Area Forecast Discussion
Issued by NWS Binghamton, NY

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640 FXUS61 KBGM 211440 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 1040 AM EDT Tue Aug 21 2018 .SYNOPSIS... As a storm system, moves across southern Canada, it will drag a frontal complex through the region, today and tonight. These fronts will bring showers to the area, and possibly a thunderstorm. Scattered showers could linger into Wednesday, with an upper level disturbance in the vicinity. Drier weather, with pleasant air, is expected later this week. && .NEAR TERM /THROUGH TONIGHT/... 1035 AM UPDATE...Light showers just now pushing into the south and west parts of the area. Models continue to show the precipitation weakening as it spreads east today, with little chance of thunder. Previous weather grids are in excellent shape for timing and coverage, so only minor adjustments to the grids at this update. Previous discussion below. 430 am update... Lower clouds are streaming northward into CNY/NEPA this morning, owing to a moist southeasterly flow. This maritime type flow pattern will only strengthen today, ahead of a surface warm front approaching from western NY/PA. Thus, skies will remain overcast, which will limit heating, and cap afternoon highs in the low-mid 70s. An upper low, evident on satellite imagery early this morning over the upper Midwest, is expected to open up today and head northeastward, reaching Ontario and Quebec by this afternoon/early evening. The associated surface low will follow a similar path, dragging the aforementioned warm front through the forecast area this evening, followed quickly by the cold front/occlusion overnight into early Wednesday. An area of showers across the OH Valley, Lake Erie, and western PA early this morning, is shown by most of our near-term guidance to track across CNY during the midday and early afternoon hours. Reduced heating (mentioned earlier) should all but eliminate any thunder potential for much of the day. Things get a little more interesting this evening, as a narrow warm sector edges briefly into CNY/NEPA. Most high resolution model members show the potential for a linear convective feature to cross the forecast area, ahead of the approaching cold front/occlusion. ML CAPE values could reach 500-750 j/kg this evening, particularly across our western counties (from the Finger Lakes region down towards Bradford county PA), along with fairly decent low-level shear (0-1 km SRH values in the 100-200 range for a time). This environment could be supportive of a few strong wind producing and/or rotating storms. We`ll continue to monitor this potential today. Additionally, a stream of fairly deep moisture will get drawn northward for a brief time tonight, with precipitable water values in the 1.75-2" range, leading to the possibility of heavy downpours. Given our sensitivity from recent heavy rainfall, the potential for isolated poor drainage area flooding, or even flash flooding, will also have to be monitored. The good news here is that this system looks very progressive, which should act to limit the overall hydro threat. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... 5 am update... Model agreement is good that the surface cold front will be east of our forecast area by around daybreak Wednesday, shunting the deeper moisture towards the coastal plain. However, a digging short-wave in the northern stream will keep an upper trough axis present over the eastern Great Lakes region. Resultant instability and lingering moisture will probably cause a few showers to form on Wednesday, along with perhaps a rumble of thunder. A gradual improving trend should commence Wednesday night, as the atmosphere stabilizes diurnally, and the upper trough mentioned above slowly moves east. Any scattered early evening showers should diminish to a few sprinkles, at worst, overnight. && .LONG TERM /THURSDAY THROUGH MONDAY/... 345 AM Update... Thursday through Friday night: After lingering clouds and perhaps a sprinkle early Thursday morning skies should become mostly sunny by afternoon. High pressure from Canada will build into the region by Thursday afternoon resulting in a period of much needed dry and refreshing weather across the region. Northwest winds could be a bit breezy midday Thursday (8-15 mph), but will gradually decrease as the high builds later in the day. High temperatures should be in the 70`s with lows in the 50`s. With favorable conditions for radiational cooling with the high overhead Friday morning a few spots may actually fall into the upper 40`s for morning lows. Some patchy valley fog is possible Friday morning as well. High pressure slowly starts to move out Saturday, with one last mainly dry day expected. A frontal boundary will approach from the west late in the afternoon, which could touch off an isolated shower/t`storm. Cloud will slowly increase through the day as well. Morning lows are expected to fall into the upper 50s/low 60s and highs generally reach in the mid to upper 70s and low 80s. Saturday night: A weak trough and associated warm front slowly push through the area from the west. This will bring a chance of showers and a slight chance of t`storms to much of the forecast area. It will not be as cool, with lows in the mid-50s to around 60. The shortwave trough remains near the region into the day on Sunday. Instability is forecast to really begin ramping up as a much warmer, more humid air mass moves into our area. An expansive upper level ridge builds over the Mississippi/Ohio valley region which will allow a southwesterly flow to develop. Continued with chance PoPs for afternoon showers/t`storms under the unstable air mass...especially across Central NY. High temperatures rise into the lower and mid-80s, with dewpoints reaching the upper 60s. The upper level ridge continues to strengthen over the Ohio Valley early next week. This will keep Central New York and Northeast PA in a fast moving westerly flow pattern along the northern periphery of the ridge. This type of pattern usually yields chances for fast moving, gusty wind producing thunderstorms; as oppose to the slow moving, widespread heavy rain producers we have had recently. Kept the chance PoPs north across central NY, further away from the center of the anticyclone...fading to slight chance over NE PA. The late summer heat continues to build, with highs reaching 85-90 in the valleys, with lower 80s in the higher elevations. This is a solid 10 degrees above average.Overnight lows will be in the mid to upper 60s. With dewpoints pushing 70, daytime heat indexes could be well into the 90s in the urban valleys. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... 12z update... At least periodic lower ceilings are expected today at KELM, KITH, KBGM, and KAVP, within a moist S-SE flow. Restrictions should be generally within the MVFR-fuel alternate range. KSYR and KRME should stay mainly VFR today, outside of possible brief restrictions in showers this afternoon. Two distinct periods of showers are anticipated. The first should come through roughly 16-22z, with the second, perhaps steadier/heavier batch during the evening, after 00-02z. Some thunder is also possible this evening, but uncertain coverage precludes mention in the terminal forecasts at this early juncture. Tonight, lower ceilings should evolve area-wide with time, owing to more persistent showers/deeper moisture, out ahead of an approaching cold front. Although periodic IFR cannot be ruled out, we`ve again indicated MVFR-alternate required. E-SE surface winds should pick up later this morning, averaging 8-12 kt into this evening. Occasional gusts near 20 kt are also possible this afternoon, especially at KITH. S-SE winds mostly 5-8 kt are expected tonight, with locally stronger gusts possible near any thunderstorms. Outlook... Wednesday morning...Restrictions probable in lingering lower ceilings/showers. Wednesday afternoon through Saturday...Mainly VFR. Early morning fog possible, especially KELM. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...DGM/MLJ NEAR TERM...DGM/MLJ SHORT TERM...MLJ LONG TERM...HLC/MJM/MWG AVIATION...MLJ/RRM is the U.S. government's official web portal to all federal, state and local government web resources and services.