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Mid-Atlantic WX Home |
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NWS Blacksburg Event Criteria |
| Product | Snow and/or Sleet | Ice | Combination Weather Hazards |
| Winter Storm Watch/Warning * | 6"
Area 1 (W of Valley) 5" Area 2 (Valley and East) |
>/=1/4 inch | hazards judged to pose a threat to life and property |
| Winter Weather Advisory * | 3" Area 1
(W of Valley) 2" Area 2 (Valley and East) |
Any accretion
up to 1/4" |
hazards cause "significant inconvenience" and warrant extra caution |
| Blizzard Warning | Sustained or frequent gusts >/=35 mph AND considerable blowing/drifting of snow reducing visibilities frequently < 1/4 mile | ||
| Wind Chill Advisory ** | Wind chill of -15o F with wind speeds 10 mph or more | ||
| Wind Chill Watch/Warning ** | Wind chill of -30o F with wind speeds 10 mph or more | ||
| Frost Advisory | Issued at the end (fall) or beginning (spring) of the growing season when frost is expected, but severity not sufficient to bring and end or delay the beginning of the growing season; also can be issued when severity level is uncertain. Under prime radiational cooling conditions, frost can form when standard observation level temps are in the mid 30s. Generally not issued between mid November and mid April. | ||
| Frost Warning | Issued in conjunction with a killing frost only (sufficient to end the growing season in fall, or delay it in the spring); how far low temperatures are below freezing, and for what duration are the factors determining if it is a killing frost. Generally not issued between mid November and mid April. | ||
| Freeze Warning | Issued in conjunction with temperatures forecast to be <300 F for a significant amount of time (with or without frost). Sufficient to end the growing season in fall, or delay it in the spring. Generally not issued between mid November and mid April. | ||
| Dense Fog Advisory | Issued for widespread fog reducing visibilities to 1/4 mile or less | ||
| Heat Advisory * | Heat Index >/=105o F to <115o F for 3 hrs/day, for 2 consecutive days | ||
| Excessive Heat Watch/Warning * | Heat Index >/=115o F at any time, for any length of time, for 2 consecutive days | ||
| Wind Advisory * | 31-39 mph (27-34 kts) sustained for 1 hour or more; or 46-57 mph (40-49 kts) of any duration | ||
| High Wind Watch/Warning * | >/=40 mph (35 kts) sustained for 1 hour or more; or >/=58 mph (50 kts) of any duration | ||
| Tornado WATCH | A watch means tornadoes are possible. You should be prepared for severe weather and the possibility of a tornado. |
| Tornado WARNING * | A warning means a tornado has actually been sighted and may be headed your way. When a warning is issued, you must immediately take cover! |
* Use highest value of forecast range ** Use lowest value of forecast range
