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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: 02/05/2004 09:26 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/freezing rain will begin soon, followed by A LOT of rain through the start of the weekend.  After that, chilly clearness will return. 

In the Long:  I'll stay in "active weather" mode tonight with a report of the badness that is to come.  We have a winter weather advisory, flood watch and special weather statement all pending for Philadelphia.  The graphic below has to prioritize which to color us with.  I've included the National Weather Service text below for you to read.  

Flood Watch / Flood Statement

Expires 4:00 AM EST on February 07, 2004 Statement as of 3:15 PM EST on February 5, 2004 ...Flood Watch Continues For Friday Afternoon Into Saturday... A Flood Watch remains in effect for the following areas... In Pennsylvania... Berks... Bucks... Chester... Delaware... Lehigh... Montgomery... Northampton and Philadelphia. In New Jersey... Camden... Gloucester... inland Monmouth... Hunterdon... Mercer... Middlesex... Morris... northwestern Burlington... Somerset... Salem and Warren. In Delaware... New Castle. In Maryland... Cecil. Low pressure beginning to lift out of the lower Mississippi Valley early this afternoon will move through the Tennessee and eastern Ohio valleys tonight and Friday. Secondary low pressure will form over the mid Atlantic region late Friday and lift northeast Saturday. Due to the path of this weather system, it will pick up quite a bit of moisture from the Gulf of Mexico and the Atlantic Ocean. The precipitation is likely to begin with frozen or freezing precipitation later tonight, but areas in the watch should see a change to rain from early Friday morning southeast to Friday evening northwest as milder air spreads over the region. Stream levels remain high from tuesday's rains. Possible rainfall amounts from 1.5 to 2 inches combined with runoff from melting snow could result in flooding of streams, creeks, and poor drainage areas. Additionally, many streams are clogged with ice, and this would increase the potential for flooding as the ice moves and possibly causes local jams. A Flood Watch means that flooding of streams, creeks and other drainage areas is possible within the watch area. People in the watch area should keep an eye on the weather and be prepared for immediate action should heavy rains and flooding occur or a Flood Warning be issued. Stay tuned to NOAA Weather Radio, your local radio or television stations or your cable television outlet for further details or updates. Additional weather information can be found on the internet at www.Erh.NOAA.Gov/phi.

Winter Weather Statement

Expires 11:00 AM EST on February 06, 2004 Statement as of 9:25 PM EST on February 5, 2004 Salem NJ-southeastern Burlington NJ-Talbot MD-western Monmouth NJ- ... Winter Weather Advisory in effect overnight... The National Weather Service has issued a Winter Weather Advisory overnight. Light mixed precipitation... in the form of snow... sleet and freezing rain... was moving into the region Thursday evening from the west... and should overspread the region by shortly after midnight. While temperatures are expected to gradually warm overnight... and the precipitation turn to plain rain in the early morning Friday... any freezing rain that falls overnight will make roadways icy and hazardous.

Special Weather Statement

Statement as of 8:27 PM EST on February 5, 2004 Atlantic NJ-Camden NJ-Cape May NJ-Caroline MD-Cecil MD- coastal ocean NJ-Cumberland NJ-Delaware PA-eastern Monmouth NJ- Gloucester NJ-inland Sussex de-Kent MD-Kent de-New Castle de- northwestern Burlington NJ-ocean NJ-Philadelphia PA-Queen Anne's MD- Salem NJ-southeastern Burlington NJ-Talbot MD-western Monmouth NJ- 827 PM EST Thu Feb 5 2004     As high pressure moves away from the region overnight... cold air will remain in place for several hours into the early morning hours. Meanwhile... low pressure moving away from the Gulf Coast will track into the Ohio Valley overnight. Strong winds in the upper atmosphere will bring an abundance of moisture to the area. Some of that moisture will initially fall as a mixture of snow... sleet and perhaps some freezing rain... before changing to all rain during the early morning hours Friday.   The temperature by the morning rush hour should be above freezing in most areas... but another problem will arise. That will be heavy rain by late morning into the afternoon. The rain will continue heavy... especially over eastern sections into Friday night. For that reason a Flood Watch continues for part of the region.   Since there is a threat of mixed precipitation and some icy spots... and the potential for streams and roadways to flood... please check the latest forecasts for your particular location.

The current surface map shows the low way down near the Gulf Coast. Already rain and snow are flying ahead of the system. 

The winter weather coded radar shows a mix of snow and ice invading Philadelphia.  But this is only the start of much to come. 

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) shows the northern jet and southern jet streams have merged into one large happy monster trough down the middle of the US.  It won't move quickly, so the area in the red circled region, the uphill right side of the trough, will linger over the eastern US for the next couple of days. 

The surface map by Friday 1am, shows the Gulf Coast low sliding northeastward towards us with a LOT of moisture and warm air ahead of it. 

Now, turning the the National Weather Service forecast maps available at:  http://weather.gov/forecasts/graphical/sectors/nemetroWeek.php 

You can see rain and freezing rain/ ice mix in Philadelphia (with maybe some snow for completeness) by 4am Friday morning. 

For 10am, the ice begins to change to just rain (but the morning drive will be bad!). 

At 1pm, we'll be well above freezing and we'll just have rain. 

By the night time drive, 4pm Friday, most of Pennsylvania will be getting only rain, but a LOT of it. 

For Friday night 7pm, the low from the Gulf will be north of western Pennsylvania and a tremendous amount of water will be falling from the Gulf Coast to eastern Pennsylvania. 

7pm Friday = rain. 

By Saturday 1am, rain will still be falling, but finally dying out. 

Saturday 4am, and more showers, and with cold air approaching from the west, you can see snow approaching. 

Saturday 7am, the low is east of Main, and the cold front has come through.  Snow is returning!

Saturday 10am, and some light snow will be following the system in. 

It will be a rough Friday morning drive and VERY wet through Saturday morning. Stay dry!

Meteorologist  John Ensworth

Surface Station sky cover color key: