Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 191825
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
125 PM CDT Sat May 19 2018


.AVIATION...
VFR across the area with moderate south and southeasterly winds of
10-17g15-24kt. Expect these winds to relax slight and back to more
southeasterly this afternoon. Expect CU to thin out even more
throughout the afternoon. Tonight MVFR deck redevelops and should
cover most of the western portions of the area but not sure how
far southeast it will extend. Leaned towards the more pessimistic
guidance for timing but not as flight restrictive. Tomorrow the
s/w nears the area in the morning and showers/thunderstorms firing
off over the Hill Country should advance eastward possibly nearing
CLL around 13-15z. MVFR ceilings (and abundant high clouds) a
little slower to improve tomorrow morning/early afternoon.
45

&&

.PREV DISCUSSION... /ISSUED 1140 AM CDT Sat May 19 2018/

UPDATE...

Water vapor imagery indicates a subtle shortwave trough scooting
across Central Texas, and while some showers far, far to our west
might be happening, things are fizzling as they approach Southeast
Texas. Did have a few radar echoes briefly over Colorado County,
but was doubtful anything was reaching the ground. Despite that,
did introduce a very brief window with a slight chance of showers.
Like yesterday, with some decent winds just off the deck, some
gusts to the 20-25 mph range are being seen from Houston westward.
With the strongest low level winds looking to drift westward
slowly through the afternoon, so this should be about as breezy as
we get today. Otherwise, the forecast is pretty well on track and
the forecast is essentially unchanged. So...hot and dry...again.

Luchs

PREV DISCUSSION... /ISSUED 608 AM CDT Sat May 19 2018/

AVIATION...
A few patchy spots of low ceilings and/or fog will persist for the
next couple of hours before improving to VFR for today. Southerly
winds to start will become gusty later this morning, with a
seabreeze likely this afternoon and evening. Low ceilings will be
possible again tonight, but confidence remains low for now. Could
see some isolated showers and thunderstorms during the daytime
Sunday. 11

PREV DISCUSSION... /ISSUED 406 AM CDT Sat May 19 2018/

DISCUSSION...
Upper level ridging will provide yet another day of unseasonably
warm temperatures and rain free skies. At the surface, the
pressure gradient between low pressure over West Texas and high
pressure over the Gulf has tightened so would expect breezy south
winds today. Mixing from the southerly winds and a bit more cloud
cover should shave a few degrees from yesterdays high
temperatures.

The upper ridge gets dampened southward on Sunday as a deep upper
trough edges into the Pacific coast. A southwest upper flow over
the area will allow a weak short wave to traverse the region and
bring scattered showers and thunderstorms. At this time, it
appears the higher rain chances will focus over the western half
of the CWA closer to the short wave. The Hi-Res guidance is rather
bullish with rain chances and matches up well with the Canadian
and the ECMWF. The GFS is stronger with the ridging and shows less
moisture. Have leaned toward the consensus and have raised PoPs
to chance over the NW half of the region. NAM forecast soundings
show some instability in the late afternoon with steepening lapse
rates and an inverted V signature, so if storms do develop, will
need to watch out for some gusty winds. Temperatures will be
strongly dependent on when clouds/precip develop. 850 temps cool a
bit so highs on Sunday should be mainly in the upper 80`s to
lower 90`s.

Another short wave trough rotating around a deep long wave trough
over So CA will approach the area on Monday. This feature coupled
with daytime heating will trigger additional showers and storms
on Monday. The upper ridge over Northern Mexico starts to build
back into Texas on Tuesday as the upper trough over CA shears out.
The Canadian and the ECMWF keeps rain chances going Tues/Wed as
they keep the upper ridge further south and maintain lower heights
over East Texas. Will introduce 20 PoPs for mid week and await a
consensus on the the position of the ridge.

By next Friday, the GFS carves out a fairly deep upper trough over
the mid Mississippi valley and brings a cold front into North
Texas. 500 heights fall and the front will serve as a focus for
rainfall. The ECMWF shows a weakness over the northern Gulf but
shifts the upper feature east allowing upper level ridging to
expand over Texas. Have leaned toward the drier and warmer ECMWF
for next weekend. 43

CLIMATE...
Houston has recorded seven consecutive days with temperatures at
or above 90 degrees. Today will likely be the eighth day. The
longest streak of consecutive 90 degree days during the month of
May is 16 days back in 1996. If the temperature reaches 90 on
Sunday, it looks like the 90 degree threshold will be reached for
the rest of next week and the streak could reach 15 days by next
Saturday. 43

MARINE...
Moderate S to SE winds are expected today and tonight with caution
flags currently flying for all waters. Caution to advisory
conditions are expected on and off through the weekend before
weakening some heading into the start of the work week.  11

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      93  74  89  70  91 /   0  10  30  20  30
Houston (IAH)              92  75  90  73  91 /   0  10  30  10  30
Galveston (GLS)            84  79  85  78  85 /   0  10  20  10  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 4 PM CDT this
     afternoon for the following zones: Coastal waters from
     Freeport to Matagorda Ship Channel TX out 20 NM...Coastal
     waters from High Island to Freeport TX out 20 NM...
     Galveston Bay...Matagorda Bay...Waters from Freeport to
     Matagorda Ship Channel TX from 20 to 60 NM...Waters from
     High Island to Freeport TX from 20 to 60 NM.

&&

$$

Discussion...25
Aviation/Marine...45



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