NATIONAL WEATHER SUMMARY

OCTOBER 2010

 

1^st-9^th…The weather pattern shifted on Friday, producing changing weather for many areas. The front that lingered over the eastern seaboard and brought torrential rain to the area the past several days finally moved eastward, allowing drenched areas to dry out. The Southeast Coast was dry for much of the day, but Flood Warnings were still posted for parts of North Carolina and Virginia. The heaviest precipitation fell in New England as the northern part of the aforementioned front remained draped over the region. Flood Watches and Warnings were posted from Maryland through Maine as rivers and lakes were swollen with the excess water.  Red Flag Warnings remained in parts of the Southeast from eastern Arkansas through Florida as low humidity combined with breezy conditions to create dangerous fire weather.  Tropical moisture streamed into Southern California and produced isolated showers and thunderstorms. This activity was expected to decrease later in the day and into Saturday.  The Northeast rose into the 60s, while the Southeast saw temperatures in the 70s and 80s. The Southern Plains rose into the 70s, 80,s and some 90s, while the Southwest saw temperatures in the 90s and 100s.
More stormy weather developed across the West on Wednesday as a cold low pressure system remained nearly stationary over southern California. The low continued to produce scattered showers and thunderstorms over portions of southern California, the Great Basin, and the Four Corners. Stronger thunderstorms with locally heavy rainfall developed over western Arizona and southern Utah. This translated into possible flash flooding across north-central Arizona and southern Utah, particularly in slot canyons, normally dry washes, and vulnerable drainage locations. Severe weather was also possible in Arizona, southeastern Utah, southwestern Colorado, and western New Mexico with strong gusty winds, severe hail, and brief tornadoes. As of this afternoon, there were a handful of tornado and damage reports from two tornadic storms in Coconino County, Arizona. Numerous events of quarter to hen egg sized hail (1.00 to 2.00 inches in diameter) were also reported from central Arizona through southern Utah. Meanwhile, in the East, damp weather continued over the northeastern corner of the nation as a low pressure system located off the Mid-Atlantic Coast finally lifted to the northeast. Wrap-around moisture associated with this system ushered Atlantic moisture across New England and the Northeast, providing a steady flow of rain in New England, upstate New York, western Pennsylvania, and West Virginia. Locally heavy rainfall created areas of urban and poor drainage flooding, especially across eastern Massachusetts and Rhode Island. Finally, calmer and drier weather conditions developed in the the Central U.S. as high pressure moved into the Northern Plains behind a dry cold front located over the eastern Midwest. In the Southeast, dry fuel moisture conditions combined with critically low relative humidity levels of about 18 to 25 percent and northwest winds to create dangerous fire weather conditions across Alabama, Georgia, and Florida.
Relatively benign weather continued in the country on Friday as many areas experienced pleasant weather. The most active weather occurred in the West as a low pressure system moved through the Rockies. This system produced scattered rain in the area, but this activity decreased as the day progressed. Cold mornings in parts of New Mexico and Colorado produced Freeze Watches that are further evidence that autumn has come. A high pressure system over the Mississippi Valley continued to produce dry conditions and clear skies through much of the East. New England remained dry, but a northwest breeze was quite strong in the area. In the tropics, Hurricane Otto spun well east of the Bahamas and was not expected to impact any major landmasses. Instead, it produced sustained heavy rain and thunderstorms throughout Puerto Rico. The Northeast rose into the 70s and 80s, while the Southeast saw temperatures in the 70s, 80s, and some 90s.

10^th-16^th…Scattered showers and thunderstorms developed near a cold front that pushed eastward through the eastern Midwest on Wednesday. The front became stretched from Michigan through Arkansas by the afternoon. Increased cloud cover and precipitation due to the cold front combined with a low pressure trough over the Upper Mississippi Valley marked the end of unseasonably warm, summer-like weather over the region. In the south, deep tropical moisture spread across southern Florida due to Hurricane Paula, located about 55 miles southwest of the western tip of Cuba. Rich moisture over the region fueled scattered showers and thunderstorms with periods of heavy rainfall across the Florida Straits. Meanwhile, mostly clear and calm conditions continued over the West as high pressure and offshore winds remained the dominant weather features of the region. The system brought another unseasonably warm and dry day to California and the southwestern deserts. The eastern and southern regions of the San Francisco Bay Area remained under Excessive Heat Warnings through the afternoon.
A Nor'easter brought heavy precipitation to the extreme Northeast on Friday. The system developed northeast of the Great Lakes and counter-clockwise rotation around the system pulled abundant moisture in from the Atlantic Ocean. This system created periods of heavy rainfall from New York to Maine, with heaviest rainfall reported across Vermont, New Hampshire, and Maine. Springfield, Vermont reported 3.83 inches of rain, while Portland, Maine reported 3.29 inches. Strong winds accompanied this system with wind gusts up to 45 mph across much of Maine. Most of New England and the Great Lakes saw cloudy skies, but precipitation did not develop. Behind this system in the Plains and Southeast, a strong ridge of high pressure dominated. This allowed for more cool and dry air to pour in from central Canada. This brought some windy conditions at the surface with gusts between 20-30 mph. Gusts up to 29 mph were reported in Atlanta, Georgia. Strong winds in combination with low relative humidity at the surface allow for favorable fire weather conditions. Thus, fires remain of concern across the Southeast and Gulf states. In the West, a ridge of high pressure started to shove eastward as a trough dips through the Pacific Northwest. This allowed for seasonable temperatures to return to the West Coast, with a few patchy clouds, but precipitation has not developed.

17^th-23^rd…The Eastern half of the country saw mild weather on Monday, while rainy conditions persisted in the West. A low pressure system sat over southern California and pushed abundant moisture onshore from the Pacific Ocean, due to its counter-clockwise rotation. The system allowed for moisture to reach well into the Rockies, which created additional strength for the system. Thus, scattered showers developed over southern California, the Great Basin, and the Southwestern U,S. Thunderstorms and severe weather have not yet developed and rainfall totals remained less than a half of an inch in most areas. Delta, Utah reported 0.32 inches and Grand Canyon, Arizona reported 0.16 inches. Also in the West, a ridge of high pressure built into the north and brought drier conditions to the Pacific Northwest and northern California. Back East, a frontal boundary stalled over the Midwest and New England, and divided the East into two halves. North of this system remained cool, as air from Canada poured in, while the South remained dry and warm. A few scattered showers developed along the front. Rainfall totals remained less than a tenth of an inch in most areas along the Ohio River Valley to Pennsylvania and New York. Warm air across the Southeast and Gulf states allowed for temperatures to remain a few degrees above seasonable with highs in the 80s. These conditions allowed for fires to remain of concern across Georgia and Florida. The Plains saw mild weather on Monday, due to a ridge of high pressure covering the Central US. This kicked up a few scattered clouds with highs in the 50s in the North and in the 80s in the South.

A large low pressure system developed in the western Plains Saturday and provided much of the active weather in the country. This low pressure system pulled significant moisture northward into the Southern Plains, instigating areas of heavy rain and thunderstorms from central Texas through eastern Oklahoma. At least one of these thunderstorms produced large, damaging hail in central Texas. Farther to the north, moisture streamed into the Upper Mississippi Valley and Upper Midwest, producing light to moderate rain in the region. Meanwhile, a Pacific storm approached the West Coast and was on the verge of producing a tremendous amount of rain and high elevation snow through the Northwest and Northern California. In advance of this significant storm, scattered rain developed in these areas and farther inland through the Intermountain West. A high pressure system along the East Coast provided dry weather along the eastern seaboard. The Northeast rose into the 40s and 50s, while the Southeast saw temperatures in the 70s and 80s. The Southern Plains rose into the 70s, 80s, and even some 90s, while the Northern Plains saw temperatures in the 40s and 50s. The Northwest rose into the 40s, 50s, and 60s.

 

24^th-31^st…Multiple areas of the nation saw active weather on Monday. A trough of low pressure developed over the Lower Mississippi River Valley and continued eastward into the Mid-Atlantic states. The system pulled in ample moisture from the Gulf of Mexico, which allowed for scattered showers and thunderstorms to develop. Some of these storms turned severe with strong winds, hail, and heavy rain. Hail the size of baseballs lasted 3 minutes in Allendale, South Carolina, while multiple trees were blown down across Tennessee and North Carolina. Rainfall totals ranged from 1-2 inches in most places, but Huntsville, Alabama reported 3.08 inches of rain. In the North, a weak front developed over the Great Lakes and Northeast as a low pressure system moved through the Plains. The warm front in the East kicked up cloudy skies with a few scattered showers. Rainfall totals across Pennsylvania and New York ranged from a tenth to a quarter of an inch. Another front extended southward from the center of the low pressure system and swept through the Central Plains into the Central Rockies. Rainfall totals from this system remained light, but strong wind gusts ranged from 20-35 mph. This system also brought cool air into the North-Central US. Highs only reached into the 30s and 40s across the High Plains and the Dakotas. Out West, rainy conditions persisted in the Pacific Northwest, while California saw a break in wet weather. A low pressure system and associated cold front moved approached from the west, which brought in more moisture with cloudy skies and scattered showers.

A record-challenging storm was clobbering the Plains and Midwest with high winds, heavy rain, severe thunderstorms and even some snow Tuesday afternoon. The thunderstorms were rolled eastward as a squall line through the eastern Great Lakes and the Ohio and Tennessee valleys. Meanwhile, soaking, windswept rain continued over the western Great Lakes area and snow was creeping in over North Dakota as temperatures fell into the 30s. The storm has had a history of downing scores of trees and power lines over the Plains and Midwest. Meanwhile, warmth was holding over much of the eastern third of the nation, ahead of the cold front associated with the storm system. A large backwash from the Plains storm continued to assist with areas of snow and snow showers over the central and northern Rockies. Locally strong winds were still being felt in through some of the passes as far southwest as the Sierra Nevada early in the morning. Rain and mountain snow was slowly diminishing over the coastal Northwest as high pressure was preparing to build inland from the Pacific.

The monstrous storm of the Midwest continued to provide more unsettled weather conditions over the Midwest and eastern U.S. on Wednesday. Breezy to very strong wind conditions with sustained winds between 25 and 50 mph and gusts approaching and exceeding 50 mph kept areas from the Dakotas and Nebraska through Michigan and northern Ohio under High Wind Warnings and Wind Advisories. Meanwhile, bitter cold air continued to filter into the Midwest, yielding to lower daytime highs throughout the region and more snowfall in North Dakota. The combination of blustery northwest winds with persistent snow created chances of whiteout conditions in areas of North Dakota as visibilities dropped down to 1 to 3 miles and below a quarter mile in open areas. Thus, much of North Dakota remained under a Blizzard Warning through this evening. To the south, the combination of strong winds and dry conditions with relative humidity levels below 20 percent in the Central Plains and Mid-Mississippi Valley caused areas from eastern Colorado through southern Illinois to be placed under Red Flag Warnings. Finally, the combination of clearer skies and lighter winds in portions of the Central and Southern Plains set the stage for below freezing late evening and nighttime temperatures. Thus, these areas remained under various Freeze and Warnings and Watches, as well as Frost Advisories. Meanwhile, in the East, a frontal boundary associated with this system stalled over much of the Eastern Seaboard and produced numerous showers, thunderstorms, and a couple of areas of severe weather activity from Maine through the Mid-Atlantic and across the Central Gulf Coast States. There was a slight chance of severe weather development from the Mid-Atlantic Coast through the Central Gulf Coast States with damaging wind remaining the primary threat, although a tornado or two remained possible. Thus far, two episodes of strong winds were reported in Randolph County, Alabama and caused damage to trees and structures. Behind the activity of the Central and Eastern U.S., calm weather conditions prevailed across much of the West through Wednesday afternoon due to high pressure over the Great Basin. Strong offshore winds associated with this system triggered a High Wind Warning and Wind Advisory near the southern California Coast.

A Pacific low pressure system continued spreading wet weather over the West Coast on Friday. The system dipped southward and hovered just offshore of California, and pushes a cold front onshore that triggered scattered showers over the state. Northern California saw more continual rainfall, while the Pacific Northwest and southern California saw scattered showers throughout the day. Rainfall totals across Oregon and Washington ranged from a tenth to a quarter of an inch, while Santa Rosa, California reported 0.56 inches of rain. Higher elevations of the Sierra Nevadas and Cascades saw periods of light snow. Snow levels in the Sierras dropped from 8,000 feet to 6,500 feet with snowfall accumulation less than an inch. Elsewhere, a ridge of high pressure brought a mild Autumn day to the rest of the US. High pressure allowed for sunny skies and dry conditions from the Plains to the East Coast. Cool air poured in ahead of this system, allowing for the Upper Midwest, Great Lakes, and Northeast to see highs in the lower 50s. Overnight lows dipped to near freezing temperatures across much of the Eastern US. The Tennessee Valley reached lows in the upper 30s. The Southern Plains and Southeast, however, remained in the 70s and 80s.

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