398 FXUS61 KBGM 211755 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 155 PM EDT Sat Jul 21 2018 .SYNOPSIS... Low pressure moving up the East Coast will interact with a deep plume of moisture and result in widespread showers tonight and Sunday morning. Scattered showers and storms are possible late Sunday. A large storm system will keep unsettled weather across the area well into next week. && .NEAR TERM /THROUGH SUNDAY/... 1030 am update... Only minor changes to the existing forecast. As of late morning, the leading edge of the steadier showers continues to move slowly northward through eastern PA. We still expect isolated-scattered showers to develop/move into NEPA by early afternoon, growing in coverage after 3-5 pm. From there, showers will quickly blossom into the southern tier of NY by early evening, then develop further north as the evening wears on. As for sky cover, breaks of sunshine over CNY will continue into early afternoon, with thickening clouds from south-north thereafter. For the most part, clouds will have the upper hand for the balance of the day over NEPA. Residual sunshine and downsloping S-SE flow across our northern zones will yield highs generally in the low-mid 80s. For the southern tier and NEPA, highs will range in the 70s, with a quicker onset of thicker clouds. If anything, the latest near-term high resolution guidance has trended a bit westward with the potential for heavier showers later today and this evening, as they shift the main low-level frontogenesis forcing to the northern/western quadrants of the hybrid surface low over time. This brings the main focus from parts of NEPA into the central southern tier/Finger Lakes regions of CNY, mostly during the evening hours. Luckily, dry antecedent conditions heading into this event, the progressive nature of the system, and also lack of deeper convection/likely less impressive rates should all factor into preventing significant hydro issues, although isolated poor drainage type problems can't be completely ruled out. Certainly, early indications are we can handle the 0.75-1.5" and locally near 2" of rainfall this system should bring us. Previous discussion... 430 am update... Main concerns in the near term remain focused on a developing low pressure system currently off the Carolina coast expected to move northward across eastern PA and central NY this evening and tonight, with widespread rain expected and periods of embedded heavy showers. Deep upper low over the srn Great Lakes will move slowly to the se into the Ohio Valley today with an embedded short wave lifting nwd along the East Coast...associated with a surface low strengthening near the Delmarva peninsula. This feature along the coast will provide strong kinematics in the low levels, and combine with a moist air mass, PWATs around 1.5-2 inches, to produce widespread light to moderate rain and embedded enhanced heavier showers...where rainfall rates may reach or exceed 0.5 inch per hour at times. Strong winds just above in the surface will wrap around this quasi-tropical system with e/se winds 1 km above the surface around 40 to 50 mph. The higher elevations of the Catskills and Poconos may be able to realize some of these stronger winds, but for the most part, most lower elevation locations will only see winds around 10 to 20 mph with occasional gusts 20 to 30 mph. The other impact from these winds will be the orographic lift induced...which will enhance the heavy rainfall potential. This system will move north through central NY tonight and into Lake Ontario and srn Ontario just after 12Z Sunday. So, even though the low tracks quickly through the area, the strong dynamics and high moisture content of the air should be able to produce 1 to 2 inches of rain...mainly from the Wyoming Valley in PA, north into the Finger Lakes of NY. Lighter amts are expected to the east along the ridge of the Catskills and Poconos where amts should be less than 1 inch. At this time it does not appear rainfall amts will produce flooding issues. Antecedent conditions are still relatively dry over much of the area, especially the Finger Lakes...rainfall rates should not be high enough for flash flooding...and the system moves through rapidly. So, no hydro headlines expected. The threat of thunderstorms tonight seems to be less with the forecast this morning. Mid level lapse rates are shallow and a fairly strong inversion just above the surface should keep conditions fairly stable. Cannot rule out a couple isolated lightning strikes, but felt the probability was low enough and consensus among models high enough to take out mention of thunder. As the low tracks north on Sunday there should be minor destabilization over the NY/PA region, which will interact with the persistent cyclonic flow and deep available moisture to trigger scattered showers and storms in the afternoon and evening. 500-1000 J/kg of ML CAPE and 30-40 kt of shear, combined with steeper low level lapse rates should create favorable conditions for a few strong t-storms. Temperatures today will be very pleasant with highs in the 70s and 80s...along with low humidity. Mild temperatures tonight into the 50s and lower 60s. After the low moves out on Sunday, temperatures should be able to climb into the 70s and low 80s with slightly higher dew points in the low 60s...which will aid in the amt of sfc-based instability. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... 315 AM Update... The forecast area will remain in a humid, unsettled weather pattern through the short term period. There will be periods of showers and thunderstorms each day as a broad upper level trough remains nearly stationary over the Ohio Valley/Southeast and a high amplitude ridge remains over the north Atlantic. This type of pattern will keep our area under a deep, moist, southerly flow. Dewpoints hold in the upper 60s to lower 70s, with PWATS running 1.75-2.0 inches. Subtle waves/disturbances will rotate into NE PA and Central NY Sunday night through Tuesday. These disturbances will combine with moderate amounts of surface based instability to allow showers and thunderstorms to develop. With such high dew points and PWATS present, any showers or storms could easily produce heavy rain. Of note is that the top analog to this weather pattern is June 26-28, 2006...which is when an historic flood event impacted much of CNY/NE PA. Current soil moisture conditions and river levels are much lower than in June 2006...however things will moisten up with the first round of rain Saturday night into Sunday. This potential for flooding will need to be watched very closely in the coming days. Even though it is expected to be mostly cloudy through the period, with an almost tropical like air-mass overhead, temperatures will warm quickly during the afternoon hours, even with short breaks of sun. High temperatures Monday and Tuesday are forecast to reach the lower to mid-80s...with overnight lows around 70. Rainfall amounts area forecast to average 1-3 additional inches Sunday night - Tuesday...with locally higher amounts certainly possible. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... Tuesday night through Wednesday, a deep southerly flow of tropical moisture will remain over the area as an upper level trough extends southward to the Gulf States while a strong upper level ridge remains in the western Atlantic. Precipitable water values remain around 2 inches through the period so heavy rain will likely occur with any convection. Difficult to time any mid level waves at this time but diurnal heating and resulting instability will lead to more coverage during the daylight hours. Upper level flow becomes more southwest Wednesday night into Thursday as the next upper level trough drops south from central Canada. Precipitable water values remain close to 2 inches with convection likely on Thursday as a cold front approaches the region and crosses Thursday night. Thunderstorms could produce very heavy rain during this period. A chance of thunderstorms remains into Friday, as a secondary front pushes through from the west. PWATs are lower by Friday behind the initial front, closer to 1.5 inches. Even though current antecedent conditions are dry the initial wet period Saturday night into Sunday followed by a long duration of possible wet weather will need to be monitored for possible hydro problems. As mentioned above, June 2006 is a top analog for this upcoming week. WPC 7 day rainfall totals are progged to be between 5-7 inches for parts of the area. Highs through the period will be slightly above normal while overnight temperatures will range 5 to 10 degrees above normal and feel rather muggy with high dew points. PoPs lower, with just a slight chance for showers and thunderstorms by Saturday. The upper level trough should be just to our north, across southern Canada by Saturday. Dewpoints /PWATs continue to lower, and temperatures drop back into the 70s or lower 80s. Overnight lows drop back to around 60. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... 00z update... VFR conditions are expected to continue for the rest of the afternoon. Initial showers at KAVP late this afternoon should be largely unrestricted in nature. This evening, as steadier showers overspread the region from south-north, fuel alternate-MVFR restrictions are expected to develop. Embedded heavier showers later this evening into the overnight period (roughly 02-08z) could well produce brief IFR- alternate required restrictions. Showers should exit the region from SE-NW towards daybreak. However, lower ceilings and light fog are likely to linger, with again fuel alternate-MVFR restrictions. Improvement to VFR is expected towards midday (15-18z). Gusty E-SE surface winds this afternoon, will switch into the E-NE for a time tonight, before settling on a S-SE trajectory Sunday morning. Especially later this evening and overnight, a strong low-level jet just above the surface should produce LLWS conditions. Outlook... Sunday night...At least occasional restrictions probable in scattered evening showers/thunderstorms, then patchy lower ceilings/fog overnight. Monday through Thursday...Occasional restrictions likely, with periods of showers and thunderstorms. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...BJT NEAR TERM...BJT/MLJ SHORT TERM...DAB/MJM LONG TERM...MJM/RRM AVIATION...MLJ