Mesoscale Precipitation Discussion 0952
NWS Weather Prediction Center College Park MD
445 AM EDT Tue Oct 09 2018

Areas affected...Western/Central TX...Southwest/Central OK

Concerning...Heavy rainfall...Flash flooding likely

Valid 090845Z - 091445Z

Summary...Widespread showers and thunderstorms will continue
through mid-morning with a gradual shift off to the east with
time. Some flash flooding will be likely.

Discussion...The latest radar imagery shows an elongated and
expansive axis of showers and thunderstorms across western TX,
including areas of the TX Big Bend and the TX Hill Country, and
extending northeast up across southwest OK. The activity is again
focusing out ahead of a deep layer trough over the Four Corners
region which is edging slowly into the southern High Plains.

The convection is again being facilitated by the presence of
right-entrance region upper-level jet dynamics which is
interacting with the pooling of a very moist and at least modestly
unstable airmass across much of western and especially central
Texas. The latest IR/WV satellite imagery also shows a
well-defined shortwave lifting out of the base of the trough which
is going negative tilt across western TX. This has been providing
strong upper-level divergence and more focused ascent for
organized convection over the last several hours.

PWATs across the region are running about 2 standard deviations
above normal and much of this is connected to a well-defined
low-level east-southeast fetch of moisture in off the Gulf of
Mexico. This will allow for the convection to remain relatively
efficient and capable of producing enhanced rainfall rates.

The aforementioned shortwave trough will lift north-northeast
going through 12Z and will continue to focus a general north/south
axis of heavy showers and thunderstorms which over time will be
shifting farther east across the TX Hill Country, adjacent areas
of central TX and up north across southwest and central OK.

The latest 00Z hires model suite, along with recent runs of the
HRRR, support as much as 2 to 3 inches of additional rain going
through mid-morning, however, one notable exception is down over
portions of the TX Hill Country where the HRRR in particular
supports as much as 3 to 6
inches of rain with isolated heavier amounts.

Given the anticipated rainfall amounts, and locally wet antecedent
conditions, some flash flooding will be likely going through
mid-morning.

Orrison

ATTN...WFO...EWX...FWD...LUB...OUN...SJT...TSA...

ATTN...RFC...ABRFC...WGRFC...

LAT...LON   36799812 36329794 35869728 35849630 34019687
            32059766 30709831 29919887 29379943 29120017
            29230080 29760137 30250143 30620135 31140108
            32040059 33250005 34409967 35679942 36239929
            36709874