Monthly Archives: June 2021

Summer Storms

THUNDERSTORMS & HEAVY RAIN

Wed 09:42 PM Forecast Review — Not all models were onboard with very heavy rain tonight. I think the GFS overdid the rain forecast for tonight. But most models agree with a forecast for periods of heavy rain starting Thursday afternoon, 1-3 PM.  

Updated Wed 3:32 PM with precip map

A quick post here….As described in my previous post, a front will move through and stall just south of the Philadelphia area.

Some scattered pop-activity possible late this afternoon.

The main frontal activity will move in this evening (Wednesday evening). Latest models have storms affecting immediate PHL area from about 8 PM through midnight, starting in far northwestern suburbs earlier. Severe activity possible far northwestern suburbs; heavy activity here.

GFS Accumulated Rain forecast at 1 AM Thurs morning. Note that the GFS is forecasting additional 1-2 inches of rain in some areas Thursday afternoon into Friday. Please note that weather models cannot exactly predict precise location and amounts of rain, but it gives an idea of the general quantity. (Click on image for a larger view.)

Not all models are on-board with the above GFS forecast of excessive rain.

Main event appears to be Thursday mid-afternoon (2-3 PM) into night with additional heavy rain/storms.

Stay tuned for updates.

Philadelphia Weather Outlook

HEAT, THEN RAIN

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Tue 06:19 PM Update — The models are coming together to forecast a severe weather day Thursday.  It looks like we’ll have very heavy thunderstorms in the afternoon. The GFS is showing rain accumulations in the range of 2 inches.  Stay tuned.

It’s been well-advertised that Tuesday and Wednesday will be very hot and humid days, with high temperatures in the mid to upper 90s and apparent temperatures (heat indices) approaching 100.

Update: NBM has highs on Wednesday 97º ± 2º (Blue Bell) The ICON has a high of 98º. It appears it will be in the low 90s on Thursday.

The latest NBM high temperatures for Wednesday—

NBM High Temps Wednesday (Click on image for a larger view.). (This has been updated above)

Starting Wednesday night, a front will affect our area and a significant pattern change, at least for the short run, will occur.

From Wednesday night through at least Saturday, the models are in surprisingly good agreement that a cold front will slowly move through and stall just south of the Philadelphia area. Rain, possibly heavy, appears to be the current forecast for Thursday through Saturday, as waves of low pressure move up along this front and an upper cyclonic flow and an upper closed low support rainy conditions. We may clear out by Sunday. Hopefully before.

Here’s the current GEFS forecast for Friday 8 PM showing the upper low near Chicago—

GEFS forecast Friday 8 PM, showing an upper closed low in the Great Lakes and an oblong area of low pressure centers along a stalled front. (Click on image for a larger view.)

Some of the models are cranking out a total 1-2 inches of rain by Saturday.

When fronts are forecast to stall, it’s not always a sure thing. So there’s always hope that the forecast will improve. Stay tuned.

I’ve added a weather model glossary to this site.  Hover/click on the underlined model acronym for pop-up information.