Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 201127

Area Forecast Discussion
National Weather Service Houston/Galveston TX
627 AM CDT Tue Mar 20 2018

VFR with just some cirrus moving to the southeast and east
across the area today. Northwest winds will become gusty
after sunrise then will weaken during the mid to late
afternoon hours (generally after 19Z well inland and after
23Z at the coast). Much lighter winds tonight and on into
tomorrow morning and gradually becoming east to southeast. 42

.PREV DISCUSSION... /ISSUED 403 AM CDT Tue Mar 20 2018/


A relatively quiet week of weather is ahead, with slowly warming
temperatures into the weekend. Winds will be relatively breezy
out of the northwest today, before diminishing and slowly turning
in the coming days, eventually becoming onshore again by late
Wednesday. The return of onshore winds will ramp up the humidity,
and things will be muggy again by the weekend. As moisture cranks
up again, look for rain and thunder chances to sneak back into
the picture this weekend as well, and depending on the evolution
of a low pressure center out of the Plains, particularly centered
on the arrival of a cold front.

NEAR TERM [Through Today]...

The radar is clear of all but clutter late tonight, and the
satellite is not much more interesting - a patch of high cirrus
associated with what appears in water vapor imagery to be a subtle
shortwave trough is passing over the area, but that`s close to it.
Some low clouds are dropping towards Southeast Texas from the
north, but also appears to be slowly eroding as it does so, and
am not expecting that to make for any real impact on the area
today. There

We are quite firmly under the influence of northwest flow through
the column, and we`ll begin the day with fairly breezy conditions
as the pressure gradient is still relatively tight. Additionally,
with 850 winds of 25-40 knots through mid-day, we could get
relatively gusty early on. Eventually, as high pressure begins to
dominate the region, the pressure gradient will slacken and winds
will diminish. One might also pretty safely infer makes for some
cold advection, and cooler highs than yesterday`s warmth. Of
course, yesterday was so much warmer than typical that, despite a
pretty notable cooldown, we`ll probably just be a handful of
degrees cooler than seasonal averages today.

There`ll be more to be said about this in a fire weather section
below, but in general, we are looking for another quite dry and
breezy day. But, mitigating fire weather concerns will be the
cooler temperatures and dewpoints that are no lower, and maybe
even modestly higher than yesterday. So, while RH should drop to
low values, it shouldn`t become critically dry as yesterday.

SHORT TERM [Tonight Through Thursday]...

Surface high pressure will dominate the large majority of this
stretch, along with building ridging. Look for winds to become
northeasterly tonight, and continue to veer through easterly to
ESE or SE by late Wednesday. Tuesday and Wednesday should be
modestly warmer day over day, but will really be established for
Thursday as onshore flow returns and the 850 ridge moves east and
warm advection kicks in. Skies will be pretty clear Tuesday, but
some scraps of cloud should start to crop up in the next couple
of days to add a bit of flavor to completely blue skies.

LONG TERM [Thursday Night Through Tuesday]...

As high pressure and ridging move off to the east, low pressure
will also begin to develop in the lee of the Rockies in response
to mid-level height falls to the west. This will tighten up the
pressure gradient some, and make for more moderate southeasterly
winds. Along with that, look for increasing humidity as the
onshore winds pick up. This will help hold our overnight lows in
the 60s for the weekend, and between that and being under the
mid-level ridge axis, highs should push up into the 80s again away
from the coast.

Precipitable water values should be back up to around or over an
inch by the weekend as well, and so it`s no surprise to see some
chances for showers and thunderstorms to come back into the
picture. In many ways, it will probably feel more like a late
spring or early summer day than an early spring day.

Many questions swirl around early next week. There`s strong
confidence in having low pressure continue to develop in the
Central Plains and eject northeastward into the Missouri Valley,
trailing a cold front into North Texas. And...from there...things
diverge. The Canadian blows a cold front through the area by
mid-week. The Euro is towards the other extreme, stalling the
front northwest of our area. Here, it begins to drop quite a bit
of rain. Through Tuesday, this has little impact on our area, but
may start to drift our way later in the week. The 00Z GFS poses
the most distasteful scenario of all, however. It takes a middle
tack, stalling the front at the coast. Additionally, it stalls
this front underneath a low level col. And not only that, it`s a
col in which the high to our east/southeast will continue to pump
Gulf air into the stalled frontal zone, and the convergent area of
the col will line up just right with the front to keep it in
place. We`re not getting much help from the mid-level pattern
either in providing a baroclinic forcing for the front. This
is...not ideal if you don`t like prolonged, possibly heavy, rain
(raising my hand on this one).

BUT! BUT! I am pleased to note that, at this time, the GFS is
fairly alone on this idea. Importantly, the GFS ensemble mean is
much more like the deterministic Euro than the deterministic GFS.
It`s not the scenario I`d most want, but would focus the rainiest
area to the north. We`ll have to keep an eye on this in the days
to come as the GFS is a plausible scenario, but is not the most
likely outcome for now. I, for one, will be rooting for the
Canadian to verify best.


Elevated north winds and seas (caution in the bays and
advisories offshore) can be expected this morning in the
wake of a cold front. The offshore flow will diminish
during the afternoon and evening hours (bays starting
late this morning and offshore this afternoon) as high
pressure builds into the area. The high will move off to
the east on Wednesday and will allow southeast winds to
resume. Look for increasing southeast to south winds and
building seas during the second half of the week and on
into the weekend as pressures fall to the west and onshore
fetch lengthens. Caution flags are likely, and advisories
might be needed. 42


Elevated fire weather conditions will continue today. Expect
increasing gusty north winds this morning through early this
afternoon, but with the cooler temperatures, relative humidities
look to bottom out between 25% and 35%. Will continue to monitor
closely. 42


Galveston soared to a high of 89 degrees on Monday. This is nearly
20 degrees higher than the normal high, and even demolishes the
day`s previous record high of 80 degrees (1954). The day also set
the record high temperature for the entire month of March. The
previous record high was 87 degrees, which occurred in 2008.


College Station (CLL)      69  46  75  51  79 /   0   0   0   0   0
Houston (IAH)              71  49  76  53  77 /   0   0   0   0   0
Galveston (GLS)            70  58  70  62  73 /   0   0   0   0   0


     for the following zones: Galveston Bay...Matagorda Bay.

     Small Craft Advisory until 10 AM CDT this morning for the
     following zones: Coastal waters from Freeport to the
     Matagorda Ship Channel out 20 NM...Coastal waters from High
     Island to Freeport out 20 NM...Waters from Freeport to the
     Matagorda Ship Channel from 20 to 60 NM...Waters from High
     Island to Freeport from 20 to 60 NM.


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