Monday, April 12, 2021

Apr. 12 21

 Area Forecast Discussion

Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 130207
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
907 PM CDT Mon Apr 12 2021

.SHORT TERM [Tonight Through Tuesday Afternoon]...
Clouds continue to spread inland as low levels moisten further.
This should lead to a mostly cloudy to cloudy night across much of
the area as well as warmer. Some sprinkles or showers will be
possible after 2 am or so beneath the cap but accumulations if any
will be light.

Will be keeping a close eye on the storms near the cold front well
northwest of Austin that will be slowing as it sags southward.
Storms though near the boundary in the vicinity of Austin should
weaken as they move southeastward so will be holding off on any
mention of TSRA in the overnight forecast...just SHRA.

45


&&

.AVIATION [00Z TAF Issuance]...
Expanding deck of VFR/MVFR will spread inland to the northwest and
then northeast through 12z with gradual lowering throughout the
night. By 12z expect widespread MVFR ceilings at CXO southward and
even down into IFR closer to the coast. Spotty showers will be in
the offing as well and will be carrying VCSH in the TAFs for most
sites after 08z. Warming in the late morning should give rise to
the ceilings and may even go VFR IAH northward 17-19z as front
sags into the area. But this heating will also increase the
threat for TSRA mainly after 20z. Do have some concerns for the
areas northeast and east of IAH where low level convergence near
the frontal boundary gets maximized. So may need some significant
changes to the forecast near IAH/CXO if these pan out. Round of
lower CIGS Tuesday evening with IFR/LIFR more widespread across
the hubs.

45


&&

.PREV DISCUSSION /Issued 308 PM CDT Mon Apr 12 2021/...


.LONG TERM [Wednesday through Monday]...

No significant changes in the long term forecast. On Wednesday,
models still show an upper-level low over The Great Lakes deepening
slightly as it pushes east. With this deepening low, WAA will
strengthen across The Gulf Coast and keep PWATS at 1.5-1.75 along
Southeast Texas. The upper-level low`s associated surface cold front
will be weak and hovering across our southern and coastal counties
as it slowly pushes off our coast. Therefore, with moderate
instability and daytime heating, afternoon thunderstorms are
expected along with scattered showers on Wednesday.

In the wake of Wednesday`s front, winds will become NE and persist
through at least Friday, allowing daytime highs to remain cool and
in the 70s. Overnight cloud cover will remain dense which will trap
excess heat and keep overnight temperatures in the 50s to 60s
throughout the rest of the work week.

Through the rest of the work week, small and embedded shortwaves
within largely zonal flow will keep rain chances approximately 20-
40% across our CWA with scattered showers and isolated thunderstorms
possible. A stronger cold front is expected to push through
Southeast Texas on Friday afternoon, and bring with it more
widespread showers and thunderstorms. Much needed rainfall from
Wednesday through Friday will range from 0.5-1.0 inches with locally
higher amounts possible. Behind this front, NE winds will resume
behind this front and CAA will help keep daytime highs this weekend
in the 70s and overnight lows in the upper 40s to lower 50s.  KBL


.MARINE...

The pressure gradient will briefly tighten tonight in response to
a weak coastal trough that tries to develop along the mid/lower TX
coast. Have issued a SCEC for the offshore waters for tonight but
the gradient is expected to begin relaxing prior to sunrise. A
weak cold front will approach the coast on Tuesday and stall
before reaching the waters. The pressure gradient should relax
further as the front nears the coast. E-SE winds should prevail
Tuesday and gently veer to S-SE as low pressure develops over
South Texas. Wind speeds should remain light as the weak front
waffles back and forth near the coast. An area of low pressure
will move into LA Wednesday night and this should drag the cold
front into the coastal waters late Wednesday night or early
Thursday. A moderate NE wind is expected Thursday as high pressure
builds into the southern plains. A SCEC may be needed for
Thursday. Pressures will begin to fall over northern Mexico as the
surface high moves east. This will induce an east wind on Friday
ahead of another front that will cross the coastal waters Friday
night. 43

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  65  80  64  75  58 /  30  40  60  30  40
Houston (IAH)          69  85  70  79  61 /  40  50  50  40  40
Galveston (GLS)        71  80  72  79  66 /  30  30  40  40  40

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...High Rip Current Risk until 11 PM CDT this evening for the
     following zones: Bolivar Peninsula...Brazoria
     Islands...Galveston Island...Matagorda Islands.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 1 AM CDT Tuesday for
     the following zones: Waters from Freeport to Matagorda Ship
     Channel TX from 20 to 60 NM...Waters from High Island to
     Freeport TX from 20 to 60 NM.


&&

$$


SHORT TERM/AVIATION...45
MARINE...11

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