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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

FXUS64 KHGX 161729

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1229 PM CDT Fri Aug 16 2019

.AVIATION [18Z TAF Issuance]...

Latest radar imagery is showing the development of showers and 
thunderstorms offshore, which should begin to impact coastal 
terminals shortly. Soon after, VCTS triggered by daytime heating
should affect all inland sites except CLL. Activity is expected to 
persist until approximately 00Z this evening.

Some MVFR cigs are possible at northern sites tomorrow morning, 
particularly at CLL. Otherwise, mainly VFR conditions are 
expected at all terminals through the duration of the TAF period. 
Winds should remain out of the S/SE at 5-10 kts across the area.



.PREV DISCUSSION... /ISSUED 1018 AM CDT Fri Aug 16 2019/ 

12z soundings support high temperatures in the middle 90's and
current forecast is a bit higher than that. Considering guidance
has been too cool over the past couple of days will shave a degree
or so from MaxT but not go as cool as models suggest. PoPs look ok
for now as PW values remain around 2.20 inches and convective
temps are between 89-93 degrees. Conditions over the water/near
the coast also look favorable for short lived funnel clouds and
waterspouts through the early afternoon. 43 

PREV DISCUSSION /Issued 425 AM CDT Fri Aug 16 2019/...


Some showers have sprung up this morning along the southern tip of  
Harris County moving northward, and short term guidance continues 
to have isolated showers and thunderstorms through the morning 
hours mainly near and north of Galveston Bay. Activity picks up 
during the afternoon as a tongue of PWATs nearing 2.25 to 2.5 
inches looks to move through the area. This combined with daytime 
heating should bring some scattered showers and thunderstorms. 
Shower activity settles down after sunset, but then looks to pick 
up again by around 09z tomorrow with some streamer showers. 

The amount of showers and thus cloud cover will really dictate how  
warm today is going to get. Right now heat index values look to 
stay just below Heat Advisory criteria, so decided not to push any 
highlights. Tomorrow has a better chance of crossing into Heat 
Advisory territory, but confidence is not the highest at the 
moment, so have will defer to later shifts. Fowler

LONG TERM (Saturday night through Friday)...

An elongated upper ridge whose west-east axis that will roughly 
parallel the northern Gulf will encompass most of the Lone Star. 
Early week upper ridging will gradually settle back across the 
Desert Southwest. Relatively weaker heights over eastern Texas 
will keep diurnal POPs moderate as weak disturbances pass by 
within mid layer northeasterly flow and into a seasonable near 
1.70 inch pwat air mass. Texas Panhandle low pressure will 
maintain a tight enough onshore pressure gradient to produce more
moderate southerly winds, especially across our local waters, on 
Sunday. The possible overlap of a weak mid-level Arklatex trough 
extending down into the Piney Woods, in tandem with a developing 
afternoon inland-advancing sea breeze boundary, may spark off 
primarily southeastern to eastern CWA Sunday and Monday showers 
and thunderstorms. A sharper mid-upper trough sagging further 
south, along with a higher moisture surge and clearer early day 
skies promoting a strengthening afternoon bay/sea breeze, 
indicates higher POPs for more areal shower and storm (central 
forecast area) coverage in kicking off the work week. Despite 
these higher precipitation chances, early week heat indices may 
reach Heat Advisory criteria for a couple of hours before the 
commencement of any mid to late day convection. Thus, the highest
probs of future Heat Advisories will likely be during both Sunday
and Monday afternoons.

Other than slight chances for mesobreeze-driven widely scattered
showers and isolated thunderstorms, Tuesday and Wednesday will be
high and dry for many. Mainly clear to partially cloudy skies and
no appreciable surge of high moisture expected along low to mid 
level steering flow spells near normal overnight interior middle 
to upper 70s / coastal lower 80s with slightly above normal 
average middle 90 F maximum temperature behavior. 

Late week weather will be highly dependent on whatever evolves 
out of the Bay of Campeche. As of now, confidence is highest on a 
northern-moving weak broad closed-off low or an open wave moving 
into a lower height channel positioned over Texas. A few GEFS 
ensemble members do place closed-off surface circulations off the
Texas coastline by Day 10. This feature is currently progged by 
both the GFS and ECMWF to skirt up the Texas coastline and be a 
rain maker for the western Gulf and many Texas coastal communities
Friday through possibly Sunday. While on the extended cusp of 
this forecast package, this scenario will certainly garner much 
attention from us as we head into early next week. 31


Light onshore flow is expected through the week with slightly
higher  wind speeds during the overnight and early morning hours.
Isolated showers and thunderstorms are expected in early morning 
hours today and tomorrow, and winds may become gusty and erratic 
near any thunderstorms that do form. Seas will generally by 1 to 2
feet through tomorrow, then becoming 3 to 4 feet by the end of 
the weekend. The start of next week looks relatively quiet as high
pressure build across the region. Fowler


College Station (CLL)      77  99  78 100  78 /   0  20  10  10  10 
Houston (IAH)              80  96  81  97  81 /  10  30  10  20  10 
Galveston (GLS)            84  90  85  92  85 /  30  40  10  20  20