Since winter is just around the corner- heres a review of winter weather explanations-keep in mind some national weather service offices have different criteria but the same general concept applies

WINTER STORM WATCH

This means there may be hazardous winter weather due to various elements such as heavy snow, sleet, or ice accumulation from freezing rain. In our region, heavy snow means 7 inches or more of accumulation in 24 hours or less. A "WATCH" is a long range prediction. They are issued at least 12 hours before the hazardous winter weather is expected to begin. When the storm becomes imminent, or has a high probability of occurring, the watch will be upgraded to a "WARNING".

HEAVY SNOW WARNING:

A Heavy snow warning was a weather advisory issued by the National Weather Service of the United States during times when a high rate of snowfall was occurring or was forecast. Generally, the warning was issued for snowfall rates of 6 inches (15 cm) or more in 12 hours, or 8 inches or more in 24 hours

ICE STORM WARNING

Heavy accumulation of ice due to freezing rain will down trees and power lines. Electricity, or telephone communications, may be out for a long period of time. Roads may become impassable for most vehicles. Ice accumlations are expected to be >1/4 of an inch.

BLIZZARD WARNING

This is issued for a combination of strong winds averaging or frequently gusting to, or above, 35 miles an hour and very low visibility due to blowing or falling snow. These are the most dangerous winter storms and can be especially severe when combined with temperatures below 10 degrees.

WINTER WEATHER ADVISORY FOR SNOW

This is issued for snowfall greater than 4 (but less than 7) inches in a 24 hour period. The snowfall is usually expected to begin within the next 12 hours.

BLOWING SNOW ADVISORY

This is issued when the visibility will be significantly reduced, or when the roads become snow covered over a large area.

WIND CHILL ADVISORY

This is issued for cold temperatures and winds, with wind chill temperatures computed to be -25 degrees or less for at least 3 hours. Exposure to this combination of strong winds and low temperatures without protective clothing can lead to frostbite and/or hypothermia, Prolonged exposure may be fatal.

WINTER WEATHER ADVISORY

This is issued for a combination of snow, sleet, and/or freezing rain. Advisories, in general, are issued for weather conditions that are expected to cause significant inconveniences and may be hazardous, These situations are normally not life threatening if caution is exercised.

Okay, but what is a freezing fog advisory. I noticed the panhandle had that warning a couple of times recently.

Great question Jo Ann! A Freezing Fog Advisory is issued when fog is present while temperatures are below freezing. This causes the fog to leave a thin layer of ice that can accumulate on roadways and overpasses resulting in hazardous travel.

Cara, I love your signature image. I never knew a tornado could be so pretty.

Okay, call me stupid, but I do not understand. Fog is in the lowest levels of the atmosphere. So the moisture should be the same temp as the air. Correct? If this is true, why does not the moisture causing the fog freeze, and fall from the air.

Thanks Jo Ann for the signature compliment!!

And you are NOT stupid. There is actually a difference in freezing fog and frozen fog. Freezing fog occurs when liquid fog droplets freeze to surfaces, forming white soft or hard rime. It is equivalent to freezing rain, and is essentially the same as the ice that forms inside a freezer which is not of the "frostless" or "frost-free" type. The term "freezing fog" may also refer to fog where water vapor is super-cooled filling the air with small ice crystals similar to very light snow. It seems to make the fog "tangible", as if one could "grab a handful". Frozen fog (also known as ice fog) is any kind of fog where the droplets have frozen into extremely tiny crystals of ice in midair. Generally this requires temperatures at or below −35 °C (−30 °F), making it common only in and near the Arctic and Antarctic regions. That would be why we never have "frozen fog advisories" here in Oklahoma.

I hope that answered your question!! Sorry for the late response. We've been very busy here at OSN with the ice storm at hand but ALWAYS welcome questions such as these!

Thanks for your answer Cara. I really really appreciate it.

I never have questions when it is sunny and 60degrees!!!!!  Sorry  !!!!!!!

If you do not mind, I have another question. I keep hearing Zack talk about "dry slot". He has been talking about in this storm, in the Christmas storm, and the hail storm we had last week. I intuitively get it is an area of dry area. 1st - what is it? 2nd - why is it a slot as apposed to an area?

Jo Ann at 10:26PM on Jan 28, 2010

Thanks for your answer Cara. I really really appreciate it.

I never have questions when it is sunny and 60degrees!!!!!  Sorry  !!!!!!!

 

If you do not mind, I have another question. I keep hearing Zack talk about "dry slot". He has been talking about in this storm, in the Christmas storm, and the hail storm we had last week. I intuitively get it is an area of dry area. 1st - what is it? 2nd - why is it a slot as apposed to an area?

Hey Jo Ann,

The dry slot referrs to a layer of dry air that is entrenched into a dynamic storm system as it deepens. The dry air is usually pulled in from the desert southwest as seen in the water vapor imagery above. Dry slots can be challenging to predict and can usually affect how much precipitation falls in a given area. For instance, you could have a forecast calling for 8" of snow but if you are dry slotted then that total can be lowered significantly due to a layer of dry air overhead preventing precipitation from developing(that's what a dry slot is -- layer of dry low level air). Dry slots can sometimes cause very tight snow gradients with one area seeing 12" and another area could see less than 2". It's complicated.

In severe weather season we refer to a dry line which is the boundary that separates moist air from dry air. You'll hear this term a lot in the spring.

Hope this answers the question...

I find the very rare terms that are used in weather forecast here and I am so glad I have read this. 'dry slot', 'freezing fog' 'frozing fog', everything is well explained, (thanks to Cara and OSN admin). I have new terms to learn about weather.

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