Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 231029 AFDALY Area Forecast Discussion National Weather Service Albany NY 629 AM EDT Mon Oct 23 2017 .SYNOPSIS... Another warm day is expected today with above normal temperatures, despite increasing amounts of cloud cover. It will continue to mild and muggy tonight, with showers becoming more numerous towards daybreak Tuesday. An approaching frontal boundary will bring some heavy rain showers and thunderstorms to the region tomorrow into tomorrow night, some of which may produce gusty winds. Although some rain showers may linger into Wednesday, drier conditions are expected later in the week, along with somewhat cooler temperatures. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As of 629 AM EDT...Upper level ridge axis is located just east of the region, extending from just off the Southeast coast up through eastern and northern New England. At the surface, strong high pressure is located off Atlantic Canada, and the low-level south to southeast flow around the high pressure area is allowing for some low stratus across the mid-Hudson Valley and NW CT. These clouds have been trending northward over the past few hours and are also now reaching into the southern Berkshires and into the central Taconics. Further north, skies continue to be mainly clear this morning, with some patchy fog and passing high cirrus clouds. Through the morning hours, the persistent s-se flow will allow low stratus to gradually expand northward. Despite the increasing cloud cover, another mild day is expected today, thanks to rather warm temps aloft (850 hpa temps around 10 C). Highs should reach at least the upper 60s in valley areas, with low to mid 60s for the higher terrain. It should be dry for most areas today, although cannot rule out a few showers or light drizzle across parts of western New England by this afternoon, as the S-SE flow upslopes the higher terrain. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... ...Multi-hazard storm to impact the region Tuesday with heavy rainfall, gusty winds and thunderstorms... As the upper level ridge shifts eastward, a large and deepening trough over the Midwest and Ohio Valley will be heading towards our area. The result will be a deep meridional flow across our area, with a strengthening southerly low-level jet. 850 hpa winds will be reaching 50-70 kts by late tonight into Tuesday morning, and ensemble guidance suggest 850 v-wind anomalies of about 3-4 STD above normal. This deep southerly flow will help advect plenty of moisture into the region, and the 850/925 moisture transport is off the charts, according to the 00z GEFS. Although some showers are possible overnight, the best chance will be late in the night and especially for Tuesday. With the strong southerly flow, upslope areas of the Catskills will be favored late tonight into Tuesday morning for heavy rainfall. Winds will be increasing through the night, especially for the higher terrain, with some gusts over 45 MPH by late in the night. It`s still tough to say if valley areas will see strong winds overnight. Although there certainly will be stronger winds due to funneling up the Hudson Valley, a low-level inversion could help prevent the strongest winds from mixing down for valley areas. There may be a window for gusty winds in valley areas on Tuesday morning, as the mixing depth increases before more widespread showers into the region. With the clouds/increasing wind, temps overnight will be held steady in the upper 50s to mid 60s, which is very mild for late October. During the day Tuesday, the occluded/cold front to the west will slowly be heading towards the area. However, this boundary will be slowing down even further, as the surface boundary and upper level flow become parallel to each other. As a result, periods of showers and possible thunderstorms will be occurring through the day, as moisture streams up the surface boundary. With PWAT values exceeding 1.50 inches, locally heavy rainfall will be possible. Some training of showers/thunderstorms looks to occur, so poor drainage and flash flooding will be a concern (see hydro discussion below). WPC has much of the area in a slight risk for flash flooding. In addition, surface CAPE values look to be around 500 J/kg. Despite the limited instability, the strong wind-field just above the surface will be available for any low-topped convection to mix down gusty winds. SPC has a slight risk for severe t-storms over the entire area. Any discrete storms could also provide the risk of a brief spinup tornado thanks to the low LCL heights and moisture-rich environment, so will have to watch for that too. 3km NAM suggests that broken lines of showers/t-storms will be occurring throughout the day, but the main threat may be just along/ahead of the boundary late in the afternoon and into the early evening hours. Showers and thunderstorms will gradually end on Tuesday night from west to east as the boundary slowly moves across the area. By late Tuesday night, the heaviest precip will be east of the region over central and eastern New England. If a wave of low pressure develops along the boundary, it could try to linger some showers into the day on Wednesday for our eastern zones, although this is still uncertain. Even without this, there still could be a passing shower in spots, as the cyclonic flow around the deep upper level trough will be in place. However, this rainfall won`t be as heavy as Tuesday. Otherwise, clouds will break for some sun during the Wednesday with temps in the mid 50s to mid 60s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... An active period of weather remains in the forecast as we watch the departure of the frontal boundary to our east Wednesday night to be followed by a cold upper low/trough that crosses the region. H500 temperatures are expected to drop close to -25C overnight Wednesday as this chilly upper low transverses the region through Thursday morning. This will be sure to keep the chance for showers in the forecast and per the thermal profiles, some graupal will be possible with any deeper convective elements through Thursday morning and early afternoon. Ridge both at the surface and aloft are expected to influence our weather toward a more tranquil side Thursday night into Friday. In fact, warm advection through Friday as a strengthening low level jet thanks to approaching deepening trough upstream will result in temperatures moderating back into the 60s for valley locations. The weekend looks rather unsettled as a few meteorological players to watch closely. First, the aforementioned nearly full longitudinal trough across the eastern third of NOAM slowly approaches with its associated frontal boundary(ies). Second, moisture transport from the Gulf and deep Atlantic will advect in higher PWATS yet placement of this plume remains in question. Third, what if anything develops in the tropics that could become entrained into the large scale synoptic flow regime and impact the region. Per the National Hurricane Center, the area being monitored in southwestern Caribbean Sea has a 40% chance to develop in the next 5 days. Global models and ensembles suggest the potential for this entity to influence our weather through the second half of the weekend. For now, we will place chance PoPs for rain showers/periods-of-rain. Temperatures through the period will likely average near normal and precipitation near to potentially above normal. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... Enhanced GOES 16 satellite date and surface observations reveal MVFR stratus was advancing northward across the mid-Hudson Valley and up the Taconics. Trends favor this deck to spread northward through the morning hours as flight conditions should remain MVFR. This will likely persist through the remainder of the daylight hours as lowering the CIGS are expected into nightfall. Southerly winds will increase through the day along with winds aloft. In fact, latest guidance is a bit more robust as we will include a LLWS at all TAF sites this afternoon into tonight. Chance for showers/drizzle increase through the afternoon hours from south to north and will become more apparent tonight. Outlook... Tuesday Night: High Operational Impact. Breezy Definite SHRA...TSRA. Wednesday: Low Operational Impact. Slight Chance of SHRA. Wednesday Night: Moderate Operational Impact. Chance of SHRA. Thursday: Moderate Operational Impact. Chance of SHRA. Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. && .FIRE WEATHER... Although much of today will be dry, wet weather is expected for tonight into Tuesday, with periods of showers and thunderstorms expected. RH values will only to fall to 60 percent today and 70 to 80 percent on Tuesday. Southerly winds of 10 to 15 mph today will increase to 15 to 25 mph on Tuesday, with higher gusts possible. && .HYDROLOGY... Although recent dry weather has allowed for low river flows, a period of excessive rainfall may still allow for some hydrologic impacts this week. A deep and persistent southerly flow will allow a very moist air mass to move into the region for Tuesday, with PWAT values reaching 1.50 to 1.80 inches. These values are 2-3 STD above normal for late October. As a slow moving frontal boundary approaches the region, bands of heavy rain showers and thunderstorms will train over the region. In areas that see repeated bursts of heavy rainfall, flooding of poor drainage and low lying areas looks to occur. This will especially be true in urbanized areas and flash flooding is possible as well. A Flash Flood Watch may be needed for parts of the area, as high rainfall rates (over 1" per hour) may cause flooding to occur, despite the initially low flows. Main stem rivers will have large rises and some will come close to bankfull. Overall, basin average QPF will be 1 to 3 inches, although localized point totals that see repeated heavy rainfall may be close to 5 inches. While widespread river flooding is not expected, some flashier river points could see a brief period of minor flooding for Tuesday into Tuesday night. Although there could be some lingering rain showers Wednesday into Thursday, any additional rainfall looks rather light. Dry weather will then return for Friday into Saturday, which should allow flows to recede somewhat. However, additional rainfall will be possible to end the weekend and into early next week. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Frugis NEAR TERM...Frugis SHORT TERM...Frugis LONG TERM...BGM AVIATION...BGM FIRE WEATHER...Frugis HYDROLOGY...Frugis

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