Monthly Archives: February 2020

Philadelphia Weather Outlook

WEEKEND WEATHER OUTLOOK

The weather forecast for this weekend continues to be uneventful with high pressure bringing fair skies and near to above average temperatures on Saturday, then even milder temperatures with the return southwesterly flow on Sunday.

With sunshine both days, high temperatures on Saturday 49 and Sunday 53.  The statistical EKDMOS has temperatures on Sunday near 58.

Long range, the pattern we’ve see these past weeks is likely to continue through the end of February.  There is some question about a low pressure system expected to develop next Thursday, but rain rather than snow in our area is the most likely precipitation type according to the GFS.   The Canadian GDPS and the German ICON models suggest a different position of cold air and a low possibility of snow, but they have been wrong several times in past weeks.  The GFS has been the best model this season.

Since there’s not much weather to talk about, here’s a photo of the altocumulus translucidus visible this afternoon —

Altocumulus translucidus

Posting cloud pictures makes me nostalgic for the days when I would forecast the weather with just a barometer, wind vane and a view of the sky.  (It worked pretty good in the summer seasons, not that good in the winter.)

Here’s an image taken from a cloud chart that I’ve had since I was 11 years old showing the cloud type and recommended forecast:

From Downeaster Cloud Chart

With the winds from the NW this afternoon, the cloud chart recommended forecast would have been correct.

Philadelphia Weather Outlook

WEATHER OUTLOOK

The weather pattern this winter and specifically this February, has been unusual to say the least.  Apart from the roller-coaster temperature swings and the over-all mild weather temperatures, the ‘predictability’ of the weather systems this season has been above average.

Indeed, the ‘spread’ of the probability-based ensemble models seems to have been below average in recent weeks indicating higher confidence and lower expected variations in the longer term forecasts.

This is something I haven’t seen much.  Put another way, in past winters, I would check the GFS in the morning and again later in the day and the model forecast had a fairly high chance of having changed in the interim, often dramatically.  Not so in the past few weeks.

For the most part, the remaining two weeks of February look to be similar to recent weeks— Rain, followed by a couple of days of cold weather. then a return to over average temps and more rain as another front moves in.

A cold front moves through tonight (Tuesday) with light rain and cold air and high pressure build in for a two or three day period of cold temps.  Temps moderate by Sunday.

As discussed last week there just haven’t been large/dense cold air masses to sink straight south into the continental US, nor have there been similar masses to set up in the North Atlantic, giving us a ‘blocked’ pattern.

The current pattern looks to continue until near the end of February.  No snow expected.

There have been signs that a pattern change is possibly occurring the very end of February or the first week of March.  The EKDMOS temp stats show very large “spreads” developing in the long range.

EKDMOS High Temp forecasts, showing spread increasing

While there are always larger spreads in the longer range, the latest GFS extended range model forecast is suggesting something is changing.  We’ll see.