409 FXUS61 KBOX 040003 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 703 PM EST Mon Feb 3 2020 .SYNOPSIS... High pressure briefly moves across the region tonight. An approaching warm front may bring some light rain Tuesday, especially south of the Mass Pike. A cold front will move south across the region Tuesday night followed by high pressure building to the north on Wednesday. Another system will likely bring a period of snow and ice changing to rain late Wednesday night into Thursday, then more rain heavy at times Thursday night into Friday which may end as a period of snow. High pressure returns Saturday, then watching a possible coastal storm tracking to the south next Sunday. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 7 PM Update... A weak ridge of high pressure has allowed for skies to temporarily become mostly clear early this evening. Clouds return overnight ahead of a shortwave and approaching warm front. Temp forecast tonight is tricky as a period radiational cooling this evening will allow temps to drop before stabilizing overnight. Used a blend of 2m temps and MOS guidance which yields lows upper 20s to lower 30s for much of the region. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Tuesday... Warm front moves into SNE from the SW with model guidance suggesting a weak wave developing on the front. Deep moisture in place with weak low level convergence should bring some light rain to SNE. Convergence is not very strong so expect a light QPF event, generally under 0.10" and focused south of the Pike with timing from late morning to mid afternoon before moving out. Temps will reach mid 40s across CT/RI and SE MA with upper 40s near the south coast, but holding near 40 across northern MA which should remain north of the warm front and weak wave. It is possible temps hold in the upper 30s in portions of northern MA with light N/NE flow. Tuesday night... Surface wave exits early evening with a cold front dropping south across SNE during the night. Flow aloft is west so moisture will not be in a hurry to depart and could see a renewed area of light precip develop assocd with weak low level frontogenesis. Ptype mostly rain, but there could be some light snow north of the Pike after midnight if any precip does develop. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Highlights... * An overall very active period with multiple systems impacting the area bringing a variety of precipitation types. * Round 1 (Wednesday Night into Thursday): Wintry mix changing to rain. Thursday AM commute could be messy. * Round 2 (Thursday night into Friday): Soaking rain with potential downpours and localized flooding. There may even be a rumble of thunder. After a mild & muggy start, falling temperatures through the day. May end as a little snow, especially in interior high elevations. * Round 3 (Sunday): After a dry and cold Saturday, there is potential for light accumulating snowfall on Sunday. Pattern looks progressive so not looking at tremendous amount of snowfall. But confidence is low this far out. Details... Wednesday into Thursday... * Wintry mix changing to rain potentially impacting Thursday AM commute * There may be some lingering leftover showers but much of Wednesday looks dry with weak high pressure over Southern Ontario. The surface high will reinforce colder air in the lower levels, so expect seasonably cold temperatures in the 30s, light northwest winds and a mix of sun and clouds. But by the afternoon, clouds will be on the increase ahead of the first in a series of shortwave troughs coming up the Appalachians. The series of shortwave energy coming our way is in response to a positively tilted upper level trough centered over the Four Corners region. Some of the Bufkit soundings support the initial onset of precipitation as snow during the pre-dawn hours. However, as warmer air moves in aloft, snow will likely change over to freezing rain and/or sleet. The timing could be problematic for the Thursday morning commute. By mid morning, the threat of freezing rain should come to an end for the coastal plains as surface temperatures warm above freezing and winds shift to the east out of the relatively warmer ocean waters. The interior higher elevations could see a more prolonged period of freezing rain due to the difficulty of getting rid of the low-level cold air. Thankfully, this is a relatively progressive system and all areas should dry out by Thursday afternoon. Overall, looking at possibly up to a couple of inches of snow, with higher amounts north of the MA turnpike. Also, a few hundredths of an inch of ice is possible in the coastal plains with up to two tenths of an inch possible in the interior high elevations. Thursday night into Friday night... * Soaking rain possible with locally heavy downpours * The main upper level trough moves east into the Mississippi River valley, resulting in a potential severe weather for parts of the Southeast. By late Thursday and early Friday, the upper level trough will move northeastward up the Eastern Seaboard. As it does so, it will lift a low across New England. While we are increasingly confident that this is a rain event, the track of the low will determine how much rain we can get from an anomalously loaded atmosphere. The GEFS Ensemble shows PWATs 3 to 4 standard deviations above normal, indicating the potential for a heavy rain event Thursday night into Friday. The question is, will the loaded atmosphere translate to observed rainfall. The ECMWF shows a 80 to 90 kt low level jet screaming up the coast. The placement of the low level jet will be key to where the heaviest rain sets up. As of now, it looks like just off shore but with the event still more than 3 days away, will have to keep a close eye due to the potential for over 2 inches of rain. The good news is that the system lifts off quickly into the Canadian maritimes, but the heavy rain rate enhanced by a strong low level jet could lead to localized flooding. Friday morning could be a raw one with wind driven rain. There may even be a rumble of thunder near the coast as EC Ensemble shows a few hundreds joules of CAPE. The other question is how much of the 850mb wind translate to the surface. With cold ocean temperatures (low 40s), there will likely be an inversion near the surface with 850mb temperatures surging to +12 or +13C. But then as colder air moves in by Friday afternoon, lapse rates are expected to steepen and winds will likely pick up at the surface. Gale headlines could be needed Friday night into Saturday, especially for the outer waters. In addition, there could be a period of light snow Friday night into early Saturday as the system exits and cold air returns. This is a strong cold front with 850mb temperatures falling to -14 to -16C by Saturday morning. There is also a small risk of freezing spray early Saturday morning. Saturday into Monday... * Seasonably cold Saturday with potential for light accumulating snow Sunday. Confidence is low this far out * Saturday looks dry and cold with sub-freezing highs possible away from the immediate coast. Models swing another trough through heading into Sunday. If Saturday temperatures pan out as they are currently forecasted, the precipitation will be mostly in the form of snow. Unfortunately for snow lovers, the overall pattern looks to be rather progressive so currently not looking at tremendous amount of snow. Obviously, confidence remains low in the forecast at this point in time and this system will be impacted by how things pan out during the work week. After the system exits late Sunday, Monday looks mostly dry and seasonably cold. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday Night/... Tonight...High confidence. VFR, with cigs 4-8k ft returning after 06z. Light winds. Tuesday...Moderate confidence. A period of MVFR cigs are likely to develop between 15z and 18z focused south of the MA Turnpike. Localized IFR possible late near the south coast. A few light showers are possible, mainly south of the MA Turnpike. Light winds. Tuesday night...Moderate confidence. Becoming VFR in the interior, but MVFR/IFR cigs may linger near the coast, especially Cape/Islands. Spotty light rain is possible, especially south of the Pike after midnight. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Wednesday through Saturday/... Wednesday: VFR. Breezy. Wednesday Night: Mainly VFR, with areas IFR possible. Breezy. SN likely, PL likely, FZRA likely. Thursday: Mainly IFR, with local MVFR possible. Breezy. PL likely, FZRA likely, chance RA. Thursday Night: Mainly MVFR, with areas IFR possible. Breezy. RA. Friday: Mainly MVFR, with local IFR possible. Windy with gusts up to 35 kt. RA. Friday Night: Mainly VFR, with local IFR possible. Windy with gusts up to 35 kt. Slight chance SN. Saturday: VFR. Windy with local gusts up to 30 kt. && .MARINE... Short Term /through Tuesday Night/...High confidence. A brief period of west gusts to 20-25 kt possible this evening, especially eastern waters then winds and seas diminish overnight and become light. Light winds and seas below SCA Tue/Tue night. A period of light rain may briefly reduce vsbys Tue. Outlook /Wednesday through Saturday/... Wednesday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain. Wednesday Night: Winds less than 25 kt. Seas up to 5 ft. Rain likely, chance of snow, chance of sleet, freezing rain likely. Visibility 1 to 3 nm. Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain, sleet likely, freezing rain likely. Areas of visibility 1 to 3 nm. Thursday Night: Winds less than 25 kt. Areas of rough seas. Rain. Friday: Low risk for gale force winds with gusts up to 35 kt. Rough seas up to 16 ft. Rain. Friday Night: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 16 ft. Slight chance of rain. Saturday: Low risk for Small Craft Advisory winds with areas of gusts up to 30 kt. Rough seas up to 11 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 1 AM EST Tuesday for ANZ250. Small Craft Advisory until 3 AM EST Tuesday for ANZ254>256. && $$ SYNOPSIS...KJC/Chai NEAR TERM...Frank/KJC SHORT TERM...KJC LONG TERM...Chai AVIATION...Frank/KJC/Chai MARINE...KJC/Chai