316
FXUS64 KHGX 181123
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
623 AM CDT Tue Jun 18 2024

...New AVIATION...

.SYNOPSIS...
Issued at 424 AM CDT Tue Jun 18 2024

Potential Tropical Cyclone One will bring a variety of hazards to
our area over the next few days. Below is a list of primary
concerns.

1) Heavy Rainfall

 Periods of moderate to heavy rainfall are likely this evening
 through Wednesday, especially over our southern and coastal
 counties. The best chance of heavy rainfall capable of flash
 flooding will be from I-10 points south to the coast. If you
 encounter water covered roads while driving, please turn your
 car around. Have multiple ways to receive weather updates and
 warnings.

2) Hazardous Marine Conditions

 Strong winds and rough seas are likely for the bays and Gulf
waters through Thursday. Sustained winds up to 35 knots with gusts
over 40 knots expected in the Gulf waters. Offshore seas of 10-15
feet are likely. Higher winds likely within and near
thunderstorms.

3) Rough Surf / Coastal Flooding

 Saltwater inundation of low-lying roads, property, and businesses
 during high tide is possible, especially on Wednesday. High
 water levels may disrupt ferry services. Rough surf and strong
 rip currents will result in conditions too dangerous for
 swimming.

4) Strong Winds

 Winds near the coast could gust over 40 MPH at times today and
 tomorrow, with stronger gusts possible within thunderstorms.
 Isolated damaging gusts associated with thunderstorms possible.
 Inland winds gusts up to 25-30 MPH could result in hazardous
 driving for high profile vehicles.

&&

.SHORT TERM...
(Today through Wednesday Night)
Issued at 205 AM CDT Tue Jun 18 2024

Deep tropical moisture will continue to pool into southeast Texas
thanks to the slowly organizing tropical disturbance in the
southwest Gulf of Mexico and the persistent LL high pressure
system over eastern CONUS. Though development into a tropical
storm appears likely, it is worth emphasizing the system`s impacts
will not be dependent on whether or not it develops. Strong
coastal winds, high coastal water levels, and periods of heavy
rainfall will be a concern regardless. As the system moves towards
towards Mexico, deep LL onshore flow will send PWATs well over 2
inches with coastal PWATs possibly approaching 3 inches by this
evening. The coverage of rainbands will gradually increase on the
north side of the disturbance, extending well north of the center
of circulation. Though isolated to scattered shower and
thunderstorm activity is expected this morning and afternoon, the
bulk of these rainbands are expected to remain offshore. By late
this afternoon/evening and especially by tonight, these bands of
showers and thunderstorms should be moving into SE Texas from the
Gulf. The Weather Prediction Center (WPC) has kept our
southern/coastal counties (including the City of Houston) in a
Moderate (Level 3 of 4) risk of excessive rainfall capable of
flash flooding for the Tuesday night to Wednesday time period.

So how much rainfall will occur? HREF ensembles strongly suggest
the presence of training rainbands that drop 5-10 inches of rain
over the effected area. But where will those rainbands occur?
Areas south of I-10, and particularly areas near the coast, appear
to have the highest chance of seeing totals this heavy. HREF
ensemble maxima suggest the potential for locally over 10 inches
of rainfall. But the overall total QPF forecast trend has been
downward. Both hi-res and global guidance have been trending
southward with the heaviest rainfall. These trends have resulted
in a significant reduction in the expected rainfall over our
northern counties. Expected totals from the Brazos Valley to
Montgomery County have fallen to 1-2 inches while our northern
Piney Woods counties have fallen under an inch. We still cannot
rule out one of the aforementioned training rainbands impacting
some of our northern counties. For that reason, WPC has our
northern CWA in a Marginal (Level 1 of 4) to Slight (level 2 of 4)
excessive rainfall risk. Once you get south of I-10, rainfall
totals are expected to average 3-6 inches, with higher totals
likely in locations impacted by training rainbands. HREF guidance
is most aggressive with potential training bands in our SW
counties from Brazoria and Fort Bend down to Matagorda Bay.
Locations not impacted by training rainbands will likely receive
manageable rainfall. Most of the flash flooding should be
associated with these bands.

The steeping LL gradient will also enhance winds today and
tomorrow. Winds inland could easily gust over 25 MPH and possible
over 30 MPH near and to the south of I-10. Closer to the coast,
winds are expected to gust around 40 MPH. In addition, winds in
the 925-850MB layer are expected to increase to 45 to 60 MPH. Any
thunderstorm embedded within the rainbands will be capable of
mixing some of the winds down to the surface, especially near the
coast. Therefore, isolated damaging wind gusts cannot be ruled
out. The long fetch of winds across the Gulf will also push the
ocean waters towards the shore, enhancing water levels along the
coast. Minor coastal flooding is possible during high tide today.
The highest levels are expected to occur during high tide on
Wednesday, when there is a greater chance of saltwater inundation
of low lying roads, property, and businesses. Water levels may
become high enough to disrupt ferry services.

By Wednesday evening / night, the bulk of the rain and
thunderstorms should pull west of our CWA. However, gusty coastal
winds and coastal flooding are likely to continue.

Self

&&

.LONG TERM...
(Thursday through Monday)
Issued at 205 AM CDT Tue Jun 18 2024

Things will begin settling down on Thursday as the current
troffiness, and whatever becomes of the PTC, across the western Gulf
transitions further inland into Mexico. Ridging over the eastern
parts of the country begins to expand westward into Texas. Moisture
levels will be trending down, but by down I mean PW`s falling into
the 1.75-2" range. This will still be ample enough for scattered,
mainly diurnally driven, precip across southern parts of the CWA
where a prevailing llvl easterly flow continues and less subsidence
from ridging will be situated. Same type situation exists Friday.

Sat-Sun should be even a touch drier/warmer with broad, flat ridging
stretching across most of the area. Mainly isolated activity
expected near the coast/offshore. Late in the weekend into early
next week, we`ll have to turn our attention back toward the Gulf.
Could see another easterly wave make its way across the Yucatan. By
early next week it should be positioned in somewhat of a weakness
between mid/upper ridging to our west and east.  47

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 611 AM CDT Tue Jun 18 2024

VFR conditions will prevail through the first half of today, but
increasing tropical moisture will cause increase cloud cover
and showers/storms beginning this afternoon and continuing through
Wednesday. Scattered showers will develop as early as 17z with
some isolated thunderstorms possible, mainly south of IAH. There
will be a lull in the thunderstorm activity during the late
afternoon/evening, but widespread moderate to heavy showers with
embedded thunderstorms will slide into SE Texas from the coast
during the overnight hours tonight continuing into the day on
Wednesday. MVFR conditions are expected to prevail beginning late
this evening with CIGs down to 1500-2500ft. Gusty winds up to
around 20-25kt inland, and up to 30-35kt along the coast
(impacting mostly GLS) will begin to pick up this afternoon and
continue through Wednesday.

Fowler

&&

.MARINE...
Issued at 205 AM CDT Tue Jun 18 2024

Hazardous winds and seas as well as well above normal water levels
are likely to continue through Thursday. Sustained winds 25-35
knots with gusts potentially over 40 knots are likely today and
tomorrow, along with offshore seas of 10-15 feet. Occasionally
higher seas are likely. In addition, heavy bands of showers and
thunderstorms are likely later today through Wednesday. Locally
much strong winds are likely within and near thunderstorms.
Coastal flooding is likely during high tide today, Wednesday, and
Thursday. Water levels could reach 4-6 feet above MLLW during high
tide on Wednesday. Although conditions should begin to improve on
Thursday, winds and seas of at least Small Craft Advisory level
could linger until week`s end.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  91  75  82  74 /  30  40  70  30
Houston (IAH)  88  75  84  76 /  50  60  80  40
Galveston (GLS)  87  79  87  82 /  70  80  90  70

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch from this evening through late Wednesday night for
     TXZ197-210>214-226-227-235>238-300-313-335>338-436>439.

     Coastal Flood Warning until 7 AM CDT Thursday for TXZ214-313-
     335>338-436>439.

     Wind Advisory from 3 PM this afternoon to 7 AM CDT Thursday for
     TXZ214-238-313-335>338-436>439.

     High Rip Current Risk through late Wednesday night for
     TXZ436>439.

GM...Tropical Storm Warning for GMZ330-350-355-370-375.

     Small Craft Advisory until 7 AM CDT Thursday for GMZ335.

&&

$$

SHORT TERM...Self
LONG TERM....47
AVIATION...Fowler
MARINE...Self