Comparing The Trends In Computer Forecasts
The prospects for a snowy Saturday look a little bit better in Philadelphia this morning compared to last night and look really good to the north of Philadelphia. Trends in the computer forecasts have shifted somewhat to the south.
What would each computer forecast would result for the area?
EURO: The farthest north of the three, it brings a snow to rain event to the Philadelphia area, with more snow to the north before some mixing takes place, and a general rain event across Delaware and extreme South Jersey. The National Weather Service did a comparison of the computer forecast models last night and the EURO through last night at 7 PM was more accurate compared to the other models and was picking up on a slightly sharper trough out west with this system. If you may remember, the concern of a sharper or deeper trough was that it would bend back more sharply once it hit the bottom of the trough axis and turn more to the north. While the track has shifted southward somewhat with the EURO, bringing a little more snow to the region, the trajectory of the low is still the most northward.
NAM/GFS: The NAM is weaker than the GFS but both have a similar track south of Philadelphia. The track is flatter and shows less of a northward movement. This track does bring more snow to the city but even in Philadelphia there could be some changeover issues to sleet and/or rain (especially down by the Airport and across South Philly). Across the northern suburbs above the PA Turnpike a decent snowfall event is expected, with the potential for six inches of snow or more across the Lehigh Valley and Poconos. Across the northern burbs, 2-4 or 3-5" of snow would be expected, with 1-3" of snow across Philadelphia.
Below, a comparison of last night's computer forecast paths of the storm (first map below) with the midday forecasts (second map below), showing the slight shift south in the guidance from midday yesterday to last night.
I will have my forecast call for the area out by 5 PM tonight.
What would each computer forecast would result for the area?
EURO: The farthest north of the three, it brings a snow to rain event to the Philadelphia area, with more snow to the north before some mixing takes place, and a general rain event across Delaware and extreme South Jersey. The National Weather Service did a comparison of the computer forecast models last night and the EURO through last night at 7 PM was more accurate compared to the other models and was picking up on a slightly sharper trough out west with this system. If you may remember, the concern of a sharper or deeper trough was that it would bend back more sharply once it hit the bottom of the trough axis and turn more to the north. While the track has shifted southward somewhat with the EURO, bringing a little more snow to the region, the trajectory of the low is still the most northward.
NAM/GFS: The NAM is weaker than the GFS but both have a similar track south of Philadelphia. The track is flatter and shows less of a northward movement. This track does bring more snow to the city but even in Philadelphia there could be some changeover issues to sleet and/or rain (especially down by the Airport and across South Philly). Across the northern suburbs above the PA Turnpike a decent snowfall event is expected, with the potential for six inches of snow or more across the Lehigh Valley and Poconos. Across the northern burbs, 2-4 or 3-5" of snow would be expected, with 1-3" of snow across Philadelphia.
Below, a comparison of last night's computer forecast paths of the storm (first map below) with the midday forecasts (second map below), showing the slight shift south in the guidance from midday yesterday to last night.
I will have my forecast call for the area out by 5 PM tonight.
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