ITHACA, N.Y. — If you’ll be chaperoning some trick-or-treaters Thursday night, make sure their costumes are waterproof. Though the week will be comfortably mild by late October standards, the second half will be rather unsettled ahead of a strong cold front that will usher in some true late autumn cold for the start of November.

Precipitation, mean sea level pressure and 1000-500 mb thickness (temperature proxy) for 8 AM Friday morning. A cutoff low will result in widespread rain and windy conditions Thursday night into Friday. GFS Model output courtesy tropicaltidbits.com.

Your Weekly Weather

At present, the Sunday morning rainmaker is shifting further eastward, now centered over Cape Cod and moving out to sea at a steady clip. An area of high pressure centered over the central Appalachians is expanding its influence into the Southern Tier, allowing for fairly mild and tranquil weather over the next couple of days as it moves northeastward, shifting the airflow from a westerly wind to a warmer southeasterly direction by late Monday.

Sunday night will be quiet. Some clouds linger due to some remnant instability and moist ground levels, but while it will be overcast, it will also keep the temperatures from dropping much. Temperatures will settle in the upper 40s by daybreak.

Monday will see mostly cloudy skies early, with decreasing clouds as the day progresses, down to just a few passing cumulus by sunset. Highs will be mild, in the low 60s. A weak frontal boundary will be passing to our west for Monday night, and it looks like its SW-NE course will keep its moisture out of our region. It will however, be cloudy, especially after midnight, with lows in the upper 40s.

Tuesday should see some blue skies reappear as the low quickly moves away, and since we’ll remain in its warm sector, there will be a strong southerly breeze with partly to mostly cloudy skies as some instability lingers in our column of the atmosphere. Highs will be in the mid-60s. Tuesday night will be mostly cloudy with a low in the upper 40s.

As the high shifts offshore Wednesday and the ridge of warm air shifts with it, the jet stream will shift eastward and closer to the Southern Tier. That will allow it to channel moist, unstable air from the Gulf of Mexico. While the moisture and instability make their way in, the southerly heat will not, in part due to an area of high pressure just to our north; this will limit rain, but temperatures will top out in the low 60s with overcast skies. As the atmosphere becomes more moist and unstable, rain is likely to develop after midnight, in the early hours of Thursday morning. Lows Wednesday night will be in the mid 40s.

For your Halloween, it will be, well, fitting with the holiday. It will be dark and cloudy, with scattered rain showers as a cutoff low lurks to our west, It will also be just cool enough to raise your goosebumps if you step outside without a jacket, as highs will be in the upper 50s. The low does a rather unusual shift of energy to a new core to its northwest later Thursday, shifting from the Ohio River Valley to near Chicago. Cutoff lows are not attached to the jet stream, so they tend to move slowly and meander in unusual paths. Weather-wise, the key thing of note is that this will pump a lot of moisture into the northeast, so widespread rain is likely Thursday night. Do your Monster Mash inside, folks. Lows will be in the mid-40s. It could be worse – a swath from Iowa to Wisconsin, Illinois and Michigan is looking at a White Halloween as snow falls in the cold sector of the low.

Interestingly, by the time the low is in our latitude and effectively places us in the cold sector, it will have moved so far north into Canada that the snow won’t even be close. So while it rains, heavily at time after midnight Thursday, there’s no frozen precipitation in this forecast. That being side, we’ll see a strong cold front sweep through late Friday morning. The rain should start to wind down Friday afternoon, with showers continuing before sunset, and it will be a very windy day as the low strengthens to the north, increasing the pressure gradient and the winds by extension. Gusts of 35 MPH from the south and west are possible, and with such strong winds, the temperature won’t rise much, only mid 50s for highs. Friday night will see the winds settle as the low moves away, and mostly cloudy skies giving way to partly cloudy skies, and lows in the mid 30s.

That cold shot behind the low may not be the most potent given how far north the low will be, but with as strong as it will be, it will wrap lots of polar air into its circulation and be able to shunt that southward. Temperatures will be a bit below average, but only a little bit given typical highs are in the low 50s for the start of November. Saturday will be partly cloudy with highs near 50 °F. Lows will be near freezing under mostly clear skies Saturday night, and highs will be in the upper 40s Sunday as that trough of colder air hangs around; its maximum amplitude will shift eastward and closer to us Sunday, allowing freezing temperatures as far south as Nashville and Norfolk.

Image courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Extended Outlook

A deep and sustained trough in the jet stream will result in colder than normal temperatures throughour much of the continental United States during the first week of November, and that pattern looks like the hold through the first half of the month, and perhaps into the second half, with some moderation along the edges (i.e. the Northeast, Southeast and West Coast). The bright side ot this is that with the jet stream shifted eastward, relatively benign, dry conditions should be the general rule. It will be chilly, often in the 40s or low 50s at best, but at least there’s no snow to speak of…yet.

Brian Crandall

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