Oklahoma City, OK...St. Paul, MN...Des Moines, IA...Sioux Falls, SD...Norman, OK...
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.
Oklahoma City, OK...Minneapolis, MN...Wichita, KS...St. Paul, MN...Sioux Falls, SD...
San Antonio, TX...Dallas, TX...Austin, TX...Fort Worth, TX...Kansas City, MO...
Probabilistic Large Hail Graphic
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk
Area (sq. mi.)
Some Larger Population Centers in Risk Area
Dodge City, KS...Big Spring, TX...Altus, OK...Liberal, KS...Pampa, TX...
Hutchinson, KS...Dodge City, KS...Big Spring, TX...Altus, OK...Pampa, TX...
Oklahoma City, OK...Omaha, NE...Minneapolis, MN...Wichita, KS...St. Paul, MN...
San Antonio, TX...Austin, TX...Fort Worth, TX...Kansas City, MO...Tulsa, OK...
SPC AC 161252
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0752 AM CDT Tue May 16 2017
Valid 161300Z - 171200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
WEST TEXAS TO PARTS OF IOWA...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
ENHANCED RISK AND EXTENDING TO PARTS OF THE CENTRAL HIGH PLAINS AND
UPPER MISSISSIPPI VALLEY...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
Episodes of severe thunderstorms are expected today and tonight
within a swath from west Texas across the central Plains to the
western Corn Belt and mid Missouri Valley. Tornadoes, severe gusts,
and large, damaging hail are expected within this corridor.
Progressive synoptic-scale troughing will dominate the upper-air
pattern today over the western/central U.S., with two
primary/embedded perturbations influencing low-level mass fields and
1. A strong, compact, mid/upper-level cyclone -- now apparent in
moisture-channel imagery over Vancouver Island, forecast to move
southeastward to southern ID by the end of the period. As heights
fall across the northwestern U.S. and Great Basin ahead of that
2. A strong shortwave trough, with embedded 500-mb low over
southern NV at this time, will pivot eastward then
east-northeastward across the Four Corners and northwestern MX. By
12Z, the trough should extend from eastern CO across eastern NM and
far west TX.
The 11Z surface analysis showed a surface low over northeastern SD,
warm front from there across northeastern IA and southern Lake
Michigan, and cold front southwestward across central NE to
northeastern Co, and a reinforcing cold front over central SD and
south-central WY. A wavy dryline was drawn from near IML southward
across the KS/CO border area to the western TX Panhandle,
southeastern NM and far west TX. The SD low should move
northeastward across MN to northern ON through the period, while a
second low deepens by 12Z along the combined frontal zone over
southern NE. The dryline will mix eastward across western KS, the
TX/OK Panhandles and South Plains today, and off the Caprock by
mid/late afternoon. Cold frontogenesis is expected over eastern NM
and west TX this evening and overnight as the shortwave trough
ejects, with the resulting baroclinic zone overtaking the dryline
from the west tonight.
Though the combined "slight" and "enhanced" outlook area appears as
one continuous swath on the map, it mostly represents the spatial
overlap of three rather distinct severe-storm regimes. We'll
emphasize those below, in rough start-time order.
...Early afternoon through evening: northern TX/OK Panhandles,
Western/central KS to IA...
Widely scattered to scattered thunderstorms should form during
early-mid afternoon near the dryline where the EML and MLCINH weaken
soonest. This activity initially will risk large/damaging hail,
severe gusts and a few tornadoes. Within the first few hours after
initiation, however, a preponderance of guidance from synoptic down
to high-res/convection-allowing progs indicate aggregation of
convection into a forward-propagating MCS, which may sweep
northeastward across KS and the Missouri Valley at least across
parts of IA through this evening and tonight, before encountering
enough stable air to weaken. This convection-evolution scenario
appears plausible given:
1. The geometry of the deep-layer flow,
2. Sufficiently weak afternoon/early-evening CINH to be prone to
forced slab ascent by aggregating cold pools,
3. A moist axis already in place to support a corridor of maximized
buoyancy later today from central KS to IA, southeast of residual
outflow pools from prior overnight convection, and
4. Well-mixed subcloud layers in forecast soundings that support an
increasing damaging-wind potential with northeastward extent, given
such modal morphology.
Activity will be supported by a southwest-northeast plume of
preconvective MUCAPE ranging from 2000-3500 J/kg, weakening late
tonight in the northeastern part as CINH increases, along with 35-45
kt effective-shear magnitude. Pockets of favorable low-level SRH
may develop to support some tornado potential even in a QLCS mode,
whether with embedded supercells or misovortices.
...Midafternoon into evening: Southern Plains dryline...
In mid/late afternoon, several discrete to semi-discrete supercells
are expected to develop and move northeastward at 25-35 kt off the
dryline. As this activity crosses the eastern Panhandle region,
northwest TX, and parts of western OK, it will offer tornadoes, very
large/damaging hail and sporadic severe gusts. Some giant (3-inch
or more) hail is possible, along with potential for a couple of
strong, relatively long-lasting tornadoes, from the mature phases of
at least one or two cyclic supercells within convective arc. The
all-hazards threat from these storms should last at least an hour or
two into early evening, when the low-level jet increases and
enlarges hodographs, and before the boundary layer stabilizes too
much to permit sustained surface-based inflow. Thereafter, these
supercells should spin down over western OK and northwest TX, south
of the relatively fresh/cold outflow from the KS complex.
Te environment will be characterized by strong surface heating and
mixing along the dryline, with forecast soundings suggesting:
near-zero MLCINH as early as around 20Z, 60s F surface dew points
beneath steep midlevel lapse rates, 2500-3500 J/kg MLCAPE in a
narrow plume ahead of the dryline, 60-65 kt effective-shear
magnitude, and afternoon effective SRH 150-250 J/kg increasing to
near 400 J/kg along the western rim of the 40-55 kt evening LLJ.
Winds aloft should be oriented with enough of an orthogonal
component to the dryline to support some discrete storms, though a
few forecast hodographs show evidence of slight veer-back-veer
weaknesses in the 2-4-km AGL layer. CINH will strengthen
considerably eastward toward the US-81 corridor ahead of this
activity and ahead of the main plume of large-scale forcing arriving
later overnight. This should lead to late-evening demise of most of
these afternoon/dryline supercells.
...Overnight: Southern Plains front/dryline...
A mixture of initially discrete supercells and a band of
thunderstorms should develop along the dryline and the overtaking
front this evening and tonight. Any supercells will pose the risk
of large, damaging hail, given the available moisture, large lapse
rates/buoyancy, and favorable deep shear. Frontogenetic forcing and
large-scale DCVA/cooling aloft will impinge on the moist sector and
lead to a mostly quasi-linear belt of convection overnight, with
damaging wind becoming the dominant threat before the activity
encounters increasing CINH and weakening LLJ-related storm-relative
flow late overnight. A tornado or two cannot be ruled out
throughout either phase as well.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z