New WPC Meso Discussion
Mesoscale Precipitation Discussion 0875
NWS Weather Prediction Center College Park MD
751 PM EDT Fri Sep 21 2018
Areas affected...Southern OK...North Central TX
Concerning...Heavy rainfall...Flash flooding likely
Valid 212350Z - 220550Z
Summary...Dangerous flash flooding will continue across areas of
southern Oklahoma while expanding into north-central Texas through
the evening hours. Additional rainfall totals of 3 to 5 inches
with locally higher amounts will continue the high risk of flash
flooding.
Discussion...A strong setup continues for slow-moving convection
in a highly efficient and moist airmass across southern Oklahoma
and central Texas. Aloft, there is a broad area of divergence
across the region while at the surface, a low was analyzed near
KABI with a stationary draped across northern Texas near the Red
River into west-central Arkansas. GOES-16 satellite imagery
depicted a mid-level low across west-central Texas which is
facilitating this forcing aloft.
Sufficient instability exists across Texas with MLCAPE values of
1000 to 2000 J/kg northward to the Red River. Impinging on the
surface boundary is highly anomalous moisture from the Gulf of
Mexico where recent RAP mesoanalysis showed PWATs of 2.2 to 2.3
inches, which is nearly 3 SD above normal. Strong 850mb moisture
transport overrunning the stationary boundary has led to west/east
oriented bands of convection since earlier this morning. Observed
totals across southern Oklahoma generally show widespread areal
averages of 3 to 6 inches with local pockets of 7 to 10 inches.
The highest total observed so far as of 7 pm EDT is 15.50 inches
just south of Stonewall, OK as reported by emergency managers.
There is good consensus in the recent runs of the HRRR and other
CAMs depicting convection will continue slowly shifting from
southern Oklahoma into north-central Texas as the surface low
drifts eastward. This should set up a localized area of strong
convergence, and given a continued influx of moisture, very
efficient rainfall will persist through the evening hours.
Forecast soundings for the Dallas/Ft. Worth area depict
tall/skinny profiles with near saturation all supporting the
tropical moisture allowing for efficient rainfall. Latest runs of
the RAP show warm cloud depths of 4.5 to 5 km continuing through
the evening hours. Over the next several hours, there is good
agreement for an additional 3 to 5 inches of rain across
north-central Texas with locally higher amounts likely. This will
include the Dallas/Ft. Worth metropolitan area.
These ingredients all suggest life-threatening and dangerous flash
flooding will continue in the short-term across southern Oklahoma,
but will likely expand across north-central Texas through the
evening and into the overnight hours.
Taylor
ATTN...WFO...EWX...FWD...OUN...SHV...SJT...TSA...
ATTN...RFC...ABRFC...LMRFC...WGRFC...
Winter time post are almost exclusively focused on the DFW area.