641 FXUS61 KBGM 262331 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 731 PM EDT Sun Aug 26 2018 .SYNOPSIS... Warmth and humidity increasing during the next couple of days, isolated showers and thunderstorms will be possible this evening and potentially again Monday afternoon. Especially hot and humid conditions will occur Tuesday and Wednesday, with peak heat indices of at least 95 to 100 degrees. After a cold front late Wednesday with showers and thunderstorms, the weather turns cooler later this week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 400 pm update... Main concerns this evening and tonight remain focused on the potential for a few showers and isolated weak thunderstorms through about 10pm...then the possibility of fog developing later tonight into early Monday morning. Upper trough exiting to the east this afternoon with a weak surface front lingering behind from NY into PA. Much of the region was enshrouded in a broken layer of low-mid clouds this morning, but has since lifted and scattered out enough to warm much of the region into the upper 70s and lower 80s. Air mass has destabilized as well with ML CAPEs above 1000 J/kg. Convection has been able to initiate along a Lake Ontario lake breeze...and should continue to progress to the e/se through the rest of the afternoon and into the evening hours...remaining weak as they track into the nrn Catskills. A lack of deep layer shear and minimal upper level support will keep any convection that does develop on the weak side. After sunset this evening, much of the region will likely stabilize and most of the cloud cover should dissipate. This set up should lead to fog developing tonight into Monday morning. The most favorable areas for fog will be in the valley locations. Temperatures will cool into the lower to mid 60s. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/... 400 pm update... Hot and humid conditions expected Monday and Tuesday. Heat Advisory in effect Monday afternoon and evening...with additional advisories and/or warnings likely on Tuesday. Upper level ridge building over the eastern U.S. on Monday with very warm air moving in will create very hot and humid conditions in the afternoon and evening. Temperatures will climb into the mid to upper 80s with dew points in the lower 70s. Heat index values will rise into the lower to mid 90s for much of the region...especially along the lake plain of the northern Finger Lakes into the Syracuse metro area...also into the Wyoming Valley of ne PA. There will be a weak upper s/w sliding through in the late morning and early afternoon, which may trigger a few late morning showers, but the presence of large scale subsidence should keep convection to a minimum. Precipitation is expected to drop off in the evening with the collapse of the boundary layer. Temperatures will likely not cool that much...only into the lower to mid 70s Monday night. The stage will be set for the hottest day on Tuesday with temperatures starting out in the lower to mid 70s in the morning and quickly warming through the 80s into the lower 90s. Dew points in the lower 70s...potentially inching into the mid 70s...will create heat indices in the mid 90s to 100-105. The hottest conditions will be across the Finger Lakes into the Chemung and Susquehanna basins...and into the Delaware river basin. The presence of warm air aloft and at the surface should allow for enough of a capping inversion on Tuesday to keep any convection at bay. A layer of low-topped cumulus is possible with s/sw winds increasing to around 10 to 15 mph in the afternoon. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... 400 pm update... For Tuesday night, we should start to see southwesterly flow strengthen as ridging starts to slide east/weaken. Even though the odds of seeing at least isolated showers or thunderstorms will likely increase over far northern/western areas late Tuesday night, most of the region should see a continuation of humid and dry weather conditions. Some flattening of the upper ridge over the Eastern Seaboard is expected as we head into mid-week. This should allow a shortwave trough to "top the ridge" and push a cold front into and across the forecast area sometime in the Wednesday-Thursday time frame. Before the front's arrival, we'll likely see another warm day, with temperatures likely again hovering around the 90 degree mark. Timing of the front remains problematic this afternoon, which is to be expected at this stage of the game. Ensembles suggest upper ridging will remain on the stronger side, which implies to me a slower, and possibly weaker frontal passage for our area. The latest deterministic model output seems to be leaning toward this idea, with the cold front into our area Wednesday afternoon and moving through our area before sunrise Thursday. Values of surface-based CAPE will likely average between 1000-2000 J/kg across the region Wednesday afternoon. Other thermodynamic fields, such as mid-level lapse rates, are not as impressive (probably due to stronger ridging aloft). Kinematic fields (such as the surface to 500mb bulk shear) while not impressive, appear sufficient for thunderstorm organization ahead of the front even though much of the dynamical support associated with the upper jet will likely pass well to our north. Long and short - we'll likely see some thunderstorms Wednesday afternoon and night. And while a few stronger storms with gusty winds can't be ruled out, the overall risk of organized severe weather appears minimal. The front should move through the forecast area Thursday morning. Surface high pressure is then expected to quickly move across the region for the end of the week and should bring a respite to the heat/humidity for much of the region. A couple of flies remain in the ointment, though. Medium range models continue to suggest a couple of weak perturbations will likely top the ridge in a broad southwest-west flow aloft. These features could combine with slightly deeper moisture across (mainly) southern areas to yield isolated to scattered showers and thunderstorms. By next weekend, it looks like moisture will likely start to deepen as the southwesterly flow strengthens on the back side of the high. Discrepancies abound in the Day 6-7 time frame amongst the deterministic model output. NAEFS output suggests the presence of a strengthening upper ridge over our region (and amplification of a large scale trough out west) as the center starts to retrograde. So, we'll likely see a return to warmer and more humid conditions with at least some isolated convection as weak disturbances break through the ridge. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... Terminals all start out VFR as diurnal cumulus in NY and some stratocumulus in northern and central Pa mixes out and fades as the day's heating wanes. We expect more stratocumulus and patchy MVFR to IFR ceilings to form again tonight with net radiational cooling of the still fairly moist boundary layer. At KELM and KBGM we expect conditions to go to LIFR at KELM and IFR at BGM between about 08z-09z and 13z-14z. At KRME, KITH, and KAVP we expect MVFR in ceilings again between 08z-09z to 13z- 14z. Confidence is medium to high at KELM for IFR to LIFR conditions, low to medium at KBGM for IFR conditions and medium for MVFR at KRME/KITH and KAVP. With strong insolation we expect the boundary layer to grow enough to lead to few to scattered cumulus clouds in the afternoon VFR all TAF sites. This should occur after 14z. We do expected isolated showers and a thunderstorm or two in the afternoon but too early to mention in TAFs. Outlook... Monday night through Wednesday morning...VFR, though isolated evening thunderstorms will be possible for the NY terminals. Wednesday afternoon through early Thursday...Showers and thunderstorms likely with associated restrictions. Thursday and Friday...Mainly VFR. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...Heat Advisory from noon to 8 PM EDT Monday for NYZ016>018. && $$ SYNOPSIS...BJT NEAR TERM...BJT SHORT TERM...BJT LONG TERM...DAB AVIATION...DJN