Sioux Falls, SD...Abilene, TX...Wichita Falls, TX...Sioux City, IA...Cheyenne, WY...
Probabilistic Damaging Wind Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
SPC AC 171254
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0754 AM CDT Fri May 17 2019
Valid 171300Z - 181200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF NEBRASKA AND SOUTHEAST SOUTH DAKOTA...AS WELL AS PARTS OF WESTERN
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN OHIO
EAST-SOUTHEASTWARD ACROSS MUCH OF MARYLAND AND VIRGINIA...
Severe storms with very large hail, damaging winds, and a few
tornadoes (a couple of which could be strong) are expected, mainly
from the central High Plains northeastward to the mid Missouri
Valley. Several severe storms -- capable of producing very large
hail and damaging winds, and a couple of tornadoes -- will also be
possible across portions of the western half of Texas. Finally,
scattered afternoon storms -- capable of producing locally
gusty/damaging winds will be possible from Ohio through the Middle
Large-scale upper trough over the western U.S. will shift eastward
through Friday night as a pronounced jet streak becomes established
over the central/southern Plains. A strengthening surface low over
northeast CO/western NE, along with the eastward progression of the
upper trough, will result in strengthening low/mid-tropospheric wind
fields and favorable deep-layer shear for organized/severe storms.
A warm front will extend east from the surface low, transitioning
into a cold front across the OH Valley/mid-Atlantic region, while a
surface dryline extends southward across western portions of KS/TX
by late afternoon. Lower/mid-60s surface dew points will be
transported northward beneath an expansive EML, resulting in
moderate/strong surface-based instability by afternoon.
...Central Plains/mid Missouri Valley Region...
Strong/isolated severe storms will remain possible this morning
vicinity of southern IA where a modest/veering low-level jet has
resulted in warm advection/lift in the 700-800 mb layer. MUCAPE of
500-1000 J/kg supports some risk for hail.
Large-scale ascent with the upper trough and left exit region of the
aforementioned jet streak should contribute to severe thunderstorm
development near/north of the warm front and surface low over
southeast WY/northeast CO this afternoon. A supercell mode will be
favored with a risk for very large hail, damaging winds and some
tornado risk. With time, additional thunderstorm development is
anticipated across western/central NE aided by strong low-level warm
advection near the warm front as the surface low moves northeast.
With strong deep-layer shear and effective SRH at or above 300 m2/s2
near the warm front, supercell storm mode will initially be favored
with a risk for a few tornadoes, a couple of which could be strong,
very large hail, and damaging winds. Upscale growth into an MCS
north of the front should occur this evening, with large hail as the
Farther south along the dryline, warm mid-level temperatures at the
base of the EML should result in very sparse storm coverage, however
given the favorable large-scale environment, a conditional risk for
very large hail/damaging gusts and possibly a tornado will exist
with any storm that develops.
Diurnal heating of a moist air mass (upper 60s surface dew points)
and steep mid-level lapse rates will result in strong surface-based
instability and gradually diminishing CINH by late afternoon. A
conditional severe risk with all severe hazards possible will exist
with any storm that can develop along the dryline over the eastern
TX Panhandle/far western OK this afternoon. Lift associated with a
perturbation lifting northeast across eastern NM/West Texas should
contribute to thunderstorm development by evening across southwest
TX, with an initial supercell mode evolving into a linear/bowing
storm mode overnight as storms move into north/northwest TX and
southwest OK. The more discrete storm phase will see a risk for very
large hail, damaging winds and a couple tornadoes, with damaging
winds potentially a greater concern late associated with the
linear/bowing structure. Large hail and some tornado risk will
remain during the overnight as moderate/strong instability and
around 40 kts of southwesterly deep shear persists.
...Ohio Valley/Mid-Atlantic Region...
A convective complex over WV/southwest VA this morning should
continue to weaken as it moves south/southeast within a weakly
buoyant environment. Daytime heating will result in pockets of
moderate surface-based instability near the front, and 35-40 kts of
west-northwest mid-level flow will result in sufficient shear to
support organized storms. Frontal convergence should lead to
additional scattered thunderstorm development during the day, with a
risk for damaging gusts and perhaps large hail.
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