Sun 08:48 AM Forecast Review — As suspected, the GFS forecast with its earlier clearing and minimal rain, was far superior to the higher resolution models’ forecasts. In fairness, the HIRES models did show the earlier clearing in last night’s runs. Today will be mostly sunny, breezy and cooler than previous forecasts. Some instability cloudiness possible at times. The ICON model should be noted as having picked up the early trend of temperatures in the low to mid 80s.
I’m always looking to find the best way to offer the most transparency to the process of weather forecasting. Recent feedback suggests that my attempts to show all updates/edits may have made the forecasts too confusing.
Going forward, I’m inclined to have any update to the initial post contained in a single update box; previous updates will be deleted. But let’s hear what YOUR preferences are before I make any changes.
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Thank you very much for your feedback. (Over the past few days, you’ve probably noticed that I’ve been experimenting with a newer format that includes all updates, since that’s where it looks like your preferences lean towards). I’ll be taking down the feedback poll on Monday.
The weekend outlook that I posted on Wednesday has changed from the simple jet stream transition from a trough to a ridge with a warm front.
The trough (dip) in the jet flow seems to want to linger longer than had been expected. Its presence spawns a weak low pressure system late Saturday off the coast of Delaware. The location of this low pressure, both in upper atmosphere and at the surface, differs between models, as does the forecast for Sunday.
The weather on Saturday and Sunday will be much warmer and more humid than its been this past week, but current models are keeping us below 90º with mid 60s dew points for the weekend.
The models are in reasonably good agreement for Saturday. Saturday starts mostly sunny, with considerable high cloudiness that thickens during the afternoon. Skies turn mostly cloudy by late afternoon. High 88.2º sd 2.1º (NBM Blue Bell)
Saturday Forecast Updated Sat 7:40 AM — Lower level clouds move in Saturday about 1-3 PM
Showers move into South Jersey and perhaps into Philadelphia after 11 PM Saturday evening.
Sunday Forecast Update Sat 9:45 PM — Tonight’s models continue with the idea of less rain and clearing by noon, especially from Philadelphia and westward. The latest NBM joins the ICON model forecast from Friday in predicting a high of only 83º but with a very high sd of 4.4º (uncertain)
NBM Sunday 00z forecast (clouds- dark shading) (rain- green blue) for noon on Sunday. (Click on image for a larger view.)
Sunday Forecast Updated Sat 6:30 PM — This afternoon’s models have speeded up the clearing and have the low pressure system somewhat further east. There’s still a difference between the high resolution models and the GFS but I’m leaning towards the GFS. So expect less (or no) rain showers during the night and more sun and less cloudiness on Sunday.
Sunday Forecast Updated Sat 7:40 AM — Last night’s models continue with the dichotomy of forecasts. The GFS maintains the upper level low, but still has skies clearing by late morning with minimal showers in PHL and west. The HIRES models vary, but maintain showers and clouds in the morning. The NBM has taken the middle ground, with some scattered showers in the morning, with clearing by afternoon. (Note that all models have significant rain for the southern Jersey shore, clearing late.)
Forecast Updated Fri 10:10 PM — Tonight’s high resolution models continue with clouds and scattered showers on Sunday.
Forecast Updated Fri 8:10 PM — Sunday may be cooler than previously forecast, with northeasterly winds and some clouds. The ICON has a high of only 82°.
Things are more complicated for Sunday. The models differ with regards to the strength of the upper low and the position of the weak surface low.
The high resolution models, including the new HIRESW-FV3 and older NAM-NEST, maintain clouds and showers into Philadelphia and eastward during the morning with slow clearing, while the GFS clears things out by noontime. The GFS has little in the way of any rain making it westward or northward of Philadelphia.
NBM model 1 hour total rainfall at 1 AM Sunday. This is as far north as the showers get. Note that this amount in Philadelphia north and west, will keep your lawn thirsty. (Click on image for a larger view.)
The GFS, despite its relatively low resolution, has done really well lately, so I’m leaning towards its optimistic forecast for Sunday— clouds in the morning give way to a mix of sun and clouds. The model blend (NBM) also has things clearing out. High temp 88º sd 2.1º (NBM Blue Bell)
HIRESW Model 11 AM Sunday
