Marine Weather and Tide Forecast for Williams, MA

KEY MESSAGES
1) Periods of rain expected today into tonight. This will be a beneficial rain, with no concerns for flooding.

2) A cold front will bring medium to high chances for rain showers Tuesday into Tuesday night, with below normal temperatures returning in its wake for the middle to end of the week.

DISCUSSION
KEY MESSAGE 1...As of 2:35 AM EDT...Current sfc analysis shows a 1032 mb sfc high centered just east of Cape Cod, with the remnant circulation of Isaias tracking over Tennessee. Deep southerly flow ahead of this sfc low has allowed widespread cirrus to overspread the region, with increasing coverage and thickening of the high clouds expected as we head through the rest of the night. Given our proximity to the sfc high, winds are calm across the region, so areas north and east of the Capital District we able to radiate into the mid 30s where the clouds were thinner early tonight. However, with thickening clouds moving into the region, temperatures likely hold steady or even rise slightly as we head towards sunrise.

Today into tonight, the remnant, weakened sfc low of Isaias tracks south of Long Island. As it approaches, moisture begins to increase (PWATs getting up to 1.5", highest in southern areas).
The best low to mid-level forcing (warm advection) remains near the southern edge of our CWA near I-84, but guidance still suggests there will be a band of mid-level FGEN further north near I-90, and the right entrance region of an anticyclonically curved upper jet streak to our north will help the precip shield expand across our area today. Based on current radar and CAMs, rain begins in the southeastern Catskills shortly after sunrise, slowly overspreading the rest of the region through the day. It may take until late afternoon/evening until the rain makes its way into the eastern ADKs, upper Hudson Valley, and southern VT. Rain becomes steady shortly after it begins, falling light to occasionally moderate at times. Given lack of any real instability, rainfall rates look to remain under a quarter to half inch per hour. Total rainfall amounts generally look to average a half inch to an inch, but our far northern areas may see a little less, with some localized 1-1.5" amounts possible near I-84 and in the eastern Catskills due to some SE upslope enhancement. Given that the southern half of our area hasn't seen appreciable rain in over 10 days this will be a very beneficial rainfall. Rainfall amounts and rates look too low to cause any flooding concerns. Today will be fairly cool (highs in the 50s to around 60) due to the widespread clouds and rain.

KEY MESSAGE 2...Rain tapers to showers overnight tonight, coming to an end by early tomorrow morning. Tomorrow looks like a tranquil weather day with a narrow ridge of high pressure at the sfc building over the region. Rising heights and a slightly warmer airmass aloft will allow highs to climb into the mid 60s to low 70s, which is a few degrees above normal for this time of year.

Monday night into Tuesday, a sfc low tracking into the Great Lakes region will help lift a warm front across our region. This sfc low will track to the north of our are Tuesday into early Wednesday, dragging a cold front across the region. Guidance has trended further north and slower with this system since yesterday, with the cold front now not expected to arrive until Tuesday night or even early Wednesday. Therefore, PoPs have decreased for areas of I-90 on Tuesday. Temperatures south of I-90 may also need to be increased from the current forecast for Tuesday afternoon if this forecast trend continues, as mid 70s are not off the table there. Further north trend with the track of the sfc low would also put more of our region into the warm sector. With Showalter values <0 Tuesday afternoon/evening, have expanded the slight chance for thunder to cover much of our area. Despite impressive low-level shear profiles, the combination of instability remaining mainly elevated and overnight timing of the frontal passage should prevent any severe weather.

Wednesday, cooler air infiltrates the region behind the cold front. Temperatures are expected to run a few degrees below normal, especially by Thursday and Friday. Wednesday and possibly Thursday look breezy ahead of sfc high pressure that will build overhead for the end of the workweek. By the end of the week or early next weekend, guidance continues to suggest that a fairly strong sfc low will track somewhere near (likely west) of our region. This would bring additional chances for showers, and perhaps a brief warmup depending on the strength of the storm and its exact track. Another, more impressive cold shot appears likely behind this system next Saturday or Sunday.

Through 18Z Monday... Widespread rain associated with Post- Tropical Cyclone Isaias is beginning to move in from the southwest this afternoon, with all terminals except for KGFL expected to start off this TAF period with persistent light rain. However, KGFL will see the rain move in within the first few hours of this period. Cigs will quickly drop to MVFR this afternoon, with vis also staying consistently MVFR to IFR into this evening. Heavier periods of rain throughout this evening will cause conditions to continue to deteriorate, with cigs and vis expected to lower to IFR at all terminals after sunset. The widespread rain will start to move northeast out of the region in the early morning hours of Monday, although some lingering showers can be expected through around 11Z-12Z Monday. Low cigs will persist into Monday morning while vis starts to improve after the rain moves out, with all terminals expected to return to VFR after 12Z.

Winds are expected to remain light throughout this TAF period.
Southeasterly to easterly winds throughout this afternoon and evening will begin to shift more northerly during the overnight period, with some slight weakening throughout that time. KPOU could experience from LLWS this evening, although this will be fairly short-lived. Northerly winds will then begin to shift northwesterly after sunrise Monday, remaining light through the end of the TAF period.

Outlook...

Monday Night: Low Operational Impact. NO SIG WX.
Tuesday: Moderate Operational Impact. Breezy
Likely SHRA
TSRA.
Tuesday Night: Moderate Operational Impact
Likely SHRA
TSRA.
Wednesday: Low Operational Impact. NO SIG WX.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.
Thursday Night: Moderate Operational Impact. Chance of SHRA.
Friday: High Operational Impact. Breezy. Likely SHRA.

ALY WATCHES/WARNINGS/ADVISORIES
CT...None.
NY...None.
MA...None.
VT...None.