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
ACUS02 KWNS 270602
SPC AC 270601

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0101 AM CDT Sun May 27 2018

Valid 281200Z - 291200Z


Strong/severe storms are expected across portions of the central and
High Plains, and into a broader area of the Great Plains.  A couple
of brief tornadoes will also be possible once again, in conjunction
with Alberto.

While Alberto shifts across the northeast Gulf of Mexico and
eventually shifts inland Monday, within background large-scale upper
ridging, a western U.S. upper low is progged to devolve into an open
wave as it ejects slowly east-northeastward toward the northern and
central Plains.

At the surface, high pressure will prevail east of the Mississippi
River away from the circulation surrounding Alberto.  Farther west,
a lee trough is progged to reside over the High Plains, with a
menagerie of outflow boundaries from prior convection expected over
the Dakotas/western Nebraska vicinity through the first half of the
period.  Afternoon cyclogenesis may occur along the lee trough over
eastern Colorado, as an upper disturbance rotating around the main
western low/trough shifts across the central High Plains region.

...The north-central U.S. southward across western portions of the
Plains and into the central High Plains...
A rather complex convective scenario appears likely to unfold for
Monday, as Sunday/early Monday convection from the Wyoming vicinity
into the Dakotas/Nebraska -- along with associated convective
outflow and cloud debris -- will likely alter/influence favored
zones for subsequent Monday convective development.

At this time, it appears that threat will be somewhat lessened with
northward extent into North Dakota, with greatest heating and
destabilization suppressed westward to the higher terrain of
Wyoming, and southward across the High Plains/Plains ahead of the
lee trough.

As an upper disturbance rotates northeastward out of the southern
Rockies toward the central High Plains, a moderately unstable
airmass should support afternoon storm development, with ascent
focused near the lee trough and possible weak cyclogenesis occurring
over the eastern Colorado area, as well as over portions of eastern
Wyoming -- both in upslope-favored areas and along possible/residual
outflow.  With enhanced southwesterly flow aloft associated with the
aforementioned disturbance overspreading the central High
Plains/Plains atop low-level southeasterlies, shear will favor
development of organized/supercell storms.  While uncertainty
regarding evolution of intervening convective events precludes an
outlook upgrade at this time, expect potential for large hail and
damaging winds, along with the potential for a couple of tornadoes.
Storms may grow upscale linearly into one or more lines/bands by
evening -- shifting northeast out of Wyoming into parts of South
Dakota, and eastward out of the High Plains across western Kansas
and the Texas/Oklahoma Panhandles, with risk for hail and damaging
winds continuing well into the evening.

...The Southeast...
Alberto -- progged to have evolved into a tropical storm -- is
forecast to make landfall over western portions of the Florida
Panhandle Monday evening.  Within a large envelope east/northeast of
the center of circulation, bands of showers and thunderstorms
occurring within a kinematic field featuring enhanced 0-3 km shear
will result in occasional cells acquiring low-level rotation.  Thus,
will maintain a rather large 5%/MRGL risk to cover potential for
occurrence of brief tornadoes.

Tornado:   5%     - Slight
Wind:     15%     - Slight
Hail:     15%     - Slight

..Goss.. 05/27/2018

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