The SPC is forecasting ...Severe thunderstorms expected over parts of the north-central High Plains this afternoon and early evening....
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the latest public statement about this event. View What is a Watch? clip.
Categorical Graphic
Day 1 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
MODERATE
17,207
89,587
Scottsbluff, NE...Torrington, WY...Douglas, WY...
ENHANCED
52,464
435,987
Rapid City, SD...Cheyenne, WY...Gillette, WY...Pierre, SD...Sterling, CO...
SLIGHT
242,881
7,532,897
Madison, WI...Sioux Falls, SD...Fort Collins, CO...Cedar Rapids, IA...Billings, MT...
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
SIG SEVERE
17,047
80,938
Scottsbluff, NE...Torrington, WY...Douglas, WY...
15 %
11,840
69,346
Scottsbluff, NE...Torrington, WY...Douglas, WY...
10 %
20,297
189,751
Cheyenne, WY...Gillette, WY...
5 %
54,176
496,171
Greeley, CO...Rapid City, SD...Evans, CO...Sheridan, WY...Windsor, CO...
2 %
119,757
3,542,080
Madison, WI...Sioux Falls, SD...Fort Collins, CO...Billings, MT...Rochester, MN...
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
30 %
37,925
253,091
Rapid City, SD...Pierre, SD...Spearfish, SD...Rapid Valley, SD...Sturgis, SD...
15 %
237,261
6,754,692
Madison, WI...Sioux Falls, SD...Cedar Rapids, IA...Billings, MT...Rochester, MN...
SPC AC 121622
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1122 AM CDT Mon Jun 12 2017
Valid 121630Z - 131200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
SOUTHEAST WY...THE NE PANHANDLE...AND SOUTHEAST SD...
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
WY...CO...NE...AND SD...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EXTENDING FROM
SOUTHERN MT INTO SOUTHERN WI...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
ME...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
NORTHERN ROCKIES INTO THE GREAT LAKES REGION...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
WEST TX...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
ME...
...SUMMARY...
Severe thunderstorms with tornadoes, very large hail, and damaging
winds are likely this afternoon into tonight across the
north-central High Plains. Other severe thunderstorms are expected
from parts of the northern Rockies to the Upper Midwest, as well as
across Maine and west Texas this afternoon into evening.
...Northern High Plains...
An upper low is centered over NV this morning, with a progressive
shortwave trough rotating through the base of the low and into UT.
Lift and mid-level cooling ahead of this feature is expected to
promote thunderstorm development over parts of the northern Rockies
and High Plains this afternoon and evening. East-southeasterly
low-level winds over southeast WY and northeast CO have transported
rich boundary-layer moisture back to the foothills, where daytime
heating and approaching trough will likely result in first
initiation of thunderstorms. Forecast soundings in this area show
very steep lapse rates and large CAPE values, as well as favorable
low-level and deep-layer vertical shear. Discrete supercells will
be likely as activity moves off the higher terrain and into the
adjacent High Plains. Parameters appear quite favorable for very
large hail and tornadoes with these storms. Strong tornadoes are
possible today. This evening, several CAM solutions suggest an
upscale evolution to one or more bowing complexes as storms move
into western NE/SD.
...NE/IA/MN/WI...
Scattered strong/severe thunderstorms are ongoing this morning over
parts of southeast SD and southwest MN. This activity is in
proximity to a surface boundary that extends eastward into southern
WI. Given the strong heating and destabilization occurring along
the boundary, it appears likely that this activity will persist
through much of the day and build eastward along the front. Large
hail and damaging winds will be possible in this corridor. Models
hint at the development of a bowing MCS this evening, affecting
parts of IA/WI.
...MT/WY...
To the northwest of the primary severe concern today (southeast WY),
there will be a risk of severe storms capable of large hail and
damaging winds into parts of western MT and northern WY.
Thunderstorms may form through the afternoon over parts of eastern
ID and central WY, and build northward into MT during the evening.
Large hail and gusty/damaging winds will be possible in the
strongest cells.
...Maine...
Strong heating is occurring today over much of ME, with fast
westerly flow aloft and dewpoints in the 60s. A consensus of 12z
model guidance shows considerable coverage of afternoon
thunderstorms in this region. Forecast soundings show moderate CAPE
values and sufficient deep-layer shear to support a few rotating
storms. Hail will be the main threat in the stronger cells, but
gusty outflow winds will also be possible.
..TX..
A few high-based thunderstorms capable of gusty winds and hail will
be possible this afternoon over parts of west TX, in a corridor of
strong CAPE and steep low-level lapse rates. This threat should be
focused in the 23-03z period.
..Hart/Jirak.. 06/12/2017
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