11:15 AM | **Torrential rain and possible strong thunderstorms in the Mid-Atlantic/NE US late Thursday night as cold front arrives...it'll begin a colder-than-normal pattern going into November**
Paul Dorian
06Z GEFS forecast map of 850 mb temperature anomalies for Tuesday evening with colder-than-normal air across the western and central US and warmer-than-normal air in the East; courtesy NOAA, tropicaltidbits.com
Overview
Record-breaking cold has spread from the western US into the central part of the nation and several sites have experienced their coldest temperatures ever for the month of October during the past couple of days. In fact, there is an unofficial report of nearly 35 degrees below zero in a remote observing station in northern Utah on Monday morning which would be the coldest temperature ever recorded in the Lower 48 during the month of October. Accumulating snow is accompanying the record cold in many places with several inches likely again today across much of Colorado and the region from Nebraska to Wisconsin is in store for some accumulations as well over the next couple of days.
The slow-moving strong cold front at the leading edge of the cold air mass will arrive in the I-95 corridor later Thursday night and it could be accompanied by torrential rain and possible strong thunderstorms. Once the cooler-than-normal air arrives in the eastern US, it looks like the below-normal temperature pattern will stick around for awhile as we head through the month of November.
Numerous records have been set during the last couple of mornings across the western and central US for the date and month of October. In addition, there is an unofficial report of -34.7 degrees (F) in Utah on Monday morning which would be the lowest ever recorded in the Lower 48 during the month of October; courtesy coolwx.com, NOAA
Western/central US cold and snow
Many sites in the western and central US have seen daily record low temperatures during the past couple of mornings and accumulating snow has piled up in parts of the Rocky Mountain States. As an example of the extreme weather, Denver, Colorado has seen temperatures in the teens today with accumulating snow and they could drop to near 0 °F by Thursday morning which would be very close to the coldest October temperature ever recorded there of -2 °F in 1917. In addition, Denver is on a pace to have one of their top three snowiest Octobers in the last 50 years. The snow will extend to the central US over the next day or so in the region from Nebraska to Wisconsin as the cold air mass slides slowly to the east.
Several sites have also seen possible lowest temperatures ever for the month of October including the following locations: Merced, CA, Garden City, KS, San Luis Obispo, CA, Rock Springs, WY, Jackson Hole, WY and Vernal, UT. The California cold this morning is especially concerning as many areas have their power cut off as a result of the continuing threat of wildfires. In addition, there is an unofficial report of -34.7 °F on Monday morning in the remote observing station of Peter Sinks, Utah which would be the lowest temperature ever recorded in the Lower 48 during the month of October. Peter Sinks is a natural sinkhole in northern Utah at an elevation of around 8000 feet and it has recorded the second coldest temperature ever recorded in the continuous United States (–69 °F on February 1, 1985). The temperatures there on Monday actually rebounded more than 30 degrees in 30 minutes after bottoming out at nearly 35 degrees below zero as the winds kicked up and mixed out the cold, but this was still come very impressive cold indeed for this time of year.
00Z Euro model forecast for 1AM Friday with heavy rain depicted along and just west of the I-95 corridor; courtesy WSI, Inc, ECMWF
Eastern US warmth and threat of torrential rainfall
Meanwhile, in the eastern US, temperatures are generally running at or above-normal and will continue to do so through Halloween Day which promises to be wet and windy in the I-95 corridor for the “trick-or-treaters”. The cold air mass out across the western and central US will modify noticeably by the time it reaches the Mid-Atlantic region and NE US at the end of the work week, but it will set off a longer-term pattern change of below-normal temperatures for much of the eastern US as we go through the month of November while the western US stays warmer-than-normal.
06Z GEFS forecast map of 850 mb temperature anomalies for 8PM Friday evening with colder-than-normal air now reaching the Mid-Atlantic and NE US; courtesy NOAA, tropicaltidbits.com
As the strong cold front finally arrives in the I-95 corridor region on Thursday night, heavy rain is likely to break out and there can be strong thunderstorm activity as well. The heavy rainfall is most likely to break out after 8 or 9 o’clock which is after most of the “trick-or-treating” is completed and it should continue into overnight hours with strong thunderstorms a threat as well in the I-95 corridor. It’ll turn much cooler on Friday with highs some 15 degrees or so lower than the unusual warm temperatures expected on Thursday with 70 degree highs on the table in much of the DC-to-Philly-NYC corridor. Even cooler air will arrive later in the weekend in the I-95 corridor and highs by Sunday afternoon may struggle to pass the 50 degree mark in many spots.
One final note, this is the weekend in which we turn the clocks back an hour which will certainly make it easier getting up in the morning.
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com
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