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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

                            
000
FXUS64 KHGX 182323
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
623 PM CDT Thu Apr 18 2019

.AVIATION...
Skies are continuing to clear from north to south this evening. 
Radar imagery shows a weak line of showers continuing to sag 
southward along the surface front, but short term guidance does 
show these showers fizzling out along I-10. VFR ceilings will 
prevail through the TAF period. Mainly a wind forecast with gusty 
conditions lowering shortly after sunset, with winds out of the 
northwest between 7 to 15 knots overnight. Shortly after sunrise, 
wind speeds will pick up once more with sustained northwesterly 
winds between 15-25 knots with gusts between 20 to around 30 
knots possible. Winds will slacken by tomorrow evening, just 
outside of the current TAF period, as high pressure builds back 
into SE TX.

Hathaway

&&

.PREV DISCUSSION... /ISSUED 403 PM CDT Thu Apr 18 2019/ 

DISCUSSION...

After strong to severe storms overnight into this morning, you
might think we're done with the rain. That's...not...entirely
true. Another round of showers and storms are popping up on a 
cold front as it pushes into Southeast Texas. This will give at
least the northern third of the area another shot at showers and
possibly a thunderstorm over the next few hours. Once the front
works through, the weather will become more fair, but gusty
northwest winds will reign through tomorrow. This weekend looks
pretty outstanding with sunny skies bringing a warming trend,
though the return of onshore flow will boost the humidity for the
start of next week. Speaking of moisture return, depending on how
quickly we humidify early next week, our first shot at showers may
return as early as Monday night, but we'll really be focusing on a
Tuesday-Thursday window, which is when another front will slowly
droop through the area.

NEAR TERM [Through Tonight]...

A broken line of showers and even a pop or two of lightning is
occurring on a cold front as it pushes into Southeast Texas at 3
pm. So, if you thought you were done with rain after this morning,
especially well north of Houston, you may want to think again.
Impact with this should be nigh on nil, though, outside of another
quick drop of rain before the sun goes down and we lose the energy
of heating today.

Perhaps the bigger impact of the front as it sweeps through will
be to introduce a drier, and gusty new airmass. Northwest winds
will flirt with the wind advisory threshold in the far west and
on the barrier islands, but expect that we'll stay below enough
that an advisory is not needed at this time. Still, this is
probably not a good evening for letting light, unsecured objects
hang out in the yard. Though the incoming airmass is not
particularly cold, some modest cold advection and drier air should
let lows fall into the 50s away from the water.

SHORT TERM [Friday Through Saturday Night]...

Gusty northwest winds continue into tomorrow, and we'll see
another day with the west and barrier islands toying with the
threshold for a wind advisory. Right now, the forecast is still
for winds to stay on the low side of the threshold, but it's
something the overnight shift will definitely want to ponder
tonight before making their call. I will choose not to handcuff
them with a marginal (at most) forecast.

After the slightly cooler start, and winds mixing up surface layer
heating, tomorrow's highs should be noticeably cooler, ending up
5-10 degrees below seasonal averages. However, don't get too
attached to cooler temps, as we'll start ramping up as early as
Saturday underneath continued sunny skies and light winds
underneath high pressure. With dewpoints still relatively low,
Saturday looks pretty dadgum glorious for outdoor activities.

LONG TERM [Sunday Through Thursday]...

Onshore winds look to return as early as Saturday afternoon, and
certainly by Sunday. As usual, this will bolster overnight lows
from the beginning of the new week, and help entrench the warming
trend. Of course, this is a very familiar tale. Give the onshore
flow enough time, and we'll see moisture ramp up, eventually
clouds will begin to form with isentropic lift, and, yes,
eventually we'll start to squeeze out some showers. So, our
sunshine will winnow out (at the coast, anyway) later on Sunday,
covering the area early in the work week, and light showers could
be back in the picture as early as Monday night. More likely?
Those first spritzes aren't until Tuesday, with rain chances
increasing into the midweek as a cold front slowly drops into
Southeast Texas. 

We'll have to do our due diligence on severe potential, of 
course, but with the main upper disturbance working from the 
Northern Plains into the Great Lakes region, this isn't exactly a 
textbook form for a severe outbreak. What maybe stands out a bit 
more to me is how slowly the boundary moves through the area, 
while a southern stream jet streak also slowly crosses Texas. 
Fortunately, inflow looks pretty weak through this window. Still, 
I don't like slowly moving boundaries in April - I look forward to
future model runs being more progressive and eliminating the need
for me to even think about rainfall totals.

AVIATION [18Z TAF Issuance]...

Warm drier air and westerly winds spreading across in the very 
short term with gusty northwest winds soon to follow as cold front
pushes through mid afternoon. Will see some showers across the
northern sites and will continue with VCSH for CXO/UTS/CLL through
the afternoon though shorter for CLL. The brief IFR ceilings
should be ending abruptly with the westerly winds and then a
period of MVFR ceilings from northwest to east across the area as
the wrap around moisture swings through this afternoon/early
evening. Winds inland should relax between 02-04z then resume
early 12-15z NW15-25g20-30kt Friday as nose of the CAA pushes 
down over the area with VFR.

45

MARINE...

Northwest winds increasing throughout the evening with sustained 20-
25 knots gusting to 30 to 35 knots with seas building to 6 to 10 
feet. Gradient relaxing Friday afternoon with SCA conditions 
gradually coming down Friday afternoon and night. 

Onshore flow resumes Saturday as high pressure departs to the Gulf.
 
45

FIRE WEATHER...

Much drier air will spread over the area tonight/Friday and with 
gusty northwest winds. Mixing tomorrow is still a big question and 
could see RH values below 30 percent if deeper mixing occurs.
Winds relax Friday night.

45

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      52  72  49  79  59 /   0   0   0   0   0 
Houston (IAH)              54  73  51  80  61 /   0   0   0   0   0 
Galveston (GLS)            59  73  60  74  68 /   0   0   0   0   0 

&&

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

&&

$$

Discussion...43
Aviation/Marine...08