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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: 01/28/2004 07:26 PM
Good Afternoon Philadelphia!
I'm glad to announce that these
discussions will continue until at least the end of February
(it's a short month)!
I
have the necessary server space (especially with missed days!).
In short: Snow now and then and moderate cold...nothing REALLY bad for a while...
In the Long: The 500mb map, showing winds as they blow west to east across the continent at about 18,000feet above sea level (where the steering winds are for most storm systems) you can see the trough that kicked up our snow/ice fest at the end of the weekend now moving off to the east. There is yet a new pool of cold air up in Canada, but it will hit the central and east central part of the nation first. You can see (in green letters) the northwest slope/slide of cold air though... nasty.
This same pattern is visible on the temperature map. The cold air and the trough are one in the same entity.
The surface map shows nothing notable near by. Some remaining show showers are drifting around our last storm way off the map to the northeast.
The snow on the ground now is pretty serious for the western 3/4ths of the state. Even Philadelphia has a few inches or more around.
But with the core of the cold air over the northern central US, we have warmed to the 30's here near sunset...
But with winds in the 20mph (from the west) zone we see wind chills...
...that are down near 0F. It is still nasty outside!
The 500mb map by 1pm Thursday show the northwest flow over the area and a new shortwave moving through New Mexico and west Texas...
We have some lake effect snow out west, but nothing big around here. The shortwave in the SW US is kicking off showers at this time (Thursday 1pm) in Texas.
For Friday 7am, we are in almost the same identical situation, and the trough in the SW hasn't moved much.
For Friday 7am, another front has slipped by with little fanfare here (just colder temperatures) as cold air continues to follow our northwest flow aloft. And showers expand up the Mississippi valley. We'll watch this for some weekend snow.
Stay warm, drive safely and I'll see you here Thursday!
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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