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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

FXUS64 KHGX 211945

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


Not much in the way of significant weather on the horizon. Looking
for temperatures to run a few degrees above seasonal averages, and
combined with the humidity, we may be looking at peak heat indices
up to 105 degrees in the hottest parts of the area. Most days will
feature some sort of isolated to scattered afternoon convection,
but neither coverage nor rainfall amounts are expected to be 
excessive at this time.

.SHORT TERM [Through Sunday]...

Isolated showers have popped up around Southeast Texas this
afternoon, with the most coverage currently over Colorado and
Austin counties. So far, the strongest cells are only producing
rain rates of a third of an inch per hour - heavy rainfall is not
a concern here. Given the location of today's rain, it's likely
not enough, given pre-existing drought conditions and the relative
lack of rainfall there during Imelda.

In the southeast, rain has been more sparse - also welcome, as
there is still standing water in the areas hardest hit by this
week's rain. While this part of the area is not likely to be
completely dry today, we're looking at a quick spritz at most as
convection here is very anemic.

Regardless of the amount of activity, the setting of the sun will
bring any showers around to an end towards evening, and clouds
look to disperse overnight. Like last night, low clouds and
perhaps even some very patchy fog is possible. Do go with
relatively low ceilings in the north down to around Houston,
staying more scattered closer to the coast.

As tonight is expected to be quite similar to last night, so too
is tomorrow expected to be much like today. All expectations are
that we will end up on the edge of stacked ridging, and along with
that comes temperatures a little bit warmer than typical, and
chances of isolated to scattered diurnal showers and storms.

.LONG TERM [Sunday Night Through Saturday]...

Onshore flow will be the persistent feature in the forecast this 
week. Upper ridging from SETX up into the SE U.S. Monday will be 
slowly shifting back to the west then south. As this southward sag 
occurs Tuesday expect the upper flow to favor the path of weak 
disturbances to move into the area from the southeast then southwest 
as the upper ridge meanders down over Florida. The fluctuations in 
the moisture over the area should help to drive the rain chances 
with Monday being more favorable then drier Tuesday with the 
decrease in lower level of moisture.  Wednesday through Friday 
indicate the greater moisture transport should be into LA/Extreme 
SETX and rain chances bottom out with little if any storms expected 
Tuesday then gradually ramping up into Thursday. Rain chances then 
dip back toward climo with slight to chance mainly driven by diurnal 
heating. During the period not expecting any heavy rainfall that 
would significantly aggravate any flooding that is 
ongoing/diminishing.  Although the area will be warming up thanks in 
large part to the upper ridging and compressional warming the 
temperatures this week should'nt be record setters by any stretch 
but still above normal. Galveston record high minimum Wednesday 
might get close. 

Tide levels will remain elevated Sunday night into Monday but then 
should gradually be improving or edging slightly lower. Rip currents 
should be relaxing as well more into the moderate to strong 


.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.



Marginal SCEC conditions tonight as winds creep back up but by mid 
morning Sunday the area should be down to winds less than 15 knots 
and seas trending down toward the 2-4 foot range. Expecting an 
increase in coverage of showers and thunderstorms to widely 
scattered to scattered in nature tonight through Monday morning then 
returning Thursday with the plume of deeper moisture.



Area rivers continue to fall as Imelda and its rains have
transitioned to a more diurnal pattern. Four flood warnings remain
in effect at this time:

- Moderate flooding on the West Fork of the San Jacinto near
  Sheldon is currently forecast to fall below flood stage Monday 
- Minor flooding on the East Fork of the San Jacinto near New
  Caney is falling quickly and is forecast to fall beneath flood
  stage later tonight.
- The minor flooding of the Trinity at Moss Bluff is expected to
  fall below flood stage sometime tomorrow morning.
- Cedar Bayou near Crosby, unlike the other points in flood, is
  holding fairly steady in minor flood, roughly one foot above its
  flood stage. 



College Station (CLL)  73  94  74  93  73 /  10  20  10  20  20 
Houston (IAH)          76  91  75  91  74 /  30  50  10  30  10 
Galveston (GLS)        81  90  82  90  81 /  20  30  30  30  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.