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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

FXUS64 KHGX 231211

Area Forecast Discussion
National Weather Service Houston/Galveston TX
711 AM CDT Sun Jun 23 2019


Very similar flying conditions to the past couple of days. That 
of periodic early day MVFR ceilings scattering out to various VFR
decks through the mid-late morning hours. Widely scattered 
afternoon showers with better chances for isolated thunderstorm
cells later this afternoon from the city northward. After an 
early evening break from convection, VFR conditions will transition
to MVFR through early Monday morning. An overnight late period 
squall line passage will increase the areal coverage of northern 
showers and thunderstorms. This squall line or subsequent outflow 
emanating from a line of northeastern Texas storms has a high 
likelihood of advancing into the metro area before sunrise. 31


.PREV DISCUSSION... /ISSUED 417 AM CDT Sun Jun 23 2019/ 


- Heat index values will be near advisory criteria again in a few
  areas, but cloud cover and winds should make it feel not quite
  as hot as the heat index would indicate. We are also expecting
  more shower/thunderstorm activity than yesterday which could
  keep temperatures in check as well.

- Marginal risk of severe storms early Monday morning as a squall
  line moves into the area during the morning hours. HREF/WRF-ARW
  seem to have best handle on timing. Storms should be weakening
  as they enter SE Texas and move towards the coast. Damaging
  winds will be the main threat should there be a severe storm.

SHORT TERM [Today Through Monday]...

A moisture rich and weakly (700-800mb) capped regional environment 
has allowed for the formation of pre-sunrise streamer showers across 
the coastal counties. The passage of these showers will put down no 
more than a couple tenths of an inch along their northern passage. 
Another very warm morning that will again threaten to tie or break 
high minimum temperature records. A shortwave trough passage through 
the central Rockies will place Texas within a more favorable upper 
level pattern for better jet forcing/diffulence across east state. 
Near 90 F convective temperatures that will be met late this morning 
will initiate more widespread convection and, with slightly better 
upper exhaust, far interior shower and isolated storm chances will 
rise through the day. As we will be starting out in the lower 80s, 
it will not take much despite the mostly overcast to warm back up 
into the lower 90s by noon or 1 PM. Maximum heat indices will be in 
the 103 to 106 F range with the occasional higher reading if that 
site's dew point does not mix out of the upper 70s during peak 
heating. While hot, overcast skies and moderate southerlies will be 
subtle counters to the heat and humidity.  

The shortwave trough's passage into the Central Plains this evening 
will initiate the development of a central/eastern OK and 
northeastern Texas QLCS feature. This line will be slowly sagging 
southeastward towards us through the late evening hours. Very good 
near orthogonal 15 knot inflow into this line or subsequent outflow 
will likely allow it to maintain its structure as it reaches our far 
northern reaches late tonight or early Monday morning. While the 
global models keep the bulk of the precipitation off to the 
northeast, the short range higher resolution solutions bring a 
broken line of rain and thunderstorms through the CWA from shortly 
before midnight to the coast by 7 AM. SPC has placed our northern 
CWA within a Marginal threat overnight tonight. This line may hang 
up close to the coast through Monday morning and provide additional 
focus for return -TSRA through the Monday afternoon hours. Thus, 
modest POPS will hang on through the short term with the main 
threats being that of strong winds and hail. 


LONG TERM [Monday Night Through Sunday]...

Going into Tuesday models show a weak short wave trough over the 
area that will then move east during the day. This means the 
overall pattern will be support of scattered convective activity. 
There does not appear to be an organized thunderstorm threat, but 
mainly scattered storms that initiate with daytime heating along 
any remaining outflow boundaries from previous convection. There 
will be more of a mesoscale element to the convective evolution. 
Precipitable water values will range from 1.7 to 2.0 inches so we 
could see a brief heavy downpour in some of the stronger storms.

It looks like Wednesday into Thursday the pattern will transition
to being a little less supportive of convection with weak ridging
aloft developing. The main ridge stays over the southern Rockies 
and Plains but hard to say how much subsidence will occur over SE 
Texas. By the end of the week models still point to a weakness in 
the ridge or an inverted trough. Models seem to be backing off on 
the strength of this inverted trough. Nonetheless, the forecast 
will carry at least some chances for showers and storms for the 
end of the week and weekend.



This persistent multi-day onshore fetch has kept seas elevated 
and the rip current stronger than normal this weekend. While Gulf 
seas have reached 5 to 7 feet nearshore to 7 to 8 feet offshore, 
coastal runup issues have not occurred. Water levels during high 
tides have stayed under 3 feet and, with subsequent lower high 
tides, coastal flooding is not expected as water levels max out 
between 2 and 2.5 feet. Gulf winds and seas will begin to weaken 
back to more caution levels late Monday as the western Texas 
pressure fills in and eastern high pressure moves a bit more west 
across the Gulf. 31 


ICYMI - all four climate sites of College Station, Houston, 
Houston Hobby and Galveston had set record high minimum 
temperatures yesterday. This was the second day in a row to set or
tie record high minimum temperatures. This will probably happen 
again today except for Galveston where the record high minimum 
temperature is 86.


College Station (CLL)      92  74  91  73  90 /  30  70  50  40  40 
Houston (IAH)              93  77  91  77  91 /  30  60  70  30  30 
Galveston (GLS)            91  81  88  80  90 /  30  40  70  20  30 


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: Galveston Bay...Matagorda Bay.

     Small Craft Advisory until 10 AM CDT Monday 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.



LONG TERM...Overpeck