Thursday Forecast Update

Posted Thursday 07/25/24 @ 8:52 AM — No significant change in the forecast. The vast majority of today’s models continue to show showers in areas southeast of the city, in Delaware, Maryland and southern South Jersey. The exceptions, not to be ignored, are the Canadian RGEM and HRDPS, which show some showers as far north as Philadelphia. The timing is between 3 PM and 6 PM.

Here’s the HRDPS precipitation forecast through 6 PM. An outlier of a forecast, but the HRDPS has a history of sometimes being correct with when the NOAA models show no precip—

Forecast Update

Posted Wednesday 07/24/24 @ 4:32 PM — A few upper air disturbances triggered showers today, but the heavier rainfall was spotty and was not enough to break the rainfall deficit we’re in.

A few additional showers are developing late this afternoon and evening ahead of a surface front moving through tonight.

Winds will shift to the west and then northwest during the day Thursday reducing the chance of showers to isolated, as drier air moves in. The upper level trough still has to move through, so periods of lingering clouds mixed with some sun are expected. Heavier showers possible in Delaware.

Friday looks to be sunny and seasonably warm with much lower humidity.

Wednesday Forecast

Posted Tuesday 07/23/24 @ 5:54 PM — As I had forecast this morning, our area didn’t have any showers or thunderstorms; we had considerable sunshine.

As for showers, there’s a wide range of model forecasts, but overwhelmingly the trend is for any heavy rain to be south and east of Philadelphia. The latest HREF captures this—

Earlier models had forecast some heavier showers in the immediate Philadelphia area before daybreak Wednesday into the morning hours. The latest Canadian models have backed off of that, but I think it’s still a possibility, based on the HREF.

More definite is the chance of scattered showers and thunderstorms, late morning, early afternoon and especially Wednesday evening.

As I’ve been saying for several days, this pattern is diffuse and the triggers are mostly upper air disturbances that are difficult to predict and time. Check back Wednesday morning for an update.

Tuesday Update

Posted Tuesday 07/23/24 @ 9:00 AM — Some areas had showers Monday night but most of our area received little rain.

For today, Tuesday, the clouds we have may break for some sun or sunshine through clouds. Despite the forecast I heard on the radio this morning, I don’t see much in the way of showers or thunderstorms during the daytime hours today, based on the models.

That said, there are disturbances in the upper air flow that could theoretically result in showers, so no guarantees of a dry day.

There’s much more chance of showers and storms tonight, especially south and east of the city.

Tuesday Outlook

Posted Monday 07/22/24 @ 7:30 PM — The first round of rain on Monday mostly missed the Philadelphia area and immediate surrounding counties. Here’s the MRMS Precipitation Estimate for the past 12 hours—

While some showers are moving in this evening, most of the rain this evening will remain to our west… and to our east. The latest HRDPS captures this—

The daytime on Tuesday looks to be just cloudy with perhaps some sun through high and mid-level clouds. There’s a chance of showers mostly north of our area.

I’m going to be taking the forecast day by day. This weather pattern is a bit too diffuse to try to forecast more than 36 hours in advance. It does look like more rain is likely on Wednesday, timing to be determined.

Monday Update

Posted Monday 07/22/24 @ 9:04 AM — Based on last night’s models, the main bolus of rain will come in this evening and its trajectory is to keep the heaviest rain south and east of the immediate Philadelphia area.

That’s probably correct in part, but the latest radar shows showers and some embedded storms several hours ahead of the model forecast—

Getting the timing right with this system is going to be a challenge. But I would expect some spotty showers by early this afternoon and sooner in South Jersey. It doesn’t look like this first bolus of rain today will impact our overall dry conditions.

Originally Posted Sun 9:16 PM —An upper level trough combined with a stationary front to our south will result in unsettled conditions for much of this upcoming week.

A moisture riding over the stalled front will bring showers and possible thundershowers late Monday morning and continue for the balance of the day. Showers will be spotty in our area, while areas west (central PA) will have heavier rainfall.

Weak low pressure will form on Tuesday.

Additional waves of low pressure and moisture moving over the stalled front will bring additional periods of shower, rain and thunderstorms Tuesday through Thursday. Exact timing of these waves of moisture and the axis of heaviest rain to be determined.

Right now, the heaviest activity seems to be timed for the evening and nighttime hours, but that could easily change.