Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
420 AM EDT Wed Jun 05 2019
Day 1
Valid 12Z Wed Jun 05 2019 - 12Z Thu Jun 06 2019
...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL ACROSS THE MIDDLE TO
UPPER COAST OF TEXAS INTO SOUTHWEST LOUISIANA...
...Eastern Texas into Southwest Louisiana...
There is a strong model consensus for very heavy to excessive
rainfall amounts day 1 along the Central to Upper Texas coast into
Southwest Louisiana. PW values 2.25 to 2.50+...3+ standard
deviations above the mean...expected to impact much of eastern TX
into the Lower MS Valley day 1 in an axis of strong southerly low
level flow...850-700 mb moisture flux anomalies 3 to 5 standard
deviations above the mean...off the western Gulf of Mexico.
Rainfall intensities likely to increase early this period along
the mid to upper TX coast in the above mentioned axis of anomalous
850-700 mb moisture flux off the western Gulf that will be moving
only slowly up the TX coast into southwest LA day 1. SREF
probabilities for 5"+ rainfall amounts are in the 70-100% range
across much of the coastal sections of WFO HGX and LCH
CWA...inland by approximately 50 nm. In this region...the latest
hi res model consensus is for 6-10"+ amounts with these amounts
depicted in WPCs day 1 qpf. Changes to the previous Excessive
Rainfall Outlook for this period was to introduce a high risk in
the consensus very heavy qpf axis. Otherwise...only some minor
changes made to the slight and moderate risk areas...suppressing
them slightly southward to match the consensus heaviest precip
axis. Widespread major to life threatening flooding possible in
the high risk area...especially across the Houston metro region
which is susceptible to major flooding issues.
...Upper Ohio Valley into the Central Appalachians...
A slight risk area was added for portions of the Ohio Valley into
the Central Appalachians for the potential for 2 rounds of heavy
rain this period. The initial round possible early day 1 as
convection may enhance ahead of the lead shortwave pushing from
the mid OH Valley into the Central Appalachians. This will be
followed by additional convection firing Wednesday afternoon along
and ahead of the cold front pressing south from the Lower Lakes
toward the Ohio Valley in an axis of increasing
instability...mu-cape 1000-15000 j/kg...LI values -4 to -6. An
axis of anomalous 850-700 mb moisture flux values..2+ standard
deviations above the mean...expected in the low level westerly
flow along and ahead of this front. There may be a period of
training of cells in a west to east direction in this westerly low
level flow...supporting isolated runoff issues.
...Central to Southern Plains...
A broad marginal risk area was maintained across the Central to
Southern Plains from southeast CO/northeast NM into much of OK and
northwest to central Texas. The slow moving southern stream
closed low...initially over the Southwest...will push into the
Southern High Plains this afternoon. Another round of widespread
scattered convection likely in the difluent upper flow pattern
ahead of this system. Similar to past days...confidence is not
great with qpf details...but model consensus is for additional
widespread moderate to heavy rainfall potential across these
areas...with isolated runoff issues possible where convection does
become organized.
...Western to Northern NY State into Northern New England...
The marginal risk area from the previous outlook for this period
was extended eastward into Northern New England. A west to east
oriented surface front expected to stretch from the Lower Lakes
eastward into Northern NY State and Northern New England. Model
consensus is for a west to east oriented axis of moderate to heavy
rains across this region. After collaboration with WFOs
BUF...BGM..ALY and BTV...the risk level was kept as marginal given
limited instability and precip values over the past few weeks that
have been slightly below average across these regions.
Oravec
Kidding aside, Wednesday is shaping up to be a soaker around here. Early tropical fun.
