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1 posts from October 2011

10/28/2011

10/28/11: Weekend Weather Advisory

The Office of Emergency Management (OEM) has released the following information:

The Office of Emergency Management (OEM) is monitoring an early season Nor'easter storm that will bring heavy rain, wind, and possible snow to the City of Philadelphia.

The National Weather Service has issued a Winter Weather Advisory for the City of Philadelphia, in effect from noon Saturday through 2 am Sunday.

A Coastal Flood Warning has been issued for the tidal Delaware River on Saturday afternoon from noon to 5 pm.  Moderate flooding is possible on the Delaware River.  No flooding is expected on the Schuylkill River or the smaller creeks in Philadelphia from this event.

According to the Winter Weather Advisory:  

* Accumulations... 1 to 2 inches. The greatest accumulations should be on non-paved surfaces.

* Timing... Rain will overspread the region after midnight tonight, then mix with wet snow around midday before changing to wet snow during the afternoon.

* Impacts... Areas of slippery travel developing, and the heavy wet snow will weigh down tree limbs which still have leaves on them.  This will potentially lead to some downed tree limbs and power outages. There could be a burst of heavy wet snow during the height of the storm, locally increasing the accumulation rate for a time Saturday evening.

* Winds... North 15 to 25 mph with gusts up to 35 mph.

* Temperatures... Around 40, but then falling into the lower 30s Saturday night.

* Visibilities... Reduced to well under a mile at times.

Winter Storm Warnings have been issued for Bucks, Chester, and Montgomery Counties, with forecasts of 2 to 6 inches of snow.

This is a challenging forecast. It is unlikely that there will be much clarity on the timing of a transition to snow until during the day on Saturday.  A worst case scenario would see an earlier transition to snow in Philadelphia and several hours of heavy, accumulating snow during the afternoon and evening, with total amounts reaching 6-8"  Power outages and downed tree limbs could be a significant issue if snow totals approach the worst case scenario.  

However, it is also possible that the rain doesn't transition to snow until late in the day and that no accumulations occur in Philadelphia.  

Refer to the National Weather Service website at www.weather.gov/phi for updated forecast information.

For an updated snowfall forecast from NWS, refer to http://www.erh.noaa.gov/phi/StormTotalSnow/index.php

Low temperatures on Sunday morning are expected to be in the low 30s, and the high temperature Sunday is 50, so any snow that falls should melt quickly.