NATIONAL WEATHER SUMMARY

 

SEPTEMBER 2012

 

1^st-8^th…Wet weather persisted for the East on Labor Day as the remnants of Isaac slowly into the Ohio River Valley. The system merged with a frontal boundary to the north, and created heavy rain showers from the Ohio and Tennessee Valleys, through the Mid-Atlantic states. Heaviest rainfall in the region was reported at Wilmington, Ohio with a mid-day total of 1.24 inches of rain. Some areas of the Ohio River and surrounding tributaries saw flooding as the remnants of Isaac slowly moved eastward throughout the day. There was a slight risk of severe weather development across Alabama and Mississippi as the southern side of Isaac pulled more moisture onshore. This kicked up moderate to heavy showers and thunderstorms with strong winds and heavy rains. Heaviest rainfall was reported in Birmingham, Alabama with a mid-day total of 2.60 inches. Strong winds with gusts from 30 to 40 mph were reported across the Eastern Valleys. Behind this system, a ridge of high pressure brought hot and sunny conditions to the Central and Southern Plains. Heat advisories were issued across Oklahoma into Louisiana as high temperatures surpassed 100 degrees. In the North, another cold front dropped in from Canada and pushed through the Northern Plains and Upper Midwest. This triggered scattered showers and thunderstorms, some of which turned severe, while it also pulled in cooler air from the Canada. Out West, high pressure over the West Coast maintained sunny and dry conditions. High fire danger remained in effect for the Northern Rockies. The Southwest, however, saw more scattered thunderstorm activity as monsoonal moisture lingered over the region.

Heavy rain and thunderstorms developed in the Northeast as a low pressure system moved through New England and an associated cold front extended southwestward across the Upper Mid-Atlantic. Rainfall totals of up to 2.85 inches were reported in the Northeast this afternoon, while lighter and more scattered precipitation developed in the Upper Mid-Atlantic. To the south, an area of low pressure located along the coast of the western Florida Panhandle kicked up rain near the northeastern Gulf Coast. Meanwhile, in the Midwest, a progressive cold front and waves of low pressure pushed across the Midwest this afternoon and brought showers and thunderstorms to areas from the Upper Great Lakes through the Mid-Mississippi Valley and the Central Plains. Additional rain and thunderstorms formed in areas of Illinois and Indiana as impulses reached across the Ohio Valley. Areas from the Great Lakes southward into parts of the Ohio, Mid-Mississippi and Tennessee Valleys remained at slight risk of severe thunderstorms with hail, severe wind, and possible tornadoes through this evening. Thunderstorms with severe wind and hail development are also possible in areas of the Southern Plains through tonight due to energy ejecting out of Colorado. Elsewhere in the East, hot and humid conditions continued in the Deep South as daytime highs climbed into the triple digits and heat index values reached to 110 degrees. In the West, fire weather conditions continued in areas of northern California, northwestern Nevada, southeastern Idaho, southern Wyoming and north-central Utah. Elsewhere, scattered monsoonal moisture led to areas of scattered showers and thunderstorms in the Southwest.

 

9^th-15^th…A relatively quiet day took place in the country Monday as no major storm systems formed. The heaviest rain actually occurred over Florida as a stationary front stalled over the state. This front produced scattered showers and thunderstorms mainly over the southern half of Florida and represented a majority of the precipitation in the country. To the north, a large high pressure system moved from the eastern Plains to the Ohio Valley and provided widespread dry conditions through the eastern half of the country. Some showers did move into the Northwest, ending the record breaking dry streak the city has experienced this summer. Some monsoon moisture also crept into the Southwest and instigated a few thunderstorms mainly in the afternoon. The Northeast rose into the 60s and 70s, while the Southeast saw temperatures in the 70s and 80s. The Plains rose into the 80s and some 90s, while the Southwest saw similar temperatures.

Wet weather activity continued across the Four Corners on Wednesday as ample monsoonal moisture remained over the region with several weather disturbances. This setup translated into showers, periods of heavy rainfall and thunderstorms during the morning and afternoon. Flood Advisories and Flash Flood Watches and Warnings were issued for areas of southern Utah and southern Colorado in response to today and this week's significant rainfall. In the afternoon, precipitation, winds, and thunderstorm activity began to pick up across eastern Colorado, New Mexico, and western Texas as a cold front dropped across Colorado and the Southern High Plains. A Winter Weather Advisory was issued for elevations above 11,000 feet in the southern and northern Sangre de Cristo Mountains, the western Mosquito Range, and eastern Sawatch Mountains in anticipation of potential snowfall associated with this storm. Total snow accumulations were expected to range between 4 and 8 inches today with local 10 inch snow amounts possible at the highest elevations. Meanwhile, showers and thunderstorms also developed from the Central High Plains into the Upper Midwest through the afternoon as the aforementioned cold front reached through the Central Plains and into the Upper Great Lakes. In addition to unsettled conditions, cooler daytime highs were anticipated behind this cold front. To the east, high pressure remained the dominant weather feature of the rest of the East with generally quiet weather conditions. Breezy winds associated with this system ushered moisture across the Florida Peninsula and the Gulf Coast. This translated into showers the peninsula and showers with chances of thunderstorms along the Gulf Coast as a frontal boundary stalled from the western Gulf Coast through the Gulf of Mexico.

 

16^th-22^nd…Heavy rain drenched the South and East, while dry weather covered the western half of the nation. Weekly precipitation totaled 4 inches or more in parts of the Appalachians. Cool weather trailed the rain, holding weekly temperatures generally 5 to 10F below normal in the Midwest. The season’s first widespread freeze occurred across North Dakota and eastern South Dakota on September 22, followed the next day by a freeze throughout the upper Midwest as far south as Iowa. Midwestern rainfall was mostly light and confined to the Ohio Valley and the Great Lakes region. Little or no rain fell on the Plains, where some producers continued to await improved soil. Elsewhere, warm, dry weather prevailed in the West, except for cool conditions along the Pacific Coast. Heat built across the West and persisted for most of the week. From September 19-21, Yakima, WA (90F, 90F, and 89F), posted a trio of daily-record highs. Pendleton, OR, attained 94F on September 19, setting a daily-record high. Farther south, Yuma, AZ (108F), collected a daily-record high for September 20. Late in the week, hot weather returned to the southern Plains, where McAlester, OK (99F), notched a daily-record high for September 21. In contrast, chilly air settled across the north-central U.S., where record-setting lows for September 18 included 20F in International Falls, MN, and 31F in Sisseton, SD. A day later, records for September 19 dipped to 28F in Rhinelander, WI, and 37F in Dubuque, IA. Even colder air arrived at week’s end, and by the morning of September 23, readings of 25F in both Sioux City, IA, and Sisseton were among a parade of daily-record lows. With a low of 31F on September 23, La Crosse, WI, tied with 1974 for its second-earliest freeze on record behind September 14, 1923. The normal date of La Crosse’s first autumn freeze is October 14. Nearly all of the week’s precipitation highlights occurred across the East on September 17-18. In Tennessee, Knoxville received a September 17-18 total of 6.10 inches, highlighted by daily-record amounts on both days (2.94 and 3.16 inches, respectively). Other daily-record totals for September 17 included 3.09 inches in Muscle Shoals, AL; 2.95 inches in Tupelo, MS; and 2.37 inches in Evansville,

IN. The following day, record-setting amounts for September 18 reached 5.41 inches in Mt. Pocono, PA; 3.65 inches in Chattanooga, TN; 3.28 inches in Asheville, NC; and 3.19 inches in Albany, NY. By the night of September 21-22, the season’s first snowflakes were noted in portions of the upper Great Lakes region. On September 22, Wisconsin Rapids, WI, reported a trace of snow, while Duluth, MN (0.1 inch), tallied a daily-record amount. Meanwhile, long-running dry spells persisted across the northern High Plains and northern Intermountain West. In Sheridan, WY, no measurable rain fell from August 11 - September 22. Sheridan’s 43-day dry spell, which continued through week’s end, was its second-longest such streak on record behind a 46-day stretch without measurable precipitation from December 5, 2002 - January 19, 2003. Powerful, early-autumn storms pounded south-central Alaska, resulting in high winds, heavy precipitation, and flooding. Weekly rainfall totaled 13.92 inches in Valdez, aided by daily-record amounts on September 16, 19, and 20

(3.86, 2.59, and 4.27 inches, respectively). Valdez also set a monthly record with 21.95 inches through the 23rd. Prior to this year, the wettest September in Valdez had occurred in 1982, with 16.69 inches, while the wettest month had been November 1976, with 20.59 inches. Record flooding developed along the Resurrection River, where the crest at Exit Glacier Bridge exceeded the October 2006 high-water mark by nearly 1½ inches. Significant flooding was also reported in the Susitna Valley. Wind gusts in Palmer were clocked to 56 mph on September 15-16 and 54 mph on September 18-19. On the Harding Icefield, the two storms produced gusts to 96 and 91 mph, respectively. High winds even reached interior Alaska, where Delta Junction recorded a gust to 71 mph during the September 15-16 storm. Warmth accompanied the second storm, with daily-record highs reported in locations such as Delta Junction (66F on

September 19) and Northway (70°F on September 20). Farther south, most of Hawaii continued to experience drierthan-normal weather, perpetuating drought conditions across more than half of the state. On the Big Island, September 1-22 rainfall in Hilo totaled just 2.99 inches (42 percent of normal).

 

23^rd-30^th…Heavy rains continued across Texas on Saturday, while showers and thunderstorms moved into the Carolinas. A low pressure system strengthened as it moved over Texas and spread tropical moisture across the state. At the same time, the system pulled moisture in from the Gulf of Mexico, which kicked up heavy rainfall across most of central and northern Texas. The system moved eastward throughout the day and approached the Lower Mississippi River Valley. Heaviest rainfall was reported in Abilene, Texas with a mid-day total of 3.84 inches of rain. Thus, flash flood advisories were issues throughout the region. Strong winds also accompanied this strong low pressure system with gusts from 40 to 50 mph across parts of Texas and the Lower Mississippi River Valley. Meanwhile to the east, a low pressure system over the Northeast pulled northeastward and into far eastern Canada. The system pushed a cold front offshore, which allowed for showers and thunderstorms to diminish across New England. However, rain showers persisted for parts of Maine, as well as along the southern side of the front as it moved into the Carolinas and the Southeast. Heaviest rainfall associated with this frontal boundary was reported in Burlington, North Carolina with a mid-day total of 1.17 inches of rain. This system has a history of producing strong and damaging winds, but severe storms have not developed. Out West, a cold front dropped into the Pacific Northwest from British Columbia and brought cooler temperatures and partly cloudy skies. High pressure built over the rest of the West Coast and created a hot and dry day. Fire danger increased for most of California.

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