-- Discussion containing changed information from previous version are highlighted. --
678
FXUS64 KHGX 161751
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1251 PM CDT Sun Jun 16 2024

...New AVIATION...

.SYNOPSIS...
Issued at 256 AM CDT Sun Jun 16 2024

Heavy rainfall, hazardous marine conditions, and dangerous coastal
surf are expected this week.

A broad area of low pressure is expected to materialize over the
western Gulf of Mexico bringing unsettled weather to the region
from Monday to Thursday. As of 2AM CDT, the National Hurricane
Center is giving the system a 60% chance of development by the
middle of the week. However, the expected impacts are the same
regardless of development.

Below are the primary weather concerns for this week.

1) Heavy Rainfall

 There is a good chance of showers and thunderstorms Monday
 through Thursday. There will be a daily risk of heavy rainfall
 during this time frame. However, the time frame of most concern
 is Tuesday evening through Wednesday. A Moderate Risk (Level 3
 of 4) of excessive rainfall has been issued across most of the
 southern half of our region (including the Houston metro) for
 late Tuesday into Wednesday. The rest of our region is under a
 Slight Risk (Level 2 of 4). Street flooding as well as rising
 creeks, rivers, and bayous are a concern this week.

2) Hazardous Marine Conditions in the Bays and Offshore

 Winds and seas will gradually build through Wednesday. Small
 Craft Advisory criteria is likely to be met by Monday. Gale
 conditions are possible offshore, and potentially in the bays,
 by Tuesday and Wednesday. Seas are likely to exceed 10 feet
 offshore and could approach 15 feet Tuesday afternoon through
 Wednesday afternoon.

3) Coastal Flooding

 Water levels at the coast are likely to remain higher than
 normal all week. By Tuesday and Wednesday (possibly Thursday),
 water levels may become high enough to result in coastal
 flooding, especially during high tide. Water levels could exceed
 5 feet above MLLW (Mean Lower Low Water) during high tide on
 Wednesday.

4) Dangerous Surf / Rip Currents

 The beaches will not be safe for swimming Monday-Thursday due to
 rough surf and dangerous rip currents. It is possible that
 hazardous beach conditions could extend beyond Thursday. In
 addition, there will be a daily risk of lightning from
 thunderstorms. Not a great weather week for beach activities.

&&

.SHORT TERM...
(Today through Monday Night)
Issued at 256 AM CDT Sun Jun 16 2024

Today marks the beginning of a transition from the hotter, drier
beginning of the weekend to the unsettled pattern that will dominate
the coming week. Looking for highs today to be largely in the lower
90s, with some hot spots around the Houston metro and coastal plain
pushing into the mid-90s, and folks right on the Gulf only getting
to around 90. So...fairly seasonable, all around. With onshore flow
getting reestablished, boundary layer moisture - especially nearer
the coast - will be a bit more stout this afternoon. This will help
give us peak heat index values that are in the triple digits for
virtually the whole area, and maxing out in the 105-108 range from
portions of the Houston metro southwest along the coastal plain. As
far as precip goes, today should still be mostly dry over the land,
though we can probably expect some isolated shower/storm development
off the seabreeze.
My thinking is the best bet will be in the southwest, where boundary
layer moisture quality looks slightly better.

For the most part, however, the best potential for showers or some
storms will be out over the Gulf waters today. Eventually, as this
Gulf airmass continues to blob its way over Southeast Texas, we may
start to see some quick-hitter showers make their way in from the
coast. Don`t expect to see this until late tonight, after midnight.
I`m envisioning something that looks like when we get the routine
late night/pre-dawn streamer showers at the coast.
Quick, light, and ending as quickly as they start.

Monday looks to give the first taste of the week to come, as we come
more fully under the influence of the tropical airmass causing that
orange commotion down in the Bay of Campeche. Showers should become
numerous to widespread near the coast...generally coastward of
Houston. Farther inland, widely scattered to scattered showers and
some storms can be expected. In general, I`m thinking most of the
area is still looking for light to moderate rainfall. We`re still
early in the process, and the current airmass in place is pretty
dry. It should change quickly...but not instantaneously. There`s
maybe a little more concern for heavier storms near the coast around
Galveston Bay. With precipitable water progged to increase to around
or above 2 inches, a particularly strong updraft could produce some
briefly heavy rain over localized spots. As a result, WPC`s day one
outlook for excessive rain does include a marginal risk area
extending to the Galveston Bay area (threat level 1 of 4).

On the bright side, the higher levels of cloudiness and more
numerous showers and storms will more noticeably tamp down high
temperatures. Much of the area looks to struggle to reach 90 degrees
- those with the best shot to get into the lower 90s will likely be
in the inland west, where the incoming airmass will be last to
arrive. Elsewhere, I`m thinking something more in the middle to
upper 80s. It`ll be humid, so that is likely to keep heat index
values up - in the upper 90s to a little above 100. But hey, better
than nothing, I suppose. The relief will be most apparent for those
performing physical tasks outdoors - the wet bulb globe temperature,
which for several days has been rising into the high, or even
extreme threat levels across the area (levels 4 and 5 of 5), looks
to only be in a moderate threat level (level 3 of 5) on Monday. Of
course, you`ll probably also be dodging showers, so...win some lose
some, I guess.

Rains are expected to make themselves a much more significant part
of the forecast going forward, but I`ll leave discussion of that to
the long term forecaster...

&&

.LONG TERM...
(Tuesday through Saturday)
Issued at 256 AM CDT Sun Jun 16 2024

On Tuesday into Wednesday, the LL gradient will steepen between a
high pressure system over eastern CONUS and the low pressure
system over the west and southwest Gulf of Mexico. The increased
ESE to SE flow will continue to push deep tropical moisture into
southeast Texas from the Gulf. This enhanced flow will be
noticeable via gusty winds, especially near the coast where winds
could gust over 40 MPH. Surging PWATS (2.50 to 3.00 inches) and
sufficient lift should allow for scattered to widespread showers
and thunderstorms. This set up alone would suffice for locally
heavy rainfall. However, vort maxes embedded in the low/mid level
flow could introduce additional lift and LL convergence. Global
determinist guidance agrees that a cluster of vort maxes will push
towards the Texas coast sometime between Tuesday evening and
Wednesday afternoon. That being said, there is quite a bit of
model variance regarding exactly where these vorticity maxima
track which has huge implications on the location of heaviest
rainfall. There continues to be some consensus that the highest
risk of heavy rainfall and flooding will be across the southern
CWA. The Weather Prediction Center has upgraded the excessive
rainfall risk to Moderate (Level 3 of 4) over much of the southern
half of our CWA while areas farther north are in a Slight Risk
(Level 2 of 4). Showers and thunderstorms are likely to linger
into Thursday and could linger through the end of the week.

Forecast rainfall totals through Thursday have once again been
revised upwards, ranging from 8-11 inches near the coast, to 5-8
inches near the I-10 corridor, and 2-4 inches across our northern
counties. Given the high PWATs and the potential enhancement from
LL disturbances, rainfall totals could exceed 12 inches in some
locations. Near the coast, any heavy rainfall related problems
could be exacerbated by the enhanced tides, especially if heavy
rainfall occurs near high tide.

Please have multiple ways to receive warnings this week. If you
encounter flooded roads while driving, turn around and avoid water
covered roads. Stay weather aware and please regularly check for
forecast updates in case the risk of heavy rainfall increases
further.

Self

&&

.AVIATION...
-- Changed Discussion --
(18Z TAF Issuance)
Issued at 1246 PM CDT Sun Jun 16 2024

The current TAF period will begin a period of deteriorating
conditions that will likely last several days. For the remainder
of today and into tonight, VFR conditions are expected to prevail
with winds remaining around 5-10 knots. Shower and thunderstorm
activity will begin to increase after around 09Z tomorrow morning,
with rainfall beginning along the immediate coast and expanding
inland over the course of the day. This will be accompanied by an
increasing SE wind, with wind speeds reaching around 10-15 knots
with gusts occasionally in excess of 20 knots. Any stronger storms
that do develop may produce the occasional stronger wind gust
and/or visibility reduction, but in general cigs are expected to
remain in the MVFR range.

Cady
-- End Changed Discussion --

&&

.MARINE...
Issued at 256 AM CDT Sun Jun 16 2024

Relatively light southeast winds this morning will become more
moderate by this afternoon. In addition to the increasing winds,
there will be a chance of scattered showers and thunderstorms.
Winds, seas, and rain chances increase further on Monday, with
Small Craft Advisory level conditions likely by the afternoon.
Conditions further deteriorate on Tuesday into Wednesday as winds
increase to 25-30 knots with gale force gusts. Offshore seas are
likely to exceed 10 feet and possibly reach 15 feet on Tuesday and
Wednesday. Winds and seas may be locally higher within or near
heavy showers and thunderstorms. It is worth mentioning that some
of our model guidance suggest that winds and seas will be higher
than currently predicted. Winds and seas are expected to gradually
decrease during the Thursday to Friday time frame. However,
showers and thunderstorms remain in the forecast through the end
of the week.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  94  76  91  75 /   0   0  40  10
Houston (IAH)  94  77  88  76 /  10  30  80  40
Galveston (GLS)  89  79  87  79 /  20  60  90  60

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

SHORT TERM...Luchs
LONG TERM....Self
AVIATION...Cady
MARINE...Self