ITHACA, N.Y. — May in Ithaca. The flowers are out, the leaves are coming out, and bumblebees are all over the place, and it seems like every highly-trafficked road in the county is under construction. This week is looking fairly unsettled due to multiple storm systems, but temperatures should be rather comfortable.

Graphic courtesy of the Cornell CALS Gardening Center

Weather Recap

Last week was mostly a quiet one by Tompkins County standards – and you know, let’s take that for what it was. During the work week, temperatures were consistently in the 70s for highs, although the overnight low last Tuesday night into Wednesday was a brisk 34 °F at Cornell’s Game Farm Road weather station in Dryden, and 37 °F at the airport. Thunderstorms did churn through the area on Thursday, giving a good, quick dose of rain to the area, and chasing a bunch of inebriated college kids off Libe Slope. As one student Twitter account put it, nature had enough of Electronic Dance Music.

A rather unusual setup this past weekend resulted in an unusual temperature pattern over the region – thanks to high pressure to the north and an outgoing cutoff low pressure storm system to the southeast, the sun had a chance to warm up areas to the north where thick clouds prevented any such luck further south, and Tompkins County was on the cusp of the two weather regimes. The result was that much of central Pennsylvania was stuck in the 40s, while Syracuse hit the low 70s on Sunday.

On that note, let’s take a look at the traditional last frost of the season. According to the Cornell CALS Gardening Center webpage, in Tompkins County, the typical range for the last frost of the season is May 10th-20th, while the southern part of the county actually clocks in a little earlier for its last frost, April 20th – May 10th. The mean at Cornell is May 12th according to the Northeast Regional Climate Center with the earliest last frost being April 9th, 1896, and the latest being June 9th, 1983. This year, it looks like that, at the moment, the last frost is May 1st at the Cornell Game Farm Road weather station, and April 29th at the airport. You’ll average about 143-163 growing days before that first frost in early-mid October, so take advantage.

No chance of any frosts of freezes this week, far from it. Lows will be unusually mild, but that’s what happens when you have a lot of cloudiness around during the night. Unfortunately, it’ll also be around during the day.

Graphic courtesy of NWS Binghamton

Your Weekly Forecast

This morning, most of Tompkins County is starting off cloudy even with high pressure aloft, but that should change as drier air works its way into the lower levels of the atmosphere. The clouds will break up, and Monday should be a fairly pleasant, with partly cloudy to mostly cloudy skies and temperatures topping out in the mid 70s with a light southwest breeze. Clouds will increase again late in the day ahead of the next frontal boundary.

Monday night is looking mild, as clouds thicken and temperatures only fall back to the upper 50s. Most of the area should remain dry, but developing rain and showers and thunderstorms could deliver a sudden downpour closer to daybreak, as the approaching front triggers development in an increasing unstable atmosphere.

Tuesday is a day to keep a close eye on. There’s a warm, moist air mass attempting to edge in from the south and southwest, and the cold front to the north and northwest. The combination of warm, moist air, low-level atmospheric instability, upper level dynamics, and wind shear (moving in different directions in different levels of the atmosphere) could trigger and grow many strong to severe thunderstorms with damaging wind and hail across the Southern Tier. The risk is greater to the south of Ithaca, and the threat will be highest in the early to mid afternoon, 12-3 PM. The area of strongest storms is still rather flexible, so be wary and mindful if severe thunderstorm warnings are issued and the need to take shelter arises.

Otherwise for Tuesday, expect periods of rain, heavy at times, and cloudy skies with highs in the mid 70s. Total rainfall will be around half an inch with locally higher amounts. By Tuesday night, rain will shift southward as the front eventually stalls over the mid-Atlantic, and Tompkins County will begin to dry out, with decreasing clouds and lows in the low 50s.

The second half of the work week will be quiet thanks to the high pressure to the north. Expect low 70s and partly cloudy to mostly cloudy skies for Wednesday with perhaps a shower or two south of Ithaca, and partly cloudy skies with lows in the low to mid 50s Wednesday night.

Thursday will be another fairly pleasant, dry day, with partly cloudy skies and temperatures in the low to mid 70s, as well as a light north breeze associated with the high pressure center over Canada. Thursday night will be partly cloudy with lows in the mid 50s closer to Ithaca, low 50s in the towns and outlying areas.

Friday is looking like a potential soaker from evening on, as the high pressure shifts eastward and a surge of very moist, warm air comes in from the southwest. With another low pressure area moving in from the Great Lakes, and a strong Bermuda high to the southeast to keep the low and the moisture in place, it’s looking like rain from Friday afternoon through much of the weekend, with steadier stratiform rains giving way to more scattered rain showers by Saturday night into Sunday. No flash flooding is expected as the atmosphere will be fairly stable overall, but NWS Binghamton is expecting 1-1.5″ of liquid sunshine. If you have weekend plans, let’s hope they’re indoors. Highs will be in the upper 60s Friday, low 70s for Saturday and Sunday, with lows in the mid and upper 50s.

Extended Outlook

The rest of the month is expected to be on the warm side of normal. The NOAA Climate Prediction Center is expecting a pronounced ridge in the jet stream over much of the country, resulting in warmer than normal conditions for much of the continental United States. However, with tropical moisture streaming in over the southwest and mid-Atlantic, and occasional low pressure storm systems passing over or near the Great Lakes, it’s looking likely that precipitation will also be above normal for the remainder of the month.

Brian Crandall

Brian Crandall reports on housing and development for the Ithaca Voice. He can be reached at bcrandall@ithacavoice.com.