Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 232038

Area Forecast Discussion
National Weather Service Houston/Galveston TX
338 PM CDT Fri Sep 23 2016

Forecast is on track for this evening. Scattered
showers and thunderstorms continue to redevelop, while storms from
over the coastal waters continue to move onshore. Isolated cells
are associated with frequent lightning, and some are dropping
higher rain rates up to about 1.5 inches per hour. Forecast
soundings still show precipitable waters remaining higher at
1.6-1.8 inches Friday night. Therefore, the lower levels of the
atmosphere will stay fairly saturated, aiding in early Saturday
morning development along the coast especially in the western
coastal counties of our CWA.

The moisture and chance for precip will linger throughout the
weekend. According to forecast soundings, on both Saturday and
Sunday, our convective temperatures remain low around 83 degrees
while our high temperatures get up into the upper 80s, lower 90s.
This should allow for convective initiation, as daytime heating
primes the atmosphere for shower and thunderstorm development. An
upper-level disturbance also moves into the eastern half of our CWA
early Saturday into Sunday. This should also help enhance the lift
in this region, helping in storm development.

Our best chance for widespread precipitation really moves in Sunday
evening into Monday. Winds remain onshore, helping to advect the
moisture plume sitting over the northwestern Gulf of Mexico as seen
on water vapor imagery into our forecast area. A weakness in the
winds becomes evident as we move into Monday, with the approach of
first "cold" front of the season. A majority of the moisture driving
the precipitation will be brought in ahead of the front, rather than
associated with the moisture in the Gulf. Models are continuing to
diverge of the timing of the front, keeping confidence low.  The GFS
and European guidance are trending towards bringing in the precip
ahead of the front between 12Z Monday into 00z Tuesday. This front
will drop our temperatures a tad starting Tuesday, placing low
temperatures in the upper 60s and high temperatures in the mid 80s.
This front should place our temperature back to normal climo for mid-
September. The more significant impact associated with this front
will be the surplus of dry air that filters into the region from the
northeast. Precipitable waters start to drop Tuesday night to about
1.67 inches, drying out the lower layers of the atmosphere.
Maximum relative humidity values will remain in the 70s throughout
the week until next Saturday.



South to southeast winds around 10-15 knots are
expected to persist through Sunday, but may approach caution
criteria late tonight and again Saturday night as a frontal system
approaches Texas. This onshore flow will continue to push deeper
Gulf moisture onto the Upper Texas Coast, resulting in periods of
showers and thunderstorms this weekend. There is still
considerable uncertainty regarding the timing of the cold front as
it moves into Texas on Sunday (and whether or not it will make it
off the Upper Texas Coast). With mid and upper level flow
continuing to look unfavorable for the front to make considerable
progress across Southeast Texas, expect the onshore flow to
continue through Monday as the front stalls inland. However,winds
look to back to the east/northeast by late Monday as a weak
surface low develops over the southwest Gulf.

Increasing winds tonight and Saturday night combined with
elevated astronomical tides may result in tide levels approaching
2.7-3.0 feet above MLLW at high tide along the coast. Another period
of elevated tides is possible early to mid next week as east
to northeast winds become established. 43


College Station (CLL)      76  93  75  90  73 /  10  50  20  60  60
Houston (IAH)              77  90  75  88  74 /  20  40  30  60  60
Galveston (GLS)            81  86  80  86  79 /  30  40  40  50  60



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