STATE COLLEGE, Pa. — AccuWeather has issued a summer outlook for the U.S. every year, focusing on the major highlights of the season.
Most areas from the Mississippi Valley to the mid-Atlantic coast will have more days with rain and near-normal temperatures this summer, while heat and drought build over much of the West.
Many areas in the Eastern states will have good growing conditions with lower cooling bills for the Midwest. Lower temperatures in much of the Mississippi Valley and the East should result in a lower-than-average number of tornadoes for the year. The weather conditions in the West will be ripe for wildfires, and a lack of water could become a serious concern for agriculture and some communities.
An atmospheric road block will allow a southward dip in the jet stream centered over the eastern half of the nation and a compensating northward bulge in the jet in the western half during much of the summer. (The jet stream is a ribbon of strong winds high in the atmosphere that guides weather systems along. During the summer, it often marks the dividing line between hot air and relatively cooler air).
Conditions will change over time in parts of the nation.
Following are some of the highlights of the summer grouped into weather regions.
Abundant sunshine for New England, New York State
During the first part of the summer, a path frequently taken by thunderstorms is likely to set up from the Great Lakes to the lower mid-Atlantic. This will leave a zone of largely storm-free conditions and warmth by way of plentiful sunny days farther north.
The warmest and driest part of the summer from upstate New York to interior New England is likely to be June into part of July.
According to Paul Pastelok, head of the AccuWeather.com Long-Range Forecast Department, “This will not finish as a top-10 summer for heat in the Northeast, but there can be a few episodes of heat.”
In the end, temperatures are expected to average only slightly above normal for the three-month period spanning June, July and August.
During the second half of the summer, the pattern will begin to change. Moisture from the Gulf and the Atlantic are likely to come into play, allowing two things. One would be more liberally spread shower and thunderstorm activity, which would limit temperature extremes. The second would open the door for impact from one or more tropical systems.
AccuWeather.com will release its 2013 Hurricane Season Forecast May 15.
Frequent Rain from the Great Lakes to the South
With the exception of the Florida Peninsula, no widespread areas of drought are anticipated from the Upper Midwest to the South, including the lower part of the mid-Atlantic.
AccuWeather.com meteorologists expect a higher frequency of showers and thunderstorms from Minnesota, Wisconsin and Michigan to Louisiana, Georgia, Pennsylvania and New Jersey, which in turn, will keep seasonal temperature averages close to normal, rather than much above normal.
Crops in most areas should have plenty of moisture, but in some cases conditions could be less than ideal because of persistent wetness. Flooding problems that developed in part of the area during the spring could continue or expand to new locations into the first part of the summer. Parts of the middle-Atlantic Coast that were teetering on abnormally dry conditions from the spring are likely to trend wetter.
A prevailing northwest flow associated with the jet stream will raise the risk of complexes of severe thunderstorms. Sometimes these will swing from the Upper Midwest to the mid-Atlantic, and other occasions the complexes could turn more toward the Ohio and Tennessee valleys and into the Deep South. The greatest threats would be from damaging wind gusts, hail and flash flooding.
A slight pattern change is likely later in the season. Somewhat less frequent rainfall is likely during the second half of the summer over the Midwest, but not to the point of returning widespread drought.
Rainfall during part of the spring over the Florida Peninsula will only help in the very short-term. Until the pattern shifts a bit later on, drought conditions continuing over the Peninsula will result in an elevated brush fire threat, and concerns for agriculture ranging from citrus crops and vegetables to livestock grazing lands through much of June.
In the Southern states, it is possible the northwest flow of air could be disrupted long enough during the first part of the summer for impact from a tropical system.
Later in the summer, the frequency of storms from the northwest will diminish with a more typical flow of moisture from the Gulf of Mexico and the Atlantic setting up over the South. Not only would this bring rainfall to the Florida Peninsula and continue thunderstorm activity in the South in general, but it would increase the chance for direct impact from one or more tropical systems from the central Gulf Coast through the Atlantic Coast.
Drought worsens, expands in the West
As much of the eastern half of the nation has cooler and wetter conditions relative to last summer, the West will bear the brunt of this summer’s drought and heat.
“The core of drought and heat will build west of the Continental Divide to California during the first part of the summer, then will expand northward as the season progresses,” Pastelok said.
A lack of snowfall this past winter and a lack of rain this summer, could lead to serious water resource problems.
While drought, heat and wildfire issues are expected to be far-reaching in the West as the summer progresses, the heavily populated and major agricultural state of California could be at the center of drought-related issues ranging from water problems to wildfires. Some water for agriculture use was already being cut back to start the spring.
The monsoon is forecast to become active from west Texas to the California and southern Nevada deserts beginning during the middle and latter part of the summer. However, farther north, the moisture supply will be very limited.
Many of the thunderstorms will have little or no rainfall, especially farther away from the flow of tropical moisture from Mexico. When combined with the expected heat and dryness, an above-average wildfire season is likely. Fires could be just as much of a problem in Washington, Idaho and Montana as they are in California, Arizona and New Mexico.
“The Northwest will trend drier and warmer much faster, when compared to last summer,” Pastelok said.
Great Plains, Texas caught in the middle
A very challenging area to forecast for this summer is the swath from Texas to North Dakota.
Late-winter and early spring storms have delivered moisture from the northern and central Rockies to part of the southern Plains.
Early this summer, like an echoing effect from the spring, rounds of showers and thunderstorms are projected to be more frequent than last summer from the Dakotas to eastern parts of the southern Plains and perhaps part of northeastern Texas.
However, heat and dryness could build eastward later in the summer throughout the Plains.
“If there is going to be impact in Texas from a tropical system during June, July and August, it would probably be June rather than August,” Pastelok said.
A large area of high pressure is likely to get so strong in the West that its influence would tend to keep tropical systems away from the northwestern shores of the Gulf of Mexico.
The weather patterns suggested in this article represent a greatly simplified version of what is expected to unfold. Effects at the local level are beyond the scope of this analysis. Regional and sub-regional impact stories will follow on AccuWeather.com.
Posted May 2, 2013