Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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697 FXUS61 KBUF 272336 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 736 PM EDT Thu Jun 27 2024 .SYNOPSIS... High pressure will drift from the western Great Lakes to the New England coastline tonight and Friday providing us with dry and comfortable weather. Low pressure tracking from the upper Great Lakes to Quebec will bring a return to much more unsettled weather Friday night and especially Saturday with periods of showers and thunderstorms. High pressure and drier weather return later Sunday and early next week. && .NEAR TERM /THROUGH FRIDAY/... A compact shortwave dropping southeast out of southeast Ontario has brought a few convective showers, that are flattening as they exit Lewis County this early evening. Surface high pressure centered over the Central Great Lakes this evening will build into the region tonight, before drifting east into New England on Friday. This will provide the region fair dry weather through Friday. Mainly clear skies and light winds will allow for ideal conditions for radiational cooling tonight with overnight low temperatures dropping into the mid to upper 40s across the interior Southern Tier/North Country to the lower 50s elsewhere. Some patchy fog is possible within the Southern Tier Valleys overnight. On Friday, a developing southeasterly flow on the backside of the departing high will help send temperatures into the mid 70s across the North Country and the upper 70s to near 80 elsewhere. Humidity levels will remain comfortable with surface dewpoints in the mid 40s to lower 50s. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... An active period is expected this timeframe as a mid level shortwave trough crosses the Great Lakes region. This shortwave trough will carry a surface low from the western Great Lakes Friday night to near the SOO Saturday morning and then deepen the surface low some as it crosses southern Quebec through Saturday night. A warm front ahead of this surface low will bring initial prospects for rain showers, with the cold front arriving Sunday morning sweeping the high humidity and precipitation chances eastward. Friday evening will start dry, and still on the comfortable side with dewpoints in the low to mid 50s. A deep southerly flow ahead of this shortwave trough will begin to increase moisture, and subsequently increase surface dewpoints and humidity through the night. Moist isentropic lift Friday night as a warm front extends eastward towards our region, coupled with convergence along the nose of a 30 to 35 knot LLJ will bring scattered showers and even a few late thunderstorms to our region as MUCAPE values rise to 500 to 1000 J/KG generally along and west of the Genesee Valley. Scattered showers and a few rumbles of thunder Saturday morning will only increase in coverage area as moisture deepens, and a mid level convective shortwave trough passes across our region. The early evening timing of the pre-frontal trough, cloud cover holding elevated instability back to around 1000 J/KG or less and poor mid level lapse rates under 6 C/KM are not favorable for strong to severe storms. However, 0-6 km bulk wind shear values 35 to 45 kts could aid in strength and structure to better organized storms such that stronger wind gusts within such storms remains possible. SPC has our region within a marginal risk for severe storms for Saturday. Hail should be little to none. Wetbulb zero heights are just too high, around 15K and a very moist airmass encouraging melting on the way down will make for smaller hail stones if they do develop. It will be humid Saturday with dewpoints in the low to mid 70s. Perhaps the bigger threat will be heavy rainfall Saturday afternoon and evening. Pwats on the 12Z GFS/NAM/ICON/GEFS are forecasted to near or even exceed 2.00 inches. A measured PWAT of 2.00 inches is uncommon for late June on radiosondes launched at the Buffalo Airport. Only 7 instances (12Z or 00Z) of a PWAT of 2.00 inches or more have been recorded since 1948. The time period for heavy rain will be roughly noontime through 10 pm when peak heating of the day can increase instability, and 0-6 km bulk shear increases to 50 knots allowing for better storm structure. Clusters of showers and thunderstorms collecting ahead of a convective shortwave will be moving owing to the wind fields aloft, but any thunderstorm can quickly deposit an inch or more of rainfall in a short period of time, and any training to cells will aggravate the potential for poor drainage flooding. A wind fields weaken aloft through the night and instability lowers, as well as the eastward shift to the axis of deeper moisture, thunderstorms, becoming scattered showers will diminish through the night. It will remain muggy Saturday night, with patches of fog forming as the cold front will remain off to our west. Sunday the cold front will slice across our region. Temperatures around 14 to 15C at 850 hPa Sunday morning will fall to the upper single digits by late Sunday afternoon. We could still see a few showers Sunday along the front, with chances higher to the east as increasing instability will encourage showers growth. Dewpoints will be falling through the day, with a much more comfortable afternoon in store with temperatures in the low to mid 70s. Cool Sunday night as a ridge of high pressure passes overhead. The 850 hPa temperatures around 7C over the warm lakes may encourage some lake induced clouds within a northerly flow. Towards the west fog will likely form within the river valleys. Lows will drop back into the 50s, and in the colder locations of the inland Southern Tier and Tug Hill may even reach the upper 40s. && .LONG TERM /MONDAY THROUGH THURSDAY/... Surface high pressure will move across the eastern Great Lakes region Monday through Monday night. This will bring a period of dry, and seasonable weather for the region Monday through Tuesday. Then, warmth and humidity will increase as the high shifts to the east Tuesday through Thursday. Weak troughing will replace weak ridging and a cold front is expected to move across the region Wednesday through Thursday. This will increase the chance for showers and thunderstorms during this time. Temperatures will begin below normal Monday with highs in the low to mid 70s. Day to day warming will occur Tuesday through Wednesday with highs averaging the upper 70s to low 80s Tuesday to the mid to upper 80s Wednesday. Temperatures Thursday will depend on the timing of the cold front with high temperatures ranging from the low to upper 80s. Humidity values will increase Wednesday. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... For the 00Z TAFS VFR flight conditions are found and these will largely continue through the TAF cycle as high pressure over the central Great Lakes builds eastward towards the eastern Great Lakes. Northwest winds will become light and variable a few hours after sunset. Within these light winds, valley fog is expected to form, that may near KJHW after midnight. High clouds will spread across the TAF region tomorrow, with VFR flight conditions after any morning fog dissipates. Outlook... Friday night...Mainly VFR with a chance of showers. Saturday...Localized restrictions likely in increasingly widespread showers and scattered thunderstorms...some of which may produce locally heavy rainfall. Sunday...A chance of a leftover shower or two...otherwise mainly VFR. Monday and Tuesday...VFR. && .MARINE... Winds on the lower Great Lakes tonight will become light and variable as high pressure from the western Great Lakes builds into the region. Mainly easterly winds at 12 knots or less will develop Friday as the high departs across New England, but some local onshore breezes will likely develop during the afternoon. Southeasterly winds early Friday night will veer to southerly as a warm front lifts into the lower Great Lakes. These southerly winds may increase to over 15 knots Saturday, but wave heights in US waters likely remaining 3 feet or less. A cold frontal passage will bring scattered thunderstorms Saturday afternoon and Saturday evening with the potential for locally gusty winds and higher waves. Behind the frontal passage, westerly winds will strengthening to near 20 knots with a period of advisory conditions possibly developing Sunday on both Lake Erie and Lake Ontario. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...JJR/TMA NEAR TERM...Thomas/TMA SHORT TERM...Thomas LONG TERM...HSK AVIATION...Thomas MARINE...TMA