Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 251204

Area Forecast Discussion
National Weather Service Houston/Galveston TX
704 AM CDT Sun Sep 25 2016

SHRA/TSRA activity continues to focus along the coast this
morning and timing of SHRA/TSRA near the terminals will be the
main aviation concern for the 25/12Z TAFs. Expect coverage to
focus near Galveston and Angleton through mid-morning, before
expanding inland with heating. Short-term guidance continues to
show the upper Galveston Bay focusing SHRA/TSRA activity towards
Houston IAH by late morning, but with SPC mesoanalysis showing
some weak upper lift over the region this morning coupled with
deep Gulf moisture have gone ahead and added TEMPO TSRA mentions
at all terminals. Have lower confidence on when SHRA/TSRA will end
with this weak lift in place, but expect coverage to decrease by
late afternoon to early evening. Main thunderstorm hazards will be
gusty and erratic winds and IFR TO MVFR ceiling/visibilities in
stronger cells.

Conroe and Huntsville have briefly seen IFR/LIFR ceilings this
morning and may continue to experience temporary ceiling
restrictions before low clouds lift with heating. Otherwise, VFR
conditions and east/southeast winds 10 knots or less are expected
to prevail at all terminals outside of SHRA/TSRA.

For planning purposes... a cold front with a weak north to
northeast wind shift is expected to move across the terminals
during the day on Monday, with scattered to numerous SHRA/TSRA
possible ahead of this boundary.




Large swath of showers and thunderstorms from near Sugarland to
Palacios and out into the Gulf beyond 150nm. Ridging in the
central region of the Gulf keeping the mean flow from the SSE.
With the abundant moisture plume over the Gulf flowing into SETX this
should keep rain chances high today generally along and south of a
line from College Station to Anahuac with scattered coverage to
the north. Soundings today look conducive to rapid growth of
storms today especially during the afternoon hours with
temperatures in the mid to upper 80s yielding 2500-2800 CAPE/PW
2-2.2" with no capping to speak of over most of the
region...perhaps slight capping in the northeast counties. Storms
will be slow movers 10-15 knots and some potential for storms to
line up and traverse the same areas with redevelopment in such a
moist unstable atmosphere a good bet. Locally heavy rainfall
possible and can expect 2 to 4 inch accumulations within a short
period of time if these storms line up. Minor street flooding
possible this morning through late afternoon. With the low level
flow from the ESE-SE may see a greater chance for waterspouts
again today near the coast through at least early afternoon.
Overnight may see the outflow from the storms along and ahead of
the cold front push southeastward with the focus for storms
mainly in the west and over the Gulf overnight...streaming mainly
into the coastal counties after midnight. During the day Monday
the winds back to the northeast with the cold front dropping to
near a Crockett to Conroe to Wharton line by late afternoon/early
evening. Deeper moisture gets shunted west and pooled along and
south of the boundary. Still some instability and plenty of
moisture for scattered showers and thunderstorms Monday. May have
some heavy rain in the southwestern-most counties too. Monday
night into Tuesday morning the cold front should be along the
coast or just out into the nearshore waters pushing south during
the day on Tuesday. Drier air will expand southward with the weak
CAA and rain chances quickly taper down from north to south.
Temperatures should only reach the lower to mid 80s. Clouds will
likely linger most of the day Tuesday before clearing again from
the north to the south on Wednesday with a slow afternoon warming
trend Wednesday through Friday. Larger diurnal temperature range
thanks to the much drier air as high pressure builds in across TX.
Upper ridging axis over Mexico/TX looks to remain strong Wednesday
through Monday.

In the tropics...GFS model continues to bring tropical wave into
the Caribbean and intensifies it rapidly Tuesday the 4th through
Wednesday the 5th and now ECMWF has a much weaker system much
slower and veering off to the right skirting the Caribbean.
Caribbean would likely be a low shear environment and very warm so
conducive to development if the system gets into Caribbean. Still
in the monitor mode as this system `might` be in the central
Caribbean 10 days from now.

Scattered showers and thunderstorms continue to develop across the
coastal waters early this morning, with greatest coverage being
focused in two wind convergence zones stretching from KBQX south
towards Buoy 42019 and another stretching from Buoy 42035 towards
Platform KEHC. Expect periods of showers and thunderstorms to
continue across the coastal waters today with deep tropical
moisture(CIRA layer precipitable water satellite imagery estimating
2-2.2 inch PWATs just off the coast) pooled along the Upper Texas
Coast. Main thunderstorm hazards appear to be locally enhanced winds
and waves. However, deep tropical moisture, little wind shear, and
steep low level lapse rates along the coast today will result in
conditions favorable for tropical funnel cloud and waterspout
development. Favorable conditions may linger into Monday before the
cold front sweeps into the Gulf on Tuesday. Caution flags may be
needed behind the front on Tuesday as wind speeds approach 15 knots.

Otherwise, southeast winds around 10-15 knots are expected
today before backing to the east on Monday ahead of a cold front.
Slightly stronger winds have been observed across the western waters
this morning (likely a combination of the surface pressure gradient
and ongoing showers/thunderstorms), and have issued a short Small
Craft Should Exercise Caution statement through 7 AM CDT as a
result. Persistent east/northeast flow behind the cold front on
Tuesday is expected to last over much of the upcoming week as
surface high pressure builds over the southeastern United States and
a surface trough develops near the Bay of Campeche. This flow will
result in slightly above normal tides along the Upper Texas Coast
mid to late week.



College Station (CLL)      90  72  82  68  82 /  50  70  40  10  10
Houston (IAH)              89  74  88  71  83 /  50  40  60  30  10
Galveston (GLS)            87  78  85  76  82 /  60  40  60  40  20


     FOR THE FOLLOWING ZONES: Coastal waters from Freeport to
     the Matagorda Ship Channel out 20 NM...Waters from Freeport
     to the Matagorda Ship Channel from 20 to 60 NM.



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