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The potential for snow to impact areas in the vicinity of I-90 during the Monday morning commute has increased...but impacts to roadways are still uncertain.
1 Key Message 1
Periods of rain tonight that will change to a brief period of wet snow in many locales between 4-8 am with a coating to 2" possible before ending by late morning. Snow accumulations favored on grassy surfaces...but can not rule out roads briefly becoming snow covered in heavier bands. Any snow accumulations that occur will melt quickly.
2 Key Message 2
Scattered snow showers and a few snow squalls develop later Mon into Mon night especially across eastern MA. Some neighborhoods may pickup a coating to 1" of snow with localized 2" amounts possible.
3 Key Message 3
Dry and seasonable Tuesday becoming unsettled again after mid-week with a few rounds of showers. No significant precipitation expected.
KEY MESSAGE 1... Periods of rain tonight that will change to a brief period of wet snow in many locales between 4-8 am with a coating to 2" possible before ending by late morning. Snow accumulations favored on grassy surfaces...but can not rule out roads briefly becoming snow covered in heavier bands. Any snow accumulations that occur will melt quickly.
A cold front will drop south across the region this evening as a wave of low pressure approaches from the west. This is a classic ana- frontal setup...where a narrow but strong band of mid-level frontogenesis sets up north of the surface boundary. Periods of rain should continue through tonight...especially south of I-90 where we expect the heaviest rain to occur on the order of 0.75 to 1.50 inches.
The biggest uncertainty is the potential for the rain to change to a brief period of wet snow from north to south between 4 and 8 am. There may also be a bit of sleet mixed in during the transition. The primary area of concern is 20 miles north or south of I-90...where soundings become isothermal for a time while moisture remains long enough for a brief band of potentially accumulating wet snow. While this will be short-lived...the NAM soundings are showing a brief period of 30-40+ units of omega in the snow growth region in the KORH-KBOS areas between 08z to 14z. Meanwhile...the GFS/RGEM has already pushed the best forcing and moisture well south of the region. The ECMWF seems to be similar to the NAM.
The tricky thing with these ana-frontal waves are is if you can realize the narrow band of very strong mid level frontogenesis before the moisture dries out. If the HRRR/NAM/EC are correct there certainly is the potential for a quick 1-2" of snow with even a low risk of 3" in the vicinity of I-90 right around the morning rush hour. While the bulk of the snow accumulations would occur on grassy surfaces...if we are able to generate that very strong lift in the snow growth region roads would briefly become snow covered too. However...if the stronger forcing has already slid south such as the GFS/RGEM just some light rain/snow showers would occur with no accumulations. This will be more of a nowcast situation...but something we will need to watch for the morning commute. Regardless...any steady precipitation should wind down by late Mon morning. It will remain cloudy/raw with a few rain/snow showers still possible. Any snow that did fall should begin to melt with temps above freezing rising into the middle 30s to the lower 40s.
KEY MESSAGE 2... Scattered snow showers and a few snow squalls develop later Mon into Mon night especially across eastern MA. Some neighborhoods may pickup a coating to 1" of snow with localized 2" amounts possible.
The second part of this event will be later Monday afternoon and night. This in response to a strong northern stream shortwave/cold pool aloft dropping into southern New England. This will combined with plenty of left over low level moisture along with some MUCape and negative 0-2 lapse rates. This should allow scattered snow showers and a few snow squalls to develop later Mon into Mon evening. While the activity will be possible anywhere...the guidance seems to highlight eastern MA as the greatest/most widespread area especially Mon evening. This is likely the result of a subtle inverted trough and land/sea interface. Therefore...scattered snow showers and a few heavy snow squalls may result in some neighborhoods seeing briefly poor visibilities and snow covered roadways. While this will not impact every neighborhood...the potential increases Mon evening given sunset and colder temps working into the region. So some neighborhoods may see a coating to 1" of snow with even localized 2" amounts not out of the question. Again...not everyone will see this activity but some brief snow squalls may impact the Mon evening commute especially across eastern MA.
KEY MESSAGE 3... Dry and seasonable Tuesday becoming unsettled again after mid- week with a few rounds of showers. No significant precipitation expected.
A very different day on Tuesday as high pressure brings the return of sun and much warmer temperatures, in the mid to upper 40s. This will be 5 to 10 degrees warmer than Monday so after a cold and raw day on Monday with snow, it will feel like a switch to early Spring.
Beyond Tuesday the synoptic pattern becomes quasi-zonal with overall low impact weather expected as a result. A series of shortwave disturbances moves through the steering flow which will bring a few rounds of unsettled weather. The first and weaker of the two arrives Wednesday night into Thursday with a weak surface low moving from the Great Lakes into the maritimes. Moisture is lacking (PWATs 0.4- 0.7") as is strong forcing so only expecting widely scattered light showers. The more robust shortwave and deeper surface low moves overhead or to our north around Thursday night into Friday and this comes with better moisture (PWATs >1") and forcing (surface cold front and stronger LLJ). For this reason we expect more widespread rain with higher rainfall totals and breezy wind gusts. Even so, not expecting it to be a significant storm. High pressure then moves in for at least the first half of the weekend keeping a dry forecast.
A cold front will drop south across the region this evening as a wave of low pressure approaches from the west. This is a classic ana- frontal setup...where a narrow but strong band of mid-level frontogenesis sets up north of the surface boundary. Periods of rain should continue through tonight...especially south of I-90 where we expect the heaviest rain to occur on the order of 0.75 to 1.50 inches.
The biggest uncertainty is the potential for the rain to change to a brief period of wet snow from north to south between 4 and 8 am. There may also be a bit of sleet mixed in during the transition. The primary area of concern is 20 miles north or south of I-90...where soundings become isothermal for a time while moisture remains long enough for a brief band of potentially accumulating wet snow. While this will be short-lived...the NAM soundings are showing a brief period of 30-40+ units of omega in the snow growth region in the KORH-KBOS areas between 08z to 14z. Meanwhile...the GFS/RGEM has already pushed the best forcing and moisture well south of the region. The ECMWF seems to be similar to the NAM.
The tricky thing with these ana-frontal waves are is if you can realize the narrow band of very strong mid level frontogenesis before the moisture dries out. If the HRRR/NAM/EC are correct there certainly is the potential for a quick 1-2" of snow with even a low risk of 3" in the vicinity of I-90 right around the morning rush hour. While the bulk of the snow accumulations would occur on grassy surfaces...if we are able to generate that very strong lift in the snow growth region roads would briefly become snow covered too. However...if the stronger forcing has already slid south such as the GFS/RGEM just some light rain/snow showers would occur with no accumulations. This will be more of a nowcast situation...but something we will need to watch for the morning commute. Regardless...any steady precipitation should wind down by late Mon morning. It will remain cloudy/raw with a few rain/snow showers still possible. Any snow that did fall should begin to melt with temps above freezing rising into the middle 30s to the lower 40s.
KEY MESSAGE 2... Scattered snow showers and a few snow squalls develop later Mon into Mon night especially across eastern MA. Some neighborhoods may pickup a coating to 1" of snow with localized 2" amounts possible.
The second part of this event will be later Monday afternoon and night. This in response to a strong northern stream shortwave/cold pool aloft dropping into southern New England. This will combined with plenty of left over low level moisture along with some MUCape and negative 0-2 lapse rates. This should allow scattered snow showers and a few snow squalls to develop later Mon into Mon evening. While the activity will be possible anywhere...the guidance seems to highlight eastern MA as the greatest/most widespread area especially Mon evening. This is likely the result of a subtle inverted trough and land/sea interface. Therefore...scattered snow showers and a few heavy snow squalls may result in some neighborhoods seeing briefly poor visibilities and snow covered roadways. While this will not impact every neighborhood...the potential increases Mon evening given sunset and colder temps working into the region. So some neighborhoods may see a coating to 1" of snow with even localized 2" amounts not out of the question. Again...not everyone will see this activity but some brief snow squalls may impact the Mon evening commute especially across eastern MA.
KEY MESSAGE 3... Dry and seasonable Tuesday becoming unsettled again after mid- week with a few rounds of showers. No significant precipitation expected.
A very different day on Tuesday as high pressure brings the return of sun and much warmer temperatures, in the mid to upper 40s. This will be 5 to 10 degrees warmer than Monday so after a cold and raw day on Monday with snow, it will feel like a switch to early Spring.
Beyond Tuesday the synoptic pattern becomes quasi-zonal with overall low impact weather expected as a result. A series of shortwave disturbances moves through the steering flow which will bring a few rounds of unsettled weather. The first and weaker of the two arrives Wednesday night into Thursday with a weak surface low moving from the Great Lakes into the maritimes. Moisture is lacking (PWATs 0.4- 0.7") as is strong forcing so only expecting widely scattered light showers. The more robust shortwave and deeper surface low moves overhead or to our north around Thursday night into Friday and this comes with better moisture (PWATs >1") and forcing (surface cold front and stronger LLJ). For this reason we expect more widespread rain with higher rainfall totals and breezy wind gusts. Even so, not expecting it to be a significant storm. High pressure then moves in for at least the first half of the weekend keeping a dry forecast.
CT: None
MA: None
RI: None
MARINE: Small Craft Advisory from 8 PM this evening to 8 PM EDT Monday for ANZ230>237. Small Craft Advisory from 8 PM this evening to 2 PM EDT Tuesday for ANZ250-251-254>256.
MA: None
RI: None
MARINE: Small Craft Advisory from 8 PM this evening to 8 PM EDT Monday for ANZ230>237. Small Craft Advisory from 8 PM this evening to 2 PM EDT Tuesday for ANZ250-251-254>256.
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