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Area forecast discussion 
National Weather Service Houston/Galveston Texas
1013 PM CDT Sat may 23 2015

Discussion...
line of storms and Bow echo have developed over Hill Country and
now making a Beeline toward northwest counties. Some of the mesoscale models
incorrectly weakened this feature. It appears main threat will be
damaging winds but cant rule out an isolated brief tornado.

Pattern in general will shift west to east over the forecast area
over the next 6 to 12 hours setting the stage for a stormy Sunday
and Monday time period with potential for 3 to 6 inches of rain
with locally higher amounts...along with an isolated tornado and
damaging wind threat. 46

&&




Previous discussion... /issued 639 PM CDT Sat may 23 2015/

Discussion... the flash watch for southeast Texas is now in
effect from midnight tonight through Monday evening. Expect
showers and thunderstorms to move into the area from west to east
during the overnight hours with the more likely beginning time
(give or take an hour or two) around 4 am from the Burleson to
Columbus to Matagorda Bay areas. Locally heavy rainfall will
accompany these storms...and there is a chance of some severe
weather too. &&

Aviation...
rain showers/thunderstorms and rain coverage has decreased significantly early this evening
with the loss of heating. Expect spotty rain showers coverage for the
remaining evening hours...then increasing rain showers/thunderstorms and rain from west to
east during the overnight hours. With these storms...MVFR ceilings
are anticipated...and IFR ceilings along with +tsra and very gusty
S to southeast winds should accompany the line of storms that move through
the area. We should have decreasing coverage from west to east as
the day progresses tomorrow...but cannot rule out more rain showers/thunderstorms and rain
development as we head on into Sunday night and Monday. 42

Previous discussion... /issued 343 PM CDT Sat may 23 2015/

Flash Flood Watch remains in effect...

Discussion...
ongoing scattered rain showers/thunderstorms and rain should taper off (but not completely diminish)
this evening west/ loss of heating.

There are going to be at least two 2 additional rounds of
rain showers/thunderstorms and rain between now and Monday night - with some potentially
serious concerns in between as well. Grounds are pretty saturated
from recent rains and it won't take a whole lot of rain to produce
runoff and flash flooding. Tide levels are up so bayous from
Houston metropolitan area won't drain as efficiently as they otherwise
would. It also won't take a whole lot of wind to blow down some
trees either.

The first round will be late tonight and sunday:
a large band of rain showers/thunderstorms and rain should take shape to our west this
evening and move eastward and into southeast Texas after midnight and
probably to the I-45 corridor by roughly 7 am (+/- a few hours).
Although overall band should be moving...individual strong cells
within it will be training south-north. With favorable diffluent
wind field aloft and deep Gulf moisture in place...potential for
several inches of rain is there along west/ flash flood threat. Forecast soundings
are fairly saturated...but enough low level shear is in place whereas
one cannot discount some isolated tornados especially west/ any discreet
cells just ahead of primary line. Won't take much for stronger
fast moving storms to lay down some 35-50 miles per hour gusts as well.

Concern and questions about late Sunday afternoon & night:
the vorticity/disturbance associated west/ 1st round of precipitation will move
off to the NE/east-northeast later in the day. Question is if it'll take all
the precipitation west/ it and provide a short and needed precipitation-free
recovery period. Earlier hires models and also 12z European model (ecmwf) suggests
tail end of the upper disturbance might be left behind somewhere
across S part of southeast Texas. Particularly troublesome because strong
low level jet will also continue feeding into the area from the Gulf.
European model (ecmwf) is also now showing a distinct surface boundary setting up along
the I-10 corridor. This set up could provide continued heavy
training rainfall into Monday afternoon. Overall confidence isn't
high how everything will play out...but if I lived south of a
Livingston-Conroe-Columbus line (including Houston metro) I would
take note as these signals have been consistent enough for some
concern. This is a somewhat similar set up as the recent Clear
Lake flooding. ------ Option #2/2a...brief break behind the Sunday
morning precipitation until round 2 and/or with additional scattered activity
developing in the afternoon with daytime heating.

Round 2:
a second disturbance will move across North Texas Monday afternoon and into
OK/AR/la Monday night. This will likely trigger additional rain showers/thunderstorms and rain
development as it occurs with highest qpf's likely across north half
of southeast Texas. That being said...we'll also need to keep an eye if the
tail of this system lingers behind and provides continued good precipitation
chances through Tuesday.

Realize there are a lot of what ifs...but just take away that the
potential is there for many locations to receive around 5" of
rain between now and Tuesday - west/ localized much higher amounts. The
flash flood threat is real.

Upper pattern should flatten somewhat during the midweek time
period west/ just typical scattered diurnal activity. Precipitation chances again
increase going into next weekend as another western trough approaches Texas
and the plains. 47

Marine...
moderate onshore winds will increase in strength to advisory levels
later tonight and then persist Sunday into Monday. Wave run-up may cause
minor flooding on the lowest areas on the Gulf side of the
Bolivar Peninsula...mainly during the high tide time period
around middle morning Sunday morning through about midday. The winds
and seas do not look to diminish much on Monday and another high
tide period may bring minor flooding again to the Gulf side of the
Bolivar. Adding to the wind and seas hazards will be rip currents
and the possibility of isolated strong or severe storms on Sunday
and Monday. 40

&&

Preliminary point temps/pops...
College Station (cll) 72 78 73 83 72 / 70 80 50 80 70
Houston (iah) 74 78 74 82 75 / 50 90 70 70 60
Galveston (gls) 78 80 78 83 77 / 30 80 80 80 60

&&

Hgx watches/warnings/advisories...
Texas...Flash Flood Watch through Monday evening for the following
zones: Austin...Brazoria...Brazos...Burleson...Chambers...
Colorado...Fort Bend...Galveston...Grimes...Harris...
Houston...Jackson...Liberty...Madison...Matagorda...
Montgomery...Polk...San Jacinto...Trinity...Walker...
Waller...Washington...Wharton.

High rip current risk through Monday evening for the following
zones: Brazoria...Chambers...Galveston...Matagorda.

GM...Small Craft Advisory until 1 PM CDT Sunday for the following
zones: Galveston Bay...Matagorda Bay...waters from Freeport
to the Matagorda Ship Channel 20 nm to 60 nm...waters from
Freeport to the Matagorda Ship Channel out 20 nm...waters
from High Island to Freeport 20 to 60 nm...waters from High
Island to Freeport out 20 nm.

&&

$$

Discussion...99

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