ITHACA, N.Y. — A nice start to the week will take a turn for the ugly by Wednesday as a potent storm system moves in, bringing rain, wind, and much cooler temperatures for the second half of the work week. If it’s any consolation, the weekend is looking nice and warm for late October.

Your Weekly Weather

The weather has been fairly interesting in the past few days, it that it seemed as if everyone else was getting socked with awful weather while Ithaca was relatively quiet. While a nor’easter like storm transitioned into Tropical Storm Melissa off the Atlantic Coast and lashed areas to our east, a powerful storm system swept in and strengthened over the Rockies and Great Plains, dropping as much as 30″ of snow in North Dakota and sending Denver’s temperature plummeting from a toasty 83 °F to a bone-chilling 19 °F the following morning. Granted, inland continental climates are prone to these type of wild weather and temperature swings, but this is extreme even by their standards.

Over Tompkins County, a weak cold front pushed through Saturday with some scattered showers in attendance, but otherwise it’s been fairly calm with temperatures near normal. That pattern should persist for the next couple of days as the storm that walloped Denver has weakened and will past well to our north, with negligible impacts on the Southern Tier. However, the next storm developing in the leeward side of the Rockies does appear to have a track that will send it over our region, and while not as strong or as cold as its predecessor, it will have a deep low pressure center that will likely drive in much cooler air and windy conditions for Wednesday through Friday.

For the short-term however, things will be quiet, seasonably mild, and a pleasant ending for those folks enjoying a three-day weekend. For tonight, expect mostly clear skies with a few more clouds by morning, a light south breeze, and a low in the mid 40s.

Monday should be a lot like Sunday was – seasonable and partly cloudy. It will transition from a few passing clouds to mostly cloudy by Monday afternoon as the low pressure system to the north ushers in a weak cold front, but with the dry air in place, no precipitation is expected. Winds will turn to the northwest for at least a few hours in the evening before taking a more westerly to southwesterly direction after sunset, thanks to high pressure to our south. Highs will be around normal for this time of the year, about 60 °F. It will be mostly clear Monday night, but the backside of the low will direct some cooler air in our direction (recall air flows counterclockwise around lows), so temperatures will drop a little further Monday night, into the upper 30s.

Tuesday will be another quiet day with mostly sunny skies and highs around 60 °F and a light south wind as the high shifts to our southeast. That southerly flow will stay in place Tuesday night as the next storm system approaches and clouds thicken, and lows will be in the mid 40s.

Rain should start not long after sunrise Wednesday morning. Scattered rain showers will be more prevalent in the morning and early afternoon hours, but generally stick around for the whole day. It will be mostly cloudy between batches of rain, and being in the warm sector of the low, temperatures will climb into the low 60s for highs with a south breeze. Rainfall amounts will be between one quarter and one half of an inch. The low should pass through late Wednesday evening after sunset, and winds will turn to the northwest during the night as we enter the cold sector of the storm system. Thanks to the ample moisture in the air and generally overcast conditions, temperatures should only fall back to the low 40s Wednesday night.

The storm system will undergo a transition of low pressure centers as it moves to the northeast, actually adopting some Nor’Easter like features as the initial storm over Ontario transfers energy to a developing coastal low off New Jersey. This juiced-up secondary low will rapidly strengthen as it passes off Cape Cod, and as it does, the pressure gradient will rapidly tighten in response to the deeper storm core (the stronger a storm is, the deeper or “lower” the low pressure center is, and the pressure gradient grows). A tighter pressure gradient translates to a stronger flow of air, in effect wind and temperature advection, which in this case means cold air coming in from the north and northwest.

Thursday will be an unsettled day, but the bulk of the precipitation will have moved to our east by that time, so only a few light showers are expected. However, it will be a cloudy and windy day, with a steady northwest wind of about 15 MPH and gusts of up to 25 MPH. It will be an uncomfortable day to be outdoors, and with that stiff wind, temperatures will only top out in the low 50s. However, a funny thing about wind is that it agitates the air and keeps temperatures from dropping as well as warming up, so Thursday night, with its mostly cloudy skies, remnant moisture and gusty winds, should see only modest drops in temperature, to about 40 °F in Ithaca and the upper 30s on the exposed hilltops.

Friday will see some improvement as the coastal low pushes away and into Atlantic Canada, with decreasing winds, increasingly sunny skies as the day progresses, and highs in the mid 50s. The low cloud cover and calmer winds Friday night will allow temperatures to slide back further, to the mid and upper 30s in most areas, with some frost possible in the typically cooler spots.

The weekend is looking good by October standards, as an area of high pressure parks itself off the Carolina coast and channels milder, stable air into the Southern Tier. Expect low to mid 60s and sunny Saturday, mid 40s and mostly clear Saturday night, and sunny and upper 60s on Sunday, a perfect weekend for catching the fall foliage at its local peak.

Graphic courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Generally speaking, the “cool west, warm east” pattern should continue over the continental United States through to the end of the month. The recent heavy snowfalls out west create a positive feedback mechanism, in that the reflectivity of snow and the cooling effects on the surface layer of air will keep temperatures cooler out east and enhance the persistent trough in the jet stream that has allowed cold, stormy conditions to persist in the Rockies and Great Plains – large-scale weather tends to reinforce itself until a major storm system comes along and resets the jet stream wavenumber pattern. It is looking that may potentially happen around Halloween or shortly thereafter, so enjoy the unseasonable late October warmth while it lasts, because you know you’ll be digging out the snow shovels and parkas soon enough.

Brian Crandall

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