http://www.weather.com/forecast/national/news/three-big-changes-next-week-gulf-moisture-southwest-dry-temperature-flip-flop
Three big changes in the weather are expected this week
across the U.S., and many will appreciate the difference a week can make. Moisture
from the Gulf of Mexico is expected to bring rain to parts of the South, while
the Southwest will finally see drier conditions. Temperatures will also
flip-flop. The West will experience temperatures closer to average for this
time of year and the Northeast and Midwest will feel a warming trend after the
recent cold shot.
Tropical Moisture Surges North
This map is intended to show areas where the heaviest rainfall
potential exists through next weekend. Locally heavier rain amounts may occur. A
pattern shift is expected by midweek with moisture returning to the Gulf Coast.
Moist southeasterly winds will also interact with an area of low pressure aloft
coming out of the Southwest to produce heavy rainfall in parts of the southern
Plains later this week. This includes areas from eastern New Mexico to Texas
and Oklahoma.
Wet conditions will persist through the end of the week and
into the weekend, and it may be windy at times. Rain may also spread east into
Louisiana, Arkansas, as well as parts of lower Mississippi Valley.
The rain will be welcome in many areas, as drought
conditions have developed over the summer in much of Texas as well as
Louisiana, Arkansas, Oklahoma, Mississippi, Alabama and the Florida Panhandle. Some
spots are now in extreme and exceptional drought, even after seeing record
rainfall during April, May and June. Wildfires have also developed due to the
persistent hot and dry conditions in portions of the Plains. The rainfall late
this week could help firefighters and bring down the fire risk.
A few examples of the recent dryness: Houston is almost 5
inches below average in terms of rainfall since Sept. 1, as just over 2.5
inches has fallen. San Antonio has received less than half of their average expected
rainfall since Sept. 1. Dallas has only measured a trace of rainfall so far in
October. Despite the drought relief, the rain could be locally heavy, resulting
in flash flooding.
There is also the chance that a low pressure system, perhaps
with tropical characteristics, may develop in the Gulf of Mexico in the week
ahead or this weekend.
Even without tropical cyclone development, the threat of
heavy rain and thunderstorms is still expected due to the abundant moisture
pushing north.
Temperature Flip-Flops
A break from the record heat has arrived for much of the
West and southern Plains. In addition, after a shot of cold air this weekend
and into Monday in parts of the East, warmer temperatures will return. The
coldest air of the season so far made its way across the Midwest and into parts
of the East this weekend. Many areas saw their first frost and freeze with lows
dropping into the 30s as far south as North Carolina and north Georgia. Lows
tumbled into the 20s in parts of northern Minnesota and Michigan on Saturday.
Parts of the Ohio Valley and northern New England saw lows in the 20s Sunday
morning. Some areas from the northern Great Lakes into the interior Northeast
have also seen their first snow of the season this weekend.
The chilly conditions will just be a distant memory by
mid-to-late week across the East as highs and lows will rebound quickly to near
and even above average. High pressure will slide eastward this week and as it
does, a more southerly flow will develop, allowing warmer temperatures to
return. High temperatures will climb back into the 70s by Tuesday or Wednesday
in the Ohio Valley, Southeast and Mid-Atlantic. Meanwhile, much of the West and
southern Plains saw record high temperatures this last week courtesy of a ridge
of high pressure. A few cities saw their hottest temperature ever recorded in
October including Little Rock, Arkansas, which reached 98 degrees on Oct. 15,
and Colorado Springs, which tied its October record of 87 degrees on Oct. 11. An
all-time record high temperature for any month of the year was set in
Camarillo, California, on Oct. 9 when the mercury climbed to 108 degrees. Las
Vegas crushed its record for number of days with a low in the 70s for October,
with nine of them through Oct. 15.
The average temperature for Los Angeles month-to-date in
October is more than 7 degrees above average and San Diego is more than 8
degrees above average. Two areas of low pressure will move through the West
through Wednesday, allowing temperatures to take a dip in most areas, so the
record-breaking trend has come to an end. After the storm systems move east
temperatures will warm but are expected to remain closer to average for much of
the week ahead compared with this past week.
Drier in the Southwest
After flash flooding in portions of the Southwest this past
week and this weekend a change is on the horizon. Some of the worst flooding
was seen in California, where mudslides stranded motorists. The
upper-atmospheric low that has plagued the region for two weeks has finally
begun to push eastward. Another low pressure system is now bringing another
round of rain to the West through early this week. As the second system pushes
east into the Plains, high pressure will bring a break from the rain by midweek
to most of the Southwest. Portions of Arizona and New Mexico may not see the
dry conditions until the end of the week. By late in the week, sunshine will
become more widespread across the Southwest.
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