Area Forecast Discussion
Issued by NWS Binghamton, NY

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000 FXUS61 KBGM 261420 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 1020 AM EDT Wed Sep 26 2018 .SYNOPSIS... A cold frontal boundary will move through the region today with another round of showers and scattered thunderstorms. Some of the storms may produce heavy rainfall and gusty winds. High pressure will then build southeast into the region tonight into Thursday bringing dry weather. A few showers then return Thursday night through Saturday as weak weather systems move through. && .NEAR TERM /THROUGH TONIGHT/... 1015 AM Update... Forecast expectations remain generally the same with this update. Showers driven by mid-level warm advection were passing through portions of the area this morning and this will be followed by a relative break during the midday hours, although our western Southern Tier and Finger Lakes region will remain with the highest chance for continous shower activity as the cold front moves in. Mesoscale models continue to advertise an organized squall line, or broken lines of thunderstorms, developing this afternoon and evening. Instability is in question under this blanket overcast, however, deep shear around 50 kts is more than sufficient along and behind the cold front with the advancing upper trof. Low-topped convection with a wind signature threat seems to be the mode of the day, if things get going. Our severe weather analogs support this idea as well. In addition, a localized flood threat remains a moderate- high concern as the deep southwesterly flow can support a thunderstorm training environment. Already seeing hints of this across SW NY and NW PA. Rainfall amounts have been generally light this morning, thus still confidence is still not high enough for a Flash Flood Watch given the forecast progressive nature of the cold front later today. Will monitor and issue a short-fused one if necessary. Previous Discussion...430 AM Update Complex and unsettled weather expected today. A deep trough of low pressure is moving slowly across the upper Great Lakes this morning. A cold front extends across eastern Lower Michigan down into the Ohio Valley currently. Initial shortwave out ahead of the front are bringing intermittent showers and isolated thunderstorms across the western portion of our forecast area early this morning. The next shortwave and area of showers/storms is evident across KY/OH and NW PA at this time. Latest CAMs show this area of convection moving mainly across western NY through mid to late morning...but it could also clip our far western zones again. If this area of convection were to track even slightly further east, we could begin to see issues with heavy rain and even flash-flooding. The flash-flood guidance remains very low across much of Central NY/Northeast PA...generally 0.5-1"/hr....except closer to 1.5"/hr across the NW Finger Lakes and Mohawk Valley regions. After this round of showers moves off to the north and east, additional showers and scattered t`storms will enter our forecast area from the west during the early afternoon hours. These showers/storms are associated with the fast moving cold front. Went with categorical PoPs for a several hour period later this afternoon as the front tracks east. Added mention of heavy rain and gusty winds into the forecast grids as well. The front should approach the I-81 corridor from SYR-BGM between about 1-4 pm...then move into the Catskills and Poconos during the late afternoon and early evening hours. Our CWA will be under a very moist air-mass, with high shear and modest amounts of instability forecast. This equates to some potential for gusty winds as storms develop this afternoon, which could cause isolated damage, such as downed trees and power lines. Parameters going again severe weather include very limited instability (<500 J/Kg of MLCAPE) and poor mid-level lapse rates. SPC continues the slight risk for severe t`storms over our entire area this afternoon. With the extremely wet antecedent conditions another worry will be for localized areas of flash-flooding...if any showers or storms end up training over the same areas this could certainly cause issues. PWATs will rise up to around 1.75" today, with localized rainfall rates of 0.5-1"/hr possible. Will continue to evaluate and fine tune the forecast to see if any portions of our forecast area need to be placed under a flash- flood watch for this afternoon. For now continued to mention the threat for heavy rain and gusty winds with t`storms in the HWO. Otherwise, expect mostly cloudy skies today with south winds 10-20 mph turning west-northwest behind the front in the late afternoon. High temperatures will be mild, in the upper 60s to mid-70s most locations. Tonight: The frontal boundary quickly moves east away from our area by 8-10pm...leaving dry weather and partially clearing skies. As a surface high pressure system builds overhead expect decreasing winds and cool temperatures. Overnight lows dip down into the mid-40s to lower 50s. Areas of valley fog are also expected. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... 430 AM Update The frontal boundary that moved through our area today will be well off to the south across the Mid-Atlantic through the day Thursday. We will be under a deep southwesterly flow in the mid and upper level, with a 1022mb surface high centered directly over Central NY and NE PA Thursday morning. As mentioned above expect valley fog to be around in the early morning, but should dissipate by mid to late morning. The area of high pressure quickly slides off to the east by Thursday afternoon. This should allow some high level cirrus clouds to move into the region from the south. High temperatures will be in the mid to upper 60s Thursday afternoon in most areas. Another weak wave of low pressure will attempt to push the front back north toward our area Thursday night. As the wave of low pressure passes by moisture will increase, bringing a chance of showers to the southern half of the area. Latest model guidance has come into better agreement that showers will be across our CWA, especially from the NY southern tier south to NE PA. With the increased clouds and showers around it will not be quite as cool Thursday night, with lows in the upper 40s to mid-50s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... 300 AM UPDATE...Old frontal boundary to the south may generate a few showers on Friday over the southern zones, meanwhile a cold front racing through the Great Lakes will push through on Saturday also generating a few showers,especially over the NY counties. Behind the front, a large and cool high pressure area will build in and keep dry weather over the area into Monday. On Tuesday, yet another front moves into the area with another chance for showers. Made some adjustments to the grids to align to the latest guidance and model timing. In general no major changes at this update. Previous discussion below. Model uncertainty grows for the weekend into Monday with several waves moving into the northeast and middle Atlantic through the period. Models vary on timing and extent of these waves and potential for light precipitation. So used the superblend and have slight chance to chance POPs for a few showers through this period. Temperatures will average close to normal to slightly above normal. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... Low level moisture around this morning resulting in spotty MVFR ceilings. A strengthening SW flow ahead of a cold front will help mix out the moisture and raise the ceilings to VFR. Around 18 Z a cold front will push through the TAF sites with a line of convection bringing brief IFR conditions and gusty winds. Much drier air behind the front will result in VFR returning into the evening. Late night fog is possible, especially at ELM and LIFR conditions. Outlook... Wednesday night...Ceilings lifting during the evening then patchy valley fog with restrictions around sunrise Thursday. Thursday...Improving to VFR early, then VFR. Winds under 10 knots. Thursday night and Friday...More restrictions possible with showers at KAVP and KBGM. Some possibility the showers reach KITH, KELM, KSYR and KRME for a time in the morning. Winds generally 10 knots or less. Saturday and Sunday...VFR conditions expected. Winds generally 10 knots or less. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...MJM NEAR TERM...JAB/MJM SHORT TERM...DJN/MJM LONG TERM...DGM/DJN AVIATION...BJG/DGM/MJM/MWG

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