Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 241727
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1227 PM CDT Tue Apr 24 2018

.AVIATION [18Z TAF ISSUANCE]...
VFR with light and variable winds. Slight chance of patchy fog
early Wednesday morning.

11

&&

.PREV DISCUSSION... /ISSUED 1045 AM CDT Tue Apr 24 2018/

UPDATE...
Another beautiful day in paradise. Surface high pressure centered
over eastern Texas has kept skies clear and winds either calm or
variable. No near to short term changes other than the western
entrance of scattered cirrus and today`s northerly breezes becoming
weak onshore by early tomorrow afternoon. Maximum temperatures
will achieve late April standard lower to middle 80s with overnights
cooling into the upper 50s to lower 60s. Due to the southeastward
advancement of an upper low/trough moving across Kansas and Oklahoma
tomorrow afternoon...rain probabilities will begin to increase to
moderate chances across our far northern tier counties during late
Wednesday afternoon. The surface reflection will be of a passing
cold front that will reach our northern counties tomorrow evening
and then pass off the coast shortly after midnight Thursday. Scattered
showers with a few isolated thunderstorms can be expected across
the northern half of the forecast area...or just ahead of along
this frontal boundary as it advances towards the coast during the
overnight hours. Not much fanfare is expected with this latest
shortwave trough/cold frontal passage as the regional atmospheric
column will not have much time to saturate and there are little to
no upper level forcing dynamics as it relates to jet stream positioning.
A reinforcing shot of drier and slightly cooler air on Friday behind
a secondary shortwave trough passage will only be noticeable in
the northerly wind field as wind speeds pick up a bit during the day.
31


PREV DISCUSSION... /ISSUED 350 AM CDT Tue Apr 24 2018/

DISCUSSION...

Relatively quiet week ahead, though that will be more a function
of a progressive, but lower amplitude, pattern rather than much in
the way of stagnation. A mid-week cold front will bring a chance
for rain and some thunderstorms Wednesday afternoon into Thursday
morning. After that, a series of weak upper troughs will multiple
chances of rain, but those chances look to be relatively low at
this time. Otherwise, look for temperatures to be pleasant in the
upper 70s and lower 80s.

NEAR TERM [Through Today]...

If yesterday was your thing - sunny skies, generally seasonable
conditions - not much is going to be different today. Surface high
pressure will drift just east of us, and light onshore flow may
set up at the coast, making today a bit more humid there. But,
winds should be light and most will see dewpoints still stuck in
the 50s. We may see enough moisture aloft to finally get a few
scraps of clouds, but if skies aren`t completely blue, it should
be pretty close.

SHORT TERM [Tonight Through Thursday]...

Look for light and variable winds to return tonight, but dewpoints
should be modestly higher, helping tonight be similarly modestly
warmer. However, more established onshore winds don`t look to show
up until Wednesday morning. With the front expected Wednesday
night, that doesn`t give us much chance for quality moisture
return. Still, by Wednesday night, the GFS and NAM both have
precipitable water increasing to around 1.5 inches (the SREF is a
little more modest in the 1.25 to 1.5 inch range), along with some
modest instability. Upper dynamics look fairly lousy with the
upper jet lingering too far behind the front. But, a decent low
level jet should help increase low level convergence into the
frontal zone. Expect that this will push convection back into the
cool sector some and elevate the convection. This will generally
limit severe potential, but steeper lapse rates aloft may allow
for the strongest storms to squeeze out some small hail. This is
likely more of a worst-case scenario. On the other hand, things
could play out more like the 00Z TTU-WRF. Not dry, but not really
stormy, either. Some cooler and drier air will cool things down
for Thursday, but only by 5ish degrees, cutting highs into the
upper 70s rather than the lower 80s. Still fairly close to
seasonal averages.

LONG TERM [Thursday Night Through Tuesday]...

In the late week, surface high pressure will drop into the area,
then eventually move off to the east, continuing our recent
pattern of rapid shifts from offshore winds in the wake of fronts
to the return of onshore winds as high pressure shifts east of the
region. In the stretch from this weekend into early next week,
multiple weak shortwave troughs pass near/across Southeast Texas,
which may provide some low chances at showers. The weekend may be
too dry to squeeze anything out, so early next week should be the
next best shot at some showers. Next week, a more significant
upper trough should drop off the Rockies, accompanied by lee
cyclogenesis. Right now, it appears the troughing will not dig
enough, and the front stalls out before reaching our area. Will
have to see which way the setup trends in the coming days. But,
for now, with relatively weak deep moisture and lack of strong
forcing, precip potential looks fairly limited.

MARINE...
Light winds and low seas should persist through Wednesday. A weak
cold front and associated showers will move off the coast
Wednesday night. Offshore winds behind the front might reach
caution levels for a short period Thursday morning. The offshore
flow will persist through the end of the week as another cold
front moves through the area on Friday. Onshore winds that are
expected to return late Saturday or Saturday night should persist
for the remainder of the weekend and then strengthen into the
start of next week. At this time, it looks like caution flags
might be needed beginning late Monday or Monday night for the
increasing winds and building seas. 42

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      60  82  54  76  54 /   0  10  40  10  10
Houston (IAH)              62  84  59  78  56 /   0  10  40  10  10
Galveston (GLS)            67  80  63  74  64 /   0  10  40  10  10

&&

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

$$

Discussion...31
Aviation/Marine...11



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