Severe Storm Outlook Narrative (AC)
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
ACUS01 KWNS 250540
SWODY1
SPC AC 250539

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1239 AM CDT Thu May 25 2017

Valid 251200Z - 261200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL HIGH PLAINS...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST
WY TO CENTRAL KS...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
MIDDLE ATLANTIC...

...SUMMARY...
Isolated severe storms will be possible Thursday and Thursday night
across portions of the central High Plains, and during the day
Thursday across portions of the mid-Atlantic region.

...Central Plains...

Early-morning water vapor imagery depicts a well-defined short-wave
trough over the northern inter-mountain region.  Large-scale forcing
ahead of this feature should aid a band of mid-level moistening
across southern WY during the day such that convection should
develop relatively early in the diurnal cycle as surface
temperatures warm to near 60F.  It appears a forced-corridor of
convection will evolve across northern CO/southern WY by early
afternoon then slowly grow upscale as it spreads/propagates
southeast into the central High Plains.  While low-level moisture
will be somewhat lacking, mid-upper 40s dew points should be more
than adequate for robust surface-based thunderstorm development
ahead of the short wave.  Forecast soundings across northeast CO
suggest adequate deep-layer shear for a few supercells and large
hail and gusty winds can be expected with this high-based activity.
As LLJ strengthens across the Plains, in response to the short wave,
strong thunderstorms could spread into northwest KS during the
evening hours.

...Middle Atlantic...

Strong 12hr mid-level height falls will spread across the Middle
Atlantic region early in the period as a negative-tilt trough
translates east of the Appalachians.  Latest short-range model
guidance suggests 500mb speed max will round the base of the trough
over southern GA at 12z then eject off the Carolina coast during the
afternoon.  Exit region of this feature should aid convection across
the Middle Atlantic and isolated strong storms may evolve within a
corridor of focused ascent.  NAM guidance suggests much of this
region will see appreciable boundary-layer warming - more than
adequate for surface-based parcels to reach their convective
temperatures.  Latest thinking is thunderstorms should concentrate
across the northern Middle Atlantic where low-level convergence will
be stronger in the presence of a pronounced east-west surface front
draped across the Delmarva into southern PA.  Forecast buoyancy is
not that great across this region but shear profiles seem adequate
for at least low severe probs, including hail, wind, and perhaps a
brief tornado.

...FL...

Have opted not to include severe probs across the central and
southern Peninsula despite the possibility for frontal convection
early in the period.  Latest short-range guidance, including several
high-res solutions, differ considerably regarding the coverage and
intensity with this early-day activity.  With large-scale forcing
expected to lift north of this region it`s not entirely clear how
organized thunderstorms will be despite convection evolving along
the southern fringe of strong mid-level flow.  If it becomes clear
early-day convection will be organized or more robust, severe probs
may be added at 13z.

..Darrow/Mosier.. 05/25/2017

$$


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.