MUWIC Newsletter - November 2004

(Issued: November 1, 2004)

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

************************************************************************

LEAD STORY: “Wet Pattern Dries Out”

After the wettest summer in eight years and a September that produced three soaking tropical events, October turned decidedly dry. Only 1.82 inches of rainfall was recorded at the Millersville Weather Center, which is only 61 percent of the long-term average for the month.

The drier pattern in the East resulted from a less energetic jet stream pattern and a significant decrease in tropical activity. Meanwhile, two strong storms ripped into the western U.S. with flashing flooding and early-season snowfall, and heat dominated across the deep south with high temperatures reaching the mid-90s. So, in classic fall fashion the October weather maps featured glimpses of summer- and winter-like weather.

Locally, temperatures averaged near normal with an equal number of above- and below-normal days. The month ended on a spectacular note with a balmy high of 75F on Halloween, however, a pattern change may loom in the near future. See the November Outlook (below) for a look ahead.

************************************************************************

EVENT OF THE MONTH

October lacked any remarkable storms in the Lancaster area, although, we did experience a notable cloudy period during mid-month. A stagnate pattern produced stubborn low-level cloudiness from October 13^th until the 23^rd, making for this most gloomy “event of the month.”

************************************************************************

OCTOBER CLIMATOLOGY (MU Weather Station)

Average High Temp: 62.9 F

Average Low Temp: 44.7 F

Average Monthly Temp: 53.8 F

(Departure from Normal: -0.1 F)

Precipitation: 1.82 inches

(Departure from Normal: -1.18)

Annual Precipitation: 36.05 inches

(Departure from Normal: +1.12.)

************************************************************************

NOVEMBER NORMALS, RECORDS & FACTS

November features the largest beginning-to-end drop in normal temperatures. The month begins with pleasant average high/low temperatures of 60/38, but ends with much more winter-like normals of 46/28. Average rainfall for the month is 3.53 inches, while average snowfall is about one inch. Measurable snow occurs roughly once every four years. Extremes: Record high - 84 on 11/2/82; Record low - 1 on 11/29/38; Wettest November - 8.05" in 1972; Driest November - 0.58" in 1931 & 1938.

************************************************************************

NOVEMBER OUTLOOK

October concluded on a remarkably warm note across the mid-Atlantic region as high temperatures soared to 75 degrees in Lancaster and the mid 80s across parts of Virginia and the Carolinas. Don’t get used to it—we may not see that kind of warmth again until next March!

Since late August, the jet stream pattern has tended towards a trough in the West and a ridge in the East (in the mean). Although the most extreme conditions have been across parts of the central and western U.S., temperatures locally have averaged about two degrees above normal from August 23^rd through October 31^st. I see this ten-week trend as ending on November 4^th, and a new pattern may take hold for much of November and, possibly, beyond.

While I am not prepared to make a bold forecast for extreme cold, I do see a fundamental shift in the jet stream pattern for the period of November 5^th through about November 10^th. This six-day stretch could easily average 6 degrees (or more) below average and it will likely produce the first significant lake-effect snow showers of the season in the mountains of Pennsylvania. Right now, I do not see the jet stream blocking needed to lock-in this cold pattern long-term, however, I also do not see a quick return to above normal conditions in the East. It may be that increasingly chilly air masses will drop into this East this month with only brief mild spells between cold intervals. Therefore, I’m inclined to forecast a slightly below-normal month with near-normal precipitation. Such a pattern will surely produce a few rounds of mountain snow showers, but only a modest chance (say, one-in-three) of an early-season snowfall in the Lancaster area.