Alert archive / Wyoming / Special Weather Statements in 2021

Special Weather Statement, NWS Cheyenne, WY

July 15, 2021Laramie County, Wyoming

NWS Cheyenne, WY issued this special weather statement at Jul 15, 2021, 5:33 PM MDT for Laramie County, Wyoming. It was in force for 12 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jul 15, 2021, 5:33 PM MDT (23:33 UTC)
Expired: Jul 15, 2021, 5:45 PM MDT
In force: 12 min
Issued by: NWS Cheyenne, WY

County Laramie County, WY

The radar

The Cheyenne radar (KCYS), 38 km from the middle of the area, began a volume at 23:32 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Denver, CO (KDNR), launched 12:00Z, 11.6 hours before the alert went out and 233 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 6 J/kg
Mixed-layer CIN: -427 J/kg
Mixed-layer LCL: 1726 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: 23 m²/s²
0-3 km storm-relative helicity: 45 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

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What forecasters said that day

The local office's own words before this special weather statement went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Cheyenne, WY wrote its last area forecast discussion before this special weather statement went out at Jul 15, 5:03 PM MDT, 30 minutes earlier.

Area forecast discussion, Jul 15, 5:03 PM MDT, 30 minutes before

Area Forecast Discussion
National Weather Service Cheyenne WY
503 PM MDT Thu Jul 15 2021

.SHORT TERM...(This evening through early Sunday)
Issued at 200 PM MDT Thu Jul 15 2021

Current Visible Satellite loop shows pretty quiet weather so far
across the region with a few showers trying to develop over the
mountains early this afternoon. The primary concern will be the
potential for severe thunderstorms today, with some potential on
Friday as well. LAPS surface analysis shows a weak convergence
boundary at the surface just west of the Laramie Range/across the
Laramie Valley. Looking further up in the boundary layer shows
hardly any shear with maybe 25-30 knots of effective shear across
portions of the eastern plains but it's poorly defined. Expect
instability to continue to increase across the region, but shear
values may struggle to increase since the surface analysis still
shows a surface high near across western Nebraska. Will keep an
eye on this since severe weather will become unlikely if southeast
winds struggle to strengthen over the eastern plains. Assuming
high res models are correct, 0-6 km shear values should approach
30 to 35 knots by this evening which should be enough to generate
a few strong to marginally severe thunderstorms southeast of a
line from Cheyenne to Lusk. Large hail will be the primary threat
with a smaller chance for strong damaging winds. Probability for
severe weather is still pretty low and under 10 percent today
under a marginal risk. Models show a weak vort max slowly moving
across central Wyoming which may keep a few thunderstorms going
through midnight tonight across the east central plains and the
northern Nebraska panhandle.

Warmer temperatures expected for Friday as the upper level high
continues to strengthen southwest of the area. With increasing
subsidence aloft and a somewhat drier airmass over the area,
expect the severe weather threat to shift east into the western
Nebraska panhandle through the day. Some storms may produce brief
strong gusty winds and marginally severe hail well east of I-25
through Friday evening.

Hot temperatures likely for the weekend with highs in the mid to
upper 90s possible north of the I-80 corridor, with highs in the
upper 80s to low 90s near the I-80 corridor and Colorado border.
Although we can't rule out some afternoon and evening thunderstorms
and widely scattered showers across the area, expect the coverage
to become less each day through Sunday as the strengthening 599dm
upper level high shifts northward into southwest Wyoming.

.LONG TERM...(Sunday night through Thursday)
Issued at 109 PM MDT Thu Jul 15 2021

Starting Monday afternoon, a ridge pattern is dominate over the
region giving us no relief from the heat and dry conditions. Clear
skies and low PoPs are expected in the long-term forecast; the
highest chance of precipitation will most likely fall on Wednesday
and Thursday afternoon with a shortwave of mositure. Total rainfall
will not reach  above 0.25". This shortwave will most likely include
parts of Albany and Carbon counties but lower chances for the
Nebraska Panhandle and areas east of Interstate 25. Pressure
gradients increase along the western Nebraska Panhandle increasing
wind gusts up to 25 MPH. Otherwise, this quiet pattern persist into
next Thursday. Although, it is important to note that CPC has
highlighted our region experiencing excessive heat Thursday
afternoon.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 500 PM MDT Thu Jul 15 2021

VFR to MVFR conditions expected through the forecast period for
all terminals. Main concerns remain with thunderstorm potentials
throughout the evening today and again tomorrow afternoon as a
several disturbances are expected to clip through the CWA.
Current radar imagery has captured a decent slow moving cell just
to the east of Cheyenne producing one inch hail and some flooding
concerns. Expecting similar setups throughout the evening till
around 02z tonight, primarily east of the Laramie Range.
Nevertheless, could see some storm development later tonight after
02z, but confidence remains low at this time. Moving into
tomorrow, the severe threat is expected to shift eastward into the
Panhandle with higher confidence for showers and thunderstorms
over those terminals. Strong and erratic winds remain possible
near any thunderstorm activity tonight/tomorrow.

&&

.FIRE WEATHER...
Issued at 109 PM MDT Thu Jul 15 2021

Minimal fire weather concerns late this week and through the
weekend. Although a drier airmass will develop over mainly Carbon
and Albany counties Friday through Sunday with minimum humidity
values around 15 percent, winds will be relatively light as the
upper level high pressure center strengthens over
Utah/Wyoming/Colorado border. Further east, low level
moisture and return flow from the central plains will keep
daytime humidities above 20 to 25 percent along and east of the
Interstate 25 corridor.

&&

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

SHORT TERM...TJT
LONG TERM...AW
AVIATION...MD
FIRE WEATHER...TJT

Hazardous weather outlook, Jul 15, 10:56 AM MDT, 6 hours 37 minutes before

Hazardous Weather Outlook
National Weather Service Cheyenne WY
1056 AM MDT Thu Jul 15 2021

NEZ019>021-054-055-WYZ101-103-106>108-116>119-161700-
Scotts Bluff County-Banner County-Morrill County-Kimball County-
Cheyenne County-Converse County Lower Elevations-
North Laramie Range-
Central Laramie Range and Southwest Platte County-
East Platte County-Goshen County-South Laramie Range-
South Laramie Range Foothills-Central Laramie County-
East Laramie County-
1056 AM MDT Thu Jul 15 2021

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

.DAY ONE...TODAY AND TONIGHT

Widely scattered afternoon thunderstorms are expected across
far southeast WYoming into the southern Nebraska Panhandle from
early afternoon through this evening. Some of these storms could
become severe with large hail and strong gusty winds around 60
MPH.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

Afternoon thunderstorms are expected to develop on a daily
basis...mainly in the afternoon...in and around our southeast
Wyoming mountains. Probability for thunderstorms to become severe
is low

.Spotter information statement...

Spotter activation may be needed.

NEZ002-003-095-096-WYZ102-161700-
Dawes County-Box Butte County-Northern Sioux County-
Southern Sioux County-Niobrara County-
1056 AM MDT Thu Jul 15 2021

This hazardous weather outlook is for portions of panhandle
Nebraska and east central Wyoming.

.DAY ONE...TODAY AND TONIGHT

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

Afternoon thunderstorms are expected to develop on a daily
basis...mainly in the afternoon. Probability for thunderstorms to
become severe is low

.Spotter information statement...

Spotter activation will not be needed.

WYZ104-105-109>115-161700-
Ferris/Seminoe/Shirley Mountains-Shirley Basin-
Central Carbon County-North Snowy Range Foothills-
Southwest Carbon County-Sierra Madre Range-
Upper North Platte River Basin-Snowy Range-Laramie Valley-
1056 AM MDT Thu Jul 15 2021

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

.DAY ONE...TODAY AND TONIGHT

Isolated thunderstorms are possible this afternoon and into this
evening. The probability for severe thunderstorms is low, but a
few storms may produce gusty winds.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

Afternoon thunderstorms are possible each day...mainly in the
afternoon...in and around our southeast Wyoming mountains.

.Spotter information statement...

Spotter activation will not be needed.

In the hours before

Local storm report, Jul 15, 4:25 PM MDT, 1 hour 8 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
425 PM MDT THU JUL 15 2021

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

0424 PM     HAIL             4 ESE NORTH CHEYENNE    41.20N 104.71W
07/15/2021  M1.00 INCH       LARAMIE            WY   LAW ENFORCEMENT

            NICKELS TO QUARTERS REPORTED.

&&

Local storm report, Jul 15, 4:27 PM MDT, 1 hour 6 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
427 PM MDT THU JUL 15 2021

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

0427 PM     HAIL             4 ESE NORTH CHEYENNE    41.20N 104.71W
07/15/2021  M1.00 INCH       LARAMIE            WY   PUBLIC

&&

Local storm report, Jul 15, 4:37 PM MDT, 56 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
437 PM MDT THU JUL 15 2021

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

0437 PM     HAIL             6 E CHEYENNE            41.15N 104.68W
07/15/2021  M0.70 INCH       LARAMIE            WY   PUBLIC

&&

Special weather statement, Jul 15, 4:59 PM MDT, 34 minutes before

Special Weather Statement
National Weather Service Cheyenne WY
459 PM MDT Thu Jul 15 2021

WYZ118-119-152345-
Central Laramie County WY-East Laramie County WY-
459 PM MDT Thu Jul 15 2021

...SPECIAL WEATHER STATEMENT...

At 458 PM MDT, Doppler radar was tracking a strong thunderstorm near
Hillsdale, or 17 miles east of Cheyenne, moving east at 20 mph.

Half inch hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Pine Bluffs, Burns and Hillsdale.

This includes Interstate 80 in Wyoming between mile markers 376 and
400.

LAT...LON 4107 10448 4114 10456 4121 10454 4125 10447
      4122 10427 4116 10406 4100 10406 4100 10411
TIME...MOT...LOC 2258Z 288DEG 19KT 4115 10445

Mokry

Special weather statement, Jul 15, 5:00 PM MDT, 33 minutes before

Special Weather Statement
National Weather Service Cheyenne WY
500 PM MDT Thu Jul 15 2021

WYZ117>119-152315-
Central Laramie County WY-South Laramie Range Foothills WY-
East Laramie County WY-
500 PM MDT Thu Jul 15 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL LARAMIE COUNTY
UNTIL 515 PM MDT...

At 500 PM MDT, Doppler radar was tracking a strong thunderstorm 11
miles southeast of South Greeley, or 12 miles southeast of Cheyenne,
moving southeast at 20 mph.

Penny size hail and winds in excess of 40 mph will be possible with
this storm.

This storm will remain over mainly rural areas of south central
Laramie County.

LAT...LON 4101 10470 4105 10470 4110 10464 4101 10448
      4100 10450 4100 10468
TIME...MOT...LOC 2300Z 329DEG 18KT 4101 10462

Mokry

Special weather statement, Jul 15, 5:33 PM MDT, 0 minutes before

Special Weather Statement
National Weather Service Cheyenne WY
533 PM MDT Thu Jul 15 2021

WYZ116>118-152345-
South Laramie Range WY-Central Laramie County WY-
South Laramie Range Foothills WY-
533 PM MDT Thu Jul 15 2021

...SIGNIFICANT WEATHER ADVISORY FOR WEST CENTRAL LARAMIE COUNTY UNTIL
545 PM MDT...

At 533 PM MDT, Doppler radar was tracking strong thunderstorms near
Whitaker, or 17 miles northwest of Cheyenne, moving southeast at 20
mph.

Half inch hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Horse Creek and Federal.

This includes Interstate 25 in Wyoming between mile markers 22 and
28.

LAT...LON 4140 10526 4145 10527 4150 10527 4153 10519
      4150 10505 4137 10482 4128 10486 4120 10508
      4128 10517
TIME...MOT...LOC 2333Z 326DEG 18KT 4137 10497

Mokry

The office that day

Everything else NWS Cheyenne, WY issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 14, 6:03 PM MDT	Special Weather Statement	CYS	Albany	27 min
Jul 14, 6:17 PM MDT	Severe Thunderstorm Warning	CYS	Albany	43 min
Jul 14, 6:19 PM MDT	Special Weather Statement	CYS	Albany	26 min
Jul 14, 6:34 PM MDT	Severe Thunderstorm Warning	CYS	Albany	26 min
Jul 14, 6:59 PM MDT	Severe Thunderstorm Warning	CYS	Albany	46 min
Jul 14, 7:13 PM MDT	Special Weather Statement	CYS	Carbon	32 min
Jul 14, 7:45 PM MDT	Special Weather Statement	CYS	Carbon	45 min
Jul 14, 7:53 PM MDT	Special Weather Statement	CYS	Albany	37 min
Jul 14, 8:48 PM MDT	Special Weather Statement	CYS	Carbon	27 min
Jul 14, 8:51 PM MDT	Severe Thunderstorm Warning	CYS	Carbon	24 min
Jul 15, 3:55 PM MDT	Special Weather Statement	CYS	Laramie	35 min
Jul 15, 4:22 PM MDT	Severe Thunderstorm Warning	CYS	Laramie	38 min
Jul 15, 4:42 PM MDT	Areal Flood Advisory	CYS	Laramie	3 hr
Jul 15, 4:59 PM MDT	Special Weather Statement	CYS	Laramie	46 min
Jul 15, 5:00 PM MDT	Special Weather Statement	CYS	Laramie	15 min
Jul 15, 5:46 PM MDT	Special Weather Statement	CYS	Laramie	29 min
Jul 14, 7:58 PM MDT	Special Weather Statement	CYS	Banner	32 min
Jul 14, 8:54 PM MDT	Special Weather Statement	CYS	Banner	36 min
Jul 15, 5:43 PM MDT	Special Weather Statement	CYS	Kimball	32 min

Nearby

Special Weather Statements in Wyoming, 2021 Every special weather statement in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.