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Area forecast discussion
National Weather Service Houston/Galveston Texas
915 PM CST sun Jan 21 2018

Near term [through monday]...
no major changes were made to the
forecast this evening. Current radar imagery shows scattered
showers splattered across much of the region tonight. The surface
low associated with the cold front is currently situated over
northeastern Oklahoma and southeastern Kansas. This has left the
area with the best surface convergence, along with upper level
divergence well to the north of even our northern most counties
from Burleson to Houston. Amdar soundings still reveal a strong
cap in place between 800-700mb this evening, which has helped to
hinder thunderstorm development. Forecast soundings continue to
indicate the best moisture available through 06z, with
precipitable water values ranging between 1.0-1.3 inches. Low-
level lapse rates and k-index values also decrease after 06z.
Therefore, our best chance for an isolated thunderstorm would be
most likely before 06z tonight. Short term guidance such as the
hrrr and Texas tech WRF have begun to back off on thunderstorm
coverage as this line of precipitation slides east of I-45. The
main front will eventually overtake the dryline/Pacific front, as
it continues to push westward across East Texas this evening
between 06-09z.

Nine o'clock observations have temperatures and dew points in the
middle to upper 60s across much of the southeast Texas. Onshore winds will
begin to veer overnight and eventually turn out of the northwest
by sunrise increasing to between 10 to 15 miles per hour. Clear skies are in
store behind the front with Monday morning temperatures beginning
in the upper 40s to upper 50s. As drier air filters into the
region, high temperatures will reach into the upper 60s to lower
70s late Monday afternoon.



Previous discussion /issued 549 PM CST sun Jan 21 2018/...

Aviation [00z taf issuance]...

Radar this evening shows a smattering of showers across southeast Texas
that will intermittently pass over terminals. This will continue
through the night as a Pacific front pushes through the area. The
front should reach kcll/uts around 06-07z, kiah/khou around 08-10z
and then the coast around 12z. Ceilings should drop to MVFR
levels ahead of the front and there may be a brief period of IFR
but confidence in IFR is low. Front should feature a line of
showers but full thunderstorms and rain are yet to be determined. Amdar soundings
still show an elevated mixed layer around 800-700mb which would
need to erode before deep convection can form. Tafs will go with
thunderstorms in the vicinity but likely just have a line of showers as hrrr and a few WRF
runs indicate. Thunderstorms and rain may need to be put in for kcll and kuts but
those sites may even be just far enough south from upper level
forcing that the cap will still hold. Ceilings improve behind the
front with northwest winds which become gusty during the day.


periods of fog (some dense) will continue across the bays and
nearshore waters until the front pushes off the coast early Monday
morning. Moderate onshore flow ahead of this front is also
producing 15 to 20 knot winds and 6 foot seas in the offshore
waters, and caution flags are currently in effect. Expect some
shower development out ahead of the front this evening and
tonight, with the front itself dragging a thin line of showers and
thunderstorms through the waters Monday morning. This will be
accompanied by a gradual wind shift to the northwest. Caution
flags will likely be required Monday into Monday night.

Winds gradually become NE to east by midweek before returning to southeast
by the weekend. Sea fog could become an issue again by the end of
the week as deeper moisture moves back over the waters. Another
much stronger front should push off the coast next weekend. 11

Fire weather...
a cold front will pass through the region overnight tonight,
bringing drier and breezy conditions in its wake. Rhs on Monday
afternoon could fall into the mid to upper 20s with winds near 15
mph. This will create elevated fire conditions across the area for
Monday. Tuesday will be just as dry but with much lighter winds.
Moisture will begin filtering back over the area Wednesday. 11


Preliminary point temps/pops...

College Station (cll) 48 68 37 67 37 / 60 0 0 0 0
Houston (iah) 57 70 41 67 40 / 60 0 0 0 0
Galveston (gls) 58 70 47 64 45 / 60 10 0 0 0


Hgx watches/warnings/advisories...

GM...dense fog advisory until 3 am CST Monday 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...Galveston Bay...Matagorda Bay.

Small craft should exercise caution until 3 am CST Monday for
the following zones: 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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