NATIONAL WEATHER SUMMARY

 

JULY 2011

 

1^st-9^th…The nation saw an active day on Independence Day as multiple weather features moved through the nation. In the Southwest, a plume of moisture associated with the remnants of Tropical Storm Arlene moved northward from Mexico. While rain persisted across most of Mexico, the system also created scattered showers from southern California and Arizona to Utah and Wyoming. Rainfall totals remained light, and only ranged less than a tenth of an inch. Elsewhere in the West, a ridge of high pressure remained the dominant weather feature for the West Coast. This brought another warm, sunny, and dry day from The Pacific Northwest to moves of California. In the East, a low pressure system that hovered over eastern Canada pushed a frontal boundary over the Great Lakes region. The system stretched from the Northeast, over New England, down the Ohio River Valley,and into the Midwest. It kicked up scattered showers and thunderstorms, but severe storms have not yet developed. Heaviest rainfall developed ahead of the front, over the Tennessee River Valley. A mid-day total of 1.30 inches was reported in Bentonville, Arkansas, while Glasgow, Kentucky saw a mid-day total of 1.23 inches of rain. In the Plains, flooding remained a concern in the North. Repeated rain showers have allowed for rivers to remain swollen across the Missouri River and surrounding tributaries. With high pressure over the region, temperatures remained in the 80s across the Upper Midwest and Northern and Central Plains. The Southern Plains saw another hot day with highs near 100 degrees.

The East Coast and Central U.S. saw multiple areas of wet weather on Wednesday, while the West Coast and Great Lakes saw mostly sunny skies. Low pressure over Quebec pushed a cold front into New York triggering heavy showers and thunderstorms. This system also brought moderate rainfall to most of Maine. Severe thunderstorm warnings are in effect for most of the Northeast. However, high pressure over the Great Lakes contributed to sunny and mild conditions. To the south, ample moisture pushed onshore kicked up strong storms across the Mid-Atlantic, Tennessee Valley, and Southeastern US. Strong winds have been reported in Boones, Virginia, which contributed to trees blown down. In addition, a tropical wave positioned over Cuba brought heavy showers to southern Florida. These storms are contributing to rainfall from a fifth of an inch to 0.8 inches. To the west, a low pressure system moved into the Northern Plains contributing to heavy downpours and strong winds extending into Colorado. 40 to 50 mph winds have been reported in Hermosa, South Dakota with the highest midday rainfall total in Buffalo, South Dakota at 1.51 inches. At the same time, low pressure located over Kansas brought moderate rainfall across the central Plains. Meanwhile, the Pacific Northwest, Intermountain West, and most of northern California currently have sunny skies. Fire weather advisories are in effect for the Washington-Oregon border. However, weak low pressure over the Southwest has kicked up isolated showers over Nevada and Utah.

The Eastern U.S. saw periods of heavy rain on Friday, as a front stalled over the East Coast. The system moved over the Eastern Valleys and into the Eastern Seaboard. The warm and humid air ahead of this system allowed for scattered showers and thunderstorms to develop from the Northeast to the Mid-Atlantic states. Some of these storms turned severe with heavy downpours and strong winds. Rainfall totals ranged around 2 inches, with up to 2.38 inches reported at Fort Eustis, Virginia. These heavy rain showers allowed for flooding to remain of concern across the e Valleys. Meanwhile in the South, a low pressure system over the eastern Gulf of Mexico pushed over the Southeast. Heaviest rainfall was reported in St. Petersburg, Florida, with a mid-day total of 2.81 inches. The system had a low, 10 percent, chance of tropical storm formation, but managed to create some more heavy downpours associated with strong storms over Florida and the Bahamas. To the west, a ridge of high pressure quickly filled in behind the front, bringing a short break of wet weather for the Northern Plains and Midwest. At the same time, a low pressure system in western Canada pushed a trough of low pressure off the Northern Rockies and into the Northern Plains early on Friday. This created a warm front over the Dakotas that triggered scattered showers throughout the day. Due to already swollen rivers, concerns with flooding returned to the region. Mid-day rainfall totals ranged from a quarter to a half of an inch across the region. In the Southwest, monsoon moisture allowed for a few more thunderstorms to pop up across the deserts. Flash flooding threatened northern Arizona, after heavy downpours developed.

The eastern U.S. saw multiple areas of active weather on Wednesday, while most of the western U.S. saw sunnier skies. A storm system moved off the Rockies into the Northern Plains and contributed to widespread showers and thunderstorms from Nebraska to Minnesota. Rain from this system has brought totals between a quarter of an inch to 2 inches with the highest rainfall total at 4.45 inches in Winfield, Kansas. To the East, low pressure systems have pushed a frontal boundary through the Ohio Valley, Mid-Atlantic, and Central Plains triggering heavy showers and thunderstorms from Oklahoma to Pennsylvania. This system brought cooler temperatures to the Ohio Valley and Mid-Atlantic states by about 10 degrees. Meanwhile, low pressure over Maine has pushed clouds and isolated showers to the Northeast. In the South, a tropical wave positioned on the coast of Alabama produced moderate to heavy showers on the Southeastern coast. Heat advisories are still in effect for the southeastern portion of the US with high temperatures near 100 and heat indices at 115 degrees.  To the west, low pressure spinning over the Pacific Northwest brought light showers, clouds, and cooler temperatures to the Intermountain West and most of the West Coast. Meanwhile, high pressure is dominating the Four Corners region contributing to sunny and hot conditions. Fire weather advisories are in effect for southern Nevada.

 

17-23^rd…The central U.S. remained hot, heavy rain persisted along the Gulf, and storms developed in the North on Monday. A strong ridge of high pressure over the center of the country continued to build. Flow around this system allowed for more hot and moist air to pour in from the South. This pushed high temperatures into the 100s across the Central and Southern Plains, with mid-day highs to near 100 as far north as South Dakota and Minnesota. High humidity associated with this system created dangerously hot conditions as heat indices reached between 110 and 120 degrees. Overnight lows were extremely high across the region, which did not offer relief from the heat. The airport at Minneapolis, Minnesota reported an overnight low of 81 degrees, while most of the Central US only dropped into the upper 70s overnight. In the East, a cold front draped along the Northern U.S., stretched from the Northeast, over New England, and into the Great Lakes. Scattered showers and thunderstorms developed along this frontal boundary, some of which have turned severe with large hail and strong winds. Golf ball size hail was reported in Arcadia, Wisconsin, while multiple trees and power lines were blown down across Michigan and Pennsylvania. In the South, a low pressure system developed over the Gulf of Mexico and brought periods of heavy rains and strong storms to the surrounding shores. Salt Point, Louisiana reported a mid-day total of 1.97 inches of rain and Cocoa Beach, Florida reported 1.67 inches of rain. In the Atlantic, Tropical Storm Bret continued moving northeastward and away from Florida and the Bahamas. The system maintained its strength as a tropical storms with maximum winds at 50 mph (45 knots).

The nation saw mostly sunny skies with a few areas of active weather on Wednesday, while hot weather persisted in the Eastern and Central US. A low pressure system spinning over the Northern Plains pushed a frontal boundary through northern Minnesota and the Great Lakes, which triggered heavy showers and thunderstorms. Heavy downpours and strong winds are associated with these storms with a tornado report in Karlstad, Minnesota. Rainfall totals associated with this system range from 0.15 inches to almost 3 inches, with the largest midday total in Grand Marais Airport, Minnesota at 2.96 inches. To the east, a low pressure system located over Canada pushed rain and clouds to northern Maine. At the same time, low pressure over the Mid-Atlantic states kicked up isolated showers across the Southeast.

In the South, high pressure spinning in the Gulf of Mexico pulled moisture onshore triggering scattered showers over southern Louisiana and eastern Texas. To the west, monsoon moisture produced patchy showers over the Southwest and low pressure in the Gulf of Alaska brought rain and clouds to the Pacific Northwest. Meanwhile, most of the Western US saw sunny skies with coastal fog in southern California. A ridge of high pressure remained stationary over the eastern half of the U.S. contributing to temperatures between 90 to over 100, with heat indices over 120 degrees. Heat advisories are in effect for most of the Eastern U.S.

The East Coast saw a record-breaking hot day on Friday, as a strong ridge of high pressure shifted eastward from the Plains. Due to high humidity associated with this system, it has brought a hot and muggy week to the Plains and Midwest. Now that this system has advanced eastward, the Central US has started to see a cool down. Daytime high temperatures reached into the 80s and 90s, about 10 to 20 degrees lower than highs seen earlier this week. Overnight lows across the Midwest reduced to the upper 60s and lower 70s, whereas lows for the week have been in the 80s. This placement of the ridge brought a hot and humid day to the Eastern Seaboard. Newark, New Jersey set a record maximum temperature of 106 degrees. The previous record maximum temperature was 101 degrees set in 1957. Also, a record maximum temperature of 102 degrees was set for New York City. The previous record maximum temperature was 98 degrees set in 1978. In the North, a cold front draped across the Great Lakes and U.S.-Canadian border. This kicked up scattered showers and thunderstorms, some of which have turned severe. Numerous trees and power lines have blown down from strong winds across northern Indiana. Periods of heavy rainfall have developed associated with these thunderstorms. A mid-day total of 3.00 inches was reported in Waukegan, Illinois. Out West, monsoon moisture moved into the Southwest from Mexico. This allowed for scattered thunderstorms to develop over eastern Arizona and most of New Mexico.

More unsettled weather activity developed in the east of the Continental Divide Wednesday. In the Midwest, numerous showers, periods of heavy rainfall, and thunderstorms developed to the north of a warm front that extended from the Upper Mississippi Valley through the Central Appalachians. Ample moisture availability and daytime heating increased instability through the afternoon and lead to a slight risk of severe thunderstorm development from northeastern Wyoming, South Dakota, Nebraska across the Upper Mississippi Valley. Severe storms in these states and regions had the potential to produce damaging wind, hail, and perhaps a few tornadoes. Meanwhile, the moist and unstable airmass over the Southeast and Central Gulf Coast fueled more areas of showers, periods of heavy rainfall, and clusters of thunderstorms. Elsewhere, showery weather int he Northeast tapered off in the Northeast due to an exiting low pressure system located off the New England coast. Finally, hot temperatures and scorching heat index values remained over the Southern and Plains and the Lower and Mid-Mississippi Valleys. Various Heat Advisories and Excessive Heat Warnings remained in effect for parts of these regions. This combination of hot temperatures and high humidity levels created a dangerous heat situation. In the West, clouds spread across the Pacific Northwest as a trough of low pressure affecting the coast inched eastward. Onshore flow along the Coast kept daytime highs in much of the Pacific Northwest and California at below normal values. Meanwhile, chances of scattered to numerous thunderstorms persisted in areas of the Four Corners due to the continued moist and unstable environment over this region. Thus, a handful of Flood Watches remained in effect for areas of western, central, and northern New Mexico.

The nation saw plenty areas of active weather on Friday, while the West Coast and Pacific Northwest saw mostly sunny skies. A low pressure system spinning over Quebec pushed a frontal boundary southward through the Northern US. The front extended from the Northeast to the Central Plains and triggered showers and thunderstorms. Rainfall totals associated with these storms ranged from a half of an inch to over two inches, with the highest mid-day rainfall total reported in Lamoni, Iowa at 2.18 inches.

To the south, Tropical Storm Don approached the southeastern coast of Texas and brought heavy showers and strong winds to the region. The rotation of this system has pushed warm, moist air from the Gulf of Mexico onshore, which triggered scattered showers across the South and Tennessee Valley. Wind gusts associated with these storms ranged from 30 to 50 mph. Meanwhile, a ridge of high pressure over Florida continued to bring hot and humid temperatures to most of the Eastern US. Temperatures reached over 100 degrees, with heat indices between 110 and 120 degrees.

To the west, monsoon moisture in the Southeast brought scattered showers to the Four Corners region and Central Rockies. This moisture extended to central California and Nevada, which kicked up additional showers and thunderstorms at higher elevations. Meanwhile, a ridge of high pressure over the West Coast continued to bring sunny and warm conditions to the Pacific Northwest, Intermountain West, and Northern Rockies.

Jim G. Munley, jr.
http://www.jimmunleywx.com