448 FXUS61 KBOX 130554 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 154 AM EDT Tue Sep 13 2022 .SYNOPSIS... Low pressure south of New England will move offshore this early evening, along with its showers along the south coast of MA/RI. Thereafter, dry weather prevails, however an approaching cold front overnight, will bring the risk of showers after midnight from west to east. Scattered showers and thunderstorms expected Tuesday across southern New England, as the cold front moves through the region. A few strong to severe storms are possible along with heavy rainfall, especially across western Massachusetts. The cold front will be followed by seasonably warm and dry weather Wednesday, then a touch of fall for the end of the week with blustery and cool conditions as high pressure builds in from Canada. The high pressure moves offshore this weekend bringing warmer temperatures into early next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... 1000 PM Update: Forecast still looks to be in good shape with no significant change needed at this time. Humid night across all of southern New England with dewpoints commonly upper 60s. This has led to re-developing areas of stratus and also 1/2 to 4 SM visby fog across the South Coast and southeast MA. Continued expansion is anticipated for most of the overnight. Current radar shows a cluster of heavy showers with some in- cloud lightning across northern portions of New Jersey, associated with elevated instability associated with warm front. This activity should still remain to our south and west after midnight, with the risk increasing into central and northern CT towards the pre-dawn hours. Previous discussion... Overnight... Vigorous closed low moves across OH with associated surface trough/front approaching from the west. Moisture plume and forcing for ascent arrive across SNE from west to east after midnight. Scattered and isolated thunderstorms will overspread the region from west to east, probably resulting in a wet commute for the morning rush. Warm and humid overnight, with lows only in the mid 60s, along with a light S-SE wind. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... * A few strong to severe storms possible western CT/MA * Warm and humid Morning... Scattered showers with isolated thunder in the morning. Heavy downpours possible as PWATs surge up to about 1.8 inches. Then a second round of convection in the afternoon. SPC continues to keep SNE in a marginal risk, as shear and instability profiles are robust for mid Sep, as potent closed low moves northeast through NY state. Definitely some mixed signals here, while shear and instability look favorable for strong/severe convection, there are some indications that morning showers/clouds may be slow to erode in the afternoon. Thus, destabilization may be an issue. This is also evident in low level lapse rates, which are only favorable across western MA/CT into eastern NY, suggested lower convective potential across much of the region, including RI and eastern MA. Meanwhile, best height falls race to the northeast across NY state. Thus, best forcing for ascent is across this region, while best instability is farther south across western MA/CT. Where these two areas overlap is the greatest threat of strong to severe storms Tue afternoon, which appears to be over western CT/MA into VT and over the border in eastern NY. Strong/damaging winds would be the greatest concern. Can't rule out an isolated tornado in the CT River Valley westward given low level helocity. Although, it will be a race, as low level helicity departs eastward, as instability arrives from the west. HREF also displays this theme, with max updraft potential and updraft helocity swaths from western CT/MA northward thru VT and eastern NY state. Warm and very humid for mid Sep Tuesday, with highs 75-80 along with dew pts in the low to mid 70s! Yeah, definitely a summer feel to the airmass. Breaks of sunshine develop in the afternoon from west to east. Although more clouds than sun will be the theme especially across RI and eastern MA. S-SE winds in the morning shift to the S- SW in the afternoon. Tuesday night... Drying trend and becoming much more pleasant with post frontal airmass, with dew pts falling from the 70s into the 50s. West winds. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Highlights... * Seasonably warm and dry Wednesday but breezy at times * A touch of fall Thu/Fri with blustery and cool conditions * Warming trend this weekend into early next week Overview... Mid level trough sets up across New Eng around the midweek period then slides to the east as series of shortwaves rotate through the flow. This will bring a cooling trend for the end of the week, then the pattern de-amplifies next weekend with broad ridging to quasi- zonal flow leading to a moderating trend. Wednesday through Friday... Post-frontal airmass Wed with much drier conditions, but seasonably warm as cooler air lagging behind across northern New Eng. Highs should reach around 80 across much of the region, cooler higher terrain with dewpoints dropping into the 50s. Shallow moisture with cooler air aloft will lead to diurnal cu developing and a mix of sun and clouds. It will be a bit breezy with gusts to 25 mph with decent pressure gradient in place. Cooler airmass overspreads the region Thu/Fri with a touch of fall as high press builds in from Canada. Highs will be mostly in the 60s, with lower 70s near the south coast and it will be breezy at times. Overnight lows will be mostly in the 40s. Saturday through Monday... High pres moves offshore with moderating trend developing and temps getting back to seasonable normals or even a bit above normal by Sun/Mon. However, will have to watch for a possible backdoor front late in the weekend which could spoil the warmer temps. It looks mainly dry but there is a low risk for showers sometime in the Sun- Mon timeframe depending on how close northern stream energy gets to New Eng. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 06Z TAF Update: Rest of the Overnight (thru 12z Tue): High confidence in trends but moderate on the exact details and timing. IFR to LIFR is common across eastern MA and RI, with VFR across the interior. While the exact timing could fluctuate an hr or two, expect deterioration due to advancing fog and stratus through 10z, with widespread IFR- LIFR into the pre- dawn/AM push. Areas of rain, perhaps with embedded thunder expanding north/northeast from southern NY/southern CT to BAF-BDL-HFD and perhaps IJD 09-12z. Light SE winds. Today: Moderate confidence. Continued widespread IFR-LIFR as warm frontal SHRA/embedded TSRA lifts NE between 13-18z, mainly across CT-RI and SE MA (including Cape Cod/ACK and extending possibly as far north as BOS). Brief downpours possible in these SHRA/embedded TS that could result in visby reductions. Winds mostly light SE, around 3-6 kt. For the mid to late afternoon, winds become SE/S as warm front lifts north. A more scattered to broken line of TSRA associated with cold front mainly from HFD-ORH-LWM north and west. These storms could become strong to severe. As the front clears and winds shift to WSW/W around 8-10 kt, expect rapid post-frontal clearing from IFR to VFR for interior sites, though IFR may still linger after 00z for eastern MA, RI and Cape Cod/ACK. Tonight: High confidence. VFR in the interior. IFR across eastern MA, RI and Cape Cod/ACK should improve between 00-03z. Thus anticipating VFR all terminals by 04z. W winds increase to 8-12 kt with occasional gusts 18-20 kt. Wednesday: High confidence. VFR. W winds 10-13 kt with gusts 20-22 kt. KBOS Terminal...Moderate confidence in TAF. Best chance of rain ~14-18z. Low prob of TS 20-00z but should remain to the NW. KBDL Terminal...Moderate confidence in TAF. Two possible rounds of SHRA/embedded TS: between ~10-14z, brief break then a greater TS risk ~18-22z. Outlook /Wednesday Night through Saturday/... Wednesday Night through Friday Night: VFR. Breezy. Saturday: VFR. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Through Tuesday night...High confidence. Weak low pressure near Buzzards Bay Mon evening will exit offshore tonight. Any early evening showers exit with drying trend. Vsby may still be reduced in areas of fog. Tuesday, S-SE winds in the morning becoming S-SW in the afternoon. Scattered showers and isolated thunderstorms. Tue night, cold front sweeps thru the waters, improving vsby with wind shift to the west, along with dry weather. Outlook /Wednesday Night through Saturday/... Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Wednesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Thursday: Low risk for Small Craft Advisory winds with gusts up to 20 kt. Areas of seas approaching 5 ft. Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Friday through Friday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Saturday: Winds less than 25 kt. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...KJC/Nocera NEAR TERM...KJC/Nocera/Loconto SHORT TERM...Nocera LONG TERM...KJC AVIATION...Loconto MARINE...KJC/Nocera/Loconto