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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: 12/08/2003 10:15 AM
Good Morning Philadelphia!
I'm glad to announce that these
discussions will continue until at least the end of
this Year!.
I
have the necessary server space.
In short: Mostly clear to partly cloudy and cold. Warming begins Tuesday before a WET thunderstormy system hits mid to late week. This will cause rapid snow melt. This stuff isn't here to stay this time.
In long: The storm came. The snow fell. Now the shoveling continues. Below are some snow fall reports for Philadelphia County from the National Weather Service and the top amounts I could find.
...PHILADELPHIA COUNTY...
NORTHEAST PHILADELPHIA 10.5 12/06 1102 AM
SOMERTON 7.2 12/06 1200 NOON
PHILADELPHIA AIRPORT 4.8 12/06 415 PM
...HUNTERDON COUNTY...
DELAWARE TWP 14.0 12/06 245 PM
...MERCER COUNTY...
HAMILTON SQUARE 14.5 12/06 615 PM
LAWRENCEVILLE 13.1 12/06 428 PM
At first glance, the visible satellite view LOOKS quite cloudy over the eastern part of Pennsylvania, but that's NOT clouds. It is snow. Remember the visible satellite view shows whatever is white and snow is as white as any cloud. You can make out the knurled terrain, canyons and valleys across the state as places where the snow either is less or masked by thicker trees. How can you make sure you are seeing snow, not clouds? Look with infrared eyes...
The infrared satellite view is not as fooled by snow. Cold ground is cold ground whether there is snow or not. We DO have high clouds streaming in from the west, but the bare ground is visible over the eastern 1/3rd of the state (note the warm lakes and warm ocean to the distant south (warm = red).
The actual snow depth map from Weatherunderground.com shows widespread 6" snow amounts statewide with heavier amounts closer to the ocean (where all the water is). What an amazing November storm!
Temperatures are, due to the snow as much as anything else, are at or below freezing this morning.
And winds are dropping to calm as a wind switch (to the south) approaches harboring in our warm-up.
So wind chills are not far from the upper 20's. Still, chilly - but not as bad as 40mph winds in snow over the weekend!
The national map this morning shows the high passing to our distant south. Winds move clockwise around a High pressure center, so the south winds are not far away (and you can see them on the wind map above). The NEXT system is gathering itself together out west.
This western surface storm is shaping up under the right side of the new trough digging into the western states. The ridge on the east coast is what has killed the falling snow and weather of recent days (and the surface system has moved off to the east as well).
So the next big news will be the warm air and warm rain and occasional thunderstorm moving in by Wed/Thurs. This will destroy a lot of snow quickly and cause some flooding problems.
By Tuesday PM, the low is near St. Louis with rain ahead and snow behind it.
by Wednesday night, 7pm, the rain is expanding in areal coverage and intensity up the east coast.
Then by Thursday 7am, we are under strong waves of rain and some thunderstorms. Bye bye snow.
This next situation will be a problem and needs to be watched. If you live in low lying areas near streams or rivers, use what you've seen from past such situations and prepare accordingly.
And I'll see you here again tomorrow!
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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