Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 162031 AFDALY Area Forecast Discussion National Weather Service Albany NY 431 PM EDT Thu Aug 16 2018 .SYNOPSIS... An active period of weather across the region Friday into early Saturday as a series of frontal boundaries cross the region. In addition, rainfall could be locally heavy due to high moisture content in the atmosphere. The last in the series of the these fronts moves across Saturday as a cold front. This will end the showers and thunderstorms from north to south and leave behind a mainly drier and calmer weather pattern for the second half of the weekend. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... As of 330 PM EDT, Isolated convection has dissipated across the northern Taconics and southern Greens. This was the combination of the slowly moving frontal boundary drifting southward and upslope conditions as low level flow remains from the west. This front has become quasi-stationary near the I90 corridor and will likely remain in place or slowly lift northward overnight. The upper low near the central Missouri River Valley will continue to advect northward deeper moisture from the Ohio Valley. In fact, leading edge of this moisture was across southwest NY and into central PA where a sct-bkn line of convection has already evolved. Per linear extrapolation of this upstream activity, it would arrive across our western zones between 04-06Z. So we will time this out within our grids/forecast. As for best forcing, low level jet magnitudes maximize over portions of the Schoharie Valley, western Mohawk Valley and into the Dacks - Lake George region overnight. This is where those higher probabilities will be placed. Further south and east those PoPs will be lower into the low chance or slight chance. Will be rather warm and muggy tonight for most of the region with mainly mid an upr 60s...some upper 50s across the northern Dacks where dewpoints were in the upper 50s per METAR/NY-Mesonet. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... ...Slight Risk with both severe weather and excessive rainfall outlooks on Friday into Friday night... Complex pattern setting up for the region on Friday as much will depend on insolation and training echoes. As has been mentioned in several excellent discussions the past several shifts, large scale positive tilted trough axis along with the surface wave reflection will be approaching from the central Great Lakes and Ohio Valley. The warm front is expected to lift northward during the morning with elevated convection accompanying its passage. Thereafter, PWATs climb toward or above 2 inches as low level jet magnitudes and PWAT anomalies climb toward 2 standard deviations above normal. While heavy rainfall threat will remain, areas to the west and southwest of Albany will be the most susceptible for flooding concerns due to antecedent wet conditions the past several days. Otherwise, MBE speeds of 10kts or less could result in training echoes across the region. Hence the excessive rainfall outlook will be upgraded to slight risk for most of eastern NY. As for severe potential, SPC has upgraded most of our region into slight risk with the day 2 outlook. The main consideration here will be how much insolation we will receive after the warm front lifts north. Based on satellite imagery upstream, there is considerable cloud coverage at the present time as mid level lapse rates were near moist adiabatic. HREF and CAMS members vary significantly to where the best instability axis will occur and convective modes/trends. While lapse rates are not too ideal, given low LCL`s and increase instability with modest shear profiles, several multi- cells and some bows are possible. An isolated tornado risk may evolve for the Hudson River Valley locations where low level channeling and veering profiles in the lowest 1km could result in a couple supercell structures which again will be highly dependent on sunshine. Temperatures Friday should be able to tap out into the lower 80s for valley locations and well into the 70s elsewhere with dewpoints near 70F as well. The region remains well embedded in the warm and moist sector Friday night with additional convection and heavy rainfall. As overall instability does wane, shear remains in place as well as those high moisture content with PWATs near 2 inches. So additional heavy rainfall threat will continue as we remain warm and muggy once again. The cold front is expected to move from north to south through the day Saturday. There is excellent agreement between the global and hires models that this front should clear our southern zones close to 00Z Sunday. So we will have a graduated PoPs in the forecast with showers lingering along and south of I90 for most of the day. Dewpoints will drop back into the upper 50s across the Dacks and Lake George Region later in the day which will slowly advect southward heading into Saturday night. && .LONG TERM /SUNDAY THROUGH THURSDAY/... The weather will be dry at both the beginning and end of the period, with rain in between. High pressure will dominate the first 48 hours. This will give in to an area of low pressure which will track from lower Michigan to southern Quebec Tuesday and Tuesday night. Rainfall could be significant Tuesday night, but things zip through as the stagnant pattern of mid-summer finally begins to change. The cold front associated with this system is expected to slide east across our forecast area Tuesday night into early Wednesday. This will be replaced by a broadening dome of high pressure...centered over the Ohio Valley early Thursday, resulting in comfortable conditions with lowering humidities, increasing daytime sunshine, and temperatures that are near or slightly below normal with little day-to-day variation. High temperatures prior to the frontal passage will range from the upper 60s to upper 70s each day...and thereafter...from the mid 60s to lower 80s. Overnight lows initially will be in the mid 50s to lower 60s, with a brief pre-frontal boost of a few degrees Tuesday night, then back around the 50 to 60 degree range for Wednesday night. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... VFR conditions through the afternoon hours with an isolated shower or two into the Taconics, Berks and southern Greens. Scattered CU field across the region with higher canopy of CI/CS and some smoke aloft. Clouds will increase tonight with mostly VFR conditions, there could be some haze with a little reduction to the visibility overnight. The threat for showers increases late tonight and through Friday morning. Thunderstorm potential toward the late morning hours increases as well with a VCTS at this time. The winds will increase from the west to northwest at 5-10 kts with some gusts to around 20kts near KPSF. KGFL may have a more north to northeast breeze at 10 kts or less. Outlook... Friday Night: High Operational Impact. Likely SHRA...TSRA. Saturday: Moderate Operational Impact. Chance of SHRA. Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. Sunday Night: No Operational Impact. NO SIG WX. Monday: No Operational Impact. NO SIG WX. Monday Night: No Operational Impact. NO SIG WX. Tuesday: Moderate Operational Impact. Chance of RA. && .FIRE WEATHER... Minimal to no fire weather related concerns as higher moisture content will advect into the region tonight with showers and thunderstorms increasing late tonight and through most of Friday. Rainfall could be locally heavy. This will keep relative humidity values elevated through at least Saturday. Conditions dry out Saturday night and into Sunday. && .HYDROLOGY... ...Slight Risk of Excessive Rainfall across most of eastern New York into Friday... Showers and thunderstorms will be on the increase overnight and into Friday. Combine that with higher moisture content will potentially result in heavy rainfall and training thunderstorms. Portions to the west and southwest of Albany have higher antecedent conditions with wet soils compared to the Adirondacks and portions of the southern Greens. However, convection with heavy rainfall can quickly change those drier areas as we will continue to monitor trends closely. Flash flood guidance across portions of the Mohawk Valley, Schoharie Valley and Catskills are generally between 1.5-2.5 inches within 1-3 hours respectfully. The values are a bit higher to the east of those areas. Per coordination , if confidence levels increase then Flash Flood Watches would be needed. Showers will linger into Saturday, before high pressure builds in with a dry stretch of weather expected for Sunday 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...BGM NEAR TERM...BGM SHORT TERM...BGM LONG TERM...ELH AVIATION...BGM FIRE WEATHER...BGM/JPV HYDROLOGY...BGM/JPV is the U.S. government's official web portal to all federal, state and local government web resources and services.