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.
Day 1 Wind Risk
Area (sq. mi.)
Some Larger Population Centers in Risk Area
Lincoln, NE...Salina, KS...Junction City, KS...Great Bend, KS...Beatrice, NE...
Omaha, NE...Council Bluffs, IA...Bellevue, NE...Manhattan, KS...Grand Island, NE...
SPC AC 010600
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Tue May 01 2018
Valid 011200Z - 021200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF CENTRAL KS...SOUTHEAST NE...FAR SOUTHWEST IA...AND FAR NORTHWEST
Severe storms are expected mainly across north-central Kansas into
southeast Nebraska Tuesday from late afternoon through evening.
Large hail, damaging winds, and a few tornadoes are possible.
Shortwave trough currently located approximately 400nm off the
central CA coast is expected to continue southward Tuesday morning
before turning more southeasterly during the afternoon. The
trajectory of this shortwave will lead to an overall deepening of
the parent upper trough, which covers much of the western CONUS.
Additionally, a modest westward regression of the upper trough is
anticipated, which will support building heights across the central
The surface pattern at the beginning of the period will likely
feature a low centered over the MN arrowhead with a cold front
extending southwestward to another low over north-central KS. This
frontal zone is not expected to move much throughout the day with
the second low developing into a well-defined triple-point by the
afternoon. This triple-point, and the surface features extending
from it, will serve as the focus for convective development late
Tuesday afternoon through the evening.
...Central Plains into the Upper MS Valley...
A second day of moisture advection is anticipated as a deepening lee
surface low and strong low-level flow persist. Expectation is for
dewpoints to generally be in the low to mid 60s east of the dryline
across central KS, with values gradually increasing southward. Warm
temperatures aloft and weak synoptic forcing for ascent will likely
keep the warm sector free of convection throughout most of the day.
Impetus for convective initiation will likely be surface convergence
near the triple-point and along the cold front and dryline. Recent
guidance also shows a very subtle shortwave moving into the central
Plains during the afternoon, which would enhanced lift across the
region if realized. High-resolution guidance, including the HREF, is
in good agreement that convection initiation will occur around 21Z
along the dryline in central KS.
With very steep mid-level lapse rates and strong instability in
place, the airmass will be primed for explosive thunderstorm
development once convective initiation occurs. An initially discrete
storm mode is anticipated along the dryline in KS while a clustered
storm mode is more likely along the cold front from south-central NE
across IA. Veering wind profiles are anticipated along the dryline,
with current guidance suggesting effective SRH over 250 m2/s2 and
effective bulk shear over 50 kt. These wind profiles are more than
supportive of supercells, and, given the likely discrete initial
mode, tornadoes. A few strong tornadoes are possible, particularly
near the triple point where the probability of backed surface winds
is higher. Very large hail (i.e. greater than 2 inches in diameter)
is also likely with the storms along the dry line as well as initial
development farther northeast along the cold front. The hail threat
will extend into southern WI as the low-level jet supports
thunderstorms along the frontal zone.
A Moderate Risk for tornadoes may be warranted in subsequent
outlooks but the confined nature of the threat and remaining
uncertainty regarding the location of the triple-point during the
afternoon as well as the extent of the moisture return merits
waiting for more confidence before upgrading.
...Central High Plains...
Upslope flow and resulting convergence will support the development
of thunderstorms during the afternoon across northeast CO and
adjacent portions of southeast WY and southwest NE Panhandle. Some
isolated hail is possible with the strongest storms.
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