FXUS64 KHGX 180950
Area Forecast Discussion
National Weather Service Houston/Galveston TX
350 AM CST Sun Nov 18 2018
.NEAR TERM [Through Today]...
Surface analysis at 09Z has cold front through KACT to KJCT with
temperatures dropping behind the front into the 50s/40s. There is
also a thick post-frontal MVFR cloud deck evident on the RGB
Nighttime Microphysics imagery from GOES 16. Radar is picking up
on some showers off the Coastal Bend into Central Texas. Looking
at 925mb/850mb analysis, this activity looks to be embedded within
a moisture axis. Looking at 300mb there is a jet streak moving
across the Texas and Louisiana Gulf coast. It appears this feature
may not cause any enhancement in convection with it moving past
the area and any large scale ascent will be over the Gulf. Short
range high resolution models seem to be doing well to resolve
these features and increase activity over areas west of I-45 later
this morning into the afternoon as the front pushes into the
area. There could be some surface based thunderstorms ahead of the
front later this morning but more than likely the front will
undercut any surface based activity leading to weaker elevated
convection. Rain chances today then transition south along the
coast and then off the coast this afternoon in line with the
The other forecast issue will be temperatures behind the front.
Forecast shows a blend of HRRR/WRF/NAM models since they seem to
be initializing the airmass the best. The front does seem to be
moving faster than just a few hours ago which the HRRR runs have
been depicting. This will put the front entering the forecast area
right around 12-13Z, Houston area 16-17Z and then coast 20-21Z.
This means high temperatures will likely be achieved in the
morning hours with falling temperatures through the afternoon.
.SHORT TERM [Monday Through Tuesday]...
Rain chances look to continue Monday and then end by Tuesday. The
southern branch of the jet moving across Mexico looks to remain
active with another jet streak coming across Mexico into S Texas.
With the front off the coast, a weak coastal trough may form which
could enhance rainfall over the area. Models seem to be backing
off on QPF amounts and overall rainfall chances so we lowered the
rain chances slightly during this time to match this trend.
Rainfall amounts look to be around a half inch to an inch for the
Sunday/Monday time frame.
Tuesday models are now bringing a second cold front into the area
as high pressure builds over the Plains on Tuesday. The net
effect of this front is to bring in some cooler air and push the
first front further into the Gulf of Mexico.
.LONG TERM [Wednesday Through Sunday]...
The GFS/ECMWF/Canadian have had some decent consistency going
through the Thanksgiving holiday. That is still the case for
Wednesday/Thursday but beyond that models are much more divergent
in solutions than before. This is to be expected especially when
systems in the Pacific are involved. Models are trending perhaps a
bit drier with rainfall for the Wednesday night coastal trough
system. The coastal trough/low forms farther out in the Gulf since
the front is expected to be further in the Gulf. This means most
of the rainfall will be just along the coast and well out in the
Gulf. GFS is no longer bringing a warm sector airmass anywhere
close to the coast. The ECMWF still has a more potent short wave
trough coming across the area from the Rockies as this wave
undercuts the ridge in the Pacific. We do lower rain chances
inland but still keep some higher chances along the coast and in
the coastal waters. The system does clear out so Thanksgiving day
should be dry and cool. We also lower QPF amounts closer to a half
inch to an inch and really do not see where there could be
isolated higher amounts.
The problem in the extended forecast for Friday through the
weekend is that there is another trough that moves into Texas on
Friday right on the heals of the Wednesday night system. The
ECMWF/Canadian are much stronger but slower with the system than
the GFS. GFS also has the system more in the central/southern
Plains by 12Z Fri instead of southern Rockies like the ECMWF. That
makes a difference in where cyclongenesis occurs and location of
precipitation. Forecast will add in some 20 PoPs for areas east
of I-45 but think the higher chances will be NE of the area.
Beyond that there is another shortwave that comes out of the
Pacific NW for the Sat/Sun time frame that could bring another
cold front into the area. Still some time to figure out those
details but look for an active progressive pattern to continue.
A cold front continues to approach Southeast Texas late tonight.
It will push through the land portions of our area through the day
today, but be slowed up by the weak coastal trough that is also
developing. The front should push off the coast Monday morning
before stalling out over the Gulf. Once this occurs, look for
winds to become more northeasterly, as well as stronger. The
increasing winds and seas, the need for a SCEC appears likely late
Monday into Tuesday. A brief small craft advisory is much less
likely, but not impossible.
Winds should briefly lull on Wednesday, but are likely to pick up
again Wednesday night into Thursday. Though models are differing
greatly on the specifics, there at least appears to be some
general consensus about a coastal low developing in this time
frame as the low exits the region. Along with this low, rain and
thunderstorm chances will increase, and there are indications that
some storms will be strong enough to generate locally high winds
The E-NE winds will give tides a boost upward but the the
departure should be 0.5-1.0 feet above normal and astronomical
high tide isn't really that high so tide levels should remain
under 2.5 feet.
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 56 44 52 42 62 / 50 40 30 10 0
Houston (IAH) 64 48 52 45 63 / 50 30 50 40 10
Galveston (GLS) 67 56 58 52 62 / 40 40 60 50 10