Early Season Cold

Arctic air continued to linger over the mid-Atlantic northeast allowing for incredible cold high temperatures this afternoon. Sunday's high temperature was extremely cold as well, only reaching the upper 30s. Today was even colder, with Salisbury reaching 34 degrees and Dover stayed below freezing at 28 degrees. At least the winds were calm, or we could have been dealing with some brutal wind chill values. The last time we had high temperatures this cold was back in February of this year. Check this out, that coldest high temperatures ever for this date was 30 degrees in 1966.

For you cold weather fans, the forecast doesn't look to be in your favor. With the next storms system approaching, highs will reach the 60s on Wednesday but then fall back to the 40s for the end of the week. But looking over the next 10 days or so, there seems to be a pattern change possibly developing that would allow the jet stream to retreat northward and place the arctic air out west. This would allow some milder air to return to the peninsula.

Hail 101

Hail is a product of the updrafts and downdrafts that develop inside storm clouds (cumulonimbus), where supercooled water droplets exist. Water droplets change into frozen pellets when temperatures drop below freezing, as the updraft and downdrafts continue the larger the hail can get before released from the cloud. There are several stages a hailstone can go through depending how long it is in the cloud, first stage is graupel which is very small hail and has a snowflake like structure. The next stage is small hail which is the same size as graupel but has more of a frozen state and is no bigger than 1/5 inch in diameter. The final stage is hailstones, they have layers of ice and are greater than 1/5 inch in diameter; they can be as small as a pea or as large as a grapefruit.
Hail can be the most damaging parts of a thunderstorm, inflicting injury on others, destroying crops & properties. So when in a hailstorm take cover indoors and protect yourself.

Thanksgiving Forecast

First snow fall of 2008 was Friday November 21st, what a way to get you in the Holiday spirit!!! Warming back up this week. It does looks like is going to be another typical Thanksgiving with mild temperatures in the 50s, nice & breezy conditions along the shore! Normally, the past few years on Thanksgiving, temperatures have been above average with cloudy and wet conditions. However, it will stay dry this Thanksgiving & Black Friday! Late Friday night into Saturday morning there is a chance for rain showers to move across Delmarva. So besides a little drizzle for the weekend, things are looking up this year with dry conditions on Thanksgiving but just a little cooler than we are used to on previous Turkey Days. Have a safe & Happy Thanksgiving!

Wind Chill

Tis' the season for wind chill factors!!! When leaving the house on a cold wintry day you may want to check out the wind chill factor, especially if you are planning on for long periods of time. When the air is cold and the wind is blowing it feels a lot colder than it actually is; the actual wind chill temperatures are based on the rate of heat loss from exposed skin. As the wind increases, heat is carried away from the body at an accelerated rate, driving down the skin temperature and eventually the internal body temperature. Therefore, the wind makes it feel much colder. The wind chill factor is always lower than the air temperature; except at conditions well above freezing, where wind chill is considered less important. In this cases, heat index is used, where the apparent temperature is higher than the air temperature. Check out the chart below it gives you a better idea of blowing wind vs. temperatures on a cold wintry day!

Table Chart: http://www.nws.noaa.gov/om/windchill/index.shtml

Bay-Effect Snow

Bay-effect snow is most commonly know as lake-effect snow. The effect occurs in many places but is best known in the Great Lakes. Snow is produced in the winter when cold, Arctic winds move across long expanses of warmer lake, bay, or ocean water, providing energy and picking up water vapor which freezes and is deposited on the lee shores. The same effect over bodies of salt water is called ocean effect snow, or sea effect snow. Bay-effect snow produces narrow & intense bands of precipitation, which can deposit heavy snowfall amounts in a short period of time. If the air temperature is not low enough to keep the precipitation frozen, it falls as rain. Lake-effect snow forms by significantly cooler air moving across a significantly warmer body of water. Here's a few ingredients that help produce bay-effect: fetch, wind shear, and upstream moisture.

Fetch: the length in which an air mass moves across a body of water.

Wind Shear: is important because the more wind shear the further the bay-effect will be able to travel over land. The less wind shear the larger the precipitation totals will be along the leeward shore. Also wind shear plays a factor in squall lines, which are heavy bands of precipitation, weak directional shear help intensify the squall lines.

Upstream moisture: High relative humidity levels allow the air mass to pick up more condensation over the lake quicker and in larger amounts.

Bay-effect snow is more common during the later fall months and early winter months. Between Novermber, December and early parts of January.
The bodies of water get much cooler during the months of Febuary to April, so the chance of Bay-Effect Snow is a lot less.

Small Craft Advisory vs. Gale Warning

Small craft & gale winds are types of advisories and warning issued by the National Weather Service. Small craft advisories are usually issued when winds gust up to 28 knots (32 mph). Gale warnings are issued in the existence of winds of gale force or above or the imminent occurrence of gales at sea. Gale warning occurs when sustained winds are between 28­­-47 knots (32-54 mph). The purpose of small craft & gale warnings are to allow mariners to take precautionary actions to ensure their safety at sea. The insignia denoting a small craft advisory is one red, triangular flag and that of a gale warning is two such flags placed one above the other.

Dew & Frost

Clear, calm nights, objects near the surface quickly cool. The surface and objects on it, often become much colder than the surrounding air. When the surrounding air comes in contact with these types of cooler objects and eventually cool to the dew point, saturation occurs. When water vapor begins to condense on them, dew or frost is formed. Dew is when temperatures are above freezing and frost (frozen dew) occurs when temperatures fall below 32 degree F.