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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

FXUS64 KHGX 162034

Area Forecast Discussion
National Weather Service Houston/Galveston TX
334 PM CDT Sun Jun 16 2019

.SHORT TERM [Tonight Through Monday Night]...
This first round of afternoon convection, with numerous northern 
county discrete storm cells merging and forming larger storm 
clusters, expecting to subside as we head towards the sunset hour. 
After a few hour early evening break, the forecast calls for the 
northern Texas developing line of convection (northwest of the DFW 
metroplex at this hour) to sag southward and impact our CWA from 
around 01-03Z (northern forecast area) through around 09-10Z 
(southern CWA and points offshore). Thus, anticipating either 
scattered clusters of storms or more of an organized QLCS moving 
across the CWA this evening into early Monday morning. The main 
threat modes with this overnight line will be damaging winds with 
the  secondary threat that of flash flooding. As the base of the 
upper trough comes through tomorrow, there could be redevelopment 
focused across the eastern and near coastal CWA. Focus for Monday's 
activity could be along old outflow left over from tonight's storms 
but we could also witness re-development along the far southwestern 
extension of a lower level convergent line tied to a LA-MS-AR line 
of thunderstorms. 31


The short wave that brought SE TX rain on Monday will be moving
east of the region Monday night. Residual showers are expected
Monday evening before ending between 03-06z. PW values remain 
relatively high on Tuesday rising to between 1.90 and 2.10 inches 
by 21z. Convective temperatures remain in the upper 80's to lower 
90's so feel daytime heating will be the catalyst for afternoon 
showers and thunderstorms. PW values fall to around 1.60 inches 
Tuesday night as upper level ridging builds into South Texas. 850 
temperatures warm Wednesday and Thursday but 500 mb heights only 
build to around 590 dm. Will maintain high temperatures both days
in the middle 90's. Subsidence from the ridge and some drying in 
the mid levels should allow rain chances to remain low. A 
southwest flow will develop Friday night into Saturday as a weak 
upper level trough moves into the inter-mountain west. A series of
weak short waves embedded in the sw flow will move across the 
region next weekend and bring a chance of showers and storms back 
to the area. 43


Large scale background winds will weaken but the threat of an 
approaching and passing line of late night into early morning 
thunderstorms across the local waters heightens the threat for 
mariner situational awareness after sunset this evening. Boaters and 
all marine interests need to be aware of a potential overnight 
occurrence of storms. Winds and seas in or around thunderstorms will 
quickly pick up...greater than 30 knot wind gusts with an agitated 
sea state.

Scattered showers can be expected each morning from Tuesday morning 
onward. Surface high pressure over Central Texas will maintain a sub-
Caution level onshore flow...3 to 4 foot significant sea heights. 
Mid through late week lowering western Texas pressure will tighten 
the onshore pressure gradient enough to produce Advisory level 
sustained southerlies early Thursday through early Friday. Seas will 
lift to average 5 to 6 foot heights. The mention of coastal run up 
leading to minor low lying coastal flooding and stronger rips along 
the upper Texas coast will again be within the late work week marine 
products. 31


College Station (CLL)      75  91  75  93  76 /  70  50  10  20  10 
Houston (IAH)              76  91  76  93  78 /  80  60  10  40  10 
Galveston (GLS)            80  88  81  89  82 /  70  70  30  30  10 


TX...High Rip Current Risk through Monday morning for the following 
     zones: Brazoria Islands...Galveston Island and Bolivar 
     Peninsula...Matagorda Islands.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION through Monday morning 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.