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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: 01/16/2004 01:41 PM
 

Good Afternoon Philadelphia!   

    I'm glad to announce that these discussions will continue until at least the end of January! 
    I have the necessary server space (especially with missed days!).  

In short:  The worst of the mind and body numbing cold is passed. Now we go the only way we can go...up. 

 In long: We'll start this time with yesterday's forecast for last night's low.   

First is the forecast was from weatherunderground.com.  It had a low last night of 12F. 

Fri
20° | 12°
Partly Cloudy

But accuweather.com had a low (record low) of Zero F. 

Tonight

0

And the Franklin Institute had a low of 7F. 

Thu. Evening

LOW:  7°F

And the winner is... 8F for a low.  It did NOT break the record and the Franklin Institute hit it within a degree. Excellent!

The 500mb map (showing the air at about 18,000 feet above sea level as it moves mainly from west to east across N. America parallel to the dark black lines)  shows the polar vortex beginning to move on (hurray!).  But was it fast enough to save your pipes?  Sadly, another piece of very cold air is gathering in western Canada, and a slow moving wave in the desert southwest will be bringing moisture up for a shot of weekend snow. This is a memorable winter.

How memorable?  You can see the lows this morning are about 18 degrees F BELOW normal (with almost 30 degrees below normal up into New England. 

Highs Thursday were about the same... 15-30 degrees below normal over the region. Amazing cold. 

The weather otherwise is very quiet. High (cold high) pressure is settling for the moment and...

Skies are clear.  You can see the contours of the snow dusted and snow covered ridges and land forms in the visible satellite view.  The ocean and Great Lakes are dark (except for some lake effect clouds forming off them).  Clouds are forming out to sea to our east for the same reason...cold air flowing over relatively warm water. 

The infrared satellite view (showing the temperature not clouds all the time) shows how cold the air is still over the region. it is colored green/yellow...or the temperatures of typical cloud cover.  Wow. 

The current temperature map at the surface shows the pattern of below freezing temperatures (everything below light blue). Compare this pattern to the pattern of yellows and greens above. Similar, no?

The satellite view does NOT show wind chill though. Figure in the cooling effects of wind with the actual temperature, and you get all of Pennsylvania and northward suffering from AFTERNOON wind chills at and below 0F!!! Very dangerous cold still.

Our last snow storm DID miss us though.  There IS more snow on the ground than reported here (maybe all the observers are too busy huddling inside with hot chocolate) we saw that in the visible satellite view above, but not much crippling snow has hit Philadelphia yet.  Watch out for this weekend though. :(

So tonight's lows are expected to be about 13F (somewhat warmer... <weak laugh>). 

And by Sunday morning, we'll see lows climb to 21.  Step by step warmer. 

For Saturday night, the snow returns as the southern system comes eastward in waves and shoves moisture up over this remaining cold air. 

And by Sunday morning, with those 20's F lows in the region, we'll see snow pelt Pennsylvania and the east coast.   Anyone up for a trip to Hawaii for a month or so?

More on the snow tomorrow. See ya then!

Meteorologist  John Ensworth

Surface Station sky cover color key: