The GFS has been doing some trending westward all day, but any actual excitement wasnt expressed until the 18z NAM came out with a low much closer to the coast. The 500mb forecast has vort max inside the benchmark with low pressure riding outside. It is still east of the GFS but it is nice to have it in the cluster. Im not getting too excited yet. There has been too much flipping around to get confident, especially on an 18z run which has the worst verification of the four. The NARR run by PSU is one of the furthest west at the moment and at least has 70RH over most of southern and central New England.
Still, the main opprotunity for triggering snow is the inverted trough that will ride north of the coastal storm. The concern is the amount of available moisture, but if the coastal low can travel closer to the region, there would be enough of a connection for snow shower activity.
Changes will continue to occur rapidly through the next 48 hours. Right now my prediction is 30% chance snow showers 3am Saturday through noon Saturday, with a 15% chance of accumulation >.1", 10% chance for accumulation >1" and 5% chance >4"
If the models continue to trend west, my first snowfall forecast map of the season will be issued tomorrow afternoon.
|posted by Sam Lillo @ 11/08/2007 07:43:00 PM
