Wednesday, December 07, 2011

Soaking Rain & Dropping Temperatures

Today's weather is summed up in two pieces -- soaking rain, falling temperatures.   Snow is not a part of the picture during the daylight hours -- it will be with us tonight, especially if you are west/north of the city where accumulations still appear to be possible after Midnight tonight.  Until then, however, a soaking rain from a couple of rounds of low pressure will ride along a stalled frontal boundary that will slide south through the region through the course of today.    First, temperatures.  We're starting off near 60 or in the low 60's across the region this morning, which is our high point for the day in terms of warmth.  Temperatures will slip back into the 50's later on today, dropping into the 40's north and west of town this afternoon and around the dinner hour locally as the frontal boundary to our north (you can see it's just north/west of Blue Mountain this morning on the map above as temperatures in the mountains are in the 40's compared to 50's below the Poconos and Central PA hills) slips south over the course of the day.  

Adding insult to injury is a soaking rain that's going to increase in coverage an intensity through the day.  Rain stretches from our region back west and southwest to the Gulf Coast, much of it streaming northeast through the day today.  It will increase in coverage and also intensity, becoming heavier at times later on, as Gulf moisture feeds into the developing low pressure center that rides northeast along the front.   The "best" weather for today will likely be over the next couple of hours (before 7 or 8 AM), with weather trending downhill progressively through the day.

Computer model projections paint much of the region in a swath of receiving around two inches of rain between today and tonight, heaviest this afternoon and evening (those two inch amounts are in the orange shading below).  Some three inch amounts can't be ruled out.  Flooding is going to be an issue for the usual suspect streams and some of the lesser prone to flood streams as well considering we're picking up a lot of rain in a short amount of time and have saturated soils from our two inch rain event a couple of weeks ago.  It also would not surprise if we get a line of broken thunderstorms to develop along the front to the southwest of the low pressure track late this afternoon and evening.  This line, if it does develop, would impact Southern Delaware and Cape May County in New Jersey.

Winds will be an issue later this evening as the low gets cranking and we'll see those northerly winds increase a fair bit by tonight, helping to drag lower temperatures into the region and help hasten that changeover from rain to snow across the Delaware Valley later tonight.   We'll update that discussion later on but our thoughts from last night still hold.