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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

                            
000
FXUS64 KHGX 200232
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
932 PM CDT Fri Apr 19 2019

.UPDATE...
Quiet night in store across SE TX. Biggest forecast question in
the short term is just how cold will low temperatures get? Trends
in hourly temperatures have been coming in slightly colder, so
have gone ahead and lowered tonight's low temperatures a degree or
two to account for this. High pressure will build into the region
tonight and winds will become light and variable, therefore, low 
temperatures should fall into the mid 40s to upper 50s area wide.
Dewpoints should remain on the dry side in the upper 30s to 40s 
as we move into tomorrow morning. Otherwise, no major changes 
were made to the forecast in tonight's update.

Hathaway

&&

.PREV DISCUSSION... /ISSUED 632 PM CDT Fri Apr 19 2019/ 

AVIATION [00Z TAF Issuance]...

VFR conditions should last another 24 hours or more. Winds should
decrease the next hour or two and become calm. Light SW winds 
expected tomorrow.

Overpeck

PREV DISCUSSION /Issued 340 PM CDT Fri Apr 19 2019/...

DISCUSSION...

Today is a pretty pleasant day around Southeast Texas, on the
stipulation that you like it windy. Those gusty northwest winds
should calm down tonight, setting up tomorrow as a slightly
warmer, less windy repeat of today. Look for onshore flow to be
back in place by Sunday morning, which means continued warming
(moreso overnight than during the day) and increasing humidity.
This culminates in a rain event towards the middle to back half of
next week - there are some signals for heavy rain we'll have to
keep an eye on, but such signals are still fairly weak at this
time. It will take more clarity on the details of the forecast to
discern what the true threat of heavy rain in this time period may
be.

NEAR TERM [Through Tonight]...

Gusty northwest winds are the driver of today's feature weather.
It's breezy out, and while the vigorous mixing is keeping temps
cooler than they could be, it's also mixing down dry air from
aloft, driving relative humidity into the 20s across virtually the
whole area. Fortunately, heavy fuels are pretty moist down here,
and greenup is in full swing, which should mitigate most
concerns...but for more on this, you should really just slide on
into the fire weather section below.

Going ahead tonight, winds should decouple and weaken pretty
quickly this evening, especially with surface high pressure
reigning over the area and ridging building aloft. This should
also let temps get relatively chilly, with most inland spots
looking to fall below 50 degrees.

SHORT TERM [Saturday Through Sunday Night]...

Saturday looks like a day! The surface high may be right over
Houston in the afternoon, ridging is continuing to build in aloft,
which means plenty of subsidence for as sunny a sky as can be.
Winds will start to become onshore once the high pressure center
is to our east, but this is not going to come early enough to
meaningfully increase humidity, so we'll look for highs in upper
half of the 70s and perhaps even lower 80s and dewpoints that
might /might/ make it above 50. The most popular phrase among
mothers tomorrow may well be "It's great out, go outside!" But,
at the same time, tomorrow is an Ozone Action Day per TCEQ, so
listen to your body when it comes to outdoor time, particularly 
if you are among sensitive groups such as the young, elders, or
have respiratory ailments. Please help those folks out by reducing
your use of electricity and vehicles as much as you can.

By Sunday morning, onshore flow will be firmly established as high
pressure exits stage east, and Plains low pressure begins to
develop in response to an upper trough dropping off the Front
Range. This will boost humidity into next week.

LONG TERM [Monday Through Friday]...

The aforementioned return of onshore flow will really boost 
nighttime temperatures back into the 60s deeper into next week. 
The high floor should help daytime highs become a bit warmer each 
day as well, with 80s becoming more widespread, but the warming 
trend there probably won't be quite as strong as with the lows.

Finally, towards midweek, we'll look for the impacts of the next
big upper trough and cold front. However, the guidance seems to
have really started backing off on just how deep this front will
push into the region. Whereas yesterday, there was pretty strong
consensus that the front should make it well into Southeast Texas,
and gave me worries about heavy rain potential for the Houston
metro. Now...the guidance barely pushes it into our area, if at
all. Good news for Houston, perhaps less so for B/CS,
Madisonville, Crockett, etc. But, if the 12Z GFS were to verify,
the heaviest rain would stop short of even there!

All in all, the deterministic guidance has taken a good turn for
our area in regards to rainfall totals. Even further, the NAEFS
percentiles shows that moisture parameters are coming in below the
90th percentile. But...the CIPS analogs still show a small signal
for heavy rain in Southeast Texas, and in particular, a band that
cuts through the Houston metro. The Canadian, for what it's worth,
also still likes to paint its band of heaviest rain deeper into
our area. As those in Southeast Texas are well aware, the details
on these types of events can remain fuzzy even until the rain has
started to fall. So - the models have moved in a good direction, 
and I like the trend that has started. But, it's still probably 
worth checking back for the latest over the coming days, to see 
if anything has changed in that outlook.

MARINE...

SCA for moderate to strong northwesterly flow through the evening 
diminishing steadily after 6 pm. Minor tweaks to the timing to 
extend SCA in the Gulf and end it a little quicker in the bays. 
Between 7 and 10 pm winds should drop off substantially. High 
pressure moves over the waters Saturday and by afternoon south and 
southwesterly winds return. Onshore flow gradually strengthens this 
Sunday and Monday. May be back into SCEC conditions by early next 
week. 
45

FIRE WEATHER...

Warm and dry and breezy was the rule today with RH values dipping 
below 28 percent in  few locations (mainly southwest) along with 
gusts of 24 to 33 mph across the region. Such will not be the case 
after good recovery tonight. Light southwest and west winds becoming 
south less than 10 mph. But it will still be dry as moisture return 
is poor to start with before improving Saturday night/Sunday.

45

HYDROLOGY...

Flood warnings are out for the Navasota near Normangee and the
Trinity at Riverside. Neither have reached their flood stage yet,
but both have reached bankfull and are slowly rising. Both are
expected to reach flood stage tomorrow, with Normangee forecast to
hit in the morning, and Riverside in the evening. 

For now, both are forecast to be in minor flood, and this stretch
of several days without rain will be helpful in that respect. 
However, if additional rain begins to fall on or upstream of these
points before the river levels can recede, the situation may 
change. Continue to monitor flood statements from this office for 
the latest information.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      47  77  56  82  62 /   0   0   0   0   0 
Houston (IAH)              48  78  58  81  63 /   0   0   0   0   0 
Galveston (GLS)            58  72  66  74  68 /   0   0   0   0   0 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...Small Craft Advisory until midnight CDT tonight 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.

&&

$$

Discussion...08