Alert archive / California / Special Weather Statements in 2021
Special Weather Statement, NWS Sacramento, CA
NWS Sacramento, CA issued this special weather statement at May 15, 2021, 2:47 PM PDT for Shasta County, California. It was in force for 43 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
- May 15, 2021, 2:47 PM PDT (21:47 UTC)
- Expired
- May 15, 2021, 3:30 PM PDT
- In force
- 43 min
- Issued by
- NWS Sacramento, CA
County Shasta County, CA
The radar
The Medford radar (KMAX), 123 km from the middle of the area, began a volume at 21:45 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
Oakland, CA (KOAK), launched 12:00Z, 9.8 hours before the alert went out and 363 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 474 m above ground
- 0-6 km bulk shear
- 22 kt
- 0-1 km storm-relative helicity
- 22 m²/s²
- 0-3 km storm-relative helicity
- 89 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
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</html>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 Sacramento, CA wrote its last area forecast discussion before this special weather statement went out at May 15, 1:42 PM PDT, 1 hour 5 minutes earlier.
Area forecast discussion, May 15, 1:42 PM PDT, 1 hour 5 minutes before
Area Forecast Discussion National Weather Service Sacramento CA 142 PM PDT Sat May 15 2021 .SYNOPSIS... Cooler temperatures continue, with slightly warmer temperatures returning early next week. Scattered showers and thunderstorms are possible this weekend, mainly over the mountains, though a few storms may migrate into the lower elevations late this afternoon and this evening. && .DISCUSSION... This afternoon and tonight the focus will be on the low pressure area that is currently over Northern San Joaquin valley and where showers and thunderstorms develop. Currently as the low moves southward this evening wrap around moisture will be carrying any activity westward towards the valley. The best chances for any activity within the valley remains north of Sacramento. Thunderstorms will be capable of brief heavy rain, small hail and gusty winds. As the low moves southward into the Southern San Joaquin valley late tonight chances of showers moving into the valley will increase over the Northern San Joaquin valley while decreasing further north. Winds through the Delta will continue to be breezy overnight but expecting a lower marine layer so chances of low clouds are not as great as this morning. That said still think we may see some into the Delta and perhaps eastern side of the valley and foothills form by morning. By Sunday afternoon the low will be centered near Las Vegas with wrap around moisture continuing. Currently it looks like activity could reach the foothills but not the valley. Warmer temperatures are expected over the northern valley with slightly cooler temperatures over the southern areas. As the low moves east Sunday night activity will diminish. The Delta breeze looks to be stronger and we should have a slightly higher marine layer than tonight so low clouds will have a better chance of advecting into the Sacramento region by Monday morning. Monday will be dry other than a chance for some afternoon pop up showers and thunderstorms near the crest from near I-80 southward. Temperatures will be warmer for most areas with slight cooling over the north end of the valley and surrounding mountains. Weak ridging on Tuesday will keep the area dry with some warming of temperatures. && .EXTENDED DISCUSSION (Wednesday THROUGH Saturday)... No major changes to the extended forecast as confidence remains high in a cooler weather pattern for NorCal. Max temps are forecast to run some 5 to 15 degrees below normal during the period, while min temps look to be about 2 to 10 degrees below normal. Thursday still looking to be the coolest day out of this period with highs generally in the 70s for the Valley, the 60s for the foothills, and 40s and 50s for the mountains. In addition to the cooler weather, models and ensembles are hinting at renewed chances for showers. The showery regime is especially favored over the higher terrain due to topographic lift and forcing. Snow showers may occur over the higher elevations, above 5000 or 6000 feet, of the Sierra as well, mostly likely Thu/Fri. Ensembles show a little disagreement about how far east the trough is forecast to move over the weekend, but drier flow and warmer temps look likely. && .AVIATION... Localized MVFR/IFR conditions possible in showers and thunderstorms over the foothills, mountains, and northern Sacramento Valley this afternoon and into the evening, otherwise, VFR conditions. Onshore winds from the W to SW up to 15-20 kt around the Delta with gusts to 30 kt possible in the Delta after 00z Sun. Elsewhere, winds generally below 10 kt. && .STO WATCHES/WARNINGS/ADVISORIES... None. &&
In the hours before
Special weather statement, May 15, 2:47 PM PDT, 0 minutes before
Special Weather Statement
National Weather Service Sacramento CA
247 PM PDT Sat May 15 2021
CAZ013-152230-
Shasta Lake Area / Northern Shasta County-
247 PM PDT Sat May 15 2021
...A STRONG THUNDERSTORM WILL AFFECT NORTH CENTRAL SHASTA COUNTY...
At 246 PM PDT, a strong thunderstorm was located over Pollard Flat,
or 20 miles north of Shasta Dam, moving southwest at 20 mph.
Winds in excess of 30 mph and pea size hail are possible with this
storm, as well as brief, heavy rainfall.
Locations impacted include...
Lakehead-Lakeshore, Lakehead, Vollmers, Sims, Pollard Flat and
Fisher.
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 4095 12226 4079 12261 4085 12265 4090 12260
4092 12262 4098 12260 4101 12253 4106 12252
4107 12254 4109 12252 4109 12248 4113 12238
TIME...MOT...LOC 2146Z 066DEG 19KT 4100 12238
RoweThe office that day
Everything else NWS Sacramento, CA issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 14, 7:48 PM PDT | Areal Flood Advisory | STO | Shasta, Tehama | 3 hr |
| May 15, 4:39 AM PDT | Special Weather Statement | STO | Shasta | 81 min |
Nearby
Special Weather Statements in California, 2021Every 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.