258
FXUS64 KHGX 210404
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1104 PM CDT Mon May 20 2024

...New AVIATION...

.SYNOPSIS...
Issued at 323 PM CDT Mon May 20 2024

The main story through the week will focus on the heat, which will
give us a good taste of full-out summer in late May. Depending on
how power restoration efforts go, this may be a specific concern
around the Houston metro, but more broadly, heat stress tends to
have greater impacts earlier in the season while folks are not yet
acclimated. This holiday weekend is a good time to practice all
things summer - yes, grilling and boating and such, but also
practicing heat safety. A couple things to remember:
- Look for forecast temperatures to rise into the holiday, going
  from lows in the upper 60s to around 70 and highs around 90
  degrees today, to lows in the upper 70s to around 80 and highs
  in the lower to middle 90s a week from today. This should also
  push peak heat index values from the 90s today to levels that
  may exceed 105 degrees on Memorial Day.
- While rain chances will be functionally nil most places for most
  of the week, there`s a small chance for showers and
  thunderstorms coming into the northern parts of the area from
  the northwest at times during the week. Even here, rain chances
  are low...but if anything does survive into Southeast Texas, it
  could involve a strong to severe thunderstorm. The first
  opportunity for such a conditional threat looks to be Wednesday
  evening. The northernmost sliver of our area is included in an
  SPC marginal risk area (threat level 1 of 5) for severe weather.

&&

.SHORT TERM...
(This evening through Tuesday Night)
Issued at 323 PM CDT Mon May 20 2024

Visible satellite showing a scattered cumulus field across SE Texas
as onshore flow continues ahead of a low pressure system. As with
yesterday, will not see much vertical growth with these cumulus
clouds as we remain under high pressure and vertical growth is
inhibited by subsidence/drier air.

Cloud cover increases tonight, which will trap the warmer air in at
the surface. This will lead to pretty warm nighttime lows as
temperatures dip into the 70s area wide.

Breezy conditions continue Tuesday as a shortwave trough enters the
Four Corners and creates another area of low pressure near the
Panhandle. As this surface low deepens, it will interact with the
high pressure near SE Texas and create a tighter pressure gradient.
This will result in, SE winds increasing to around 15 mph during the
afternoon hours. Increased onshore flow will consequently bring PW
values up to around 1.3-1.7" making it feel rather hot and muggy
outside. Overhead a moderate (20-25kt) LLJ will battle the
subsidence from ridging aloft. Ultimately, the ridging will win as
cloud covered increases but the subsidence keeps the area rain free.

Max daytime temperatures will be in the 90s inland with low to mid
80s along the coast. Heat index values will continue to rise, and
will be in the 100-105 range for the majority of the area.

Continue to exercise heat safety by staying hydrated, taking
frequent breaks, and avoid strenuous activity during the hottest
part of the day. Remember to look before you lock, and if the ground
is too hot for your hand, it is too hot for pets` paws!

&&

.LONG TERM...
(Wednesday through next Sunday)
Issued at 323 PM CDT Mon May 20 2024

The primary feature in the long term will be subtropical ridge
aloft, centered right over Mexico. It looks to stay somewhat
stable through the period, with any fluctuations important to the
nuances of our forecast weather more to the fringes of its
influence. However, in general, a strong subtropical ridge as we
head into the summer means heat is the primary thing to pay
attention to, and that certainly is the case here.

Let`s start by taking a glance at the Euro ensemble`s Extreme
Forecast Index. When it comes to high temperatures, it`s
not...that...bad, actually. We`ve got a signal for potential
very unseasonable heat popping up near the coast, where the EFI
exceeds 0.5, but for the most part, the real torch is focused more
over South Texas. The same cannot be said for overnight lows. EFI
values for min temps above 0.5 emerge tonight, and find themselves
at a very eyebrow-waggling levels above 0.8 from Tuesday night
through the rest of the period. There are even isolated locations
exceeding 0.9 along the Gulf Coast. Given the strong ridge,
persistent onshore flow feeding in air from above an anomalously
warm Gulf, and really warm nights seem like the near certainty the
EFI implies. This can cause serious issues for folks who aren`t
able to get breaks in cooled areas, as the accumulation of heat
stress is a major factor, and unseasonably high days followed by
potentially record warm nights is not going to provide that
opportunity for a break unless air conditioning is involved.

So, the question becomes, "It`s going to be hot, but will it be
hot enough for any heat advisories or warnings?" And the answer to
that is a definite maybe. By Monday, if my forecast is perfect (I
wish), we do have some heat index values above 108 emerging which
is our threshold for a heat advisory. That said, for a derived
parameter that depends on both temperature and dewpoint, I`m not
going to get too specific on this. Suffice to say, the trend, like
with temps, will also be upwards. This also holds when we consider
an alternative look at heat like Wet Bulb Globe Temp. The trend
here also shows a drift up from widespread "Moderate" risk area
(level 3 of 5) to widespread "High" risk (level 4 of 5) by the
weekend. We should find ourselves in something very much like
we`d see fully into summer to celebrate the traditional "opening"
of summer this weekend.

Beyond the heat, we do have one other thing to talk about, and
that will be our small rain chances this week. This scenario is
typical for this time of year, when the subtropical ridge is
building in but not quite dominant. We`ll be spending our evenings
watching up to the northwest, to see if convection that fires
there earlier in the day survives into any portion of Southeast
Texas. The odds are low, and I try to keep my slight chances
restricted to areas north of Brenham, Navasota, Huntsville, and
the like. The best days still seem to be Wednesday and
particularly Thursday, as shortwave troughs pass by to our north,
then perhaps again next Monday night. Also of note - in these
situations, should anything beat the odds and survive, it could be
strong to severe. In keeping with this, SPC has the northernmost
sliver of our area in a marginal risk area (threat level 1 of 5)
on Wednesday. Though they do not explicitly delineate such areas
on Days 4-8, the placement of a 15 percent/"slight risk" area on
Thursday implies much the same situation.

&&

.AVIATION...
(06Z TAF Issuance)
Issued at 1103 PM CDT Mon May 20 2024

MVFR conditions have begun to move develop across the region,
starting near the coast, and will envelope the entire area within
the next few hours. Expect CIGs around 1500ft through the night
with periods of IFR conditions possible at times with ceilings
down to around 700ft possible. Clouds will lift and scatter out
through the late morning to early afternoon, but MVFR conditions
will return Tuesday night into Wednesday morning. Southeasterly
winds will continue overnight at around 5-9kt, but will be less
gusty and staying around 4-7kt. Clouds begin to increase to around
10-15kt and gusts to 20-25kt by the late morning.

Fowler

&&

.MARINE...
Issued at 323 PM CDT Mon May 20 2024

Generally moderate onshore winds can be expected through this
week. At times, winds and seas may increase enough for small
craft to exercise caution midweek.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  74  91  76  90 /   0   0   0  10
Houston (IAH)  75  90  76  89 /   0   0   0   0
Galveston (GLS)  77  85  77  84 /   0   0   0   0

&&

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

$$

SHORT TERM...Adams
LONG TERM....Luchs
AVIATION...Fowler
MARINE...Luchs