046
FXUS64 KHGX 131807
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
107 PM CDT Mon May 13 2024

...New UPDATE, AVIATION...

.UPDATE...
Issued at 1248 PM CDT Mon May 13 2024

Scattered thunderstorms have started to developed across central
TX and will continue to move east-northeast into Southeast TX
this afternoon and evening. The environment looks very favorable
for new convection across our region this afternoon. Upper-level
forcing (passing shortwaves) and a quasi-stationary boundary
extending over our region will serve as a focus for severe
thunderstorms. Current mesoanalysis show plenty of moisture,
steep mid- level lapse rates, MUCAPE at or greater than 4K J/kg
this afternoon, along with 0-6km bulk shear shear into the 50 to
60 knots range. These parameters will support organized/strong
updrafts/supercells capable of producing large hail. As the
afternoon progresses, 0-3 km helicity increases further to our
east, increasing the wind threat. Isolated meso-vortices/tornado
will also be possible. A Severe Thunderstorm Watch is in effect
for most of Southeast TX until 8PM CDT.

JM


&&

.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...
(18Z TAF Issuance)
Issued at 1248 PM CDT Mon May 13 2024

An active afternoon and evening with strong to severe
thunderstorms expected near/around the terminals. Thunderstorms
will continue to develop and move eastward through early this
evening. The best potential for severe thunderstorms will be for
terminals south of CXO, though an isolated strong storm or two
cannot be ruled out near/around CLL/UTS terminals. Large hail and
damaging winds are the main threats. Gusty erratic winds and
reduced visibility can be expected with any strong storms.
Conditions should gradually improve late this evening. Benign
aviation conditions are expected on Tuesday with northwest to
north winds around 5 to 10 knots.

JM

&&

.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  60   0   0
Galveston (GLS)  83  73  85  74 /  60  60   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch until 7 PM CDT this evening for TXZ163-164-176>179-
     196-198>200.

GM...Small Craft Should Exercise Caution until 7 PM CDT this evening
     for GMZ350-355-370-375.

&&

$$

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