#weather #paweather #wx #pawx #philadelphia

Update Fri 2/10 4:35 PM — A quick mobile update. The precipitation on Sunday does now appear to move into Philadephia between 6-8PM. It doesn’t appear to move much further north than the immediate suburbs. The regular Weekend Weather Forecast will be posted later.

Still Some Uncertainty

Update Thu 02/09 @ 8:04 PM — So while the NAM, GFS and ECMWF posted below keep the rain to our south until midnight or after, the statistical models are not all that sure.

Here’s the NAEFS that just became available. The NAEFS combines the Canadian ensemble model with our GFS ensemble (GEFS).

Here’s its forecast probability of light rain before 10 PM Sunday —

If we set the threshold for any rain lower, as little as 0.01 inches for the six hours preceding 10 PM Sunday, here’s the probability—

This NAEFS is more in line with the latest Canadian regional GEM, the latest German ICON model and the SREF.

So it’s going to be a close call. Some sprinkles and light rain possible here during the Super Bowl, but not a sure bet. My regular readers know my mantra, “never ignore the NAM” which currently keeps us dry.

I’m still keeping an eye on the weather for Sunday and based on today’s ECMWF along with the latest GFS , it appears that the rain will stay south of Philadelphia until after midnight Sunday. Indeed, currently there’s remarkably good agreement in the models today, considering how far apart their forecasts were just a few days ago.

Here’s the latest GFS, just available—

The forecast period in question now falls within the forecast horizon of the latest 18z NAM model (84 hours). The NAM forecast is remarkably similar to the GFS —

Even today’s ICON model (posted earlier today) has fallen in line with the other models.

So things look good weather-wise for the Eagles victory celebration.

#weather #paweather #wx #pawx #philadelphia

Continuing Forecast Change For Sunday

Update Thu 02/09 @ 8:57 AM — Regarding the coastal storm that is now forecast by all models to develop Sunday, the latest GFS keeps any significant rain out of the immediate PHL area until after midnight Sunday into Monday morning. A few other models have light rain moving in after 6 PM–

Continuing Forecast Change

Update Wed 02/08 @ 6:21 PM — Today’s models have moved away from having the coastal storm progress northward very much on Sunday and will likely skirt to our south later Sunday night into Monday.

Here’s the latest GFS—

Interesting Weather Possible Sunday

Update Wed 02/08 @ 8:39 AM — The complexity of the weather setup for this weekend has been a challenge for the numerical weather models, and over the past week or so, I’ve been watching this scenario evolve.

The GFS forecast for this weekend over past days has been described as an ‘outlier’ by the NWS chief forecasters, but interestingly, last night the ECMWF joined the ‘outlier’ GFS in forecasting a closed low and a coastal storm for Sunday!

In a “normal” winter, this might pose the potential for major coastal snowstorm, but this winter and this weekend, the thermal profiles are quite complex. As a result, the precipitation type will be a difficult forecast, but it is still leaning heavily towards rain here.

The current forecast track may keep it from moving further north than shown below at 4 PM Sunday—

GFS—

Nonetheless, an interesting setup. (While it’s going to be too warm for snow here, should the closed low (red circle) move up over us, it will be a different ball game.)

My regular readers here know that when a mid-level or upper level low closes off, forecasting movement and track of the surface low and the precip can be daunting. Stay tuned.

Forecast Uncertainty

Perhaps people have noticed that the forecasts the past two days haven’t been the best. Yesterday was supposed to be sunny but it was very cloudy in the afternoon. Today was supposed to be cloudy in the afternoon, but the cloud cover was very thin and the sun shone through.

Clearly, we’re in a pattern the models are having trouble with. Which brings us to the forecast dilemma for the end of the week into the weekend.

There remains significant differences in the model forecasts for the coming weekend. It’s been like this for days.

Here’s the latest GFS for 10 AM Sunday. In a “normal” winter there might be worries about a major coastal snowstorm, (but not this winter and not this weekend.)—

GFS forecast—

As ominous as that map looks, here’s the current ECMWF forecast showing the storm further south and east that will shear out to sea —

So we have two very different forecasts for the weekend, particularly Super Bowl Sunday. I’ll be honest…I have no idea what the weather will be this Sunday. While I’m at it, there’s too much uncertainty even Friday and Saturday. Hopefully things clarify.

When was the last time you heard that with the TV weather entertainers?

#weather #paweather #wx #pawx #philadelphia

Update Mon 02/06 @ 10:04 PM — Still no sign of any snow through Feb 18th. In fact, after a chill down this coming Super Bowl Sunday, things warm up again.

This week’s weather will be influenced by a flat to ridge configuration of the jet stream, with the jet north of our area, allowing milder conditions.

Monday will be windy and sunny. The winds the result of a nearby deep low pressure system in the Atlantic.

A weak cold front will pass through early Tuesday morning.

Wednesday will be the nicest day, with a possible runner-up on Thursday.

The 500-1000mb (540) thickness (red line) gives a quick, general position of the jet flow. Here’s the GEFS forecast for Wednesday—

Here’s the actual depiction of the jet stream (300 mb level winds). Notice where the superimposed 540 thickness level is —

Large questions marks emerge after Wednesday with expected changes in the jet flow. The forecast is unclear at this time, especially for Friday through Saturday.

This past weekend, I saw the first possible signs of a potential coastal snowstorm and posted that possibility. That possibility has since faded, but high forecast uncertainty is still the message. If there will be any snow, it now appears to be in western PA.

Here’s the latest GEFS forecast for Saturday—