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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

FXUS64 KHGX 211710

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1210 PM CDT Sat Sep 21 2019


Have been retooling PoPs to better capture where convection is
starting in the southwest, but not much change to the big picture
of isolated to scattered showers and storms that will wind down
this evening. Temperatures seem to be tracking pretty well, so
will let those go as they are outside of tweaks to match the obs
in the first couple hours.


.AVIATION [18Z TAF Issuance]...

Any lingering MVFR should scatter out pretty shortly, and bring us
to VFR around the area. It appears today's isolated showers/storms
are getting started largely to the west of all the terminals, so
will dare to go dry this afternoon. Expect roughly persistence
tomorrow, though I'm not yet confident enough in seeing IFR again
up north so stop just short there, and do bring MVFR down into
Houston for a brief time.


.PREV DISCUSSION /Issued 623 AM CDT Sat Sep 21 2019/...

.SHORT TERM [Through Tonight]... 
Upper-level ridging is continuing to build in from the east 
today, helping to dampen widespread chances for showers and 
thunderstorms today. Precipitable waters have not dried out too 
much just yet, with 1.9 to 2.1 inches remaining over the area, as 
seen in the GOES-16 total precipitable water imagery. In general, 
coverage should be more isolated to scattered, with mostly showers
and isolated thunderstorms possible. Convection should wane with 
the loss of daytime heating by the early evening hours. High 
temperatures today should rise into the low to mid 90s area wide, 
once again above seasonal normals for this time of year. Pockets 
of patchy fog looks possible tonight, with low temperatures 
bottoming out in the low 70s to 80s.


.LONG TERM [Sunday Through Saturday]...
An upper level ridge over the Deep South will extend into Texas on 
Sunday. Moisture trapped beneath the ridge will allow for scattered 
showers and thunderstorms through the day. PW values remain near 
1.90 inches and convective temperatures are only in the upper 80's. 
850 mb temps support high temperatures in the lower 90's. PW values 
drop on Monday to around 1.70 inches but a weak inverted upper 
trough sliding west beneath the ridge toward the middle coast will 
bring another chance of showers and thunderstorms to the area on 
Monday. High temperatures will again warm into the lower 90's. The 
upper ridge retreats to the east as an upper low approaches the 
southern Rockies on Wednesday. 500 mb heights slowly fall and 850 
temps also cool. Temperatures should cool a few degrees  in response 
to the lower heights. PW values drop to around 1.30 inches  so rain 
chances should decrease. The upper low gets sheared out as it pivots 
into the western high plains on Friday. This will allow the upper 
ridge over the eastern US to expand and shift west. The flow aloft 
between these two systems will become S-SW and this will allow a 
weak disturbance to move into the area and bring another chance of 
showers and thunderstorms late Thursday into Friday. Rain chances 
will fall next weekend and temperatures will warm again as a 594 dm 
upper level high settles over Texas. Unseasonably warm temperatures 
will return for next weekend and Sept 2019 will probably end as one 
of, if not the warmest September on record.  43

Moderate onshore flow will continue through the remainder of the
weekend before pressure gradient slackens over SE TX. Small craft
should continue to exercise caution over both bays and the Gulf
waters. The risk for strong rip currents and elevated tides remain
possible through the weekend. Tide levels will peak near 3.0 feet
above MLLW during times of high tide through the Sunday and 
potentially even Monday before lowering beneath the 3.0 feet 
mark. Onshore flow falls closer to 10 knots by Monday, with seas 
lowering to near 3 to 4 feet. Light to moderate onshore flow will 
continue through much of next week.


Good news for the most part. All area rivers have crested and are 
now falling. San Jac at SHeldon is the only river forecast point 
still in Major flood but will to Moderate this morning. Peach Creek 
is now below flood stage and other than Cedar Bayou, all Harris 
COUnty bayous are within banks and falling. Area rivers are all 
expected to fall within banks by Monday. 43



College Station (CLL)  73  92  72  93  74 /   0  20  10  20  10 
Houston (IAH)          75  92  75  91  76 /  20  30  10  30  10 
Galveston (GLS)        80  91  81  90  80 /  20  40  30  20  10 



GM...SMALL CRAFT SHOULD EXERCISE CAUTION through Sunday morning for 
     the following zones: Coastal waters from Freeport to 
     Matagorda Ship Channel TX out 20 NM...Coastal waters from 
     High Island to Freeport TX out 20 NM...Galveston 
     Bay...Matagorda Bay...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...Hathaway