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New Model Blend (NBM version 5.0) to become Operational April 15th!
The Model Blend (NBM) will have a major upgrade on April 15th. Many improvements in forecasting ability expected. Numerous forecast parameters have changed with the update. The full list of improvements and changes can be found here: https://www.weather.gov/media/notification/pdf_2026/scn26-24NBM_V5.0.pdf
Regular visitors here know I lean towards the NBM for snowfall predictions and high/low temperatures. The NBM is an advanced statistical “ensemble” model that forecasts hourly and is derived from the statistical weighting of 40+ other global and regional models, based on track record history and more specifically, how each of its constituent models performed over the immediately prior 6 hours.
One giant improvement will be the incorporation of the ECMWF-AI model and our own AIGFS model data.
The new model is running in trial run and available on AWS. I’ve looking at its forecasts and seeing how it compares with the current version 4.3.
More about this in coming weeks.
Sunday thru Monday Update
Posted Sunday 03/15/26 @ 9:47 AM —The cloud cover today will be variable; periods of sun and sunshine through varying degrees of mid and high level cloudiness. There are more clouds moving in from the south ahead of a warm front that passes through tonight, after midnight.
All models are fairly consistent in forecasting light rain to move in from the southwest about 11 PM, earlier south and west of the city.
As shown in the Friday’s post, a cold front will be affecting our weather with showers and thunderstorms on Monday and Monday evening. What stands out is a forecast for heavy rain, about 1″-1-.5″, from the city westward by Tuesday morning.
As for severe weather, this is a sharp cold front. Current model severity parameters are similar to our most recent cold front (rain –> snow event), but without the snow. As always, the severity parameters the day before are often muted. I’ll be posting my severity table later today.
Originally Posted Fri 7:11 PM —The strong winds that developed Friday afternoon will likely be with us again on Saturday afternoon. The jet stream (and specifically a jet streak) will be directly over us again on Saturday. Sunshine and ground warming will “mix down” some of these high velocity winds from the jet.
On Sunday, an approaching warm front associated with a deep storm in the central US will bring periods of clouds. Rain is expected to wait until evening or night time into Monday before another very strong cold front moves through.
Saturday Forecast
Mostly sunny and windy, especially by mid afternoon. Gusts to 30 mph
NBM high temperatures: Blue Bell, PA 53º Philadelphia, PA 55º
Slightly above average uncertainty (based on standard deviation): ± 2º
Sunday Forecast
Periods of clouds and sunshine through high clouds. Still windy. Gusts to 25 mph. The NBM (model blend) shows light showers moving in during the evening hours ahead of the warm front.
NBM high temperatures: Blue Bell, PA 55º Philadelphia, PA 58º
Above average uncertainty (based on standard deviation): ± 3º
