Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 190259

Area Forecast Discussion
National Weather Service Houston/Galveston TX
959 PM CDT Tue Jul 18 2017

Radar cleared out around 8 PM and am expecting a stable interior
air mass to keep any overnight shower/storm re-development focused
over the Gulf waters. As has been the case these past couple of
days...scattered early morning Gulf -TSRA activity may clip the
coastal counties through sunrise then creep further inland through
the early afternoon hours. Further northern activity may blossom
latter in the day once the lower 90s are met...but the bulk of
the precipitation should remain over the southern third of the
CWA. Energy is forecast to move down an East Coast trough axis
and pinch off around the south and eastern periphery of the large
Central U.S. ridge. This scenario should contribute to maintaining
a region of disturbed weather paralleling the Gulf Coast. An easterly
flow pattern should allow this unsettledness to still be a player
for yet another day...equating to scattered showers and embedded
ordinary thunderstorms. The main threats will be early day waterspouts
that could travel ashore as weak tornadoes...latter day bursts of
lightning and very localized flooding issues from 1 to 2 inch per
hour rainfall rates. The combination of low to mid 90 ambient afternoon
temperatures and lower to middle 70 dew points should translate to
Wednesday afternoon 100 to 105 F maximum heat indices. 31


.PREV DISCUSSION... /ISSUED 623 PM CDT Tue Jul 18 2017/

Showers currently across the northern half of the area should
diminish over the next couple of hours. VFR conditions are
generally expected, but there could be a few spots of patchy fog
right around sunrise in areas that received rain today. Expecting
showers and thunderstorms to get going again tomorrow afternoon,
with less coverage than today and primarily sticking to around
KIAH and southward. 11


PREV DISCUSSION... /ISSUED 315 PM CDT Tue Jul 18 2017/

The convection which occurred over areas along and south of the
I-10 corridor earlier today has diminished. Scattered showers and
thunderstorms were occurring along the northward and westward
moving outflow boundaries at 3:00 PM. Tweaked the rain chances
for the southwestern and northern counties for the rest of this
afternoon to account for these ongoing storms. Could see an
isolated shower or thunderstorm to redevelop to the south and
southeast but with the cirrus shield overhead think these will be

The deep layer weak trough overhead of SE Texas will likely linger
overhead one more day before the deep layer upper level ridge in
the Plains edges southward. This pattern should lead to slightly
warmer temperatures and less rain chances. On both Wednesday and
thursday the maximum heat indices could reach into the 105 to 107
for a lot of locations with some isolated locations reaching 108.
Do think that the best chances for rain will be on Wednesday;
however, enough moisture will linger overhead to keep daily shower
and thunderstorm chances in place for Thursday and Friday. By
Saturday the general upper level troughiness over the Atlantic
Region will again extend into the Upper Texas coastal areas. Both
the GFS and ECMWF show a 500 mb low pressure area over the Mid
Atlantic moving southwestward into at least the lower Mississippi
Valley during the weekend. Both models differ on the evolution of
this system early next week but both show the weak trough again
developing either overhead SE Texas or near the Upper Texas coast.
For this reason, kept daily chances for showers and thunderstorms
in place for most areas through Tuesday. 40

A light onshore flow is expected through the end of the week with high
pressure over the eastern Gulf and lower pressures over West Texas.
Night time winds will be slightly stronger especially toward the end of the
week as low pressure moves across the southern plains. Tide levels will
remain slightly elevated through the week but will remain below critical
thresholds. 43


College Station (CLL)      75  96  76  97  77 /  20  10  10  20  10
Houston (IAH)              74  94  76  95  77 /  20  30  10  30  10
Galveston (GLS)            81  89  81  90  82 /  20  30  10  30  20




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