Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
507 PM EDT Wed Jun 20 2018
Valid 00Z Thu Jun 21 2018 - 00Z Sat Jun 23 2018
...Additional flash flooding expected for portions of the Texas coast
before improving conditions by the end of the week...
...A threat for flash flooding will continue from the Midwest to the
Mid-Atlantic through the end of the week...
...Increasing temperatures expected through the end of the week from
California into the Southwest and Texas...
A slow moving front stretching from the Mid-Atlantic coast to the southern
Plains will continue to pose a threat for thunderstorms and flash flooding
over the next couple of days, but with waning coverage across the lower 48
each day. Conditions near and south of the frontal boundary will see high
humidity with anomalously high moisture values which will support
diurnally driven thunderstorms during the afternoon and evening hours.
Some of these thunderstorms will have the ability to produce strong to
locally severe weather in addition to heavy downpours with flash flooding.
One of two significant threats for flash flooding through Thursday morning
exists in the vicinity of northwestern Iowa into portions of eastern South
Dakota/Nebraska near a surface low and out head of an upper level
disturbance crossing the Plains. An equally concerning threat is in place
from South Texas, up the coastal plain into the Sabine River valley where
some locations have received 5 to 15 inches over the past 72 hours. A slow
moving upper level low over South Texas will gradually begin to shift
south and west over the next 12 to 36 hours, allowing for a reduction in
available moisture and lift which should end the flash flood threat with
Friday likely a dry day for the region as well as Saturday.
Thursday's threat for flash flooding will again be focused in the vicinity
of the front, with a focus over Illinois, Indiana into eastern Kentucky,
but with reduced coverage for much of the Plains. Widespread coverage of
thunderstorms will still be expected near and south of the front however.
Out West, ahead of an upper level disturbance approaching through the
eastern Pacific, high temperatures are expected to increase across
California, the Southwest and Texas with triple digit heat forecast for
all three locations on Friday. Excessive heat watches and warnings have
already been posted for portions of the Sacramento valley into the
Southwest in anticipation of high temperatures ranging between 100 and 120
Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php