A few days ago there were runs showing a monster snowstorm in this timeframe, but since then the models have backed off of any idea of a phasing system (when northern and southern jet stream systems combine) blowing up into a huge storm. Models now are looking at probably a minor (1-2") to moderate (2-5") event. It's looking now like there will only be a southern stream system that comes up the coast, but it is likely to be fairly far offshore, which normally would only bring light snow to the area (especially at the coast), but there are signals of an inverted trough feature forming and these can focus precip (snow here given quite cold temps in place) well NW of the low. However, they’re notoriously difficult to forecast, as they often have a narrow area of heavy precip surrounded by areas of much lighter precip; see the NWS discussion below for the gory details.
This uncertainty is why the models have been bouncing around a lot, especially almost 4 days before the Friday start to the event. To summarize, for Friday into early Saturday, today's 12Z CMC shows a 2-5" event, the UK shows a 1-3" event (but only south of 78) and the Euro shows roughly a 2-4" event, but the 18Z GFS shows a 3-6" event, after showing a 1-2" event at 12Z (hence the uncertainty). So, the 4 major global models are all showing a light to moderate event (not too different from what we're expecting tomorrow, although the snow is being generated in a completely different setup). But a complete miss (or just some light snow at the coast) is definitely possible and a more significant event is also possible, plus the main energy for this storm is still out in the Pacific, so our initial conditions for it are not robust (just like this current storm; we didn't start getting a handle on it until ~48 hours before the event). So we track. Link to the thread on AmericanWx is below.
https://www.americanwx.com/bb/topic...a-5-swath-in-part-of-the-nyc-subforum/page/2/
Edit changed thread title from, "OT: Another Snow Event on Friday (1/19)? Probably Minor/Moderate, but High Uncertainty" to current title on 1/18 at 8:45 am.
Area Forecast Discussion
National Weather Service Mount Holly NJ
323 PM EST Mon Jan 15 2024
The period Thursday night through Friday night still looks to
be the most challenging portion of the forecast as a series of
impulses continue to rotate around the base of the longwave
trough. In short, a coastal storm system is forecast to develop
to our south and east while tracking offshore into the Western
Atlantic during this timeframe. While this still has the
potential to bring the area another round of wintry precip,
there is a lot of uncertainty in the forecast at this time.
Forecast guidance as of today continues to be persistent with
the track of the main surface low, tracking off the coast to our
south and east. With cold air in place from the antecedent
arctic high, there should be an abundance of cold air in place
for the p-type to be mostly snow. In addition, guidance is also
hinting at an inverted trough (Norlun Trough) set-up on the
backside of the low, which may enhance any precipitation that
falls within the vicinity of this feature as the vortmax passes
by. As there is vast amount of uncertainty with this period,
have decided to remain close to the NBM for this forecast
package. Too early for snow amounts, but NBM probabilities at
this time, show that at least a 40-60% chance of 1 inch of snow
of more can be expected for most of the area, with the exception
of the Delmarva and extreme southern New Jersey where some
mixing may occur.
This uncertainty is why the models have been bouncing around a lot, especially almost 4 days before the Friday start to the event. To summarize, for Friday into early Saturday, today's 12Z CMC shows a 2-5" event, the UK shows a 1-3" event (but only south of 78) and the Euro shows roughly a 2-4" event, but the 18Z GFS shows a 3-6" event, after showing a 1-2" event at 12Z (hence the uncertainty). So, the 4 major global models are all showing a light to moderate event (not too different from what we're expecting tomorrow, although the snow is being generated in a completely different setup). But a complete miss (or just some light snow at the coast) is definitely possible and a more significant event is also possible, plus the main energy for this storm is still out in the Pacific, so our initial conditions for it are not robust (just like this current storm; we didn't start getting a handle on it until ~48 hours before the event). So we track. Link to the thread on AmericanWx is below.
https://www.americanwx.com/bb/topic...a-5-swath-in-part-of-the-nyc-subforum/page/2/
Edit changed thread title from, "OT: Another Snow Event on Friday (1/19)? Probably Minor/Moderate, but High Uncertainty" to current title on 1/18 at 8:45 am.
Area Forecast Discussion
National Weather Service Mount Holly NJ
323 PM EST Mon Jan 15 2024
The period Thursday night through Friday night still looks to
be the most challenging portion of the forecast as a series of
impulses continue to rotate around the base of the longwave
trough. In short, a coastal storm system is forecast to develop
to our south and east while tracking offshore into the Western
Atlantic during this timeframe. While this still has the
potential to bring the area another round of wintry precip,
there is a lot of uncertainty in the forecast at this time.
Forecast guidance as of today continues to be persistent with
the track of the main surface low, tracking off the coast to our
south and east. With cold air in place from the antecedent
arctic high, there should be an abundance of cold air in place
for the p-type to be mostly snow. In addition, guidance is also
hinting at an inverted trough (Norlun Trough) set-up on the
backside of the low, which may enhance any precipitation that
falls within the vicinity of this feature as the vortmax passes
by. As there is vast amount of uncertainty with this period,
have decided to remain close to the NBM for this forecast
package. Too early for snow amounts, but NBM probabilities at
this time, show that at least a 40-60% chance of 1 inch of snow
of more can be expected for most of the area, with the exception
of the Delmarva and extreme southern New Jersey where some
mixing may occur.
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