Monthly Archives: October 2018

Philadelphia Weather Outlook

WEEKEND FORECAST UPDATE – THURS

[su_box title=”Forecast Update Fri 8 AM” box_color=”#defcdc” title_color=”#000000″]The forecast is on track for the rain to taper and end mid to late morning on Saturday. Low level clouds remain with a chance of a light, brief sprinkle or two in the afternoon with winds shifting from easterly to west-southwesterly in the mid afternoon.

Additional Update Fri 11 AM: This morning’s NAM has the heavy rain ending by 8 AM Saturday, but continues with very low clouds and light intermittent showers for the remainder of the daytime Saturday.  The NAM and National Blend of Models crank out 0.03 inches water in the late morning and 0.07 inches of water in the afternoon. Comparing the two maps in this post, you can see that the trend has been for the system to move more slowly again.

NAM forecast
NAM forecast for Saturday afternoon

Sunday still looks to be dry. [/su_box]

Things continue to change with the forecast for this weekend.  The latest GFS model shows the coastal low pressure system moving reasonably quickly, a marked change from what the models were showing just a few days ago.  

FV3 GFS
FV3 GFS Forecast for Saturday afternoon

It appears that the rain will begin early Friday evening with the heaviest rain Friday night, ending sometime Saturday late morning.

Low clouds are expected to linger through Saturday and considerable cloudiness is expected on Sunday before the second system arrives for Monday.   Sunday will be unsettled but dry.

As good as the models are, it’s remarkable how much a forecast can change in a matter of days. Something to remember when advance forecasts for large snowstorms end up being a bust.

I’ll update the forecast Friday evening.

PHL Climate Forecasts, Winter Storm Outlook

EARLY WINTER CLIMATE OUTLOOK

I received an email from a follower of this blog asking for my thoughts regarding the upcoming winter.   Here’s what I replied:

Thanks for the confidence you expressed in my forecasts. Winter weather seasonal forecasts are more about climate than weather.  Even the National Center for Climate Prediction doesn’t do too well with these very long range forecasts.

That said, I usually take a stab at the Winter Weather Seasonal Forecast towards the end of November.  By that time, any pattern that may become established will have revealed itself.

But if you want an early sense of things, the nadir in the sunspot cycle suggests plenty of cold air.  The current dips in the jet stream suggest a stormy winter.   And an expected appearance of El Niño in the Pacific suggests plenty of moisture.

So expect a cold winter with plenty of storms and plenty of snow.   That’s my best bet right now.  But things could change if the jet stream dips change over to the western side of the US.