Update on Winter Storm...

Synopsis: Only changes made were across Upstate NY and New England. Based on 12Z NAM/GFS showing a slightly more northward track, have expanded higher amounts a bit north across northern NY/New England and also nudged 9-12 range to 9-13.

With higher QPF reaching further inland, upgraded earlier highlighted region over the Adirondacks from 5-9/locally higher to 9-13"/locally higher. Along with expanding totals north have also introduced a large highlighted area (Yellow Region) where locally higher amounts are possible.

Just a quick mention on the 5-9 range. Amounts in this range will increase from south to north, with mostly 5 or 6" amounts expected along/south of I-80 in Pennsylvania over to southern New England. Areas that reach the higher end of the range are expected to be north into New York/northern New England. Also, regarding the 2-5 range, areas within but close to 5-9 can expect to be on the high end of the range closer to 5".

...LTE

Major Winter Storm Moving In thru Thursday...

Synopsis: In general, the pink dashed line portrayed in the zoomed in map indicates the dividing line between a mainly snow to the north and snow to wintry mix to the south. I do think that some sleet could mix in north of the line, but the I used to line to point out that I expect to possibly see some freezing rain in the mix south of that line.

Accums are pretty straight forward. One area of concern is the Adirondacks of northern NY where 5-9" with locally higher amounts are possible. Elsewhere, expect most areas to end up as shown with highest amounts across northern New England.

Regardless of any mix, the damage snow-wise is going to be done before a mix occurs. What I will primarily be keeping an eye on is southeast PA down towards DC. All in all, we think that there is potential for advisory level snowfall over a large area as a result of the expected front end delivery.

...MAG/LTE

Update on Clipper Event...

Update: First things first, had to adjust the timing for both onset and end as system has moved in a bit ahead of schedule and consequentially should exit region a bit earlier. Decided to play up the downsloping a bit more across central/eastern PA. This has resulted in the 2-5" range being contracted back to the Laurel Highlands on up into Wyoming Valley. In turn, have also lifted 2-5" a bit further north across the immediate Tri-state region.

Have decided to keep area of warning snows as is in terms of placement, but did add a few inches to make it 5-10. This was upgraded from 5-8".

Lastly, have kept most of the area that was highlighted (yellow regions) from this morning as is with the idea that these areas should generally stay in the 3-5" range with locally higher amounts possible. Still don't think widespread amounts of >5" will be common enough to greatly expand on our original placement of 5"+. Did decide to drop the highlighted portion of locally higher amounts across the Adirondack region as amounts here look to remain at or below 5" in all spots.

Similar to last event, this may end up being a low end verification in certain regions, especially across Pennsylvania/New Jersey/New York.

...LTE

Potent Clipper to impact region for Weekend...

Synopsis: For this event, we are using a blend of the GFS/GEFS/NAM/SREF. One concern is that the GFS/NAM may be overdoing QPF with this event, so we’ve tweaked amounts which are bit lighter than what models would suggest. Latest check over the H8 temp profiles/coinciding Omega values across interior NY/New England look good, but not overly impressive with this event, therefore we expect snow ratios in the vicinity of 10:1 to 15:1 for most interior locations. This yields a widespread light to moderate snowfall across a similar area that was affected by the most recent clipper. We expect down sloping to play another significant role similar to the last event, with higher amounts across western PA with lighter snows east of the mountains.

We have issued a higher swath of 5-8" across a good chunk of Maine southwestward into New Hampshire. This was based on anticipated enhancement/intensification as the Low taps available moisture off the Atlantic. It should be known that this amount may be slightly increased with next update, but for now will keep it a low-end warning event here.

Lastly, we have a rather large area of highlighted real estate which are aimed toward the mountainous terrain of NY, VT, MA, NH, ME. These are areas we have flagged for a potential upgrade for higher amounts than are currently indicated. However, confidence is not high enough to expand at this time, thus we decided highlighting for locally higher amounts of >5" in these areas was best course of action for now. We will explore this potential again this afternoon following 12Z guidance and adjust accordingly.

...MAG/LTE

Cold Clipper for Wed/Thursday

Here are the coordinated MLWX maps:

Some things to know: There are areas highlighted on both maps that indicate the possibility of higher snowfall amounts but not set in stone enough to warrant a shading for the said amounts. Are a little bit more confident on the Laurels totals so I went ahead and threw possible higher amounts for that region. On the Northeast map, Logan highlighted the Laurels as well as southern New England for possible areas for higher amounts than our current highest range we have (2-5). We will issue an update with new accum categories if confidence increases.

Other concerns:
-Downsloping, I used the SREFs some in factoring in the downsloping effect east of the mountains especially in southeast PA. I'm pretty confident on 2-5 placement there and took a pretty middle of the road placement.. but it could go either way in this region with folks receiving more or receiving the shaft in a lot of southeastern PA locations.

-Other areas within the 2-5 range receiving higher amounts: I am primarily watching western and central PA for amounts higher than advertised, especially after seeing Matt's high-res WRF maps posted earlier. Overall its possible anyone in the 2-5 range could see more, snow ratios are going to play a big part in if that happens. A lot of folks are going to have the dgz (dendritic growth zone) in the ideal -12 to -18ºC range coupled with decent Omega values (lift) within the dgz. That should result in efficient snowfall ratios on the order of 15-20:1. The Laurels could see even better ratios than that with the upslope effect and associated extra lift.

-Further north extent: Logan points out the GFS printed out higher qpf totals all the way up towards Lake Ontario, so will keep an eye on possible extension northward.





...GLUNT/EGAN

Significant Winter Storm for the Weekend...

Significant Winter Storm Likely Tuesday-Thursday

Synopsis:

Once again, north of the dashed line is where we expect precip to remain frozen and/or freezing during the entire storm duration.

We kept our scenario map pretty general, anyone in the wintry mix should generally expect to see pretty much every wintry precip type at one point or another. The big question with regards to ice is going to be how much cold air aloft holds and how much of a secondary low forms. If the cold holds more aloft, expect more sleet than zr. The reason winter storm watches are issued attm (esp in Mount Holly, and State College regions) is to highlight areas under the threat for severe icing, so folks in the watches right now stand the best chance for seeing alot of freezing rain.

Most of our T-3 inch range on the snowfall map across PA/NJ is going to be accounting for the possible front end snow/sleet associated with this system. Further north across Upstate NY/New England, thermal profiles are more favorable for a prolonged period of snow...mixed with sleet...to be the dominant form(s) of precipitation lasting for most if not all the event, especially across areas to the north of I-90. During the day on Wednesday, warmer air aloft will move into western/central/southern New York leading to a changeover to mainly sleet/FzRa which will bring an end to the accumulationg snowfall across areas south of I-90. Total snow amounts here should remain under warning criteria with a general 2-5" expected. The exception to this region will be the central/eastern Catskills where snow...mixed with sleet will persist for longer period of time before a changeover/mix to Sleet/FzRa occurs. Here, low end warning amounts of 5-8" are expected.

For areas north of I-90/east of I-81, this storm will bring mainly snow...possibly mixed with some sleet (especially across Mohawk Valley/Hudson River Valleys). A general 6-10" is expected across the Adirondacks/Greens/Berkshires/Whites/Monadnocks, with slightly lower amounts of 5-8" for the Mohawk Valley/Hudson River Valley.

As the coastal Low takes over, and moves northeast into the Gulf of Maine on Thursday, moderate-heavy snow will be on-going into most of Maine, with the possible exception across the immediate coastal counties where enough warm air will result in mixing and even a possible changeover to plainrain not out of the question. Therefore, lower amounts have been forecasted for the coastline. Further inland, mainly snow... possible mixing with sleet at times will produce snowfall totals of 6-10" overall, with some of isolated higher amounts possible.

Final adjustments likely after the 0z runs.

...MAG/LTE

Complex Winter Storm to Impact the Region Midweek

For most, this will start off as a Wintry Mix or Snow. Without getting overly specific given the timeframe, we have kept it fairly general for now. We expect best accumulating snows to be along/north of I-90 from Syracuse-Schenectady thru northern New England where Snow...mixed with sleet in some areas will persist. The snow/sleet should persist thru the entire event, with a chance of some FzRa entering the picture across CNY on Wednesday.

We have drawn an estimated changeover line (Yellow line) representing where we believe precipitation will remain frozen for the entire event. Outside this region, we expect temperatures to climb above freezing before the end of the event with a changeover to rain south-to-north at some point, with areas along the coast/valleys experiencing a changeover quickest.

...LTE