Posted Saturday 11/23/24 @ 4:56 PM — The NBM is considered one of the best sources of hourly temperatures and winds and rainfall. The NWS has a link for obtaining this data in text format, albeit for local airports ( but not specific locations like Center City as I provided below.)
I’ve pre-configured the link for Philadelphia and Northeast Airports along with Wings Field in Blue Bell.
This link has been shared on this blog before, with explanations and examples to how it uses the GMT time zone (now called UTC or Coordinated Universal Time).
The hourly NBM labeled NBH is very useful once you get used to the GMT (Universal) time. (7AM here is the column labeled 12)
The extended (NBE, NBX) data is less intuitive, since as an example, next Thursday’s daytime data is shown in the column labeled 00z Friday (which occurs at 7 PM EST Thursday). You can find my NBM Text guide here.
Sunday Forecast Update
Posted Saturday 11/23/24 @ 12:06 PM — Latest NBM wind meteogram for grid point Center City Philadelphia and the marathon. Large uncertainty range (dotted lines) on wind gusts.
11-23-24 12z NBM wind meteogram for Center City (Click on image for a larger view.)
I’ve updated the regional rainfall totals map for the past 48 hours here.
Originally Posted Fri @ 6:52 PM — —The deep upper low and surface low exit our area late Friday night. Skies will clear for Saturday with high pressure building in. A weak warm front will bring a mix of clouds and sun Sunday. Clouds decrease during the mid afternoon. I’ve used the NBM data for Center City Philadelphia to cover the Marathons.
Saturday Forecast
Mostly sunny and a bit chilly and windy. We’ll still be under the influence of a cyclonic flow flow, but the GFS keeps us partly sunny.
11-22-24 18z GFS forecast for Saturday morning. The GFS keep us sunny but a cold windy flow will be noticeable. (Click on image for a larger view.)
Here’s the NBM wind/gust meteogram for Center City Saturday and Sunday—
NBM meteogram for grid point Center City Philadelphia (Click on image for a larger view.)
Sunday Forecast
A warm front will bring some clouds at times during the morning that will break mid afternoon. It will still be somewhat windy.
Here’s the NBM temperature meteogram for grid point Center City—
NBM Temperatures for Center City. (Click on image for a larger view.)
Posted Sunday 11/17/24 @ 10:03 AM — A cold front moves through around daybreak Monday morning. We’ll see some high cirrus clouds associated with this front today and especially this afternoon. Sunshine through high clouds is expected, with occasional mixing of mid level clouds.
The ECMWF shows some light sprinkles moving through between 5 AM and 8 AM Monday, although most of the other models keep us dry. The HREF suggests some radar echoes without the sprinkles reaching the ground.
The atmosphere is setting up for an active week by Wednesday. Here’s the current water vapor/radar image/RAP model —
Sunday morning satellite water vapor image with superimposed RAP model 500-1000 mb thickness lines (yellow), Mean Sea Level Pressure isobars (black contours) potential vorticity (fine violet contours) with superimposed MRMS RADAR. Several low pressure systems (1) and (2) will merge near the Great Lakes by Wednesday and a resulting upper closed low and surface low will be near the Philadelphia area by Wednesday. Additional moisture (3) from a tropical system will stream near us as well. (Click on image for a larger view.)
Additionally, showers from this developing system may move in earlier, as early as Wednesday morning. Stormy and windy by Thursday.
The models are still cranking out about 0.8″ of rain, although the current trend has been towards lower amounts.
Forecast for Rain late Wednesday Continues
Posted Saturday 11/16/24 @ 4:44 PM — Following a beautiful but windy day today, we’ll have another delightful day for Sunday with a layer of high clouds filtering some of the sunshine.
As beautiful as the weather has been, we really need some rain. I’ve been keeping my eye on a seasonally induced pattern change with a dip in the jet inducing low pressure development in a location favorable for rainfall here.
The latest operational, ensemble and AI models continue with a forecast of rain, beginning Wednesdayevening and continuing through part of Thursday. Most models are currently forecasting anywhere from 0.8″ to 1.2″ of rain in the immediate Philadelphia area and areas west and northward. Similar amounts to our east in NJ.
Unsettled, windy and much cooler weather is likely for later Thursday into Friday.
Here’s the latest ECMWF forecast—
11-16-24 12z ECMWF forecast for Thursday morning. Low pressure develops directly over our area. (Click on image for a larger view.)
We’ve been disappointed several times over recent months regarding rainfall, but I think, “this time is different”. (Famous last words.)
The consistency and continuity of various model forecasts for rain this time is encouraging. It’s also possible that some moisture from the tropical system in the Gulf may be brought into play.
Stay tuned for updates.
Originally Posted Fri @ 6:06 PM — —High pressure builds in for this weekend. An approaching cold front will bring sunshine through high clouds Sunday afternoon. As has been the case over recent months, no rain is expected here with this frontal passage on Monday.
A seasonally driven pattern change is forecast by numerous models next Wednesday into Thursday, with the jet flow dipping south to our west and spawning surface low pressure in a favorable position to give us rain! I’ve seen these potential rain-makers fall apart in recent weeks, but this one is currently looking likely—
Latest ECMWF for next Thursday early morning—
11-15-24 12z ECMWF forecast for Thursday at 4 AM (Click on image for a larger view.)
Here’s the latest available GFS – AI model forecast for early Thursday, also supported by the latest GFS—
11-15-24 06z Graphcast-GFS AI model forecast for 4 AM Thursday. (Click on image for a larger view.)
I’ll keep an eye on this over the coming days.
Saturday Forecast
Sunny and windy/gusty, especially in the afternoon.
NBM high temperatures: Blue Bell, PA 60º Philadelphia, PA 62º Uncertainty (based on standard deviation): low uncertainty ± 0.8º
Sunday Forecast
Sunny in the morning, then mostly sunny through high clouds in the afternoon. There may be some mid level clouds at times.
NBM high temperatures: Blue Bell, PA 60º Philadelphia, PA 63º Uncertainty (based on standard deviation): low uncertainty ± 1.2º
