188
FXUS64 KHGX 160743
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
243 AM CDT Thu May 16 2024

...New SHORT TERM, LONG TERM, MARINE...

.SHORT TERM...
(Today through Friday Night)
Issued at 243 AM CDT Thu May 16 2024

A mid/upper trough in SW CONUS will push into Texas today, enhancing
a mid/upper subtropical jet while increasing large scale lift over
our region. This lift will be further enhanced by shortwaves
embedded in the jet. Closer to the surface, the trough is enhancing
LL vorticity (sfc-850mb) in West Texas this morning. This LL
vorticity max / sfc low is expected to propagate eastward, roughly
along a warm front that is will to stall somewhere over our central
/ northern counties. LL shear is likely to increase this afternoon
as the LL vort max / sfc low approaches SE TX. HREF ensemble mean
850MB winds show a southerly LL 25-35 knot jet. Fcst soundings even
show ~20 knots of 0-1KM shear by afternoon. The 500MB mean winds
increase to 50-70 knots within the aforementioned subtropical jet.
Effective bulk shear by late this afternoon and evening is expected
to range from 50-60 knots across our southern counties to as high as
70-80 knots in our northern counties. In addition to volatile shear,
LL and ML instability will be increasing throughout the day. ML
lapse rates are expected to increase to 7.0-7.5 C/km while sfc based
CAPE is forecast to reach 2500-4000 J/kg south of the stalled
boundary. Though widely scattered shower/thunderstorm activity is
possible during the morning hours today, the primary concern is
later in the day when all the aforementioned atmospheric parameters
are likely to instigate persistent deep convection near the stalled
boundary.

The time frame of concern begins around 2-4PM across our northern
CWA. This is when most of the CAMs are showing heavy thunderstorm
developing on, and moving eastward along, the boundary over our
northern counties. The HRRR even suggests the potential of a few
embedded supercells. This isn`t a huge surprise given the veering
wind profile and high bulk shear. Uncertainty exists regarding when
this boundary will begin to progress southward. Much of this
uncertainty hinges on the fact that the forward motion of the boundary
will be at least somewhat dependent on mesoscale cold pool processes.
Despite the uncertainty, the boundary will eventually push southward
towards the coast by the evening or overnight hours, taking its rain
and thunderstorm activity with it.

Before we get into Friday, let`s take a moment to talk about the
severe weather and flood risk today and tonight. SPC has upgraded
areas north of I-10 to an Enhanced Risk (Level 3 of 5) of severe
weather while areas farther south are in a Slight Risk (Level 2 of
5). Large hail and damaging wind gusts are the primary concern.
However, LL shear parameters suggest some potential for tornadoes as
well. WPC has upgraded the excessive rainfall risk to High (Level 4
of 4) across our northern Piney Woods counties while our central
counties (north of Harris County) remain in a Moderate (Level 3 of
4) and areas farther south in a Slight (Level 2 of 3). Though
widespread rainfall totals north of I-10 are "only" expected to be
in the 2-4 inch range, antecedent soil moisture conditions coupled
with the prospect of locally much heavier totals have lead to the
moderate to high risk across our northern counties. HREF ensemble
max guidance indicate that 6-10 inches of rainfall could occur in
locations of training thunderstorms. In addition, it may not take
that much rain to result in flooding issues due to wet soils,
especially across our Piney Woods counties. Please have multiple
ways to receive warnings today and tonight. If you encounter water
covered roads, please turn your car around.

The aforementioned boundary is expected to hang around our coastal
counties on Friday. Meanwhile, a shortwave embedded in the jet aloft
is expected to introduce lift, allowing for the development of
showers and thunderstorms. Models vary regarding how much rainfall
will occur on Friday. WPC has placed much of our CWA in a Marginal
Risk (Level 1 of 4) of excessive rainfall. Some of the guidance
suggests potential for heavier showers and thunderstorms near the
coast on Friday. Our ~40-50% PoPs at the coast may need to be
revised upward in the next update if current model trends continue.

In case you are curious about temperatures, afternoon highs today
and tomorrow are expected to be in the 80s. However, some of our
northernmost communities could struggle to reach 80 today. Overnight
lows are expected to range from the mid 60s in our northernmost
counties to low 70s in Houston and mid 70s at the coast. Friday is
expected to be another day in the 80s.

Self

&&

.LONG TERM...
(Saturday through Wednesday)
Issued at 243 AM CDT Thu May 16 2024

This period still looks quiet/dry but increasingly warm/humid. Upper
trough axis partly responsible for the end of the week`s rain will
continue moving eastward and out of our area on Saturday. The state
will then be on the northern fringes of upper level ridging for the
rest of the weekend and on into the first half of the week. At the
surface, high pressure moving east of the area over the weekend will
set up a warm and humid onshore flow. High temperatures will respond
to these features by warming up generally into an upper 80s to lower
90s range. Low temperatures will respond too by starting out in an
upper 60s to lower 70s range on Sunday and Monday and ending up in
a lower 70s to upper 70s range on Tuesday and Wednesday. Heat index
values by Tuesday or Wednesday could end up peaking close to a 103 to
105 degree range. Heat safety precautions should be taken.

42

&&

.AVIATION...
(06Z TAF Issuance)
Issued at 1207 AM CDT Thu May 16 2024

Scattered showers/storms will be possible north of I-10 over the
next several hours. Light winds, high clouds and VFR conditions
can be expected early this morning. MVFR CIGS and isolated
showers/storms begin to develop mid Thursday morning into the
early afternoon. A complex of thunderstorms will push across the
region from northwest to southeast during the late
afternoon/evening, bringing periods of IFR VIS/CIGS. These storms
will be capable of producing locally heavy rainfall, hail and
strong wind gusts. There will be a lull in rain chances behind
this main complex during the late evening, though isolated showers
and storms will be possible during the early morning hours of
Friday.

03

&&

.MARINE...
Issued at 243 AM CDT Thu May 16 2024

An elevated onshore flow will persist through the end of the week. The
exception could be in and around any scattered storms that may impact
the waters later today and on into Friday. Highest rain chances are
anticipated inland later today and near the coast on Friday. The area
still look to be rain free over the weekend and into early next week
along with lower winds and seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  80  69  84  68 /  90  60  20  10
Houston (IAH)  83  72  86  71 /  80  70  40  20
Galveston (GLS)  81  75  83  74 /  50  50  40  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch from 1 PM CDT this afternoon through Friday morning
     for TXZ163-164-176>179-195>200-211>213-300-313.

GM...Small Craft Should Exercise Caution through Saturday morning for
     GMZ350-355-370-375.

&&

$$