Fort Collins, CO...Greeley, CO...Casper, WY...Evans, CO...Rock Springs, WY...
Probabilistic Tornado Graphic
Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
2 %
12,208
168,716
Cheyenne, WY...Laramie, WY...Torrington, 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.
Day 1 Wind Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
5 %
63,643
706,335
Fort Collins, CO...Greeley, CO...Cheyenne, WY...Laramie, WY...Evans, CO...
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.)
Area Pop.
Some Larger Population Centers in Risk Area
SIG SEVERE
4,486
16,475
No Major Population Center in Risk Area
15 %
12,530
186,844
Cheyenne, WY...Laramie, WY...Torrington, WY...
5 %
37,279
556,591
Fort Collins, CO...Greeley, CO...Casper, WY...Evans, CO...Rock Springs, WY...
SPC AC 111628
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Fri May 11 2018
Valid 111630Z - 121200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHEAST WY
VICINITY...
...SUMMARY...
A few severe storms with large hail as the primary hazard are most
likely to occur across the central High Plains this afternoon into
early evening.
...Central High Plains...
Well north of a surface cold front that has progressed into the
southern High Plains, easterly upslope flow will strengthen this
afternoon as the pressure gradient increases. A confined pocket of
greater insolation is underway across the Front Range from
north-central CO into southeast WY to the west of a nearly
stationary stratus deck over much of the plains. A few storms will
likely form off the Laramie Range during the early-mid afternoon.
Within a belt of enhanced mid-level southwesterlies around 35-45 kt
at 500 mb, atop the boundary-layer easterlies, effective shear will
be quite favorable for a discrete supercell or two. Large hail will
be the primary hazard. The spatiotemporal window for surface-based
supercells will be limited as capping/inhibition remains very strong
within the stratus deck at lower elevations. This should result in
the severe risk decaying rather rapidly eastward during the early
evening.
...Southern Great Plains...
Isolated storms should develop for a few hours along the dryline in
the late afternoon to early evening. Hot temperatures in the 96-102
F range should result in very high-based storms rooted around
600-500 mb. Capping/inhibition is increasingly large with eastern
extent from the dryline, resulting in a limited spatiotemporal
window for the severe risk. Despite weak shear within the
cloud-bearing layer, the very steep lapse-rate environment will
support dry microbursts producing strong to severe wind gusts.
...IA to southern Lower MI...
Guidance is fairly consistent in suggesting scattered overnight
convection forming north of the quasi-stationary front that should
lie near the IA/MO border through central IL/IN. While NAM soundings
appear unrealistically overdone with MUCAPE, the RAP and other
guidance suggest moderate elevated buoyancy may develop along the
northern periphery of the expansive EML plume over the central
states. Within a belt of confluent mid-level westerlies, a few
updrafts might produce hail approaching severe size. But given the
westerly flow aloft paralleling the zone of broad isentropic ascent,
convection should rapidly form into multicell clusters, likely
limiting the overall potential for severe hail. Will monitor this
area for possible upgrade to MRGL risk for hail in later outlooks.
..Grams/Bentley.. 05/11/2018
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