Wednesday, July 30, 2014
Inquirer Daily News

Bolaris: White, not green, for St. Patrick's Day

NOAA´s 6-10 day precipitation outlook predicts a 50-60 percent probability for above-normal precipitation. (NOAA)
NOAA's 6-10 day precipitation outlook predicts a 50-60 percent probability for above-normal precipitation. (NOAA)

It's been a long, taxing winter and with spring officially less than a week away, most of us are champing at the bit to inhale some milder air and be soaked in sunshine and let this bad boy of a winter melt away.

By looking at the latest computer guidance you're going to need to put those thoughts on hold.

On Saturday, we will catch a break. After some morning clouds, a west wind (those that bake us in the summer and bring delightfully milder air in the spring) will kick in and temperatures should reach close to 60, even toward the shoreline.

On Sunday, however, yet another polar front will approach from the west. Chilly air will begin to filter in as temperatures start cooling down into the 40s, before the core of the cold air takes hold on Monday with the thermometer hovering in the 20s with snow - just how much is still questionable.

The set-up

A polar front drops through Sunday evening as a couple of storm systems take shape in the Gulf states.

Storm system number No. 1 will approach Sunday night (most likely after 10 p.m.) with snow possibly mixed with sleet at the start, spreading in from the Washington, D.C. area.

The weather models are once again having trouble with the exact axis of heavier snow, but what I can see right now is that the highest probability of 4-plus inches would be across parts of southeast southern New Jersey and across central Delaware.

Philadelphia itself would fall under the 4-inch mark. (Four inches would be considered significant snow.) It's still early in the forecast cycle with some adjustments likely, but as of now, this is the way I see it.

The second wave will follow, with perhaps a late morning to mid-day break before we see another round of snow for the evening rush. This second wave should have less moisture associated with it, meaning a lighter snow event likely.

Northern and western suburbs should see lighter amounts. Western Montgomery, upper Bucks and northwest Chester counties will see perhaps 2-3 inches as it stands now.

Temperatures throughout the day will be frigid for this time of the year with highs in the mid-upper 20s.

Early timing

Snow and sleet arrive after 10 p.m. Sunday night changing to all snow and continuing into Monday morning's rush.

We get a mid-day break, and then the chance of another period of snow from later into the afternoon and early evening.

All snow moves out by Monday evening. I will be updating with any adjustments that need to be done right here on Philly.com this weekend, as uncertainties still remain.

Looking ahead

Spring arrives at 12:57 p.m. Thursday!

Also, I do see significant warming to take place for the final week of March. Hallelujah!!!

John Bolaris

John Bolaris For Philly.com
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