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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

FXUS64 KHGX 191124

Area Forecast Discussion
National Weather Service Houston/Galveston TX
624 AM CDT Mon Aug 19 2019

Mostly VFR ceilings this morning with the occasional MVFR/IFR 
deck over CLL and GLS. Could see a temporary MVFR deck across the 
metro or northern terminals shortly after sunrise. Ceilings 
should rise through the morning hours to VFR and prevail through 
the period until tomorrow morning when temporary MVFR ceilings 
will again be possible. The development of showers should push 
inland through the morning hours, with scattered convection 
possible further inland during the afternoon hours. With 
convective temperatures in reach, thunderstorms will be possible. 
Winds will remain out of the S today around 10 knots, turning more
out of the SE with the passage of the sea breeze this afternoon. 
Winds should become more light and variable during the overnight 
hours inland.



.PREV DISCUSSION... /ISSUED 356 AM CDT Mon Aug 19 2019/ 

SHORT TERM (Today through Tuesday)...

Radar imagery shows scattered showers over the Gulf waters beginning 
to push onshore along the coast this morning, and would expect 
similar activity to continue through the remainder of the morning 
hours. Better coverage of showers and isolated thunderstorms will be 
possible late this morning and into the early afternoon hours. A 
typical summer day is in store, with scattered convection possible, 
focusing along small-scale boundaries such as the sea and bay 
breezes, with development spreading further inland through the late 
afternoon hours. Anticipate most of the showers and thunderstorms to 
dissipate by the early evening hours, shortly after sunset. With 
convective temperatures in the upper 80s to low 90s across the 
region, a rumble of thunder and lightning cannot be ruled out, 
especially during peak heating this afternoon. Strong storms could 
produce brief heavy downpours and gusty winds. Short term guidance 
is fairly consistent with coverage between model solutions, with the 
better chance for development of showers and storms south of a line 
from Columbus to Huntsville where the best moisture should pool. 
Trended the forecast closer to the HRRR and RAP13 than the NMM and 
ARW, which have overdone coverage on initiation.

In terms of heat, conditions should be just slightly cooler than 
yesterday, with apparent temperatures again borderline Heat Advisory 
criteria. Better cloud cover today associated with today's more 
widespread convection should keep us below criteria for the most 
part, but isolated locations could reach the 108 degree threshold. 
Overall, looking like most heat index values should tap out between 
104 to 107 degrees, therefore will again hold off on issuing a Heat 
Advisory today. Similar to yesterday, we will need to monitor 
observations closely throughout the day in case a short-fused Heat 
Advisory is needed. As is typical for SE TX in mid August, we are 
continuing to encourage the practice of heat safety.

Tuesday looks to be fairly similar to today, with the main difference
being slightly drier dewpoints with the upper-level ridge building
in overhead. That should keep max heat index values again below 
Heat Advisory criteria, with values between 102 to 106 degrees in 
the forecast. Widespread convection will also be possible, but not
expecting as much in terms of coverage Tuesday in comparison to 
today. Hathaway

LONG TERM (Wednesday through Sunday)...

Ridge City as a series of Canadian-based troughs ride due east
within zonal flow atop of Central Plains upper ridging. As we head 
into late August, there will be very little variance in our day-to-
day Southeast Texas weather conditions. Hot and humid will remain 
the theme with lobes of more more moisture-rich (greater than 2" 
pwat) GOM air advecting in from the east to southeast. This will 
ensure continued warm, muggy overnights that will struggle to cool 
much below 83 F along the coast...sticky sunrise upper 70s inland. 
Ambient temperatures will be warming to 90 F by 10 or 11 AM with 
afternoons peaking out in the mid to upper 90s with a few 100 F 
degree locales west of the city. Afternoon heat indices will 
typically range between 103 to 107 F inland...106 to 110 F near the 
coast. Suppression brought on by upper ridging will keep convective 
activity confined to the vicinity of the local breezes. Subsequent 
day coverage will be at least 20% with higher 40 to 50% areal 
coverage strictly determinant upon early day clear skies getting us 
to convective temps faster, initiating a stronger sea/bay breeze 
inland intrusion in tandem with periods of high(er) inland Gulf 
moisture advection. Generally, daily shower and storm behavior will 
be confined to those communities along and south of the I-69 
corridor with much lower areal coverage across the northern third of 
the CWA. 

Ridging is progged to finally weaken next weekend. Lower Texas 
heights beginning on Saturday with a transition to either an 
inverted trough feature (GFS) to a southern extension of Upper 
Plains troughing (ECMWF) back over the state. Models have really
backed off on the tropical wave(s)-leading-to-higher-rainfall 
scenario across the southern forecast area next weekend. The 
19/00Z NWP solutions plant the highest rainfall amounts over 
Central Texas or off the Louisiana coastline. We fall into a 
continued diurnally-driven convection behavior pattern that will 
simply be an extension of what we will experience through the work
week. So, the good news is that GOM/Atlantic Basin tropical 
weather remains benign through the end of next week...the only 
action will be a possible weekend tropical cyclone skirting the 
southern Baja California Sur (MX) coast. 31

A Rip Current Statement for the risk of strong rip currents remains 
in effect through the late morning hours today along Gulf facing 
beaches. Light to moderate onshore flow continues across the bays 
and Gulf waters this morning and should prevail through Tuesday 
morning, when wind speeds should diminish slightly in response to a 
region of high pressure overhead. This upper level ridge should 
weaken and shift north by mid week, still allowing for the chance 
for scattered showers and thunderstorms each day, with showers 
beginning to develop over the Gulf waters in the early morning hours 
as radar imagery is also indicating this morning. Winds may become 
gusty and erratic near and beneath any thunderstorms that develop. 
Seas will remain between 2 to 4 feet through Tuesday before lowering 
to 2 to 3 feet through the remainder of the work week. Seas will 
build once again to between 3 to 5 feet Friday through the weekend 
as a weak disturbance moves into the region. Tides should also run 
near normal through mid-week. Hathaway

Record breaking heat continues across SE TX, with another three 
records set yesterday, August 18th. The City of Galveston recorded a 
high temperature of 96 degrees yesterday, which ties the old record 
of 96 degrees set in 2011. Additionally, a record high minimum 
temperature of 86 degrees was set yesterday, breaking the old record 
of 84 degrees set back in 2017. Houston Hobby also set a record high 
minimum temperature of 81 degrees yesterday. This ties the old 
record of 81 degrees set in 2011. Hathaway


College Station (CLL)      99  78  99  77  99 /  20   0  10  10  10 
Houston (IAH)              96  80  96  79  96 /  50  10  30  10  30 
Galveston (GLS)            95  84  94  84  93 /  40  30  50  20  30 


TX...High Rip Current Risk until 10 AM CDT this morning for the 
     following zones: Brazoria Islands...Galveston Island and 
     Bolivar Peninsula...Matagorda Islands.