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Area forecast discussion
National Weather Service Houston/Galveston Texas
1146 PM CST sun Feb 26 2017

Aviation...
storms moving in from the west have dissipated and a few showers
continue near hou in scattered swath to near jas. Winds from the
southeast 5-12 knots with MVFR ceilings filling in across the region.
The warm air advection will continue throughout the night with a slow increase in
ll moisture. Ceilings should continue to lower most of the night and
widespread ceilings of 1000-1500ft should be common before 12z. A few
showers should still develop over the the northern areas through
10z...for now will carry vcsh for uts. Some haze and light fog
possible near the coast in the morning. A few showers possible
tomorrow but with low level jet pulling away and the 850-700mb flow veering
a little more to the SW and west-southwest agree that capping should get
stronger limiting coverage and depth of rain showers. Near the coast in
the late afternoon hours may see visibility lower as 70 dewpoints
flow toward the coast traversing the cooler shelf waters but with
enough mixing and drier air aloft to limit the fog thickness.

45

&&

Previous discussion... /issued 957 PM CST sun Feb 26 2017/

Discussion...
made a few tweaks to the forecast for the rest of tonight...mainly
to account for the ongoing pop trends. Speed convergence/warm air advection help-
ing to produce scattered rain showers across the central/southern portions
of the County Warning Area this evening. Thunderstorms that developed near ewx/San
Marcos earlier this evening are slowly making their way into southeast Texas
at present, but are weakening. Rain chances are expected to remain
in place for much of the region overnight, as a shortwave moves in
from West Texas. Highest probability of precipitation will be over our northern areas...based
on the progged track of the disturbance...but the continued strong
warm air advection could produce widely scattered rain showers elsewhere through sunrise.
41

Previous discussion... /issued 400 PM CST sun Feb 26 2017/

Dense high cloudiness atop lower cu cloud streets this afternoon
as temperatures have warmed into the lower 70s. Southwestern warm
and more moist air riding up and over the relatively cooler drier
surface dome of air providing just enough gentle lift along the
Theta E surfaces to generate scattered light showers. Periods of
light rain will will occur through tomorrow afternoon. The passage
of a shortwave disturbance currently traveling into New Mexico
and into the northern Texas tonight may generate enough lift over
central state to pop a few thunderstorms east of the I-35 corridor
that would move east to northeast. These evening storms may clip
the far northern counties of the forecast area...possibly with a
rogue strong cell or two latter tonight into early Monday morning.
If this shortwave can push parcels past a near 7-800 mb warm
nose...there would be ample cape (in tandem with an exiting 30-40
kt low level jet) to set the stage for a more conducive strong
convection scenario. Again...low chances for thunderstorms to
mainly pass over the far northern counties generally north of a
Brenham to Huntsville to Livingston line during the overnight
hours.

Mainly overcast and mild start to Monday morning with this
continued warm air advection pattern keeping slight to low end
rain chances in place over the northern County Warning Area through the afternoon
hours. Middle to upper 60 dew point air riding over slightly
cooler shelf water in the middle 60s may allow maritime fog to
develop...confidence in patchy fog/haze around Galveston Island
and surrounding waters tonight. Despite the mostly cloudy and
showery conditions...warmer mid-level flow pulling in moist air
will equate to subsequent day warming back into the lower to
middle 80s the next couple of days. A relatively uneventful Monday
will lead to a stronger onshore wind day Tuesday...abnormally
warm and cloudy with slight shower chances over the far interior.
A passing northern Continental U.S. Upper trough will allow rocky mtn Lee
pressure to lower...the associated cold front will travel across
the state early Wednesday. Nwp has speed up the front from
previous runs and now has the boundary passing through during the
morning (daylight?) Hours. Along or ahead of this front...mainly
showers with embedded storms. The faster 84 hr NAM has a Stout cap
for the lift to contend with...the slower GFS has a more favorable
profile to tap into in producing more thunder. A fast mover of a
boundary so the main threats from any early Wednesday qlcs appears
to be strong winds.

The cool and dry backing air mass/high will scour out skies on
Thursday and regulate daily warmth to the near normal upper
60s...afternoon humidities to fall into the 20s/30s. A couple of
starry sky early mornings in the 40s Thursday and Friday. The next
system coming down the Pike is progged to affect the region next
weekend. Broad low/open wave trough hanging back over western
Mexico will set the stage for the development of a Lower Texas
coast surface trough. Better low level convergence and a disturbance
or two passing through within the southwesterly flow (per ecmwf)
has probability of precipitation up in the high end to likely category Sunday. 31

&&

Preliminary point temps/pops...
College Station (cll) 63 81 65 83 63 / 50 30 10 30 30
Houston (iah) 66 82 66 84 70 / 40 30 10 20 20
Galveston (gls) 68 76 67 78 69 / 20 30 10 10 10

&&

Hgx watches/warnings/advisories...
Texas...none.
GM...small craft should exercise caution until 11 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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