141
FXUS64 KHGX 180911
AFDHGX

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

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

.UPDATE...
Issued at 952 PM CDT Mon Jun 17 2024

No significant changes were made to the forecast tonight...mainly
updating short term POPs based on observed trends. TS Watches will
remain in place in our coastal waters, except Galveston Bay. There
are no land based TS Watches in our CWA...just locations south of
Port O`Conner. Still anticipate breezy/windy conditions esp as one
gets closer to the beaches, but sustained chances of TS force
winds appear quite low over the land at the moment.

This system is still very broad and unorganized without a clearly
defined low. Wind field is fairly expansive with 20-40kt winds
displaced well to the north in the Gulf.

Main take aways at this time: look for water to pile up along the
coast with a fairly good chance of coastal flood impacts - including
the bays. Very hazardous marine conditions with large waves will
be in place. Small craft should consider remaining in port til
things settle down. Look for rain chances to gradually increase
through the day tomorrow...and moreso tomorrow night and Wednesday
as we get into the real juicy tropical airmass. There will
probably be "haves" and "have nots" in regards to rainfall amounts
with a fairly significant zone that might set up somewhere in the
region. Right now, looking like that might occur somewhere
along/south of the I-10 corridor...but confidence isn`t overly
high given the overall unorganized nature we currently have. Like
most of these events, it`ll be important to see if/where any
training bands set up. This, and any very efficient rain rates,
will pose the higher FF threats. 47

&&

.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...
(06Z TAF Issuance)
Issued at 1232 AM CDT Tue Jun 18 2024

VFR conditions with breezy southeasterly winds and isolated
showers will prevail through sunrise. The potential for scattered
showers will continue through the day, with some bands of
thunderstorms beginning to move through the area during the
afternoon (generally around 17-22z) bringing temporary periods of
MVFR conditions due to CIGs down to 1500-2500ft and visibility
reductions due to heavy rainfall. 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
between Tuesday and Wednesday, continuing into the day on
Wednesday. 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.

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

GM...Tropical Storm Watch 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