2019
valid 181200z - 191200z
...there is an enhanced risk of severe thunderstorms across the
western half of oklahoma...and across parts of west texas...
scattered severe thunderstorms are expected to develop across parts
of the southern and central plains, with large hail and damaging
winds most probable. the greatest concentration of severe weather
will be over western oklahoma, and across west texas. other
marginally severe storms may occur from the southern appalachians to
the middle atlantic.
with upper ridges situated off both the east and west coasts, a
large area of low heights/troughiness will exist across the plains,
accentuated by 35-40 kt midlevel speed max moving across ks, ok, and
the tx panhandle, and by 50-60 kt winds in the upper levels. at the
surface, low pressure will remain situated from southeast co into
the tx panhandle during the day, shifting into western ok overnight.
a dryline will extend south from the low across west tx, with a
stationary front during the day across central ks.
the warm sector will remain very moist with mid to upper 60s f
dewpoints, beneath steep lapse rates aloft. this will yield ample
instability for severe storms, mainly across western ok and tx.
elsewhere, dewpoints of 68-72 f will exist east of the appalachians
and along the coast, beneath modest southwesterly winds aloft which
will support scattered strong storms.
...central and southern plains...
early morning storms are expected to dissipate across ks southward
into northwest tx, with a gradual heating of the air mass during the
day. stronger heating will take place over eastern co and nm, and
south of the outflow from southwest tx into ok. by late afternoon,
strong instability will develop as dewpoints rise back into the mid
60s across the panhandles and into central ks, with near 60 f
dewpoints to the co/nm border. cool midlevel temperatures will
support strong instability profiles, with mlcape of 2000-2500 j/kg
across southwest ks and ok, and around 4000 j/kg across western tx.
initial cells are expected to form across central ks into northern
ok, by early afternoon, and some of these may contain hail though
shear will be marginal. a moist boundary layer as well as weakly
veering winds with height may also support a supercell or two with a
brief tornado threat.
behind this activity, storms will form over southeast co into the ok
panhandle by 21z, assuming full air mass recovery, with most cam
solutions producing an mcs which will travel across western and
central ok during the evening. a strengthening southerly low-level
jet supports this solution. however, depending on timing, some
models suggest outflow and downward motion may emanate out of storms
over west tx, which may stabilize the air mass into southern parts
of the enhanced risk area. therefore, future adjustments may be
farther south, widely spaced clusters of storms will develop along
the dryline across west tx. very steep lapse rates will develop with
heating, with initiation between 21-00z. models suggest a few areas
of possible clustering...over the davis mountains, near lubbock, and
along the rio grande. very large hail will be the primary risk with
these cells, which may persist for several hours, but not move very
far as storm motions will be slow to the southeast.
...mid atlantic and appalachians...
strong heating will occur along the lee of the appalachians, from ga
to the delmarva, with mlcape of 2000-2500 j/kg possible over nc and
va. storms will form within this air mass during the late afternoon,
with localized wind damage possible. shear profiles are a bit weak
overall for any organized severe, but a cluster or two may produce
a pocket of greater wind threat within the instability axis from
central nc into southeast va. if severe coverage looks to be greater
than currently forecast, a small slight risk may become necessary in
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note: the next day 1 outlook is scheduled by 1300z