April 10-23, 2005 Pattern Discussion

[donsutherland1]

Last week’s discussion raised a number of issues of what one might expect for the April 2-16, 2005 period.

• For the Northeast, a major storm will likely bring a widespread 1.50” to 3.00” rainfall to the Mid-Atlantic and Northeastern states in the April 2-3 timeframe. Behind this storm readings should remain somewhat below normal on April 4. A warming trend will likely see temperatures reach the 60s on April 7 in NYC and perhaps better than 70° in Washington, DC. Another storm could bring significant rainfall to the region in the April 8-9 timeframe.

The April 2-3 period saw Boston pick up 1.25” rain, NYC 1.89” and Washington, DC 1.92”. Temperatures averaged near normal to slightly above normal on April 4. Afterward, it grew much warmer.

High temperatures were:

NYC:
April 6: 75°
April 7: 78°

Washington, DC:
April 6: 82°
April 7: 76°

Additional rain fell during the evening of April 7 into April 8. Totals included:

Boston: 0.29”
NYC: 0.85”
Washington, DC: 0.33”

• After a wet and cool start to the weekend in such cities as Chicago and Detroit, moderation should set in. Readings will likely run much above normal April 5-6 timeframe. It would not be surprising if at least one of those days sees the temperature reach 70° in either Chicago or Detroit. A sharp cold front should move through the region around April 7-8 with some rain showers possibly ending as snow showers.

April 1-2 rainfall totals included (timing was quicker than listed):
Chicago: 0.18”
Detroit: 0.23”

Temperatures warmed noticeably. The April 5-6 period saw temperatures average 18.5° above normal in Chicago and 17.5° above normal in Detroit. High temperatures were:

Chicago:
April 5: 76°
April 6: 80°

Detroit:
April 5: 77°
April 6: 78°

April 7 saw 0.01” rain at Chicago and a trace at Detroit. Cooler readings followed.

• The Central Plains will see moderating temperatures during the coming weekend. The April 3-5 period will likely be exceptionally warm. On at least one day, the mercury will probably reach or exceed 80° in Kansas City and Omaha. A storm could bring some rain around April 6 followed by a few cooler days.

Temperatures moderated during the weekend of April 2-3 with a sharp warmup occurring. The April 3-5 period was very warm. The temperature averaged 16° above normal in Omaha and 15.3° above normal in Kansas City. High temperatures included:

Kansas City:
April 3: 82°
April 4: 81°

Omaha:
April 4: 81°

On April 6, Omaha received a trace of rainfall. Kansas City picked up 0.41”. Cooler readings followed, particularly in Kansas City.

• Seattle will likely see cool and often wet weather through April 5. The April 2-4 period could see a cumulative total of more than 1” of rain. Afterward, somewhat milder temperatures should prevail for a few days.

The April 2-4 period saw less rainfall than predicted: 0.50”. After the rain, temperatures rose to somewhat above normal levels during the April 5-6 period, including a high of 62° on April 6. By April 7, a cooling trend recurred.

• The April 2-7 period will likely see temperatures run above to much above normal in Los Angeles. One 2 or more days, the temperature will likely reach 80° or higher. Through April 10, there should be little or no rainfall.

During the April 2-7 timeframe, the temperature averaged 3° above normal in Los Angeles. Downtown Los Angeles saw three days at or above 80°: 80° on April 2, 83° on April 5, and 88° on April 6. Through April 8, Downtown Los Angeles had seen just a trace of rainfall.



The April 10-23, 2005 Ideas:

The overall idea of a springlike pattern locking into the East shortly before mid-month provides general background information for this forecast. At this point, the GFS ensembles are now strongly supporting the imminent arrival of a positive NAO.

• In the Northeast and Mid-Atlantic region, a strong cold front will likely arrive on Monday, April 11 with perhaps some showers. Some of those showers could end as snow showers across parts of central and upstate New York and central and northern New England. There is a slight chance that some of the frozen precipitation might make it into the Boston area. The morning of April 12 should be unseasonably cold. Boston and possibly New York City could see readings fall below 30°. Philadelphia should see a low temperature in the low 30s. By April 13, a slow warming trend should commence. During the April 16-17 period, the warmup could accelerate. The April 18-23 timeframe looks to be unseasonably warm and generally dry. Temperatures could again reach into the 70s as far north as southern New England on one or more days. 80° or above is possible on one or more days in Washington, DC and Philadelphia.

• Ahead of the strong cold front that will affect the East, temperatures in the Central Plains could spike to much above normal levels on April 10. Detroit will likely see readings close to 70° and Chicago should make it into the 70s. The evening of April 10 into April 11 could see some rain followed by cooler but not cold readings. April 15 should mark the beginning of a warmup that will likely see above normal readings during the April 18-23 timeframe.

• In the Central Plains, temperatures will likely run above normal through April 10. Both Omaha and Kansas City could see readings reach or exceed 70°. The April 11-13 period could see rainfall and somewhat cooler readings at Kansas City, with the wet period beginning about a day earlier in Omaha. April 15 could see the arrival of much above normal readings.

The dry start in eastern Texas should end. April 10-11 and then April 15-16 could see significant rainfall of 0.50” or more.

• The April 10-15 period will likely be cooler than normal with frequent showers in Seattle. April 10-11 could see more than 0.25” rain. April 13-14 could see some unseasonably cold readings with perhaps lows falling to or below 35° on at least one day. April 16-23 will likely be cooler and wetter than normal.

• After a cool weekend in Los Angeles, temperatures should again rise. April 11-16 should see above normal readings. Toward the end of that period, it is possible that mercury will break 80°. Very little if any precipitation is likely through April 16.

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