ITHACA, N.Y. — It’s not too often Ithaca gets a fairly nice forecast like this. With the exception of a cold front Tuesday night, most of the work week ahead will feature abundant sunshine and highs in the upper 50s and 60s.
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It’s been a fairly quiet if cloudy Sunday, thanks to an upper level low pressure system passing aloft. The corresponding surface portion is weak and the atmosphere isn’t all that unstable, so rain showers have been limited. This low will slowly drift eastward during the overnight hours, and as it does, the chance for showers will decrease, but it will remain cloudy through Monday morning, with lows tonight in the mid 40s with a light northwest wind. With the relatively high dewpoint, some patchy fog will be possible in valley areas, so if you’re driving and it starts to get thick, take it slow and don’t use the high-beams on your headlights.
Monday will be a bit on the brisk side as northwest winds continue behind the low, but otherwise it will be quiet, with mostly cloudy skies and a high in the upper 50s. Monday night will see mostly cloudy skies, some patchy fog again, and lows in the mid 40s.
Tuesday morning will host a big warmup as winds shift to the south ahead of the next storm system, a low that will pass from the upper Great Lakes and over Northern New York. This will place the Southern Tier in the warm sector of the low, and temperatures will rise quickly, with upper 70s looking likely under partly cloudy skies, the warmest temperatures yet for 2019. 80 °F is not totally impossible, but it looks unlikely for Tuesday. Rain will move in ahead of the cold front by early Tuesday evening as the low continues east, and by sunset most of the region will have rain underway, maybe a few thunderstorms before the cold front pushes in a little before midnight. The wind shear (change in wind direction and speed with height) is favorable to severe weather potential, but the atmosphere is not expected to have the instability needed to fire up powerful thunderstorms; if that changes, we’ll keep you posted. The rain should quickly wind down during the overnight, and by daybreak it will be mostly cloudy and drying out. Lows will be in the upper 40s.
Wednesday will be cooler, but not chilly. As high pressure enters the region from the south, Tompkins County can expect partly cloudy skies with clouds decreasing as the day progresses, and highs in the low 60s. Wednesday night will be mostly clear and calm, with a noticeable drop in temperatures as the heat of the day radiates away, bottoming out around 40 °F.
Thursday will be a little warmer as the high pressure center shifts eastward and the winds come more strongly out of the south. Look for partly cloudy skies and a high in the mid to upper 60s, picture perfect day. A pulse of instability (shortwave) passing through Ontario and Quebec will increase the cloud cover Thursday night and pose a modest (30%) risk for showers, but otherwise won’t amount to much. Lows Thursday night will be in the mid 40s.
Friday will be mostly cloudy with a chance of light rain showers, as the shortwave approaches and eventually merges with a coastal storm. Highs will be in the mid 60s. As the combined system moves away, the clouds will begin to clear out again, with a low in the low 40s and partly cloudy skies Friday night, and partly cloudy skies Saturday and Sunday with highs near 60 °F and in the low 60s respectively, and lows in the mid 40s.
Looking at the start of May, the jet stream is likely to maintain a zonal pattern, which means it’s a fairly rapid, straight-line flow of air, with few meanders. That means warm air stays bottled up to the south, and cold air stays locked to the north. A modest amount of ridging will help keep temperatures around normal for the end of April and the start of May, which should be right around 66 / 67 °F, very pleasant for Ithaca and Tompkins County. Precipitation is expected to be near normal during the medium-range period.