933 FXUS61 KBGM 230648 AFDBGM AREA FORECAST DISCUSSION National Weather Service Binghamton NY 248 AM EDT Tue Apr 23 2019 .SYNOPSIS... A slow-moving low pressure system off the Mid-Atlantic coast will move northward toward the Gulf of Maine tonight and Tuesday. High pressure briefly builds over the region tonight. An area of low pressure will track eastward across the Great Lakes region on Tuesday before passing to our north Tuesday night and Wednesday. The next chance for showers arrives Tuesday afternoon and continues into Tuesday night when a cold front passes through. High pressure builds back in to the region Wednesday night and Thursday && .NEAR TERM /THROUGH TONIGHT/... Few changes with the midnight update. Forecast discussion below on track. 730 PM Update...Coastal low is now pulling away to the east; rain showers have also moved east of the area. Cloud cover remains across the western Catskills and much of NE PA (except Bradford county). The clouds are now beginning to also slowly pull away to the east...and should do so by late evening. Otherwise, skies are clear across the rest of Central NY as a surface high builds over the region tonight. Questions remain on if areas of fog will form in the river valleys, and some guidance is indicating a low stratus clouds deck forming as well over parts of the area after midnight. Meanwhile, some of the model guidance keeps skies clear during the overnight period. For now, used a blend of the sky cover guidance and also leaned toward the previous forecast...which is a bit more pessimistic. Cool tonight with lows in the 40s. Any stratus or fog will lift and dissipated by mid morning Tuesday, giving way to party sunny skies. Then, clouds quickly increase as a trough approaches midday and early afternoon. Chances for showers and a slight chance of thunderstorms increase by late afternoon. The best chance to see showers and a few thunderstorms holds off until evening or the first part of the overnight, with the actual cold frontal passage. Bumped high temperatures up a few degrees for Tuesday, more in line with the latest guidance. Rest of the near term forecast remains on track. Previous Discussion Below Mid afternoon surface analysis shows a 1013 mb low positioned several hundred miles east of NJ and south of Cape Cod. The western fringe of the wrap-around clouds and showers has made it into the western Catskills and Poconos this afternoon. These showers in our far eastern zones will generally be limited in coverage and intensity through this evening. A weak surface ridge that is currently over the eastern Great Lakes and OH Valley will progress eastward into the region tonight. Light winds and mostly clear skies west of I-81 will support good radiational cooling conditions tonight. Accordingly, temperatures should quickly fall after sunset followed by the development of patchy radiational fog late tonight into early Wednesday morning. With the surface high moving right over C NY, fog is favored in the Finger Lakes and nearby river valleys. A cold front will approach from the Great Lakes region on Tuesday. CAMs support the development of showers along a pre-frontal trough during peak afternoon heating in our western zones in CNY. This activity will then progress eastward across the area late in the day. Additional showers are likely with the cold front Tuesday night. Despite strong diurnal heating and relatively steep mid-level lapse rates (7-7.5 C/km in the 700-500 mb layer), a capping inversion in place, limited moisture in the boundary layer, and the better source of deeper lift with the front remaining to our west look to limit the potential for deeper convection to be sustained during the afternoon and evening. Accordingly, PoPs (showers) were generally limited to 30-50 percent and thunderstorms to 20 percent until the front arrives in the evening. Rain chances end from west to east late Tuesday night behind the cold front. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... 245 AM UPDATE... Short term will be quiet as high pressure builds into the area. Ridging aloft and increasing thickness will signal a return to seasonable temperatures with dry conditions. Made minor adjustments to the temps for the period according to the latest guidance. Previous discussion continues below. Main concerns in the short term are focused on the exiting rain showers associated with the most recent frontal passage Wednesday morning, then quiet weather with gradually warming temperatures into Thursday. Stacked low pressure system moving east over northern New England Wednesday morning will still be able to wrap enough moisture around the back side to produce a few lingering light rain showers across central NY through late Wed morning. Additional rainfall amounts should be less than a tenth of an inch. Cold air advecting in from the n/nw behind the system on Wed will keep temperatures se of Lake Ontario in the lower to maybe mid 50s. Areas from the NY/PA border south will likely warm into the lower to mid 60s. Heights aloft will rise Wed night and an area of high pressure at the surface will move in from the west going into Thursday. Should be plenty of sun by Thursday afternoon with light sw winds and temperatures into the mid to upper 60s. && .LONG TERM /FRIDAY THROUGH MONDAY/... 245 AM UPDATE... Decided to increase the pops to likely for the Friday cold frontal passage. Sharp Great Lakes short wave now phasing better with a southern stream wave bringing deeper sub tropical moisture over the area. This justifies an increase in pop for Friday. Instability looks very limited for the event, especially considering the early day passage of the front so thunder should be extremely limited. Otherwise, no major changes for the long term. Previous discussion continues below. The pattern becomes more active and wet starting Thursday night as the upper ridge axis slides to the east along with the wedge of drier air. An upper trough will dig into the upper Midwest during this time as a surface response develops over the Ohio Valley. The negatively tilted upper trough will be able to tap into a very moist, almost tropical, air mass from the Gulf of Mexico and produce a period of potentially heavy rain. The surface low track is still a bit uncertain, but most of the guidance moves it east through either PA or NY. The bulk of the rain is expected to fall just north/nw of the sfc low, so the track will play a very important factor where the heaviest rain will eventually end up. This system looks to be fairly progressive and mostly out of the area by Friday night/Sat morning. May see a brief break in the action Saturday night before the next fast- moving system rides through on Sunday...although this may change given that the pattern becomes quasi-zonal with multiple waves tracking east along various paths that do not appear to be well- defined or with much model consensus. Afternoon temperatures remain mild through the weekend with highs in the 60s...but overnight lows might be on the cool side with temperatures dipping into the upper 30s and 40s. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... Fog is still expected to form over KELM, KITH and KBGM by 09Z with conditions perhaps as low as LIFR at times. VFR at all TAF sites with light winds through the overnight. VFR expected through most of Tuesday. However, some MVFR restrictions are likely from showers by the early evening hours tonight. Winds will increase from the south before shifting to west and northwest later today with some gusts around 20 knots late this afternoon and evening. Outlook... Overnight tonight and Wednesday morning... MVFR stratus builds in for most of this period. West to northwest winds decreasing a bit overnight. Wednesday night through Thursday... VFR expected. Thursday night into Friday... Restrictions possible with showers. Friday night and Saturday... Predominately VFR. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...JRK NEAR TERM...JRK/MJM/MWG SHORT TERM...BJT/DGM LONG TERM...BJT/DGM AVIATION...DJP/MWG