Updated Fri 10/06 @ 3:48 PM — The model forecasts for today have been unusually poor with this system. Last night’s models have turned out to be convincingly wrong, especially the high resolution models. Little to no rain has fallen in our area. As I write this. radar is beginning to show some scattered shower activity, forecast to move into the immediate PHL area. We may see some showers over the next few hours around the city and its immediate suburbs.
Current Nexrad radar (Click on image for a larger view.)
I’m just beginning to prepare the Weekend Weather Forecast. I’ll post it later.
Friday & the Weekend Outlook
Updated Thu 10/05 @ 11:02PM — As mentioned in my previous post from Wednesday morning, the cold front expected to pass through late Friday into Saturday morning will not bring much rain or any extreme weather to our immediate area.
Scattered showers are expected to develop on Friday morning afternoon, as early as 6-7 AM 1-2 PM in some spots, and then become a bit more widespread in the afternoon and evening.
Today’s 18zGFS forecast for 10 AM Saturday morning. Cold air moving in behind the front (1) while the moisture of what tropical system (2) moves up into Maine and joins a secondary low that develops far north of our region. We may see some sun Saturday afternoon, along with a few instability sprinkles. (Click on image for a larger view.)
The actual front moves through early Saturday morning with some showers and an increase in winds. The amount of rainfall is forecast to be quite light in many areas and ranges from 0.10″ to 0.35″. We may see some sun Saturday afternoon, but a few instability sprinkles possible too.
Temperatures will still be in the upper 60s, so the big impact will be the windy conditions, which will make it feel cooler.
Sunday will be windy and cooler. There will likely be periods of cloudiness and maybe a few scattered sprinkles as a result of instability with the cold air aloft.
Wednesday and Weekend Outlook
Updated Wed 10/04 @ 8:38 AM — Today is looking to be our warmest day this week, with highs near 83º (± 1.5º). High temps forecast are fairly uniform across our area—
Today’s 06zNBM shows highs in the low 80s with a standard deviation of about 1.2º Black contours are 1º increments (Click on image for a larger view.)
The weekend’s weather is looking less ‘interesting’ but still a dramatic change in temperatures and feel.
Here are the changes, summed in the latest ECMWF model forecast map for Saturday afternoon—
Todays’ 00z ECMWF forecast for 5 PM Saturday shows previous tropical storm (1) moving to our east, but with its outflow moisture being brought up into New England. The influx of cold air (2), as depicted by the red 540 thickness line appears to be less robust than previously forecast. The low pressure system that was expected to develop to our south is now expected to develop to our north (3). As a result, much less rain is forecast in our area than previously forecast.
As described in the caption above, the previous forecasts have changed. There are differences among the models in the timing of the actual frontal passage on Saturday, and differences among models with the timing of showers.
There are signs that some light showers may break out as early as Friday morning, but the main front moves through sometime Saturday.
Continued Mild through Wednesday.
Updated Mon 10/02 @ 6:11 PM — No major news here, since one can’t watch a weather report without hearing about the great weather.
Here’s the latest NBM model forecast high temperatures—
Today’s 18z NBM temperature -dew point meteogram for Blue Bell, PA (Philadelphia tends to run about 1-2º higher) Highs in the low to mid 80s! (Click on image for a larger view.)
Temperatures still mild on Thursday, just below 80º
For the weekend, things continue to look ‘interesting’ as a sharp dip in the jet stream will induce low pressure somewhere. The NAEFS shows a coastal low, but the GFS and ECMWF differ significantly. Additionally, some moisture from a tropical system far off the coast may add some moisture to this developing system.
Here’s the NAEFS forecast for 5 AM Saturday morning—
12z NAEFS shows upper low over Great Lakes (blue) with potential surface secondary low over Delaware (black) There’s no clear consensus about the forecast, other than expect some rain and windy conditions late Friday into Saturday. (Click on image for a larger view.)
Previously Posted Sun 8:03 PM —
This week’s weather can be summed up with a single current water vapor image—
Water Vapor image Sunday evening (with RAP model jet level wind streamlines and 500-1000mb “thickness” contours (yellow) contours. Note the yellow 570 thickness level contour is the outline edge of unseasonably warm air, moving up in our direction. This upper and mid level “ridge” will be over us Monday through Wednesday bringing dry, sunny weather with temperatures above average, in the low 80s. The low pressure system over Nevada (blue L) will gradually move towards the east. The cold front associated with this low will bring rain Friday into Saturday, followed by below average temperatures. (Click on image for a larger view.)
Monday through Wednesday will feature sunny skies and above seasonal average temperatures in the 79º-83º This warm up has been well-advertised on the tv/radio weather.
The latest NBM model shows the forecast high temperatures for Blue Bell PA —
NBM model forecast temperatures for location Blue Bell, PA Dotted lines indicate standard deviation (Click on image for a larger view.)
By next weekend, the ridge that was over us will be replaced with a significant trough, with colder temperatures.
The NAEFS is forecasting rain with possible development of a coastal secondary low pressure system for Saturday—
NAEFS forecast for Saturday shows the 500-1000 mb thickness line (here in red) and the trough in the eastern US (blue contours) by Saturday evening. (Click on image for a larger view.)
This sharp change in temperatures is a possible set up for some ‘interesting’ weather later this week. Stay tuned.
Friday Mastodon Update: Wxcloud.social, the Mastodon server I post to, is back online after having crashed last weekend. Unfortunately, all of my previously posted graphics are still missing. I am disappointed with this situation. I’d like to stay with wxcloud.social, but I have made no final decision in that regard.
I am now simultaneously posting to a separate, much larger Mastodon server, @theweatherguy@mastodon.social. My followers on wxcloud.social are encouraged to also follow me on mastodon.social, should problems reappear on wxcloud.social or I migrate to mastodon.social fully.
As I learned over recent days, if a small Mastodon server is shutdown or fails, all lines of communication with cultivated followers can be permanently lost.
Friday and Weekend Preview
Updated Fri 09/29 @ 9:36 AM — For the immediate Philadelphia area, cloudy with light scattered showers today. The models continue with most of the rain east of the Pennsylvania – New Jersey border. It doesn’t look promising for the Phillies game tonight in NY, but who knows, maybe they’ll play in the rain.
NBM hourly rain forecast for tonight at 7PM—
This morning’s 12z NBM hourly rain forecast at 7 PM Friday night. (Click on image for a larger view.)
As for Saturday, it looks like some showers still possible in the morning with low clouds hanging in for much of the day. Maybe some breaks in the clouds towards evening.
Sunday still looks quite nice!
My regular Weekend Weather Forecast will be posted later today.
Friday Forecast Update
Updated Thu 09/28 @ 9:59 PM — Tonight’s latest NBM (00z) continues with a steep gradient in forecast rainfall for tonight into late Friday night.
There has been consistency with the forecasts, but some models (the HREF) has the 1″ rainfall totals a bit further westward, while the Canadian models are showing somewhat less rainfall overall. I’m going to hang my hat on the NBM—
Tonight’s NBM total rainfall by 8 AM Saturday. The 1″ line is somewhat further westward in to Philadelphia in the HREF forecast. Extremely heavy rainfall for NYC and CT. (Click on image for a larger view.)
Friday Outlook and Weekend Preview
Updated Thu 09/28 @ 5:17 PM — As mentioned this morning, the axis of heavy rain is trending further eastward and that trend continues with today’s 18z NBM—
This afternoon’s 18z NBM continues to forecast the heaviest rain to our east and that trend continues. The NBM now has the immediate Philadelphia area receiving less than 0.6 inches with the heaviest rainfall east into NJ. Rainfall totals are through Saturday (1 AM). Some areas are forecast to receive very heavy rain in NJ, NY and CT. (Click on image for a larger view.)
Saturday’s weather includes showers in the early morning, ending before noontime. We’ll see sunshine in the afternoon.
Sunday looks to be quite nice with highs in the 70s.
Next week looks to be nice and much warmer with temperatures approaching 80º
Thursday-Friday Forecast Fine Tune
Updated Thu 09/28 @ 9:46 AM — My earlier posted forecast violated the cardinal rule of weather forecasting:
“Always walk outside or put your hand out the window before making a forecast”
A light mist has developed in the immediate Philadelphia area, not really showing on radar, indistinguishable from background noise.
The latest NBM (12z), just available, shows the possibility of light mist/drizzle as early as NOW.
This morning’s 12z NBM model forecast simulated radar for 10 AM today. (Click on image for a larger view.)
So Thursday looks damper and somewhat wetter than previously forecast.
Updated Thu 09/28 @ 9:04 AM — It appears that Thursday will be just cloudy. While the latest NBM still has some light scattered sprinkles as early as 5-8 PM, any rain in the immediate Philadelphia area will probably wait for 11 PM to midnight.
While Friday is definitely going to be cloudy with low clouds and drizzle, there are varying forecasts for the amount of rain west of the Delaware river. The NBM has a fair amount of rain making it into Philadelphia, but the HRDPS has minimal amounts. All models have most of the rain in NJ, especially northern NJ and the trend has been increasingly eastward for the main rain axis.
Last night’s 07z NBM total accumulated rain forecast for late Tonight through Friday evening. These amounts are likely over-done(?). (Click on image for a larger view.)
Thursday – Friday Weather Outlook
Updated Wed 09/27 @ 9:20 PM — An area of low pressure is developing in the same region as Ophelia had formed. The upper air flow is different this time around and this low is expected to brush our area with rain late Thursday into Friday as it moves out to sea. Additional support to this low will be provided by an upper low pressure system over the Great Lakes.
Here’s the current water vapor image at 9 PM tonight—
Water Vapor satellite image with RAP model jet stream wind contours tonight. Low pressure off the coast will bring moisture up into our region late Thursday into Friday. (Click on image for a larger view.)
For Thursday, sunny very early, then increasing low cloudiness. Cloudy by the afternoon. Light scattered rain develops between 5 PM and 9 PM, moving in from the southeast.
Friday will be a dark, cloudy day with light drizzle and light showers.
The weekend looks better, especially Sunday.
Wednesday and the Remainder of the Week Outlook
Updated Tue 09/26 @ 4:54 PM — Today was yet another day of dark skies and drizzle and occasional rain. The radar image taken earlier this today captures the flow—
Nexrad radar image late morning shows the light drizzle moving in on the easterly flow . Where the moisture encounters elevated terrain, the increased orographic lift results in more stationary areas of showers. A very interesting appearance. (Click on image for a larger view.)
Wednesday is looking dry, but still with considerable cloudiness. There should be some breaks of sun, especially northern suburbs.
Another coastal system will affect us late Thursday into Friday. A developing inverted coastal trough will bring rain on Friday, especially areas in NJ—
Today’s NAEFS forecast for Friday at 2 PM shows a coastal low/inverted trough moving close enough to bring showers to our area Friday. The track of this system will be move it eastward away from us by Saturday and Sunday as high pressure builds in from the west.
Tuesday Update
Update Mon 9/25 10:39 PM — Tonight’s models are suggesting that Tuesday’s weather will be more similar to Monday’s than previously thought. The NAM-NEST and HIRESW show low clouds, drizzle and showers, only tapering late afternoon. Additional rain accumulations expected, about 0.25 to 0.33”
Tuesday Outlook
Updated Mon 09/25 @ 5:31 PM —Monday was ‘dark with low clouds, drizzle and some scattered showers’ as forecast. Unfortunately, Tuesday’s weather is looking only slightly less dark. Plenty of low clouds and additional widely scattered showers and drizzle expected, but the areal coverage of the showers and drizzle lessens during the afternoon.
Here’s the latest NBM forecast showing clouds and drizzle/showers at 11 AM—
This afternoon’s 18z NBM forecast for clouds (black) and precipitation (green, light green) at 11 AM Tuesday. (Click on image for a larger view.)
There may be some brighter skies at times, but things really don’t improve until Wednesday.
Monday Update
Updated Mon 09/25 @ 10:46 AM — We got a lot of rain this weekend. More dreary conditions expected today, but with much less additional rainfall.
How much rain did we get so far?
MRMS rain gauge-radar extrapolated estimate of rainfall over the previous 72 hours. (Click on image for a larger view.)
How much additional rainfall is forecast for today?
Here’s the latest NBM forecast rainfall for Monday —
This morning’s 12z NBM model total accumulated rainfall for Monday and Monday night. (Click on image for a larger view.)
Monday
What was once a strong low pressure system in all levels of the atmosphere, the remnants of Ophelia will be a weak, closed mid-level (500 mb) low on Monday—
Today’s 18z GFS forecast for 8 AM Friday shows a mid level low over northwestern NJ. This low will gradually dissipate, but considerable low level moisture and a mid level cyclonic flow will cause low clouds, drizzle and some showers on Monday.
This low will gradually dissipate, but considerable low level moisture and a mid level cyclonic flow will result in dark, low clouds, drizzle and some scattered showers on Monday. No sunshine is expected.
Tuesday through Friday
We may begin to see some sunshine on Tuesday, but still with a chance of widely scattered sprinkles.
As for the rest of the week, we’ll be influenced by an upper level closed low that will keep us cooler than seasonal averages—
Today’s 18z GEFS jet stream forecast for Wednesday shows a closed low that will affect our weather through Friday. Cooler temperatures, but I’m not certain how sunny it will be. The models have surface high pressure giving us fair weather. I guess we’ll see.
