Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 200453

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1153 PM CDT Wed Apr 19 2017

After seeing skies scatter out, IR satellite and obs indicate
lower ceilings are beginning to develop across the area. Should
see at least degradation to MVFR across the area, with scattered
patches of IFR conditions, particularly in the north. Though winds look
to stay up enough to prevent fog for most of the area, do bring
in some fog at CXO late tonight towards dawn. By mid-day, look for
things to improve back to VFR, as Thursday becomes more or less a
drier repeat of Wednesday.



.PREV DISCUSSION... /ISSUED 922 PM CDT Wed Apr 19 2017/

Overall the main forecast updates were to keep up with short term
trends in temperatures, dewpoint, sky and rain chances. Surface
analysis has weak low pressure in the Panhandle so expect
southerly winds to continue tonight/tomorrow. Upper level ridging
should be stronger so only a very slight chance at a shower or
storm. High temperatures in the 80s look on track. Only forecast
issue coming up will be timing of the cold frontal passage on
Saturday. Temperatures should be falling behind the front. Capping
will likely limit thunderstorm activity with the front but could
still be a line of showers.


PREV DISCUSSION... /ISSUED 321 PM CDT Wed Apr 19 2017/

Scattered showers and thunderstorms will persist for the next
couple of hours but will begin to wane around sunset with the loss
of heating. Upper level ridging over northern Mexico will also
begin to build into the region overnight. SREF ensembles favor
some patchy fog over mainly the W/SW zones tonight and added
patchy fog to the weather grids after 06z. Have some concern that
winds may not fully decouple tonight and this could mitigate the
fog threat. Fcst soundings on Thursday show drying above 850 mb
but PW values still hover around 1.35 inches with only weak
capping in place. Scattered showers again look possible with a bit
of heating. Capping strengthens on Friday so not expecting much
in the way of precipitation and subtle warming at 850 would
suggest slightly warmer afternoon temps.

A cold front will cross the CWA on Saturday. Still some timing
differences between models and leaned toward the slightly quicker
GFS. PW values increase to between 1.5 and 1.6 inches and the
front should be capable of producing enough lift to generate
scattered showers mainly Saturday morning as the front crosses the
area. The air mass behind the front isn`t terribly cool but it
will be drier. There should be a large diurnal range in temps Sun-
Tue and min temps cold fall into the 40s over the northern zones
Sun/Mon morning. Onshore winds will return late Monday and
overnight lows will trend warmer as low level moisture returns.
850 temps warm Tues-Thu and prefer the warmer ECE guidance for
temps and think the GFs/blended numbers are too cool considering
the 850 temps and the semi zonal upper flow. 43

A slightly weakened onshore pressure gradient will remain unchanged
through Friday as high pressure over the southeastern U.S. nudges
into the northwestern Gulf. Southeasterly winds will generally be
under 15 knots over a light chop or under 3 foot seas. An
approaching cold front will weaken veering winds a bit late Friday
into early Saturday. The front is timed to pass across the Gulf
Saturday offshore winds will strengthen to
Advisory levels overnight Sunday morning. Other than a few
scattered showers or lone storm along the front itself this
will be a mainly dry frontal passage. Northerly winds will
weaken to below Caution levels late Sunday night. 31


College Station (CLL)      67  84  67  85  63 /  10  20  10  10  20
Houston (IAH)              68  84  68  86  68 /  10  20  10  20  10
Galveston (GLS)            73  79  73  80  73 /  10  10  10  20  10




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