FEATURE GRAPHIC: May 2008 Archives

With upper-air jet stream winds stuck in a northwest flow, cooler Canadian-source
high pressure will be the dominant factor in Chicago's weather in the days ahead. Rain
may be plentiful Downstate, but Chicago and the northern third of Illinois should miss
most of the action. Light showers are expected Monday night and Tuesday, and a band
of rain is likely to skim by mainly to the south of the Chicago area later Thursday. By
Saturday, southerly winds should usher in a warming trend and an increasing chance of
significant rains that could persist well into the first part of next week.
AS WEST COAST HEAT MOVES INTO PLAINS, SEVERE WEATHER THREATENS
Sunday was the fourth consecutive day of record highs in California. An excessive heat
watch was posted for Southern California, southern Nevada and western Arizona, where
100-degree highs were commonplace. Phoenix recorded its first 100-degree high of
2008 on Sunday. This West Coast heat is expected to end by Tuesday as an upper-level
low-pressure circulation moves into the Southwest. Subsequently, warm moist
southerly flow directly out of the Gulf of Mexico will set the stage for heavy rains and
severe weather in the Plains later this week.
--By Paul Dailey, WGN Weather Center Meteorologist

Spectacular weather including a second consecutive 70-degree day greet Chicagoans Saturday. Critical steering winds aloft, responsible for guiding weather systems, are blowing from the northwest. This sends cooler air into the area above ground, a development that should make the area increasingly vulnerable to cloud formation, especially in the warmer hours of the day, and most noticeably Sunday. Several of the puffy cumulus clouds expected to decorate Saturday skies may build tall enough to generate a few spotty showers in the afternoon. But cooling aloft fosters even more cloud development Sunday and shower coverage may be more extensive. Temperatures topped out at 107 degrees Friday in Anaheim and Modesto, Calif. The northwest flow ensures the record-breaking triple-digit heat that grips much of the West Coast won't head this way anytime soon. But big changes loom in the current pattern that has lingered for more than a month, delivering cool temperatures and frequent rain. The new pattern signals warmer, more humid air next week and 2008's warmest temperatures to date.
RAINFALL FORECASTS NOT ENCOURAGING
A return to heavier rainfall is predicted over the next two weeks. As much as 2 to 4 inches may be on the way.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Californians are being warned to monitor the elderly and conserve electricity in the
coming days as temperatures soar to 100 degrees. Sections of the San Francisco area
are likely to reach or exceed 90 degrees while the state’s inland valleys bear the
brunt of the heat with sizzling highs up to 105 degrees. Desert-like relative
humidities threaten to support wildfires.

The heat isn't limited to California. Readings 20 degrees above normal may set new
records from Los Angeles north to Seattle. In Portland, Ore.—where mid 60s are
typical this time of year—unusual 90s are predicted each of the next two days.
Mid May arrives in Chicago with the month's temperatures running within a half
degree of normal—but a noteworthy 6.5 degrees cooler than a year ago. The month's
3.09 inches of rain is twice normal and nearly as much as a full May’s rainfall (3.38
inches). A year-to-year comparison is even more dramatic. Rainfall in the opening 15
days this month is 24 times the 0.13 inches recorded by this date a year ago.

ONLY TWO 80s HERE SO FAR—UNUSUAL COMPARED TO THE PAST 80 YEARS

With no 80s expected here until the week after next, the two 80s on the books stand
out. Only 14 of the past 80 years (since 1928) have recorded so few 80s by mid-May.

Monday’s chill in Chicago was an annoyance to those waiting for a sign that spring’s
warmth was close to taking over. But it beat the wind-driven rains that lambasted the
country’s Mid-Atlantic —from North Carolina to New York City. Wind gusts reached
near hurricane force along Maryland’s coast, gusting to 69 m.p.h. at Ocean City. At
nearby Washington, D.C., 3.82 inches of rain fell, marking the city’s second deluge this
month. It pushed May’s precipitation tally to 7.69 inches—five and a half times normal.
A rainfall of 7 inches was recorded at North Beach, Md.

Chicago’s 56-degree high tied May’s coolest reading—but the lakeshore area bore the
brunt of the chill. Highs reached just 44 degrees in Highland Park and in Wrigleyville,
and 46 degrees at Wilmette and Glencoe.

TUESDAY’S HIGH TEMPERATURE IN CHICAGO REBOUNDS TO THE 70s

Highs surge 18 degrees Tuesday to 74 degrees—a reading likely to be the warmest of
the coming seven days. The overall pattern continues to be cool over the next two weeks.