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The Story Behind the Weather - By Forecaster John
Ensworth M.S. -
The Discussion of Weather Events Daily for Philadelphia and Pennsylvania
Last updated: 10/23/2003 10:07 AM
Good Morning Philadelphia!
I'm glad to announce that these discussions will continue until at least the end of November.
Today's discussion will be brief due to the quiet conditions and to save server space (I'll get a tremendous increase in space Nov 3rd).
It IS chilly now, and light snow and sleet showers are falling just to our north! Temperatures are cool enough and the warp around moisture (traveling counterclockwise around the low to our distant northeast, is resulting in the first winder precipitaiton to fall over a large section of Pennsylvania.
On the visible satellite view, you can see the lanes of clouds coming out of the northwest on northwest winds. You can even make out more of the tight 'ruffles' looking cloud lanes (very clearly visible in Virginia, somewhat visible in Pennsylvania). The wind is blowing from the northwest perpendicular to how these cloud lines are orientated. The sinking air going downhill off land and out to sea warms a bit and the clouds dissipate until they pick up more water further out to sea. This creates that clearing along the coast.
The low from earlier this week is further to the northeast and it is a ripple of upper level cold air kicking off the showers over New York and north central PA. The cold airflow over the relatively warm Great Lakes is also contributing to these snow flurries... yes - lake effect snow!
It is currently only expected to get to nearly 50 in Philadelphia today...
And we should drop to freezing tonight for the first time!
So the National Weather Service has issued a Frost Advisory for our region. Here comes winter... sorry about those delicate plants outside.
Friday early morning an the winds, while weaker, keep blowing out of the northwest....
Then for Friday night, we have the high pass... very chilly air and very light winds will rule the weather.
Stay warm and I'll see you again tomorrow morning.
Meteorologist John Ensworth
Surface Station sky cover color key:
Flight category definitions:| Category | Ceiling | Visibility | |
|---|---|---|---|
| Low Instrument Flight Rules LIFR* (magenta circle) |
below 500 feet AGL | and/or | less than 1 mile |
| Instrument Flight Rules IFR (red circle) |
500 to below 1,000 feet AGL | and/or | 1 mile to less than 3 miles |
| Marginal Visual Flight Rules MVFR (blue circle) |
1,000 to 3,000 feet AGL | and/or | 3 to 5 miles |
| Visual Flight Rules VFR+ (green circle) |
greater than 3,000 feet AGL | and | greater than 5 miles |
| *By definition, IFR is ceiling less than 1,000 feet
AGL and/or visibility less than 3 miles while LIFR
is a sub-category of IFR. +By definition, VFR is ceiling greater than or equal to 1,000 feet AGL and visibility greater than or equal to 3 miles while MVFR is a sub-category of VFR. |
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