Monthly Archives: March 2018

Philadelphia Weather Outlook

PHILLY STORM OUTLOOK FOR TUES-THURS

Last night’s two model runs continue to show some snow and mixed precipitation starting Monday night into Tuesday.  Current track is a bit further south, increasing chance of snow vs. rain, but QPFs are less.

We’re NOT talking about a major snowstorm for Philly; more likely a significant snow for areas much further inland.  Details about specific accumulations still uncertain, but it appears more like a 3 inch range total with sleet and possible rain mixed in for Philly.  The usually “more likely on grassy surfaces” instead of roadways.  That’s the current best guess.

What’s more significant with the latest model runs- the second low that forms on Wednesday is now looking like it might move out to sea, essentially missing us on Wednesday;  this is true of the deterministic models (GFS, CMC, ECMWF etc).   The statistical models still show a ”signal” for snow in our area on Wednesday, so we’re not out of the woods yet.

This is a complex binary-type system.  Still too early to be sure about  details, expeciallly with the second low for Wednesday.  Changes likely.

 

Philadelphia Area Weather Forecasts

PHILLY WEEKEND FORECAST & STORM OUTLOOK

An upper cyclonic flow will continue to bring below average temperatures to Philadephia this weekend.

Saturday will be mostly sunny and still breezy and cold. High temperature will be about 46. (Average high is 54.)

(Fri 11:30 pm update-  some cloudiness in the afternoon Saturday)

Sunday will be sunny and winds will be light. High temperature warmer at 49.

[su_note note_color=”#ebf2d9″]So, what about this storm being talked about for next week?

As you’ve heard, this storm is expected to develop as a complex binary system that evolves from several areas of low pressure that redevelop off the coast into at least two secondary systems.

The forecast challenges are less about track or significant differences in the models; it’s more about the intrinsic complexity of modeling complex binary systems. Indeed, the statistical models show surprisingly strong agreement this far out.

As always, the devil is in the details, specifically about the rain/snow line and precipitation type.

Here’s what the forecast currently looks like — a mix of freezing rain, sleet or snow develops before daybreak Tuesday.

The precipitation changes to rain in Philadelphia on Tuesday but may remain as sleet mixed with snow in northern and western suburbs. The precipitation will be heavy at times. Precipitation changes to snow late Tuesday or Tuesday night before tapering.

A brief hiatus early Wednesday before mixed precipitation restarts Wednesday and changes to all snow late Wednesday afternoon into evening, ending before daybreak Thursday. Some accumulation expected with each round, more on grassy surfaces than roadways. An ugly two day period.[/su_note]

Updates

PHILLY SNOW UPDATE 10 PM

Latest NAM data  coming in.  No change from previous forecast .

[su_note note_color=”#ebf2d9″]With warm temperatures to start and slow chill-down that occurs later this evening, it’s possible we may see a wet coating to maybe about 1/2 inch of snow. Temperatures chill down to about 32 during the early morning hours.[/su_note]