Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 221137
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
637 AM CDT Sun Sep 22 2019

.AVIATION [12Z TAF Issuance]...
A mix of LIFR to VFR ceilings across the SE TX terminal this
morning, with most of the LIFR to MVFR ceilings impacting IAH and
northward. Ceilings should be on the rise through the morning
hours, with some MVFR decks developing south of I-10 as low level
moisture rises with daytime heating. Scattered showers and
isolated thunderstorms will be possible today, starting earlier
along the coast and spreading inland. The best coverage of
precipitation should be to the east of the terminals. Otherwise
winds out of the southeast between 5 to 12 knots will be possible
today, becoming light and variable overnight. Lower ceilings again
look possible tonight into the early morning hours, with pockets
of patchy fog also possible.

Hathaway

&&

.PREV DISCUSSION /Issued 421 AM CDT Sun Sep 22 2019/...

.SHORT TERM [Tonight Through Tuesday]...
Radar imagery this morning shows decent coverage of showers over
the Gulf waters stretching north across the coastal counties
through Hardin and Orange counties to our east. Taking a look at
the GOES-16 total precipitable water imagery, 1.8 to 2.0 inches
prevail across the Gulf waters with a plume of higher precipitable
water values (PWs) closer to 2.0 inches stretching across the
eastern Gulf waters and into Hardin County where the best coverage
of showers is ongoing. This axis of better moisture should
continue to shift inland through afternoon hours and act as a
boundary for more widespread development of showers and
thunderstorms. Convective temperatures should reach into the low
to mid 80s, and with high temperatures expected to top out in the
upper 80s to low 90s, isolated thunder will be possible with the
help of daytime heating. NAM12 shows decent mid-level
frontogenesis values across Chambers to Polk counties by the
afternoon hours, which should also aid in convective development.
Short term guidance such as the HRRR and RAP13 appear to have
initialized best this morning, and show more scattered coverage
this afternoon east of I-45 with more isolated development to the
west. Along the axis of best moisture, a few brief heavy downpours
look possible, with the HRRR showing hourly rain rates between a
quarter of an inch to an inch and a half per hour. That said, any
additional rainfall over Liberty and Chamber counties
specifically, is only going to delay the recession of any
lingering flooding. An areal flood warning remains in effect
through 11 AM this morning, to account for those river and local
tributary levels that remain high with very saturated soils. This
areal flood warning may need to be extended. Most of the
convection should wane with the loss of daytime heating by the
early evening hours. Tonight low temperatures should lower into
the mid 70s to low 80s.

Hathaway

&&

.LONG TERM [Monday through Sunday evening]...
Overall, the early portion of next week will be characterized by
quiet and dry conditions, with the chances of convective
precipitation gradually increasing by next weekend. By Monday the
upper-level ridge and surface high pressure continue to build in
over the south-central CONUS, and the characteristic moderate
onshore flow pattern across Southeast Texas continues. Generally
weaker moisture transport throughout the beginning portion of the
week will result in a reduced chance of diurnal showers and
thunderstorms initiating over the coastal waters and progressing
inland as we typically see in such a flow pattern. By Thursday,
however, the ridge shifts eastward and an upper-level weakness
within the prevailing zonal flow develops over the northwest Gulf
of Mexico. Global model guidance shows a plume of enhanced
moisture transport developing along with this feature, returning
precipitable water values (PWs) across the CWA to the 1.75 to 2
inch range. This will increase convective activity associated with
daytime surface heating to a more climatologically normal rate.
Moisture transport further amplifies as we move into next weekend
and PWs climb above 2 inches, bringing the potential for more
widespread coverage of showers and thunderstorms. Despite this,
precipitation amounts are not expected to be substantial enough to
produce further flooding impacts to areas recently impacted by TS
Imelda.

Cady

&&

.MARINE...
Small craft should continue to exercise caution at least through
the early afternoon hours when the pressure gradient begins to
slacken over the region. A Beach Hazard Statement remains in
effect through early Monday morning to account for the risk for
strong rip currents along Gulf facing beaches and elevated tide
levels. At Galveston Bay Entrance, tide levels should peak between
3.0 and 3.5 feet above MLLW during times of high tide. Tide
levels should fall around or even beneath 3.0 feet above MLLW
late Monday evening.

Onshore flow around 15 knots should lower to 10 to 15 knots, later
this afternoon. Seas should also lower to 3 to 4 feet by Monday
morning. Light to moderate onshore flow should prevail through a
majority of next week, with seas remaining around 2 to 4 feet.
Moderate onshore picks back up by the weekend, increasing to 15
to 20 knots.

Hathaway

&&

.HYDROLOGY...
We continue to see a gradual fall in river levels following the recent
flooding rains:
- The West Fork of the San Jacinto near Sheldon has fallen out of
minor flood stage and is expected to continue to lower below action
stage by Tuesday morning.
- The Trinity River at Moss Bluff has fallen below minor flood stage
this morning and is forecast to continue to fall below action stage
by Monday evening.
- Cedar Bayou near Crosby continues to hold steady in minor flood
stage.

Cady

&&

.CLIMATE...
A daily record high minimum temperature was observed at Galveston
yesterday. The minimum temperature of 83 degrees ties a record for
the highest observed for September 21, which last occurred in
1992.

Cady

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  94  75  92  74  92 /  10  10  20  10  10
Houston (IAH)          89  74  90  73  90 /  30  10  30  10   0
Galveston (GLS)        91  81  88  81  88 /  20  10  30   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 10 AM CDT this 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...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/MARINE/AVIATION...08
LONG TERM/HYDRO/CLIMATE...12


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