Summary: This is not supposed to be a big storm, but it could be impactful for many, especially NW of 95, since the worst conditions will likely be around sunrise Thursday and will likely include some freezing rain, which is the worst winter precip, as it can produce a thin but dangerous sheet of ice on any untreated surface. The NWS is predicting <1" of snow/sleet (but remember, sleet is ~3X as dense as snow, generally, so 1/2" of snow + 1/2" of sleet is the mass equivalent of 2" of snow) for most of the area, except for NENJ, Sussex, and the Poconos, where 1-2" are forecast. But the threat of up to 0.1" of freezing rain for much of the Philly-NJ-NYC area (including from 95 down to the coast) is the biggest reason that we're likely to see winter weather advisories for this storm soon (by tomorrow night). Most areas will warm up enough for just plain rain by 6-8 am Thursday, except for well NW of 95.
Details: Fortunately, surface temps will rise quickly Thursday morning, hopefully limiting ice accretion from freezing rain, with rain likely falling before dawn south of 276/195 and a few hours later up to 78 with the last locations to complete the changeover to sleet then freezing rain then rain being the far NW locations, like the Poconos, Sussex and the Hudson Valley. It's quite possible freezing rain accretion will be negligible, especially near and SE of 95, but predicting freezing rain is extraordinarily difficult, as one has to accurately predict the changing temps in the column of air above the surface which drive freezing rain, i.e., predicting there will be a warm layer (>32F) about 3000-5000' up that will melt the snow falling from above and that that warm layer will extend down to the last 50-300' or so above the surface, meaning that the falling liquid will only encounter sub 32F temps at or just above the surface, leading to the sub-32F raindrops freezing on contact with any untreated surface. That's why advisories often go up in these situations, but don't verify, as the NWS is conservative with such forecasts, as not warning people about freezing rain potential and having it occur is very bad.
Obviously, we're still ~48 hours from the onset of precip, so there can still be significant changes in the forecast and the outcomes, especially given that the most recent models show a fairly large spread in snow/sleet forecasts prior to the changeover to freezing rain and then rain, with some having maybe a coating to 1/2" for most, others having up to 1 or 1.5" for most and a couple showing 2-3" before any changeover to freezing rain and then rain - which will almost certainly come no matter what as the warm air will be flooding the area early on Thursday - the key questions are how much wintry precip falls before the entire column is over 32F and producing just rain - and how much of that wintry precip is freezing rain. Stay tuned. Below are some links and the NWS discussion from 4 pm today.
Note that we could have a somewhat similar system on Saturday night into Sunday with snow to sleet to freezing rain to rain, although this one might be a bit snowier before the changeover (but not a given yet). And then the real fun begins, if the long range modeling is correct, and we get a few winter storms (potentially significant ones, but way too early to forecast that yet) in the 10+ days after this coming weekend.
https://www.weather.gov/phi
https://www.americanwx.com/bb/topic...ay-linger-through-noon-parts-of-i84-corridor/
Area Forecast Discussion
National Weather Service Mount Holly NJ
725 PM EST Mon Feb 3 2025
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
For Wednesday night into Thursday, attention remains on the low
pressure system that is set to affect the area as low pressure
tracks out of the Midwest across the Mid-Atlantic and up into New
England. Guidance has continued to depict a slower onset of
precipitation, so it does appear likely that precipitation will hold
off until at the earliest late Wednesday afternoon or Wednesday
evening across the region. It is important to note with this
specific system, is there will be an antecedent high located to our
northeast on Wednesday night, so there should be sufficient amount
of cold air especially at low levels that would support a cold air
damming set-up. Point forecast soundings support this quite well as
a pronounced warm nose will surge northward through the overnight
hours into Thursday morning as low pressure approaches. This would
certainly lead to quite a mixed bag of precipitation across the
region including both sleet and freezing rain.
For now, general consensus is that most locations should start off
with a period of light snow as temperatures will be below/around
freezing early Wednesday evening. However, as the warm nose aloft
progresses northward overnight, a change over to sleet and freezing
rain is expected from south to north at the surface. By Thursday
morning, most places should be changing over to rain as surface
temperatures rise above freezing, with the exception the Pocono
Plateau and northern New Jersey which will hold onto wintry precip a
bit longer. By Thursday afternoon, temperatures should rise well
into the 40s/50s as a strong surge of warm air advection occurs, so
plain rain will be anticipated by then. The timing and specifics of
the changeover are less certain though, but greatest confidence with
the prolonged duration of wintry p-types lies over our northern
Pennsylvania and northern New Jersey counties.
In terms of amounts, the current forecast calls for 0.50-0.75" of
liquid QPF. Breaking this down into snow/sleet totals, anticipate
generally a C-1" for much of the region, with localized areas of 1-
2" across the Pocono Plateau and higher terrain of northern New
Jersey. The more concerning aspect to the forecast is with respect
to freezing rain totals...where up to 0.1-0.2" of ice accretion is
expected northwest of the I-95 corridor where surface cold air is
likely to persist longer. For the I-95 corridor itself, including
the northern portions of the Delmarva and the remainder of New
Jersey, anticipate up to 0.1" of ice. Negligible ice accretion is
expected over southern Delaware. Considering this, Winter Weather
headlines will likely be needed within the next 24-48 hours.
Details: Fortunately, surface temps will rise quickly Thursday morning, hopefully limiting ice accretion from freezing rain, with rain likely falling before dawn south of 276/195 and a few hours later up to 78 with the last locations to complete the changeover to sleet then freezing rain then rain being the far NW locations, like the Poconos, Sussex and the Hudson Valley. It's quite possible freezing rain accretion will be negligible, especially near and SE of 95, but predicting freezing rain is extraordinarily difficult, as one has to accurately predict the changing temps in the column of air above the surface which drive freezing rain, i.e., predicting there will be a warm layer (>32F) about 3000-5000' up that will melt the snow falling from above and that that warm layer will extend down to the last 50-300' or so above the surface, meaning that the falling liquid will only encounter sub 32F temps at or just above the surface, leading to the sub-32F raindrops freezing on contact with any untreated surface. That's why advisories often go up in these situations, but don't verify, as the NWS is conservative with such forecasts, as not warning people about freezing rain potential and having it occur is very bad.
Obviously, we're still ~48 hours from the onset of precip, so there can still be significant changes in the forecast and the outcomes, especially given that the most recent models show a fairly large spread in snow/sleet forecasts prior to the changeover to freezing rain and then rain, with some having maybe a coating to 1/2" for most, others having up to 1 or 1.5" for most and a couple showing 2-3" before any changeover to freezing rain and then rain - which will almost certainly come no matter what as the warm air will be flooding the area early on Thursday - the key questions are how much wintry precip falls before the entire column is over 32F and producing just rain - and how much of that wintry precip is freezing rain. Stay tuned. Below are some links and the NWS discussion from 4 pm today.
Note that we could have a somewhat similar system on Saturday night into Sunday with snow to sleet to freezing rain to rain, although this one might be a bit snowier before the changeover (but not a given yet). And then the real fun begins, if the long range modeling is correct, and we get a few winter storms (potentially significant ones, but way too early to forecast that yet) in the 10+ days after this coming weekend.
https://www.weather.gov/phi
https://www.americanwx.com/bb/topic...ay-linger-through-noon-parts-of-i84-corridor/
Area Forecast Discussion
National Weather Service Mount Holly NJ
725 PM EST Mon Feb 3 2025
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
For Wednesday night into Thursday, attention remains on the low
pressure system that is set to affect the area as low pressure
tracks out of the Midwest across the Mid-Atlantic and up into New
England. Guidance has continued to depict a slower onset of
precipitation, so it does appear likely that precipitation will hold
off until at the earliest late Wednesday afternoon or Wednesday
evening across the region. It is important to note with this
specific system, is there will be an antecedent high located to our
northeast on Wednesday night, so there should be sufficient amount
of cold air especially at low levels that would support a cold air
damming set-up. Point forecast soundings support this quite well as
a pronounced warm nose will surge northward through the overnight
hours into Thursday morning as low pressure approaches. This would
certainly lead to quite a mixed bag of precipitation across the
region including both sleet and freezing rain.
For now, general consensus is that most locations should start off
with a period of light snow as temperatures will be below/around
freezing early Wednesday evening. However, as the warm nose aloft
progresses northward overnight, a change over to sleet and freezing
rain is expected from south to north at the surface. By Thursday
morning, most places should be changing over to rain as surface
temperatures rise above freezing, with the exception the Pocono
Plateau and northern New Jersey which will hold onto wintry precip a
bit longer. By Thursday afternoon, temperatures should rise well
into the 40s/50s as a strong surge of warm air advection occurs, so
plain rain will be anticipated by then. The timing and specifics of
the changeover are less certain though, but greatest confidence with
the prolonged duration of wintry p-types lies over our northern
Pennsylvania and northern New Jersey counties.
In terms of amounts, the current forecast calls for 0.50-0.75" of
liquid QPF. Breaking this down into snow/sleet totals, anticipate
generally a C-1" for much of the region, with localized areas of 1-
2" across the Pocono Plateau and higher terrain of northern New
Jersey. The more concerning aspect to the forecast is with respect
to freezing rain totals...where up to 0.1-0.2" of ice accretion is
expected northwest of the I-95 corridor where surface cold air is
likely to persist longer. For the I-95 corridor itself, including
the northern portions of the Delmarva and the remainder of New
Jersey, anticipate up to 0.1" of ice. Negligible ice accretion is
expected over southern Delaware. Considering this, Winter Weather
headlines will likely be needed within the next 24-48 hours.
Last edited:
