Alert archive / Oregon / Frost Advisories in 2017

Frost Advisory 14, NWS Medford, OR

September 20, 2017Klamath County, Lake County, Oregon; Modoc County, Siskiyou County, California

NWS Medford, OR issued this frost advisory at Sep 20, 2017, 2:32 PM PDT for Klamath County, Lake County, Oregon; Modoc County, Siskiyou County, California. It took effect at Sep 22, 2017, 2:00 AM PDT. It was in force for 7 hr.

The area

The counties it named.

The facts

Issued
Sep 20, 2017, 2:32 PM PDT (21:32 UTC)
In effect from
Sep 22, 2017, 2:00 AM PDT
Expired
Sep 22, 2017, 9:00 AM PDT
In force
7 hr
Issued by
NWS Medford, OR

Counties Modoc County, CA, Siskiyou County, CA, Klamath County, OR, Lake County, OR

The radar

The Medford radar (KMAX), 115 km from the middle of the area, began a volume at 21:35 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

Salem/Mcnary, OR (KSLE), launched 12:00Z, 9.5 hours before the alert went out and 335 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, Salem/Mcnary, OR at 12:00Z on 2017-09-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 3 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, Salem/Mcnary, OR at 12:00Z on 2017-09-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -24 square meters per square second.1939587897117136Sfc1 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
3 J/kg
Mixed-layer CIN
-75 J/kg
Mixed-layer LCL
1061 m above ground
0-6 km bulk shear
53 kt
0-1 km storm-relative helicity
-24 m²/s²
0-3 km storm-relative helicity
19 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

Open this sounding in Storm Lab

What forecasters said that day

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

NWS Medford, OR wrote its last area forecast discussion before this frost advisory went out at Sep 20, 9:13 AM PDT, 5 hours 19 minutes earlier.

Area forecast discussion, Sep 20, 9:13 AM PDT, 5 hours 19 minutes before
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The office that day

Everything else NWS Medford, OR issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 20, 3:16 AM PDTSmall Craft Advisory for Hazardous SeasMFR47 hr
Sep 20, 3:54 AM PDTWind AdvisoryMFRKlamath, Lake13 hr
Sep 20, 4:32 AM PDTFreeze WarningMFRKlamath, Lake28 hr
Sep 20, 2:32 PM PDTFreeze WarningMFRKlamath, Lake42 hr
Sep 20, 4:32 AM PDTFrost AdvisoryMFRModoc, Siskiyou28 hr

Nearby

Frost Advisories in Oregon, 2017Frost Advisories in California, 2017Every frost advisory in 2017

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.