April 24-May 7, 2005 Pattern Discussion

[donsutherland1]

April 24-May 7, 2005 Pattern Discussion

Last week’s discussion raised a number of issues of what one might expect for the April 17-30, 2005 period.

• Through the first half of this period, genuine springlike warmth will likely prevail in the eastern United States. Temperatures could feel summerlike on at least one or two days. The latter part of the second half of the period could see significantly cooler air in the East. The April 17-22 period will likely see temperatures average much above normal in the Northeast and Mid-Atlantic regions. During this period, the highest temperature could reach close to 78° in New York City, the lower 70s in Boston, and 83° or above in Washington, DC.

The April 17-22 period saw readings average much above normal in the Northeast and Mid-Atlantic regions:

Boston: +6.8°
New York City: +9.3°
Washington, DC: +5.8°

Highest temperatures were:

Boston: 87°, April 20
New York City: 87°, April 20
Washington, DC: 86°, April 20

• A cool front could bring some showers later in the week (April 21). Afterward a short cool period, readings could again warm during the weekend (April 23-24). The following week could see a noticeably colder air mass. The potential exists for low temperatures to fall to 43° or below in Boston, 45° or below in NYC, and 47° or below in Washington, DC on one or more days during the April 25-May 5 timeframe.

Late April 20 into April 21 saw small amounts of rain. Washington, DC picked up 0.12”, Boston, 0.10”, and New York City a trace. Cooler air followed. Courtesy of a strong storm moving to the west of the region, readings will likely warm tomorrow before an unseasonably cold air mass arrives on Sunday.

• The April 17-20 period will likely see readings in the Chicago and Detroit areas average much above normal. The warmest days will likely be April 19-20. Temperatures could soar to 75° or above in both Chicago and Detroit on one or both days.

The April 17-20 period was exceptionally warm. Temperature anomalies were:
Chicago: +14.8° (Highest: 81°, April 19)
Detroit: +12.3° (Highest: 83°, April 19)

• Rain is possible late on April 20 into April 21. Much cooler readings should follow. Moderation is likely to commence during the weekend. An even colder air mass could arrive early the following week (April 25-26).

A small amount of rain fell on April 20 as a strong cold front moved through the region. Much colder weather followed, which set the stage for a late-season snowfall in parts of the region for the upcoming weekend.

• The April 17-20 period will likely feature much above normal readings in the Central Plains states. Temperatures could reach 75° or above on two or more days during this timeframe. A soaking rain is possible on April 20. Cooler weather should follow in the wake of the storm.
The April 17-20 period was exceptionally warm. Anomalies included:

Kansas City: +13.5°
Omaha: +15.5°

Kansas City exceeded 75° on all four days; Omaha exceeded it on three days. A rainstorm arrived in Kansas City late on April 20. April 20-21 rainfall came to 0.39”.

• In Seattle, the April 17-19 period will see below normal temperatures and some rainfall. By April 21, it temperatures should be running above normal.

The April 17-19 period averaged 1° below normal but April 17 was 3° below normal and April 18 and 19 were normal. Rainfall for this timeframe came to 0.04” Readings rebounded on April 21 with temperatures at 3° above normal. April 22 was even warmer as the temperature climbed to 74° in Seattle by 3 pm PDT.

• Temperatures in Los Angeles should run somewhat above normal through April 18. Somewhat cooler air could affect the city during the April 19-20 timeframe. Warmth should gradually begin to build on April 21.

The April 18-20 period saw temperatures average 3° below normal. Warmer air returned on April 21 with a high of 80° but a storm brought increasing clouds, some rain, and cooler readings to Los Angeles on April 22.

The April 24-May 7, 2005 Ideas:

Several major developments will highlight this period.

First, the April 23-25 timeframe will likely see an unseasonable late snowfall in parts of the Great Lakes region. Detroit, Grand Rapids, and Toledo could all pick up accumulating snow, possibly in excess of 3” in some places. Local amounts could exceed 6” away from these cities.

Second, another strong block will likely peak in the April 27-29 timeframe. As a result, the earlier idea from last week of one or more pushes of unseasonable cold into the East during the April 25-May 5 timeframe continues to look good.

• April 23-30 will likely see readings average below normal. Late April 22 and April 23 should bring a soaking rain. Boston, New York, Philadelphia, and Washington, DC will likely receive 0.50”-1.50” rain. A much cooler air mass will overspread the region on Sunday. The potential exists for low temperatures to fall to 43° or below in Boston, 45° or below in NYC, and 47° or below in Washington, DC on one or more days next week. April 26-27 could bring additional rain followed by a new push of colder air. May 1-7 looks to be somewhat cooler than normal and wetter than normal. Moderation should occur near the end of the timeframe as the block erodes.

• April 23-25 will see a series of storms bring snow and rain to the Midwest/Great Lakes Region. Detroit could pick up 3” or more of snow. Even Chicago could see a trace of snow. April 23-30 should experience much below normal temperatures. Both Detroit and Chicago could see temperatures fall below 32°, especially in the April 24-25 timeframe and then perhaps on April 28.

• April 24-27 will experience below normal temperatures in the Central Plains states. Some moderation is likely during the April 28-30 period. However, April 29-30 could bring rain to parts of the region. Around or just after May 2, a warming trend could commence.

• After a very warm start to the weekend with the temperature likely rising into the 70s in Seattle on Saturday, cooler air should return. April 25 and then again on April 28-29, there could be rain in the Pacific Northwest. April 29-30 should be unseasonably cool. A fresh warming trend should begin on May 2 courtesy of a building PNA + setup.

• April 24-25 will likely be somewhat cooler than normal in Los Angeles. Some showers are possible. Midweek, April 26-28 will probably be milder with readings running near or somewhat above normal. April 28 could bring showers courtesy of another storm affecting the West Coast, particularly the Pacific Northwest along with cooler readings.

Historic Late-Season Snows in the Detroit/Michigan Region:

Given the late-season snowfall that is imminent, here are some highlights of earlier late-season snowstorms for Detroit:

April 22, 1911: 1.0”
April 22, 1986: 1.0”
April 28-29, 1909: 3.0”
May 9, 1923: 6.0”
May 10, 1902: 0.5”
May 13, 1912: 1.5”
May 21-22, 1883: 5.0”

Source: National Weather Service Forecast Office, Detroit/Pontiac

Some excerpts from some notable events depicted in news accounts:

• May 8-10, 1923:

Sweeping down from the Far North, a miniature blizzard with snow and sleet storms and a cold wave of unusual intensity for this season of the year swept the Middle West today and was succeeded tonight by freezing temperature at many points. In Chicago yesterday afternoon [May 7] the thermometer stood at 77 degrees; at 9 o’clock this morning it had dropped to 40. (Source: The New York Times, May 9, 1923)

A flood of cold air sweeping down from the Arctic Circle has caused the wintry weather which has spread over the Middle West and Northeast and even the South, causing snow flurries in several areas with conditions resembling a blizzard… The deepest snow was at Grand Rapids, where five inches was recorded, but snow covered the ground at Wytheville, Va.; Elkins and Parkersburg, W. Va.; Cincinnati, Columbus and Cleveland, Indianapolis, Fort Wayne, and Buffalo. (Source: The New York Times, May 10, 1923

Snow flurries in several parts of the city [New York City], frosts in near-by sections of New Jersey and a low temperature mark equaling the coldest May 10 of which records exist…were some of the results yesterday [May 10] of the cold wave that has been gripping the West… In New England snow fell at many points. Three inches fell at Montpelier, Vt., and Winsted, Conn., and Springfield, Mass., had flurries. In Ontario, Canada, the mercury dropped to 26. Richmond, Va., had the coldest May 10 on record, with a low temperature of 35 degrees. (Source: The New York Times May 11, 1923)

• May 21-22, 1883:

Port Huron, MI: The storm is still raging, accompanied by snow and sleet.

Ohio: Snow is reported from various parts of the State… The snow in Logan County is five inches deep. (Source: The New York Times, May 23, 1883)

• June 12, 1874:

A special dispatch from Grand Rapids, Mich., says snow commenced falling at Manton, a station on the Grand Rapids and Indiana Railroad, yesterday morning [June 12], and continued for some time. (Source: The New York Times, June 14, 1874)

NOTE: After April, this discussion will appear only in the U.S. Weather Forum until next fall.