Update Fri 10/14 @ 9:39 AM — The clouds this morning were predicted by last night’s models (I hadn’t done a forecast for today.)

The clouds should dissipate by noontime.

A “closed” upper low is over Lake Superior. We’ll be getting the mild upper flow around the low for much of the weekend.

Jet stream by Sunday—

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Update Thu 10/13 @ 7:59 PM — The system has slowed down somewhat due to the low pressure development and storms are ‘training’ south to north in the area of the red box below. The NWS issuing a flash flood warning for that area. Rainfall amounts of 1-3+ inches have fallen so far in that area.

Update Thu 10/13 @ 5:26 PM — As forecast, low pressure has developed ahead of the front and will move up over us early this evening. The latest HRRR shows strong dynamics (high vertical shear and high helicity) moving through the western suburbs about 9 PM—

Update Thu 10/13 @ 7:33 AM — Showers move in early morning, then periods of rain increasing in intensity towards evening and early evening. Precipitation totals are now in the 0.4- 0.8 inch range with a few locally higher amounts.

Main front moves through between 7:30 -10 PM with very windy conditions and a fast burst of heavier rain. Severe thunderstorms not likely. (Winds gusting to 30-35 mph with front.)

Update Wed 10/12 @ 5:51 PM — The models have backed off considerably from forecasting wild weather for Thursday. Precipitation totals are now in the 0.5- 0.8 inch range. Winds will be gusting about 30 mph at times. Some thunderstorms are possible but they’re not going to be severe. Best chance for thunder is after 7 PM. Some rain is possible as early as Thursday morning, Heaviest rain late afternoon and especially the evening hours.

Complicating the forecast is the expected development of low pressure along the front which may move much of the heaviest rain off the coast. It’s certainly “confusing” the forecast and making some forecast specifics low confidence—

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Strong Cold Front Passage Thursday

Update Wed 10/12 @ 8:13 AM — It appears that some rain may move in earlier on Thursday than forecast yesterday. Some showers in the morning now expected. Strong winds and rainfall amounts 1-1.75 inches are likely with this system. I’m not so sure about severe thunderstorms. Updates later.

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Update Tue 10/11 @ 10:13 AM — A weak system will bring cloudiness in Wednesday afternoon ahead of a strong cold front that will move in and affect our weather Thursday afternoon through evening. The latest NBM is forecasting about 2 inches of rain by late Thursday night.

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Tranquil until Thursday. Then it gets interesting

A rather strong cold front is forecast to move through Thursday evening.

All the ingredients for some ‘interest weather’ appear to be in play for Thursday afternoon and early evening— elevated CAPE, elevated helicity, elevated vertical shear and a strong jet streak presence. (All the ingredients that we never really saw for much or all of our dry summer.) Stay tuned.

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Previously Posted Sun 8:01 PM —

A fairly tranquil weather period early this week as high pressure gradually moderates in temperature. Fair weather through early Wednesday. Wednesday looks to be the mildest day, but some cloudiness moves in during the afternoon.

Of interest is a rather strong cold front that will move through Thursday with rain and maybe even some thunderstorms—

Updated Thu 10/06 9:29 PM —A cold front moves through late Friday afternoon, preceded by an increase in winds early afternoon. There isn’t much moisture associated with this front and its passage will be marked by only minimal cloudiness and a wind shift. The Canadian high resolution model shows a few light widely scattered showers/sprinkles about 7 PM Friday evening after the front moves through.

A cool but beautiful weekend. Mostly sunny but a few hours of cloudiness moves in about noontime Saturday.

A nice weather weekend

Update Wed 10/05 @ 9:01 PM —The low pressure system that’s been with us for days is departing tonight. High pressure builds in Thursday and Friday. A cold front moves through Friday afternoon with possibly some clouds and an increase in wind speed.

Cold high pressure moves down from Canada for Friday and Saturday, but quickly departs—

There may be some instability cloudiness mid day on Saturday as an upper air disturbance moves through. Otherwise sunny Temperatures may go to the low 40s Friday night and Saturday night with some upper 30s northern and western suburbs. Highs upper 50s to near 60º.

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Update Wed 10/05 @ 7:35 AM — The latest GFS this morning shows light showers and clouds lingering until about 4-5 PM today.

Rain moves out Wednesday evening

Updated Tue 10/04 10:01 PM — Some showers may linger into early evening Wednesday.

Update Tue 10/04 @ 6:01 PM — Current water vapor image captures what’s going on in the atmosphere—

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Rain Continues into Wednesday Afternoon

Update Tue 10/04 @ 11:50 AM — The latest models show the rain continues into at least Wednesday afternoon. Here’s the latest HREF model forecast for Wednesday at 2 PM—

Update Mon 10/03 @ 6:05 PM — This afternoon’s models are in good agreement that an additional 2 – 3 inches of rain will fall before it tapers some time Wednesday afternoon. That’s on top of the amounts shown in the MRMS graphic below.

Here’s additional rain prediction from the Canadian High Resolution —

Updated Mon 10/03 12:43 PM — Latest models continue to show periods of heavy rain through part of Wednesday. Total additional rain accumulation is coming in at 1.5-3” in the immediate PHL area with the upper range favored.

Previously Posted Mon 8:56 AM —

Tropical systems and their remnants often change the weather pattern and such is the case with Ian, where we’ve gone from a near drought situation to over a month’s worth of rain in a few days.

Here’s the past 72 hour rain accumulation, according to the MRMS—

The current weather in the upper atmosphere is best captured by the satellite water vapor image—

An upper low, the remnants of what was Hurricane Ian, is to our west. It’s energy is being transferred to a secondary coastal low that will be slow to move.

Significant moisture in the system will be thrown back towards us over the next two-three days in the form of heavy rain.

Several models show several additional inches of rain possible in some areas on Tuesday, although the trend with some models is for the heaviest rain now to be to our west.

Last night’s models had the rain stopping for the immediate PHL area today. The 06z GFS continues with some rain for today, Monday, becoming heavy after midnight, with a soaking rain on Tuesday.

Many models have the system departing on Wednesday, but it may be slow to do so. Exact timing with such systems is tough. Stay tuned.