Severe Thunderstorm Warning 120, NWS Cheyenne, WY

100 
WWUS55 KCYS 160657
SVSCYS

Severe Weather Statement
National Weather Service Cheyenne WY
1257 AM MDT SAT SEP 16 2017

NEC033-123-160707-
/O.EXP.KCYS.SV.W.0120.000000T0000Z-170916T0700Z/
Cheyenne NE-Morrill NE-
1257 AM MDT SAT SEP 16 2017

...THE SEVERE THUNDERSTORM WARNING FOR NORTHEASTERN CHEYENNE AND
SOUTHEASTERN MORRILL COUNTIES WILL EXPIRE AT 100 AM MDT...
        
The storm which prompted the warning has moved out of the area.
Therefore the warning will be allowed to expire.

LAT...LON 4111 10291 4124 10304 4151 10268 4146 10264
      4140 10263 4139 10261 4121 10261
TIME...MOT...LOC 0657Z 238DEG 29KT 4133 10264 

$$

Levin

Area Forecast Discussion
National Weather Service Cheyenne WY
1150 PM MDT Fri Sep 15 2017

.UPDATE...
Issued at 1144 PM MDT Fri Sep 15 2017

Strong convection is firing late this evening ahead of a 70 kt
upper jet streak punching into western WY. Weak elevated CAPE in
the presence of strong shear and low level frontogenesis will
continue the threat for stronger storms over the Panhandle into
the wee hours of the morning. Already had reports of half dollar
size hail with transient elevated supercell structures the
southern Panhandle late this evening. NAM also indicating the
potential for some banded precip further west with an area of
negative EPV values overlapping with some mid level frontogenesis.
With all this in mind, have bumped POP up to categorical east of
the Laramie Range for the rest of the night.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 245 PM MDT Fri Sep 15 2017

Just a few showers noted so far this afternoon over parts of the
CWA as the area is likely seeing some subsidence behind a
departing shortwave ejecting north over the northern high plains.
Another wave over Utah should bring another round of mainly
showers to the CWA this evening, with some snow possible over the
highest peaks. Little accumulation expected however. Pcpn should
end Saturday morning with the passage of the main upper trough. A
cold front will move across the CWA this evening with mins falling
into the 40s over much of the CWA, with some 30s over western
valleys.

Saturday will feature mild temperatures across the CWA with some
fairly breezy winds out west in the afternoon as decent westerly
mid level flow mixes down. The winds will drop off in the evening
with clearing skies setting up a chilly night Saturday night. Mins
could get close to or even a bit below freezing in low lying areas
such as Alliance and western valley locations Sunday morning.
Return flow during the day Sunday will allow warmer temperatures
over the plains as upper flow backs to southwesterly.

.LONG TERM...(Monday through Friday)
Issued at 245 PM MDT Fri Sep 15 2017

Looking at a rather active week weather-wise, especially from
Tuesday onward. Southwest flow aloft will provide dry and warm
conditions to start the work week. A vigorous upper level jet will
carve out a fairly deep trough from the northern Rockies to the
southern Great Basin Tuesday. A Pacific cold front will surge
southeast across the CWA Tuesday night, accompanied by scattered
showers. Instability for thunder will be marginal at best. High
temperatures Wednesday will be 10 degrees cooler compared to
Tuesday. The upper trough lifts northeast into the northern Great
Plains and upper Midwest later Wednesday, with the next upper jet
maxima and trough tracking east then northeast across the CWA
Wednesday night and Thursday with scattered showers. Highest
elevations west of the Laramie Range may see some snow, but no
significant accumulations are expected. The third in a series of
upper troughs will be deeper as it tracks across the Intermountain
West Friday. Shortwave energy in deepening south-southwest flow will
trigger more shower activity at that time. High temperatures by the
end of next week will trend near to below seasonal normals. Most
days will be breezy, mainly along and west of the Laramie Range.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 550 PM MDT Fri Sep 15 2017

More widespread IFR conditions expected tonight across the
Nebraska Panhandle and east of the Laramie Range. Should start
earlier too with recent rainfall and upsloping winds already
ongoing. Generally followed HRRR guidance on timing/locations of
IFR onset.

&&

.FIRE WEATHER...
Issued at 245 PM MDT Fri Sep 15 2017

A cold front will move across the districts this evening with
showers and possibly a thunderstorm or two behind the front.
Wetting rains look to be rather isolated though. A little snow is
even possible over the highest mountain peaks overnight. Mild and
mainly dry weather is then expected Saturday and Sunday with some
breezy afternoon winds over western areas.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

UPDATE...DEL
SHORT TERM...RE
LONG TERM...MAJ
AVIATION...GCC
FIRE WEATHER...RE

Hazardous Weather Outlook
National Weather Service Cheyenne WY
735 AM MDT Fri Sep 15 2017

NEZ002-003-019>021-054-055-095-096-WYZ101>119-161345-
Dawes-Box Butte-Scotts Bluff-Banner-Morrill-Kimball-Cheyenne-
North Sioux-South Sioux-Converse County Lower Elevations-
Niobrara County-North Laramie Range-
Ferris/Seminoe/Shirley Mountains-Shirley Basin-
Central Laramie Range and Southwest Platte County-
East Platte County-Goshen County-Central Carbon County-
North Snowy Range Foothills-Southwest Carbon County-
Sierra Madre Range-Upper North Platte River Basin-Snowy Range-
Laramie Valley-South Laramie Range-South Laramie Range Foothills-
Central Laramie County-East Laramie County-
735 AM MDT Fri Sep 15 2017

This hazardous weather outlook is for portions of western
Nebraska...east central Wyoming...south central Wyoming and
southeast Wyoming.

.DAY ONE...TODAY AND TONIGHT

Isolated thunderstorms will move northeast across east central
Wyoming and the northern Nebraska Panhandle associated with a
upper level disturbance. Isolated thunderstorms will develop
this afternoon with the passage of a strong cold front. Severe
weather is not expected.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

The probability for widespread hazardous weather is low.

.Spotter information statement...

Spotter activation will not be needed.

Special Weather Statement
National Weather Service Cheyenne WY
1106 PM MDT FRI SEP 15 2017

NEZ054-055-160545-
Kimball NE-Cheyenne NE-
1106 PM MDT FRI SEP 15 2017

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN CHEYENNE AND KIMBALL
COUNTIES UNTIL 1145 PM MDT...

At 1105 PM MDT, Doppler radar was tracking a strong thunderstorm 11
miles east of Panorama Point, or 21 miles southwest of Kimball,
moving northeast at 25 mph.

Dime size hail will be possible with this storm.

Locations impacted include...
Kimball, Oliver Campground, Oliver Reservoir and Kimball Airport.

This includes Interstate 80 in Nebraska between mile markers 11 and
29.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4137 10377 4109 10326 4100 10347 4100 10395
TIME...MOT...LOC 0505Z 231DEG 22KT 4096 10383

Levin

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
1135 PM MDT FRI SEP 15 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1130 PM     HAIL             KIMBALL                 41.23N 103.66W
09/15/2017  M1.25 INCH       KIMBALL            NE   TRAINED SPOTTER

&&

TTRUDEL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
1147 PM MDT FRI SEP 15 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1133 PM     HAIL             DIX                     41.23N 103.49W
09/15/2017  E0.75 INCH       KIMBALL            NE   PUBLIC

&&

TTRUDEL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
1220 AM MDT SAT SEP 16 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1219 PM     HAIL             SIDNEY                  41.13N 102.97W
09/15/2017  M0.88 INCH       CHEYENNE           NE   TRAINED SPOTTER

            SPOTTER IS ON THE NORTHERN SIDE OF SIDNEY.

1221 PM     HAIL             SIDNEY                  41.13N 102.97W
09/15/2017  M1.00 INCH       CHEYENNE           NE   LAW ENFORCEMENT

&&

TTRUDEL