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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: 09/14/2003 02:17 PM

Welcome back to ... rain watch.   Taking a look at the surface map again, well, it's more rain. A warm front is passing over the top of us 

The blobs of rain yet to come can be seen strung across the US.  Right now air is sinking over the state giving us a break this morning, but this afternoon will see the first of the next three blobs of cool upper air (and lifting) approach and kick off more storms (including thunderstorms since we are south of the warm front and east of the cold front in the warm air).  Then Saturday and Saturday night will see the next two blobs move past.  These blobs of lift (and rain) are visible in the upper air map further below...

This map (the 500 mb map - see the archives for a more in depth explanation of it) was made about 10 hours earlier than the radar image above so the three blobs of upper level cooler air (black circles) are a bit farther to the west.  But you always should expect lifting air and clouds (and sometimes showers) ahead of the 'uphill' or northward bends in the air flow (the air is moving from west to east over the US following the black lines). 

Starting Sunday, we should finally see a big break with warmer and drier conditions.  Looking at the computer forecasts of the 500mb map to see this... we see... Sunday with the bottom of the trough overhead...Monday with the trough to our northeast and (relatively cool air) coming in from the northwest.  Tuesday has a ridge approaching (nice weather!).  Wednesday we have the ridge on our heads.  Thursday and Friday is our next chance of rain as another trough begins to approach. 

I'm sorry half the weekend will be soaked, but hold on a bit longer for a break.  I'll see you tomorrow!

Meteorologist  John Ensworth