Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
355 AM EDT Wed Jun 20 2018
Valid 12Z Wed Jun 20 2018 - 12Z Fri Jun 22 2018
...Flash flooding threats exist along the Texas coast as well as over the
Middle Mississippi Valley...
...Record warm minimum temperatures possible across the southeastern U.S.
and Pacific Northwest...
...Excessive heat expected over the Desert Southwest...
A slow moving, meandering upper low will loom large along the Texas coast
through roughly Thursday morning. Most recently, this system has a history
of producing flash flooding, including some water rescues across Corpus
Christi, Texas. With abundant tropical moisture in place and numerous slow
moving thunderstorms, additional flash flooding is likely to occur
somewhere along the Texas coast. A widespread 3 to 5 inches of rainfall is
possible over this region through Thursday morning with isolated pockets
of heavier amounts expected. Gradually the parent upper low is forecast to
sink southward and position itself over central Mexico by the end of the
Another region which can expect a decent threat for flash flooding is the
Middle Mississippi Valley. The prominent issues will likely extend from
eastern sections of Nebraska/South Dakota out into Iowa and adjacent
locations. A myriad of disturbances aloft will work in conjunction with a
slow moving surface cyclone to afford multiple episodes of organized
showers and thunderstorms. This combination will set a focus for a broad
axis of heavy rainfall extending over the mentioned stretch of states.
Like the Texas Gulf coast, sections of the Middle Mississippi Valley are
also within the moderate risk for excessive rainfall as shown in the
latest graphics. Not withstanding, areas farther downstream are not out of
the woods as a wavy frontal zone sprawling eastward into the Ohio Valley
and mid-Atlantic will be a site for organized heavy precipitation. A
slight risk for excessive rainfall is being advertised, generally along
South of the mentioned wavy frontal zone, it will be quite warm and muggy
with low temperatures not dropping appreciably. As such, expect widespread
mid 70s with localized upper 70s the next couple of nights across the
southeastern U.S. Based on daily records, some observed minima may
approach or locally exceed these extrema. During the daytime, while
records are not likely, hot conditions should prevail across the Carolinas
as highs soar into the upper 90s. Meanwhile, north of the boundary, highs
in the 70s will be commonplace over New England.
Looking to the western U.S., the Pacific Northwest can also expect fairly
warm overnight temperatures for mid/late June. Current forecast lows are
in the mid 60s across interior Washington/Oregon while upper 50s are more
likely closer to the I-5 corridor. If such temperatures are achieved, some
daily records may be broken. Farther south, excessive heat warnings and
watches are in effect across the Desert Southwest. This well advertised
increase in the temperatures is in response to a building upper ridge. By
Thursday, highs will likely push into the 110s across many spots including
Las Vegas, Needles, and Phoenix. And the current forecast high at Death
Valley, California is 124 degrees on Thursday.
As an upper ridge erodes across the northwestern U.S., a number of
disturbances advancing from the Pacific will enhance chances for
precipitation across the Pacific Northwest, Upper Intermountain West, and
Northern Rockies. Somewhat limited moisture should keep overall rainfall
amounts on the lower end with general maxima focusing over areas of local
Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php