Alert archive / Nebraska / Special Weather Statements in 2020

Special Weather Statement, NWS Cheyenne, WY

August 5, 2020Sioux County, Nebraska

NWS Cheyenne, WY issued this special weather statement at Aug 5, 2020, 3:59 PM MDT for Sioux County, Nebraska. It was in force for 46 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
Aug 5, 2020, 3:59 PM MDT (21:59 UTC)
Expired
Aug 5, 2020, 4:45 PM MDT
In force
46 min
Issued by
NWS Cheyenne, WY

County Sioux County, NE

The radar

The Cheyenne radar (KCYS), 156 km from the middle of the area, began a volume at 22:01 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, 10.0 hours before the alert went out and 282 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-pSkew-T log-p diagram, Denver, CO at 12:00Z on 2020-08-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 407 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Denver, CO at 12:00Z on 2020-08-05The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 1 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
407 J/kg
Mixed-layer CIN
-325 J/kg
Mixed-layer LCL
1531 m above ground
0-6 km bulk shear
28 kt
0-1 km storm-relative helicity
1 m²/s²
0-3 km storm-relative helicity
89 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

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 Aug 5, 3:22 PM MDT, 37 minutes earlier.

Area forecast discussion, Aug 5, 3:22 PM MDT, 37 minutes before
Area Forecast Discussion
National Weather Service Cheyenne WY
322 PM MDT Wed Aug 5 2020

.SHORT TERM...(This evening through Thursday)
Issued at 330 PM MDT Wed Aug 5 2020

Forecast challenges transitioning from severe thunderstorms this
afternoon...to critical fire weather conditions through the
remainder of the week.

Currently...Trough of low pressure extends along the front range
of eastern Colorado northwestward into Laramie and eventually to
near Riverton this afternoon. Radar has begun to blossom on radar
this afternoon...similar to what the short range guidance has been
showing. Probably better today than over the past several days.
Less shear today and a little more stable over yesterday. RAP
analysis showing SB CAPE of around 1800 J/KG down here near
Cheyenne to around 1000 J/KG up near Douglas. Off to the west over
Carbon County...very dry conditions being observed with Tds in the
low 20s. Red Flag Warnings look to be panning out out that way and
will continue the current afternoon RFWs for today.

Short range guidance showing storms moving out into the Panhandle
towards 00Z. Should we get this rainfall this evening...do believe
we stand a good chance at patchy fog with southeasterly upslope
flow. Did add patchy fog into the forecast for the Panhandle below
4500 feet elevations. SREF hinting at lower conditions out there
towards 12Z as well.

Drier and breezier Thursday with low humidity spreads east. Looks
like surface boundary shifts east to near the Wyoming/Nebraska
state line. GFS 700mb winds west of the Laramie Range
25-30kts...so critical fire weather conditions look to be certain
out west. Continued the Red Flag Warnings for FWZ 303 through 308.
Best chances for any afternoon showers/storms look to be east of
the Laramie Range.

Very dry conditions Friday as westerly winds continue. 850mb
humidity in the Panhandle falls to 12 percent. Did issue a Fire
Weather Watch for zones we currently have in warnings for Friday.
Later shifts may need to add the Summit and points east as we get
closer to Friday.

.LONG TERM...(Saturday through Tuesday)
Issued at 318 AM MDT Wed Aug 5 2020

A broad upper high will hold over much of the southern half of the
country through the period with the westerlies and embedded
shortwaves being lifted to the north along the international
border. Overall this will provide mainly dry and warm weather to
the CWA with just isolated convection possible where weak
shortwaves clip the CWA, right now looking like later Saturday and
again Tuesday. Temperatures will be above seasonal averages with
little day-to-day changes.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1139 AM MDT Wed Aug 5 2020

All Wyoming and Nebraska Panhandle sites persist in VFR
conditions; although a few isolated thunderstorms could temporary
decrease visibility at the following sites: KCYS, KLAR, KAIA, and
KSNY. These sites may receive strong wind gust up to 25kts during
21Z-00Z. OVC and BKN skies are possible for sites east of the
Laramie Range. Thunderstorms will most likely be isolated due to
dry air aloft and low CAPE which means these storms will battle to
develop. Tomorrow may lead to lower cloud bases and possible fog
for KSNY and KAIA.

&&

.FIRE WEATHER...
Issued at 330 PM MDT Wed Aug 5 2020

Critical fire weather conditions ongoing this afternoon across
Carbon County where Red Flag Warnings are in effect through 8 PM
this evening. Dry/Breezy conditions return Thursday for areas west
of the Laramie Range. Red Flag Warnings in effect for FWZ 303
through 308 Thursday. Conditions expected to continue into Friday
with a Fire Weather Watch in effect Friday afternoon. See a
slight reprieve Friday night into Saturday as a cold front moves
into central Wyoming. This will be short lived though as
breezy/dry conditions return Sunday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning until 8 PM MDT this evening for WYZ303>307.

     Red Flag Warning from 11 AM to 8 PM MDT Thursday for WYZ303>308.

     Fire Weather Watch from Friday morning through Friday evening
     for WYZ303>308.

NE...None.
&&

SHORT TERM...GCC
LONG TERM...RE
AVIATION...AW
FIRE WEATHER...GCC
Hazardous weather outlook, Aug 5, 4:17 AM MDT, 11 hours 42 minutes before
Hazardous Weather Outlook
National Weather Service Cheyenne WY
417 AM MDT Wed Aug 5 2020

WYZ104-105-109>115-061030-
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-
417 AM MDT Wed Aug 5 2020

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

.DAY ONE...TODAY AND TONIGHT

Isolated afternoon thunderstorms possible. Storms may produce
strong, gusty winds and dry lightning.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

Decreasing thunderstorm potential day by day as the area dries out
under the influence of a ridge. Fire weather conditions will be
the main concern.

.Spotter information statement...

Spotter activation will not be required.

NEZ002-003-019>021-054-055-095-096-WYZ101>103-106>108-116>119-
061030-
Dawes-Box Butte-Scotts Bluff County-Banner County-Morrill-
Kimball County-Cheyenne-North Sioux-South Sioux-
Converse County Lower Elevations-Niobrara County-
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-
417 AM MDT Wed Aug 5 2020

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

.DAY ONE...TODAY AND TONIGHT

Widely scattered thunderstorms will develop near and along the
Laramie Range after noon and move eastward into the High Plains
by mid-afternoon, reaching the western Nebraska Panhandle by late
afternoon. Strong to severe thunderstorms producing large hail
and strong gusty winds will be possible along and east of the
Interstate 25 corridor; an isolated tornado cannot be ruled out.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

Scattered afternoon and evening thunderstorms will develop
Thursday; some may be strong to severe. Storms become more
isolated and confined to the mountains Friday and Saturday.

.Spotter information statement...

Spotter activation may be needed this afternoon along and east of
the I-25 corridor.

In the hours before

Special weather statement, Aug 5, 3:03 PM MDT, 56 minutes before
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Special weather statement, Aug 5, 3:16 PM MDT, 43 minutes before
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Special weather statement, Aug 5, 3:42 PM MDT, 17 minutes before
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Special weather statement, Aug 5, 3:50 PM MDT, 9 minutes before
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Special weather statement, Aug 5, 3:57 PM MDT, 2 minutes before
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Special weather statement, Aug 5, 3:59 PM MDT, 0 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Aug 4, 6:17 PM MDTSpecial Weather StatementCYSAlbany43 min
Aug 4, 6:34 PM MDTSpecial Weather StatementCYS41 min
Aug 4, 7:00 PM MDTSpecial Weather StatementCYSAlbany45 min
Aug 4, 7:42 PM MDTSpecial Weather StatementCYS33 min
Aug 4, 7:59 PM MDTSpecial Weather StatementCYSCarbon46 min
Aug 4, 8:45 PM MDTSpecial Weather StatementCYSAlbany45 min
Aug 4, 9:28 PM MDTSpecial Weather StatementCYSAlbany, Platte47 min
Aug 4, 10:50 PM MDTSpecial Weather StatementCYSGoshen, Laramie, Platte40 min
Aug 4, 11:31 PM MDTSpecial Weather StatementCYSGoshen44 min
Aug 5, 12:21 AM MDTSpecial Weather StatementCYSLaramie24 min
Aug 5, 2:50 AM MDTRed Flag WarningCYS41 hr
Aug 5, 1:23 PM MDTSpecial Weather StatementCYSLaramie52 min
Aug 5, 1:59 PM MDTSpecial Weather StatementCYSLaramie46 min
Aug 5, 2:05 PM MDTSpecial Weather StatementCYSConverse40 min
Aug 5, 2:27 PM MDTSpecial Weather StatementCYSLaramie48 min
Aug 5, 2:34 PM MDTFire Weather WatchCYS13 hr
Aug 5, 2:45 PM MDTSpecial Weather StatementCYSPlatte45 min
Aug 5, 2:53 PM MDTSpecial Weather StatementCYSPlatte52 min
Aug 5, 3:03 PM MDTSpecial Weather StatementCYS42 min
Aug 5, 3:16 PM MDTSpecial Weather StatementCYSLaramie44 min
Aug 5, 3:42 PM MDTSpecial Weather StatementCYSAlbany48 min
Aug 5, 3:57 PM MDTSpecial Weather StatementCYSConverse48 min
Aug 5, 4:07 PM MDTSpecial Weather StatementCYSPlatte38 min
Aug 5, 4:22 PM MDTSpecial Weather StatementCYSConverse38 min
Aug 5, 4:34 PM MDTSevere Thunderstorm WarningCYSConverse28 min
Aug 5, 4:50 PM MDTSpecial Weather StatementCYSConverse40 min
Aug 5, 4:52 PM MDTSpecial Weather StatementCYSLaramie38 min
Aug 5, 4:58 PM MDTSpecial Weather StatementCYSPlatte47 min
Aug 5, 5:01 PM MDTSevere Thunderstorm WarningCYSGoshen, Platte44 min
Aug 5, 5:19 PM MDTSpecial Weather StatementCYSConverse41 min
Aug 5, 5:21 PM MDTSpecial Weather StatementCYSGoshen39 min
Aug 5, 5:34 PM MDTSpecial Weather StatementCYSPlatte41 min
Aug 5, 5:41 PM MDTSpecial Weather StatementCYSNiobrara49 min
Aug 5, 12:15 AM MDTSpecial Weather StatementCYSBanner, Kimball60 min
Aug 5, 3:50 PM MDTSpecial Weather StatementCYSBox Butte40 min
Aug 5, 4:32 PM MDTSevere Thunderstorm WarningCYSSioux43 min
Aug 5, 4:55 PM MDTSpecial Weather StatementCYSSioux50 min
Aug 5, 5:31 PM MDTSpecial Weather StatementCYSMorrill44 min

Nearby

Special Weather Statements in Nebraska, 2020Every special weather statement in 2020

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.