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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

                            
000
FXUS64 KHGX 181642
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1142 AM CDT Thu Apr 18 2019

.UPDATE...

The impacts of our overnight storm complex are just about over,
though Chambers County recently saw a CG lightning strike from 
storms to the east, even though it's stopped raining there. But,
as that complex pulls away, satellite shows that the sky is
scattering out pretty effectively. Despite getting to some decent
sun by mid-day, it's probably too late to reach previously
forecasted highs, so have gone ahead and pulled those down to
something that better tracks with observations and expected
conditions. Depending on how quickly the sky clears and how much
energy needs to be put into evaporating moisture from the
overnight rain, this still may not be quite enough.

Beyond these changes, the big feature of the weather for the rest
of the day will be the development of gusty northwest winds. We'll
be close to the wind advisory threshold on the barrier islands and
on the western edge of our area, but for now the forecast winds
aren't quite high enough to justify an advisory. If we see winds
ramping up more strongly than expected, a short-fuse wind advisory
may be needed.

&&

.PREV DISCUSSION /Issued 619 AM CDT Thu Apr 18 2019/...
An active morning across the northern third of the forecast area 
where a ragged line of thunderstorms is currently advancing east 
from roughly a Columbus to Conroe to Crockett line. The strongest 
storms are advancing through Walker and Houston Counties at the 
top of the 3 AM hour. Severe Thunderstorm Watch #81 has been pared
back to just include the northeastern CWA. The more southern 
extension of the line is running into quite the capped downstream 
environment and it is having a difficult time maintaining any 
semblance of organization. Thunderstorms will be rolling through 
the metro area within the next hour or two. Expect gusty winds to 
30 mph and brief heavy rainfall that may cause street ponding or 
minor flooding of low lying areas. The latest and greatest rapid 
refresh high resolution modeling has this very ragged line moving 
across the eastern CWA through 18Z. It also has the strong to 
severe cells moving across CRP's CWA turning a bit north (left) 
and merging with the southern tail of our line. This scenario 
might produce a bow echo in the Matagorda Bay area that would push
across our western waters in the 11Z through 14Z range.

West to northwest winds will kick in later this morning and
strengthen this afternoon into the evening hours. Late afternoon 
northwest to western county wind magnitudes may briefly achieve 
Wind Advisory criteria, or sustained 25 mph with higher gusts, 
before quickly coming down at sunset. As the core upper low moves
across and into the Piney Woods late this afternoon, there may be
some early afternoon wrap around cloud cover across the northern 
tier counties with a low chance for a lingering shower or possible
thunderstorm. The day will warm into the mid 70s up north (more 
clouds, rain) and the lower 80s down south (partial clearing, less
rain). Dry air advection will produce overnight clearing and 
assist in lowering temperatures into the near sunrise lower to 
middle 50s.

Friday will be a windy day with a more areawide Wind Advisory 
likely required as daytime sustained northwest winds reach and/or
exceed sustained 20 to 25 mph. Despite mostly sunny skies, strong
northwesterly winds will keep the lower layer mixed enough to 
thwart warming and keep afternoon temperature readings in the
lower to middle 70s.

A very nice Easter weekend with onshore flow returning Saturday 
and strengthening during a mostly sunny and dry Easter Sunday. 
Lower 60 F sunrise temperatures Easter Sunday will be around 10 
degrees warmer than Saturday's min Ts...both days will warm into 
the average lower 80s. 

Early next week's precipitation chances will be on the rise each 
subsequent day from Monday's slight chances to Wednesday's likely
probs. The impetus to return precipitation of (early week showers
transitioning to more stormy mid week conditions) will be the 
slow deepening of a very slow eastern-moving upper trough from 
the Great Basin Monday into western Texas Wednesday. An associated
surface reflection northeastern Mexico low may evolve an emanating
lower level trough/boundary across South Central and Central 
Texas Tuesday into Wednesday. This lower level focus, in tandem 
with a series of shortwave disturbances rounding the bend of the 
western Texas 5H trough axis, will keep high to likely chance 
POPs in the extended. 31


.AVIATION...
Shra and embedded elevated tsra will continue thru mid morning,
then taper off from west to east. Ceilings should lift areawide
into VFR territory shortly, though visibilities could be
restricted at times in the heavier downpours. Apologies in advance
for the fcst winds between now and late morning...they'll be all 
over the place in and around the precip and have low confidence. 
Prevailing direction should eventually transition the the wnw then
eventually nw thru the day as the cold front itself makes its way
in. Some of the high res models show the potential for some sct 
shra right along the front this aftn. That's not reflected in the
TAFS attm, however may need to be added later. NW winds should
become quite gusty by mid-late afternoon, taper off by late 
evening, then increase once again as we head into the mid morning 
hours Fri. 47

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  75  50  73  48  81 / 100   0   0   0   0 
Houston (IAH)          78  54  74  50  80 / 100   0   0   0   0 
Galveston (GLS)        76  54  74  58  75 / 100   0   0   0   0 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...High Rip Current Risk until noon CDT today for the following 
     zones: Brazoria Islands...Galveston Island and Bolivar 
     Peninsula...Matagorda Islands.

GM...Small Craft Advisory until 10 AM CDT Friday for the following 
     zones: Galveston Bay...Matagorda Bay.

     Small Craft Advisory until 7 PM CDT Friday 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...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.


&&

$$

UPDATE...Luchs
DISCUSSION...31
AVIATION...47