Note:
This is a very early preliminary map and is HIGHLY subject to change. This also is a very high bust potential forecast and I am going to start off by explaining why..
The models over the past several days have really been showing the potential of two waves..one would be wed night into thur and the other would be thur night into friday. Models have been mainly concentrating on the second wave for thursday night into friday while more or less making the first one of little to no effect…NOW it is possible that this could reverse itself and it could actually be the first one that becomes the more important wave. The 18 Z GFS means is the first to actually suggest this to my knowledge..
Now compare that to 06 Z means at the same time ..
Notice how this low is now more AMPED up? This is something that we are going to have to keep an eye on over the next 24 hrs of model runs.
Due to the uncertainty caused by the 18 Z GFS means we are only going to be issuing a Level 1 Alert at this point and time. There is little to no doubt in our minds that a significant East Coast System is going to occur but the question that really needs to be fine tuned is when? Wed night –thurs-thurs night to friday or wed night –friday?
Lets look at the latest guidance from 12 Z ..
12 Z GGEM has a significant system off the east coast that gets down to 983 mbs by 78 hrs with a heavy QPF axis across E PA and points to the east and northeast.
Different views of the 12 Z UKMET which also shows a significant system along the east coast ..tucked in south of LI at 985 MBS.
12 Z GFS also has a Potent system that gets down even deeper to 978 MBS and tracks just off the coast. Temperatures on the GFS are marginal at the surface and 850s are cold enough N & W of the major cities to support a heavy wet snow fall.
Now these here at the 12 Z GGEM precipitation type maps for 12 Z and 16 Z Friday. As you can see the GGEM is mainly a snow/sleet storm across the interior with rain along the coast from Central NJ south. This is from a warm biased model which has to lead some thinking that temps at the surface could be a tad colder then some of the other guidance at the surface.
12 Z ECM is probably the model that has made the biggest turn around since last night. It brought little less then .25 QPF to ABE for example and today at 12 Z it brings 1.40 QPF to ABE with marginal temperatures of 32-34 and 850s generally cold enough for an all frozen event N & W of the city.
So with the 12 Z guidance what we have is the GFS that would be marginable with snow/sleet N & W and wintery mix rain in the big cities.
UKMET would be rain in the big cities with snow inland N & W…
ECM would be snow and sleet N & W with wintery mix/rain in the big cities.
GGEM would be snow/sleet N + W and wintery mix in the big cities.
Now..another word of caution is the ECM ensemble means. These are reputably the better performing model ensembles that outperform all other models including the OP ECM…if the ECM ensemble means were to be correct..
Then we may have to push some of the heavier amounts to the SE into the big cities. Not enough evidence for this at this point and time.
So we have taken a blend of the models and what they show above and put together a preliminary map ..so that people know ahead of time that this could be impacting the region with heavy snows and rains as well as strong gusty winds…
Again this is very preliminary and refer to the special Note at the top of this post.
Stay tuned for further updates and if necessary updates to the level of Alert.
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