515
FXUS64 KHGX 131143
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
643 AM CDT Mon May 13 2024

...New AVIATION...

.SHORT TERM...
(Today through Tuesday Night)
Issued at 218 AM CDT Mon May 13 2024

Mid/upper water vapor imagery overlaid with RAP 500MB height
analysis show a well defined mid/upper trough pushing eastward into
the central plains this morning. The trough is enhancing a mid/upper
subtropical jet that extends from northern Mexico to the southern
Mississippi River Valley. Shortwaves embedded in the jet will
continue to push northeastward across our region today. Meanwhile at
the surface, strong PVA and vorticity stretching over western Kansas
and Oklahoma is gradually developing a low pressure system along
with an associated cold front that extends southward through West
Texas. All these features will continue pushing eastward and will be
the synoptic drivers in today`s forecast.

Moisture and instability will not be lacking today. Forecast
soundings are showing ML lapse rates (700-500 mb) average around 7
degrees C/KM. HREF ensemble mean sfc CAPE values are primarily in
the 3000-4000 J/kg range. Ensemble mean PWATs show good potential
for near 2 inch PWs in our coastal counties and 1.5-1.8" elsewhere.
High LL moisture/instability will be felt in the form of heat and
humidity this afternoon. Current blend used in our forecast grids
show widespread upper 80s for highs with 70s dew points. However,
our northern CWA could struggle to reach the low 80s this
afternoon due to being north of a stalled boundary (more on this
below).

In addition to plentiful moisture/instability, shear at the mid-
levels will be on the rise, with effective bulk shear values peaking
50-60 knots by late afternoon. This may coincide with the time frame
of peak UL diffluence (300-200MB). The shear and instability profile
may favor the development of a few discrete heavy thunderstorms this
afternoon. But the primary concern for widespread thunderstorms lies
with a more linear convective mode this afternoon and into the
evening hours (some uncertainty regarding timing worth
mentioning). The environment suggests large hail and damaging wind
gusts are the primary threat. Weak LL shear will limit, though
not totally eliminate, the tornado risk. However, the large hail
and damaging wind risk has been deemed high enough to warrant an
Enhanced Risk (Level 3 of 5) for severe thunderstorms as per SPC.
Our coastal zones remain in a Slight Risk (Level 2 of 5).

It is worth mentioning that the aforementioned stalled boundary
could impact the location and coverage of deep convection. If
areas north of the boundary remain cooler and LL instability is
lacking, then the bulk of the deep convection could consolidate
farther south, likely occurring near and to the south of the
boundary. This would increase the severe weather risk near the
coast. We will need to closely monitor how well defined this
boundary remains as the day progresses.

Wet soils from recent rains coupled with the risk of heavy
thunderstorms has prompted WPC to issue a Slight (Level 2 of 4)
risk of excessive rainfall across much of the region as well.
Widespread additional rainfall totals are expected to range from
1-3 inches north of I-10, to less than an inch south of I-10. That
being said, locally much heavier totals are possible. HREF
ensemble max QPF shows potential for locally over 5 inches of
rainfall. A Flood Watch remains in effect through this evening
across our northern counties. If timing of thunderstorms is pushed
back, then we will need to consider pushing the watch into
tonight.

A much needed break in the action is expected on Tuesday. The
aforementioned front is expected to push offshore by Tuesday
morning. Weak high pressure will build into the region behind the
front. Tuesday`s dew points are expected to fall into the 60s. But
with more sunshine and drier air, afternoon temperatures are likely
to be a little hotter than today. NBM showing widespread afternoon
highs around 90 degrees across the southern half of the CWA
(excluding the coast). This seemed reasonable enough for us so we
went with the toasty NBM for our afternoon highs tomorrow.

Self

&&

.LONG TERM...
(Wednesday through Sunday)
Issued at 218 AM CDT Mon May 13 2024

The break in convection will continue through most of Wednesday.
By late Wednesday night a mid/upper level disturbance approaches
from the west and we are likely to see scattered showers and
storms develop or move into the area. On Thursday deep layer
moisture returns to the area with precipitable water values back
around 2 inches. This deep moisture coupled with the subtropical
jet overhead and continued mid/upper level disturbances will set
the stage for showers and storms again with locally heavy rainfall
likely. A slight chance to chance of showers and storms will
remain on Friday and into Saturday, but not very confident yet on
the precipitation timing at the end of the week and going into the
weekend as weak mid/upper disturbances will be the main driver
with a weak frontal boundary likely lurking in the area as well.
By Sunday, we should warm up with mid/upper level ridging
developing and rain chances on the decrease due to subsidence.

Wood

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 636 AM CDT Mon May 13 2024

A very tricky forecast today. A mix of MVFR/IFR cigs this morning
expected to give way to MVFR to VFR cigs by afternoon.
Thunderstorms are expected to develop by early afternoon. Some of
these storms are likely to become strong to severe, with hail and
damaging wind the primary concerns. Though strong TS is possible
at all terminals, the best chance of severe storms appears to be
from the Houston area south to the coast. Some uncertainty exists
regarding TS timing. The wind forecast, particularly the wind
direction forecast, is particularly low confidence today. A period
of north to northwest winds is possible in the wake of the
showers/thunderstorms. Areas of fog could develop overnight.

&&

.MARINE...
Issued at 218 AM CDT Mon May 13 2024

Moderate onshore flow will continue today with wave heights
offshore in the 4 to 6 foot range. Will continue to have a
caution statement for today. This evening chances for showers and
thunderstorms increase as an organized area of storms is likely
to push off the coast and winds will become offshore. Some of
these storms could be strong or severe. Onshore flow will return
Tuesday night and increase on Wednesday. Rain chances return late
Wednesday into Thursday, and caution conditions are likely on
Thursday. Moderate onshore flow is expected to continue Friday and
into Saturday.

Wood

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  83  64  86  63 /  50  20   0   0
Houston (IAH)  87  68  90  65 /  60  40   0   0
Galveston (GLS)  83  73  85  74 /  60  50   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch through this evening for TXZ163-164-176>179-196-
     198>200.

GM...Small Craft Should Exercise Caution through this evening for
     GMZ350-355-370-375.

&&

$$

SHORT TERM...Self
LONG TERM....Wood
AVIATION...Self
MARINE...Wood