Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 191800
AFDHGX

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

.AVIATION...
Morning into afternoon south-to-north moving showers along and
east of the I-45 corridor most likely being triggered by a weak
demarcation (wind) zone within a higher moisture channel.
Overall...expect scattered afternoon showers with drier mid-level
air mixing in to keep any significant mid to late afternoon
convective activity at bay. It appears a weak sea breeze is
setting up this afternoon as skies clear closer to the coast...drier
air to mix down and likely scattered out most sites to FEW. Very
low level moisture...with a damp ground...should allow a low level
stratus deck to form on either side of midnight by an hour or
two. Overnight surface winds should remain just high enough to
preclude any sig fog formation...more patchy in nature with
visbies lowering to under 3 miles over more rural wind-sheltered
hubs. Generally areawide VFR from mid Thursday morning on. 31

&&

.PREV DISCUSSION... /ISSUED 1030 AM CDT Wed Apr 19 2017/

DISCUSSION...
12z soundings support a max temperature between 83-84 degrees with
convective temps between 82-83 degrees. PW values are between 1.35
and 1.45 inches with some slightly drier air noted near 700 mb.
At 300 mb, there is a weakness noted over SE TX between an upper
ridge over the FL Keys and a second ridge amplifying over northern
Mexico. Scattered showers and isolated thunderstorms should
persist today due to a weakly diffluent upper flow, modest PW
values and convective temps in the lower 80s. Made some minor
tweaks to PoPs, sky grids and temps but the overall integrity of
the previous forecast looks on track. 43

&&

PREV DISCUSSION... /ISSUED 446 AM CDT Wed Apr 19 2017/

DISCUSSION...
Keeping a close eye on the large area of showers that developed
offshore overnight and is presently moving toward the Matagorda
Bay/Matagorda coast. Cloud tops have warmed during the last few
hours...but we should see some of this activity make it onshore
shortly. While this particular area of SHRAs is not expected to
persist as it moves further inland, it does underscore the idea
that the airmass over the region is remaining somewhat unstable
(due in large part to the proximity of the main upper low/weakness
aloft).Daytime heating/lingering boundaries and progged PW values
AOA 1.7 inches are all supportive of scattered SHRA/TSRA across
SE TX this afternoon.

The building upper ridge from the W/SW tomorrow will help lower
POPS for Thurs...with the seabreeze as the main focus for isolated/widely
scattered afternoon storms. As the next upper trof moves into the
Central Plains we should see an increasingly warm/dry mid-level
flow develop across the area by Fri. If this does verify, we could
see much more limited activity along or just ahead of the
associated cold front which is slated to move thru SE TX on Sat.
41

&&

MARINE...
Scattered showers moving quickly through the southwest waters and
into Matagorda bay area driven in part by the pooled deep layer
moisture in the Gulf and an increase in diffluence east of the upper
trough.  Will probably see some redevelopment over the Gulf waters
this morning before the disturbances stretch and lift wanes. Brief
gusty winds of 20-30 knots look likely with the storms...perhaps
strong so will need to keep an eye on these this morning. Winds in
general will be south to southeast at 10-15 knots through Friday.
Impressive Pacific front sweeps through Saturday and given the trends
in the last few runs now expect stronger winds and probably at least
6 hours and as much as 24 hours of SCA conditions post FROPA. 45

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      67  85  67  86  64 /  20  20  10  10  20
Houston (IAH)              68  86  69  87  69 /  20  20  10  20  10
Galveston (GLS)            72  81  73  81  72 /  10  10  10  20  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

Discussion...43
Aviation/Marine...31



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