Severe Storm Outlook Narrative (AC)
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000
ACUS02 KWNS 270549
SWODY2
SPC AC 270549

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1249 AM CDT Sat May 27 2017

Valid 281200Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN PLAINS...ARKLATEX...MID MISSISSIPPI VALLEY AND OHIO
VALLEY...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OUTSIDE OF THE
SLIGHT RISK AREA ACROSS PARTS OF THE SOUTHERN
PLAINS...ARKLATEX...MID MISSISSIPPI VALLEY...OHIO VALLEY...SOUTHERN
GREAT LAKES...CENTRAL APPALACHIANS AND CAROLINAS...

...SUMMARY...
Scattered severe thunderstorms with a threat for large hail, wind
damage and a few tornadoes will be possible on Sunday across parts
of the mid Mississippi and Ohio Valleys. Large hail and wind damage
will also be possible across parts of the southern Plains and
Arklatex.

...Mid Mississippi River/Ohio Valley/Lower Michigan/Central
Appalachians/Carolinas...
An upper-level trough is forecast to move eastward into the mid to
upper Mississippi Valley on Sunday. At the surface, a cold front is
forecast to move southeastward across the mid Mississippi and Ohio
Valleys. Ahead of the front, surface dewpoints should be in the mid
to upper 60s F with moderate instability developing by afternoon.
Thunderstorms appear likely to initiate along the front in the early
afternoon with several line segments moving eastward across the
slight risk area. In addition to the instability, a 60 to 75 kt
mid-level jet will move across the mid Mississippi Valley on Sunday.
This feature will create strong deep-layer shear profiles favorable
for organized severe storms. Surface winds are forecast to be
west-southwesterly just ahead of the front. This will create a
unidirectional wind profile suggesting that the storms may tend to
organize into lines. For this reason, the greatest threat could be
for damaging wind gusts. If a few storms remain discrete, then
supercells with large hail and wind damage will also be possible. A
tornado threat may develop across the region mainly as low-level
flow strengthens during the early evening.

A marginal severe threat may also develop northward into Lower
Michigan but instability is forecast to be less there. Isolated
severe storms may also develop southeastward into the central
Appalachians and Carolinas Sunday afternoon.

...Southern Plains/Arklatex...
West to southwest mid-level flow is forecast to be in place on
Sunday as a cold front advances southeastward across the southern
Plains and Arklatex. As surface heating takes place along and ahead
of the front on Sunday, isolated to scattered thunderstorm
development should take place during the afternoon from the Texas
Hill Country northeastward into the Arklatex. Surface dewpoints
ahead of the front should be in the upper 60s to lower 70s F
resulting in moderate to strong instability by afternoon. In spite
of the instability, deep-layer shear across much of the warm sector
is forecast to be weak. This may result in a severe threat
associated with multicells that develop well to the east of the
front. Deep-layer shear is forecast to be stronger near the front
where mid-level flow may be sufficient for a few rotating storms
associated with large hail and wind damage.

..Broyles.. 05/27/2017

$$



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