659 FXUS61 KBGM 160803 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 403 AM EDT Thu Aug 16 2018 .SYNOPSIS... Brief high pressure will provide a relatively quiet period of weather this morning, before another frontal boundary with showers and storms moves through this afternoon into Friday night. Conditions turn dry and quiet again this weekend into early next week. && .NEAR TERM /THROUGH FRIDAY/... 3 AM update... Quiet early morning with limited deep moisture. Ample ground moisture and light to calm low level winds have caused river valley fog to form already. This fog will burn off between 8 and 10 am. Fog will be thickest across south central NY and NEPA as usual. In the Mohawk Valley lower clouds will slow the fog formation. Temperatures will remain from the mid 60s to lower 70swith dewpoints in the mid and upper 60s. This afternoon the flow shifts to southwest again ahead of another upper level trough. This will slowly bring deep moisture into our area from the Gulf of Mexico. Enough moisture combined with heating to create low level instability starting in western areas and moving east this afternoon. Best chances will be late afternoon into early evening in the Finger Lakes. A few thunderstorms could have heavy rain but this should be less than isolated. Severe thunderstorms are not expected with weak winds. Coverage will decrease some with the loss of heating especially in the Catskills and NEPA late evening into the overnight. Late tonight a prefrontal boundary approaches the Finger Lakes. At the same time surface low pressure moves northeast into southeast Ontario. This prefrontal boundary moves through the area during the day Friday. For severe weather best chances in the southeast where heating and instability will be better. Wind fields are weak, typical for summer, and wind shear peaks at 30 kts. Cape is marginal. With ample moisture cape will be tall and skinny. With the weak winds and pwats between 1.75 and 2", heavy rainers again possible. Warm cloud depth over 10k ft. Flash flooding will be the biggest threat Friday. With the flooding earlier this week, rainfall amounts of only 1 inch in an hour will cause problems. Widespread heavy rain is not expected so mainstem river flooding is not expected. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... 4 am update... Main concerns in the short term are focused on the continuing threat of heavy rain and flash flooding...along with strong wind gusts Friday evening with gradual improvement through the overnight and early Saturday period...the potential for light diurnal showers and storms Saturday afternoon and then dry conditions on Sunday. The primary upper trough axis and associated surface cold front will be moving ewd across NY/PA Friday evening with widespread showers and thunderstorms tracking east along and ahead of the front. Instability will be weak to moderate into the evening, becoming elevated as the boundary layer stabilizes. The dynamics should becoming more favorable with the approach of the upper trough and a 70 kt jet. Available moisture will still be quite robust with PWATs 1.75 to 2 inches, and moisture profiles showing saturation up to 300 mb in the late evening hours. So, there should still be a low threat of severe weather...mainly strong wind gusts...through Friday night, but the main concern will be heavy rain leading to flash flooding. Heavy rainfall rates on top of very wet surfaces will lead to rapid runoff, and potential flash flooding. The threat for heavy rain will likely decrease into Saturday morning with deep moisture profiles slowly drying out and weak high pressure at the surface building in from the west. Rain showers will linger, but weaken significantly before ending by the late morning/noon time frame. However, a trailing secondary upper s/w will drop in from the nw during the day Saturday and trigger another batch of light convective showers and weak storms in the afternoon...mainly east and south of the Finger Lakes. Convection will die down after sunset and weather is expected to remain quiet Saturday night through Sunday as high pressure dominates the region. Temperatures will be mild through the weekend with highs in the 80s and lows in the upper 50s and 60s. && .LONG TERM...SUNDAY NIGHT THROUGH WEDNESDAY... 4 am update... High pressure will slowly shift eastward across the area Sunday night through Monday night and keep weather conditions quiet early in the week. However, by Tuesday it appears the pattern will become quite active through at least the middle of the week as a large upper trough rotates across the Great Lakes and Northeast into Wednesday with additional chances of showers and storms. The system appears to be fairly progressive at this time, but will need to keep a close eye on the model trends of this pattern/system as we head into the weekend. 410 PM Update... Main concern will be for a cold frontal passage Friday afternoon-evening that could include thunderstorms with gusty winds and locally heavy rainfall. Low pressure is set to track from between Lakes Huron/Ontario early Friday morning, through northern New York in the afternoon-early evening, onward to New England Friday night. It will swing a cold front through our region in the afternoon- evening, with a modest amount of unidirectional shear as well as a moist environment with tall and skinny Convective Available Potential Energy profile. The shear will allow some cell organization and movement, with possible gusty winds. Given how saturated our soils are, it really would not even take a technically severe gust, to uproot some trees out of the waterlogged ground. Precipitable water values will be nearly 2 inches, with warm cloud depths again around 12 kft or so. Thus yet again, the resulting thunderstorms from this frontal passage will pose a threat for locally heavy rainfall, especially considering how sensitive and saturated our ground is from our recent very wet pattern. The good thing is that this is a progressive front, not a slow moving upper low. Thus the cells will be quick single hits, still capable of isolated flash flooding, but not repeatedly striking the same location as occurred in the last couple of days. Creeks/small streams and areas of poor drainage/urban locations will be susceptible to very quick responses and possible flooding from locally heavy rain; exactly where is not possible to pinpoint. However, larger streams and main stem rivers should be fine since this will be a quick- moving front. A complicating factor, in terms of forecast uncertainty, will be a pre-frontal trough that may take some of the energy away from the front itself. Not sure which feature - the front or the pre-frontal trough - will contain the bulk of the convection. The trough may also cause enough cloud cover to limit instability during peak heating hours, which could also hold back additional storm development. There is some possibility that showers-embedded thunder could linger well into Friday night, as front progress gets slowed awaiting passage of shortwave aloft. However, instability will also be quite spent and there is not clear indication of jet support aloft. Thus current expectations are that it will diminish in the evening with very little overnight. Saturday itself looks fairly dry as a surface high tries to edge in, but there will still be a small chance of diurnal instability showers-isolated thunder mainly east of I-81 as shortwave finishes its departure. && .AVIATION /07Z THURSDAY THROUGH MONDAY/... 130 AM Update... Early this morning some valley fog is possible. ELM could fall to IFR vsbys and cigs. Early signs of better fog there with a brief period of IFR vsbys. ITH/BGM/AVP should just fall to MVFR vsbys. SYR/RME could have MVFR cigs and vsbys at times. Moisture is dropping southeast into northeast NY ahead of a cold front and upper level short wave. Starting 13z then continuing into tonight primarily VFR conditions are forecast. Convection is expected this afternoon and evening but coverage should be scattered to isolated so have not included at this time. Models show a period of steadier rain late tonight for CNY, especially RME/SYR. Winds west at 5 kts or less early this morning. Valleys will be calm or light and variable. During the day west to northwest winds at 4 to 7 kts, then back to light and variable tonight. Outlook... Overnight tonight through Friday night...Restrictions possible due to showers and thunderstorms. Saturday through Monday...Primarily VFR. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...TAC NEAR TERM...TAC SHORT TERM...MDP LONG TERM...MDP AVIATION...TAC