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WPC Day 2 Excessive Rainfall Outlook
Risk of 1 to 6 hour rainfall exceeding flash flood guidance at a point
Updated: 0843 UTC Wed Oct 17, 2018
Valid: 12 UTC Oct 18, 2018 - 12 UTC Oct 19, 2018
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
427 AM EDT Wed Oct 17 2018
Valid 12Z Thu Oct 18 2018 - 12Z Fri Oct 19 2018
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
CENTRAL AND SOUTH TEXAS...
...Central to Southern Texas...
A closed mid level low across the southwest will lift northeast as
a digging northern stream trough dives into the upper Midwest.
Low level ridging across the central CONUS will edge eastward as
the trough approaches. This setup will continue to supply
anomalously high deep layer moisture into TX. Meanwhile at the
surface an inverted trough orthogonal to the TX coast in
conjunction with an instability axis across the west Gulf will
promote offshore convection to potentially move onshore through
One of the areas of interest is across central TX where strong
moisture flux intersects with surface convergence along the
inverted trough. With precipitable water values 2+ inches (2-2.5
standard deviations above the mean), mid-level convergence and
decent mid/upper level lift will manage to squeeze out
precipitation over potentially the same area resulting in higher
QPF totals in this region. Confidence on QPF totals in this region
is below average. A lot depends on mesoscale features that are
tough to discern this far out.
The second area of interest is along the coast as convection from
surface convergence and the aforementioned instability axis just
offshore steering inland. Some model guidance suggests the
convection will stay offshore, while some others show the activity
moving just inland. While the current thinking based on the
strength of the onshore flow is for some convection to eventually
work inland, but perhaps lose its convective characteristics as
these clusters move further north with more mid-level support.
Similar to the SLGHT in central TX, confidence on higher QPF
moving inland is below average.
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt