Major update with a snowstorm for New England and strong long-track tornadoes for the south:
Happy St. Patrick's Day!
You can see in the 1st and 2nd images, the life-threatening severe weather outbreak for the south later today and tonight and then shifting to the Carolinas tomorrow afternoon/evening.
For Long Island, the details are in the forecast below, but generally, the rain should change to a period of wet snow Friday morning with up to 1/2" possible, mostly on non-paved surfaces. Please note that it will also be very windy tomorrow night into Friday with gusts as high as 40 mph. Sunny weather then from Saturday through Tuesday!
While NWS Boston has increased their snow amounts slightly for southern New England, the models continue to show the potential for higher snowfall amounts, and they will likely have to raise amounts. Here is the very interesting discussion from NWS Boston for southern New England: "Main concern is potential for accumulating snow and strong winds Thu night into Fri as low pressure tracks SE of New England, probably just outside 40/70 benchmark per consensus of 00z models and ensembles which favors highest precip totals closer to PVD/PYM and south coastal areas. NAM is the outlier with its more "amped up" solution (and shifts heaviest precip farther N) but we are not quite ready to buy into that. However given this is a potent southern stream system that will be capable of producing severe weather in southern Plains today, it certainly is a possibility. We tend to favor the slightly more offshore track due to a more progressive and positively-tilted upper trough, which deepens as a result of phasing of southern stream trough with a northern stream trough coming out of southern Canada, but probably doesn`t become negatively tilted. Right now we`re seeing a lot of conflicting signals against heavy snow but if everything comes together we wouldn`t be surprised to see some 4-5" amounts. Where does that occur? It may not be the higher terrain but could end up being across CT, RI, and SE MA if the low track outside the benchmark holds true. Totals are highly dependent upon timing of changeover from rain to snow late Thu night as colder air surges southward once low passes our latitude and winds shift to N/NE. Lowered temps quickly into mid and upper 20s overnight which is close to higher-res NAM 2m temps. Does the colder air arrive as precip is still ongoing, or does it get delayed just long enough that bulk of precip has already moved offshore? A temperature difference of just a degree or two will also have large outcomes in precip type and accumulations - not to mention there will be some initial melting once changeover occurs. Despite fact this is occurring at night, pavement temps will be relatively mild and snowfall rates probably won`t be high enough to overcome that. Upshot is we are nudging totals up a bit, generally 1-3" across most of SNE, but we can`t rule out having to go a bit higher (3-5") in later forecasts for some areas as these issues start to become better resolved. Most of the accumulation should be on the grass, with some slush possible on roadways, but we don`t see much of an impact for the Friday AM commute right now (aside from having to clear some snow from your vehicle before heading out and perhaps some slow traffic due to wet/slushy roads). Other issue is strong winds due to passage of 950 mb jet of 40-50kt. Forecast soundings show enough mixing in cold advection to support most of that being transported to surface, on order of 40-50 mph, which may eventually require Wind Advisories for at least Cape Cod, the Islands, and coastal Plymouth County. Gale force NE winds look probable on coastal waters from roughly 4 AM to 8 PM Friday and we will issue Gale Watches for MA/RI waters.
LONG ISLAND FORECAST:
Today: Mostly cloudy with highs in the upper 40's. Light winds of 5 to 10 mph mostly from the NE, but shifting to the SSW by late afternoon. Tonight: Cloudy with lows mostly in the upper 30's with light and variable winds. Tomorrow: Cloudy with rain developing by around late morning and then becoming moderate to occasionally heavy at times by late afternoon and early evening with highs around 50 degrees. Wind mostly out of the ENE to NE at 5 to 10 mph, but increasing to 10 to 15 mph by late afternoon. Tomorrow night: Rainy and becoming windy with gusts up to 30 mph from the NE to NNE. Lows in the mid to upper 30's. Total precipitation (mostly rain) through Friday morning should be around 1.5 inches. Friday: Windy with rain likely changing to wet snow between 5 AM and 8 AM before ending around between around 9 AM and 11 AM. A coating to a half-inch of snow is possible, mostly on non-paved surfaces. Temperatures dropping from the upper 30's early in the morning to the low 30's by mid to late morning and then rebounding only slightly into the mid 30's in the afternoon. A few breaks of sun are possible by mid to late afternoon. Wind out of the NNE to N with gusts up to 35 mph. Saturday: Mostly sunny with highs in the mid 40's. Wind mostly out of the N at around 10 mph. Sunday: Sunny with highs in the low 50's, but cooler for the south shore and east end. Monday: Sunny with highs in the mid to upper 50's, but cooler for the south shore and east end. Tuesday: Mostly sunny with highs in the upper 50's, but cooler for the south shore and east end.
- 1st and 2nd images: Severe weather potential for the south from 8 AM today to 8 AM tomorrow in the 1st image, and from 8 AM tomorrow to 8 AM Friday in the 2nd image.
- 3rd to 6th images: Projected snowfall through 2 PM Friday from the GFS-Parallel, NAM, Euro, and RGEM, respectively
- 7th and 8th images: Official snow maps from the National Weather Service
- 9th image: Map from the NAM for 7 AM Friday
- 10th and 11th images: Maps from the Euro for Friday at 2 AM and 8 AM
- 12th image: Projected precipitation through 2 PM Friday from the National Weather Service
- 13th image: Projected temperatures with ranges for Long Island for the next 15 days from the Euro ensembles
- 14th image: Projected temperatures for Long Island for the next 10 days from the National Weather Service model blend