Area Forecast Discussion
Issued by NWS Albany, NY

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726 FXUS61 KALY 221042 AFDALY Area Forecast Discussion National Weather Service Albany NY 642 AM EDT Sun Oct 22 2017 .SYNOPSIS... Surface high pressure will translate off the east coast today. Its influence will continue to spread above normal temperatures for the remainder of this weekend. An approaching cold front and increasing moisture will bring about a period of unsettled weather for the upcoming work and school week. && .NEAR TERM /THROUGH TONIGHT/... As of 630 AM EDT...Occasional periods of CI/CS will filter the sunshine around the periphery of departing ridge axis today. Its surface reflection over the northeast corridor will track off the coastline later this afternoon. This sets the stage for a southerly component to the wind field to increase a bit this afternoon. Sustained magnitudes will increase and with daytime heating, mixing layer heights suggest a few gusts could approach 20kts for eastern NY counties. High temperatures today should once again climb into the 70s for valley locations and 60s elsewhere. Those aforementioned southerly winds will eventually tap into Atlantic moisture per moisture transport vectors and some lower stratus may quickly advect northward from the Capital Region and points southward. So some increase in cloud coverage as temperatures overnight should range within several degrees of 50F. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... Monday...The NCEP model suite along with international guidance show an increase of mainly low level clouds with a tightening low- level pressure gradient between the offshore anticyclone and low pressure moving into the central and eastern Great lakes by late in the day. Low-level moisture will increase further, and some lower stratus and possibly some light showers/drizzle will move into locations from the Capital District south during the day (terrain will likely be the first to experience). A weak short-wave impulse embedded in the deep southerly flow will focus the light showers, mainly in the afternoon). Highs will be still mild in the 60s to lower 70s. Monday night...Some timing differences with respect to the upstream cold front approaching as the ECMWF is now the fastest with shower potential quickly increasing. The NAM/GFS/GGEM are in better agreement with a bit slower arrival time. We will follow along this lead which is in excellent agreement with the previous forecast. Low level jet magnitudes increase toward 50KTS as will moisture transport and higher PoPs. Could be quite a bit of drizzle developing overnight as ample mixing within the boundary layer seen in the BUFKIT profiles along with high mixing ratios. As dewpoints climb well into the 50s and even some lower 60s, it will be a rather warm and somewhat muggy night. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Active weather expected to start the extended period... A sharply digging upper level trough will be strengthening over the Ohio Valley on Tuesday, allowing a strong southerly flow across our area at all levels of the troposphere, as upper level ridging shifts downstream of the region. At the surface, strong low pressure will be moving from the Great Lakes towards Ontario and Quebec, with an occluded/cold front heading towards our area for later on Tuesday. A strong low-level jet will be in place ahead of this system, with 850 hpa winds of 50 to 60 kts. Based off the latest 00z GEFS, The meridional wind (v-wind) anomaly looks to exceed 3 STD for Tuesday, along with a PWAT anomaly of around 2-3 STD above normal as well. Ahead of the approaching front, we are expecting showers to become more widespread in coverage through the day, along with gusty southerly winds. Will continue to mention in the HWO about winds possibly reaching advisory criteria. The best chance for this to occur looks to be just along/ahead of the approaching frontal boundary, as models suggest the strong sfc forcing should allow for a narrow cold frontal rainband to develop, with a line of heavy showers. Could be some thunder as well, as surface CAPE values could be up to 300 J/kg according to the latest 00z GFS. Even without thunder, some strong winds aloft may mix down within the heaviest rain showers. The models still show some subtle differences in timing but the frontal passage looks to occur somewhere between Tuesday afternoon and Tuesday evening. It still looks pretty mild ahead of the front, with highs well into the 60s or low 70s and dewpoints in the 60s, which is very high for late October. As the frontal boundary heads towards western New England, it may start to slow down and possibly even stall, as a wave of low pressure starts to develop along the boundary across the mid- Atlantic and rides up the front, as the upper level trough becomes negatively tilted. This could prolong rain for eastern areas for all of Tuesday night and even into Wednesday. As a result, rainfall amounts look to be higher than previously forecasted due to longer duration of rain, as we have leaned closer to WPC and the operational 00z GFS/ECMWF. We have generally forecasted 1 to 2 inches of rain across eastern New York with 2 to 3 inches for western New England. Although these amounts are close to the operational models, they are still higher than most members of the 00z GEFS, so some refinement is still possible, as it will ultimately depend exactly on where the front stalls. Even with these higher amounts, widespread river flooding isn`t expected due to recent dry weather and lower flows, but minor flooding of urban, poor drainage and low lying areas is certainly possible, especially during the periods of heaviest rainfall and in areas where leaves and other debris block drainage. Due to the uncertainty with the exact timing and placement of the front, have gone with generally just CHC pops for Wednesday into Thursday, with the highest chances across eastern areas, due to the nearby boundary and passing surface wave. Even western areas will still see some showers, as the cyclonic flow could still allow for some passing showers, along with plenty of clouds. The core of the upper level trough should be over the area on Thursday, so temps will finally be noticeably cooler and closer to seasonal normals on Thursday, with most areas only reaching into the 50s. Dry weather should finally return for Friday into Saturday, as surface high pressure returns to the area, as upper level heights start to build once again. Temps should be back above normal once again, especially by Saturday, as valley highs reach into the mid 60s. Another system, similar to one coming Tuesday, looks to impact the region at some point Sunday into early next week, with much colder air behind that front for the end of the month. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... An upper level ridge is currently in place over the eastern seaboard. With surface high pressure located nearby the region, winds are calm and there is just some passing thin high cirrus clouds. Some radiational fog has occurred overnight at KGFL, but with sunrise underway, this should be completely dissipated by 12z-13z. During the day today, VFR conditions are expected for all sites with light southerly winds. Just few-sct passing cirrus clouds are expected throughout the day. Winds will decrease for this evening with the loss of daytime heating and winds should become very light or calm once again for tonight. Although it looks mainly VFR for much of the overnight hours with some additional passing high cirrus, cannot rule out some mist/fog for late tonight at KGFL thanks to the good radiational cooling once again. Also, thanks to the persistent southerly flow, some low stratus may advect northward from the coastal areas and impact KPOU/KPSF towards 09z-10z with MVFR conditions. Outlook... Monday Night: Moderate Operational Impact. Breezy Chance of SHRA...DZ. Tuesday: High Operational Impact. Breezy Definite SHRA...TSRA. Tuesday Night: High Operational Impact. Definite SHRA...TSRA. Wednesday: Moderate Operational Impact. Chance of SHRA. Wednesday Night: Moderate Operational Impact. Chance of SHRA. Thursday: Moderate Operational Impact. Chance of SHRA. Thursday Night: Low Operational Impact. Slight Chance of SHRA. Friday: No Operational Impact. NO SIG WX. && .FIRE WEATHER... High pressure will drift eastward this afternoon as it continues to influence our fair and dry weather with above normal temperatures across the region. Clouds begin to increase late tonight into Monday. A slow moving cold front impacts the area late Monday night through Tuesday night with periods of showers and windy conditions. The RH values will lower to 25 to 40 percent this afternoon. An excellent recovery is expected by Monday morning with max RH values in the 90 to 100 percent range. Winds will be light to calm this morning, and then will be south to southwest at 5 to 10 mph today with a few higher gusts this afternoon. Expect southerly winds of 10 mph or less Sunday night. The next widespread soaking rainfall will be Monday night into Tuesday night. && .HYDROLOGY... No precipitation is expected prior to Monday with high pressure in control, as river flows will remain at normal to below normal levels. The next chance of widespread rainfall arrives Monday night into Tuesday night associated with a cold front. Rainfall amounts may range from three quarters of an inch to an inch and three quarters from this system. Some locally heavy rainfall is possible. The heaviest totals may be along or east of the Hudson River Valley across western New England. Some ponding of water on roadways is possible as well as clogged drains from fallen leaves. Another round of wet weather is possible later in the week, but there remains quite a bit of uncertainty with evolution and track of the system and the QPF with it. For now, light amounts of additional rainfall are expected. Overall, a trend to drier weather is expected Friday into Saturday. 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...BGM NEAR TERM...BGM SHORT TERM...BGM/Wasula LONG TERM...Frugis AVIATION...Frugis FIRE WEATHER...BGM/Wasula HYDROLOGY...BGM/Wasula

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