Wednesday, November 22, 2006

Speeding up the rain

4 PM Update

The band of rain continues to progress north slowly. Its progression is somewhat impacted by very dry air at the surface as dewpoints are in the teens just north of Philadelphia.

Sleet was mixing in with the rain within the last hour here in Collegeville with temperatures dropping now into the upper 30's. I expect temperatures to stay between 36 and 40 overnight in the suburbs and barely at 40 in Philadelphia, with very little warming tomorrow with periods of rain continuing.

Coastal flooding and high winds continue to buffet the Jersey and Delaware Coasts. For warning information for your county, check our warning page.

11:45 AM Update

Rain is continuing to spread north and is about to hit South Philadelphia as of 11:45. Don't expect temperatures to climb much higher. Temperatures will stay in the 40's regionwide this afternoon, maybe climbing to near 50 along the South Jersey Coast with an ocean influence. Expect rain to continue to inch northwards over the next several hours, reaching the Lehigh Valley and Berks regions this evening.

One thing to watch as well will be the possibility of sleet mixing in. There have been reports of sleet in New Castle County, DE, as well as other parts of South Jersey as the rain first moves in. With dewpoints in the 20's regionwide, some sleet is possible along with patchy freezing rain or pockets of sleet in the Poconos tonight in the highest of elevations.

This storm's movement has wreaked havoc on plenty a forecaster's calls, include mine. This wasn't a pretty storm to predict for any of us out there.

The coastal low is going to move less slowly and as a result our timeline on the rain forecasts for the region have moved up some as well. Rain looks to be moving up from the south on Wednesday and may reach the Philadelphia area during the evening. It looks to be a rainy Thanksgiving because of more "rapid" movement of this low.

Don't forget that has continuous radar, updated from several sites in the region.

Today, expect clouds with increasing wind. If we can get enough sun today, we can crack 50 but I think most of the region may be just of that after looking at this morning's weather data. Rain will move up from the south during the day and impact the region overnight Wednesday and Thursday. This will be a cool day but not terrible north and west.

Why is the low moving faster? High pressure is not as strong to prevent the low to stall out. The result of a weaker higher is preventing what the models were looking to do with it a couple of days ago with the low staying stalled to our south. This movement isn't real fast -- it's still a slow moving low pressure system but compared to a stalled out system a 5 to 10 mph movement can lead to a huge difference over two days.

The result of this faster movement in the coastal low is a rainy, miserable, and cold Thanksgiving with temperatures barely crossing into the 40's north and west with an off and on light rain. Temperatures around Philadelphia will be in the low and mid 40's with rain going on and off throughout the day. The heaviest rain will be from I-95 and south and east with nearly 1.5" of rain possible. North and west, progressively lighter rainfall amounts will occur but the immediate Philadelphia suburbs could get about an inch at most with 3/4" of rain possible for Reading and Allentown.

There is a blessing with a faster moving low -- a faster departure. Friday looks to be nicer now than Thursday, as well as much warmer, so shopping conditions will be much better. I'm sure the husbands out there are looking forward to that! Those milder and warmer conditions will continue through the weekend and extend into early next week.