Nothing really of note. We haven't had much rain since August up here. Will gladly take an inch or precip. this week. Maybe two.
National Weather Service Houston/Galveston TX
635 AM CDT Mon Sep 27 2021
.AVIATION [12Z TAF Issuance]...
VFR conditions will mostly prevail during the day, though an
increase in moisture will result in gradually increasing cloud
cover as well as isolated showers around the metro and coastal
terminals during the afternoon. Activity should begin within the
next few hours offshore, expanding inland by 18Z. Showers will
taper off with the loss of daytime heating just after 00Z. As
winds shift to the south/southeast, further increases in moisture
at low levels will result in the development of MVFR cigs
overnight. Model soundings currently indicate a deck of around
2000-2500 ft developing after midnight, which should persist into
tomorrow morning as shower activity picks up again.
.PREV DISCUSSION /Issued 330 AM CDT Mon Sep 27 2021/...
.SHORT TERM [Today through Tuesday Night]...
Recent surface observations and satellite-derived precipitable water
values indicate the surge of Gulf moisture pushing inland a bit
further east than originally anticipated, near Sabine Pass. While
the development of persistent and stronger onshore winds as
pressures deepen to our west will still bring about a return to
summer-like humidity today, the progression of the moisture plume
has shifted the greatest chances of precipitation to the east. That
being said, isolated showers are still expected to develop along the
coast this morning and expand inland as the day progresses. However,
have focused this morning`s PoP forecast roughly in the Galveston
Bay area and locations eastward. The slight drop in precipitation
coverage will lend favorable to slightly higher high temperatures
this afternoon, with most locations in the metro nearing 90. Coastal
locations will remain varied based on rainfall development, but
should generally remain in the mid 80s. With the expected increase
in cloud cover concurrent with the arrival of deeper moisture,
overnight lows will struggle to dip below 70 region wide with urban
and coastal locations expected to remain in the mid/upper 70s.
Precipitation coverage will expand on Tuesday as a jet streak to the
south of an advancing upper trough axis over the Four Corners region
becomes positioned to our west, placing much of the area within its
left front quadrant. The arrival of additional moisture and the
favorable upper-level divergence that this pattern shift will
provide is likely to yield more widespread showers and thunderstorms
during the afternoon hours, and as a result have maintained PoP
values in the 40-50% range. Precipitation coverage will increase
further during the evening as the jet streak advances further
eastward while an upper shortwave moves into central TX. Expect
daytime highs and overnight lows similar to Monday, though there
will be a bit more uncertainty in these numbers depending on
rainfall coverage and timing.
.LONG TERM [Wednesday through Monday]...
A strong speed max coupled with a weak short wave, a splitting
jet structure and PWATs between 2.00 and 2.15 inches will lead to
high rain chances on Wednesday. Fcst soundings around the area
show a saturated to super-saturated profile which suggests some
potential for locally heavy rain in the stronger storms. PWATs
remain high on Thursday with values near 1.90 inches but most of
the moisture is confined to below 700 mb with considerably drier
air aloft. Upper level ridging also tries to expand into South
Texas with most of the short wave activity being shunted up and
over the ridge. Not real confident with the high PoPs for
Thursday but the blends seem to like it as do most of the global
models. Upper level winds remain broadly divergent which should
aid in lift. Have gone with likely PoPs but again confidence not
real high at this time. Another upper level low over the desert
SW will push east on Friday and a series of short waves will
rotate around the upper level feature and move into and across SE
TX. PW values increase to above 2.00 inches again and upper level
winds will remain broadly divergent. Fcst soundings did not show
much in the way of capping but some dry air was noted below 700
mb. Will again go with likely PoPs.
An upper level ridge over the western Gulf will expand to the west
and SE TX will begin to dry out from the east. PW values remain
around 1.90 inches but there is more low level drying noted below
700 mb. Will continue with chance PoPS for now but activity will
be fighting some subsidence with the building ridge as heights
increase to 591 dm. Models diverge significantly Sunday and
Monday as the ECMWF keeps things wet with a short wave over the
Southern Plains dropping a trough axis into SE TX both days while
the GFS expands the ridge and dries us out with PWATs falling to
1.50 inches. Split the difference and will maintain low end chance
PoPS for both days. 43
A weak coastal trough will produce east winds today. The trough
will become diffuse as low pressure develops in the lee of the
Rockies. The flow will remain S-SE through much of the week ahead
with high pressure over the eastern gulf and low pressure over the
western high plains. The flow will become more easterly Friday
night and Saturday as weak low pressure develops over the southern
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 91 72 92 72 89 / 0 20 20 50 70
Houston (IAH) 89 74 88 74 86 / 10 40 40 60 80
Galveston (GLS) 87 77 85 77 86 / 30 50 60 70 80
- Global Moderator
- Posts: 3468
- Joined: Wed Feb 03, 2010 9:24 pm
- Location: Humble, Texas
FXUS64 KHGX 281153
Area Forecast Discussion
National Weather Service Houston/Galveston TX
653 AM CDT Tue Sep 28 2021
.AVIATION [12Z TAF Issuance]...
Challenging forecast on multiple fronts today. Period opens with
sporadic IFR CIG/VSBY at most sites, plus showers with isolated
lightning in the vicinity of SGR, HOU, LBX, and GLS. Expected
scattered to numerous showers/storms to spread inland this
afternoon, coming to an end in the early evening. Only a brief
break anticipated, with an upper disturbance bringing a new round
of showers and storms to the area.
Activity through the day will have a strong influence on the next
round of convection, and it is difficult to get too into specifics
for timing and impacts to individual terminals. Have tried to
sketch out windows with best chance for impact, for future shifts
.PREV DISCUSSION /Issued 349 AM CDT Tue Sep 28 2021/...
Expect a pretty active stretch of weather ahead right on through
to the weekend as an upper low spins more or less in place over
the southwestern US. Look for multiple rounds of showers and
thunderstorms through the week - so while we`re certainly not
looking for continuous rain through the week, and indeed, any
given point may not see rain every single day, that point will at
least have a decent shot each day until a pattern change arrives.
For the most part, the environment appears unlikely to support
any organized severe weather or widespread excessive rain.
However, we`ll have enough instability and moisture in place that
- as we see so often in Southeast Texas - a storm dropping high
rates of rain over the wrong spot could create brief spots of
localized, minor flooding.
.SHORT TERM [Through Wednesday Night]...
Showers in these overnight/early morning hours are 30-plus miles
offshore...for now. Based on GOES TPW imagery, it appears the
radar only begins to light up once precipitable water reaches two
inches. This deeper moisture is slowly making its way to the
Southeast Texas Coast; additionally, some warmer temperatures
aloft should begin to cool, weakening any remaining capping and
nudging up instability.
In other words, even though convection is currently well offshore,
we should expect that to change over the next several hours, with
potential showers and storms at the coast closer to dawn, with
coverage spreading inland and a general uptick in intensity
through the afternoon. That said, deep layer shear is pretty low,
which will temper the high end of today`s activity some. With
ample instability emerging and high moisture levels, the strongest
storms will be capable of dropping a quick inch or two, with the
best potential for this probably around the Galveston Bay area. If
this falls over a vulnerable spot, we could see localized
urban/poor drainage spots with minor flooding...pretty much par
for the course in Southeast Texas.
We`ll likely see activity chill out in the evening after the sun
goes down, but the break will be a short one. The next thing to
pay attention to will be a vort max associated with a shortwave
trough making its way out of Central Texas and across Southeast
Texas late tonight through Wednesday. This will certainly fuel
some amount of convection. I`ve got very high confidence that it
will rain somewhere in the area and some point while the vort max
aloft rolls through. The problem is...so much of the detail in
this round will depend on mesoscale details determined by what
happens today - boundaries, how much the atmosphere gets worked
over, all that fun stuff that makes getting into specifics very
tough, even 24-48 hours out.
Even better, some of the CAM guidance suggests that we`ll get
some early convection to fire, shoot west and collide with storms
moving east with the shortwave, then diving south towards Corpus.
This gives us storms in the southwest near Matagorda Bay, but
surprisingly little rain elsewhere in the forecast area. This idea
was emergent enough in the 00Z CAM runs that the HREF probability
matched 3-hr mean QPF is pushed to this solution.
It is perhaps unsurprising that, given the uncertainty involved, I
have spread out the PoP pattern areally, perhaps artificially
boosting things far inland northwest and north of the Houston
metro. Still...I don`t know that I`m totally convinced by this
aggressive right turn in the heaviest storms such that most of the
area gets missed. If things play out just how some of this CAM
guidance rolls, with strong, westward-moving convection blocking
things off, this outcome is probable. But if this "blocking"
convection isn`t strong enough, or even fails to materialize at
all, the shortwave should easily support showers and storms over
more than just our southwest.
On top of that, with an upper low spinning over the four corners,
it`s only a matter of time until the next little vort max rolls
across Wednesday night. This doesn`t appear to be quite as
substantial as the shortwave trough mentioned in the previous
paragraph, but it should be enough to drag PoPs right on through
.LONG TERM [Thursday Through Tuesday]...
The wet stretch of weather shows no signs of stopping through the
remainder of the week and into the weekend. The synoptic pattern
over SE TX will continue to be dominated by a vigorous upper level
trough positioned roughly over the Four Corners region, with a
robust associated jet streak positioned to its south. As broad
surface high pressure remains in place over the Southeastern CONUS
and pressures deepen over Western/Central TX as a developing lee
cyclone pushes into the OK Panhandle region, the resultant onshore
wind pattern will keep moisture abundant. Global models indicate PW
values hovering around 2.0 in by Thursday, with little change to
these numbers anticipated through Sunday afternoon.
As the upper trough axis pushes slowly to the east/northeast and
several embedded disturbances push through the Southern Plains, the
combination of ample moisture, favorable upper-level divergence, and
SBCAPE values on the order of 1500-2000 J/kg, will result in
scattered to numerous showers and storms developing each day with
activity peaking during the afternoon hours. Have generally
maintained PoPs of 60-80% through Saturday. Total rainfall amounts
of 2-3" are currently expected across SE TX through the end of the
weekend, though locally higher totals are certainly possible with
any stronger developing storms.
A pattern shift arrives on Sunday as the upper trough axis pushes
further eastward while the progression of a weak surface low over
the Northern Plains drags a cold front into Central/Southern TX.
While the latest GFS solution remains more progressive in its
depiction of the frontal passage through SE TX on Sunday night,
precipitation chances will nonetheless diminish with the loss of
upper-level support and drop off in total PWs to around 1.5 in.
Heading into the early part of next week, have kept PoPs in the
slight chance range with scattered/isolated diurnal activity
remaining a possibility.
Winds continue to hover around advisory criteria this morning,
though have opted not to include advisory flags in the current
forecast package as seas remain generally light. A wet pattern is
expected to continue through the remainder of the week and into the
early part of the weekend as moderate onshore flow allows for a
steady stream of Gulf moisture to move into the area. Meanwhile,
with the onshore wind pattern remaining persistent, seas should
increase to around 3 to 5 knots by Friday. Expect scattered to
numerous showers and storms to develop each day with wind speeds
remaining near 15 knots. Any stronger developing storms may produce
stronger wind gusts at times.
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 93 73 87 71 87 / 40 60 60 40 60
Houston (IAH) 87 74 84 73 86 / 70 70 60 50 80
Galveston (GLS) 86 78 84 77 84 / 70 70 60 60 80
Be Weather Aware & Prepared!
Barbara Jordan Winner in Media
Disability Integration Consultant