Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 202326

Area Forecast Discussion
National Weather Service Houston/Galveston TX
626 PM CDT Thu Apr 20 2017

Generally pleasant across the area, with a couple showers west of
the I-45 sites, but still well southeast of CLL. As diurnal
cooling kicks in, those showers will end and skies will be
scattered or better.

Overnight, do expect MVFR ceilings to redevelop, but have trimmed
up the duration of that period and gone a little more optimistic
as far as ceilings as the atmosphere is drying from the top down.
Some forecast soundings indicate this may not even be optimistic
enough, but will be conservative with changes for now. One big
exception - think this gives an opportunity for sites like CXO and
LBX to fog up, and do go with some development there late
tonight. Unsure of how hard to hit fog here, and tentatively
struck TEMPO IFR visibility for now.



.PREV DISCUSSION... /ISSUED 327 PM CDT Thu Apr 20 2017/

Upper level ridging is impinging on the area from the southwest
and showers considerably less numerous than yesterday. Any
remaining precipitation should end around sunset. Could once again
get some patchy light fog over W/SW zones late tonight. Fog will
erode quickly on Friday but upper level ridging and associated
capping should limit rain chances even more than today. Will
maintain 20 PoPs over the eastern half of the CWA but most areas
should remain dry. A cold front will cross SE TX Saturday morning
but PW values are now progged to only reach 1.40 inches. Jet
dynamics not looking impressive but low level sfc convergence
should be sufficient to generate scattered showers along the
boundary. Timing of the front will mess with temps on Saturday as
a slower fropa could yield some warmer temps over the northern
zones. A warm start over the southern zones coupled with an
offshore winds could also yield some warmer temps than currently
fcst over the south/along the coast.

Sunday looks fantastic with cool morning low temperatures and
afternoon high temps about 5 to 8 degrees cooler than normal. The
air mass will be dry so there should be a large diurnal range in
temperatures Sun-Tues. Onshore winds return Monday night and low
level moisture begins to return and overnight lows will begin to
trend warmer Tuesday morning but really warm Wed/Thu morning with
overnight lows approaching 70 by next Thursday. Warming 850 mb
temps suggest warmer daytime highs by the second half of next
week. Mid/upper 80s look reasonable for the second half of next
week. A semi-zonal flow will keep things on the dry side but south
west upper level winds develop toward Friday as an upper level
trough approaches. Rain chances should increase next weekend as
the upper trough moves across the southern plains. 43

High pressure centered over northern Florida...with pressures
lowering over the Texas Panhandle...has maintained this persistent
onshore fetch. This onshore wind pattern will persist through late
Friday. An approaching cold front will weaken and veer early to mid
Saturday winds more southwesterly with the evening frontal passage
swinging strengthened northerlies to Gulf Advisory levels Sunday
morning. 2 to 3 foot seas through Saturday night will quickly be
driven to 5 to 7 feet nearshore...7 to 8 feet offshore...Sunday per
early day 20-25 knot sustained winds. Wind driven waves and choppy
bay conditions will subside with weakening winds Sunday afternoon
and evening. Slight shower and storm chances Saturday night through
Sunday morning in association with the approach and passage of the
early Sunday cold frontal passage. Light northeast to east winds
will veer onshore by Monday night and strengthen to Caution levels
Tuesday. Moderate onshore flow is expected through Friday...with
(next weekend) strengthening to Advisory criteria...per a tightened
onshore pressure gradient between a Florida-based High and lowering
western Plains pressure. 31


College Station (CLL)      69  86  63  73  50 /  10  10  20  20  10
Houston (IAH)              69  86  69  81  53 /  10  20  10  30  10
Galveston (GLS)            74  83  73  81  60 /  10  10  10  20  20




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