Scientific Forecaster Discussion
fxus64 khgx 231143
Area forecast discussion
National Weather Service Houston/Galveston Texas
643 am CDT Sat Jun 23 2018
satellite imagery this morning shows a scattered to broken deck
streaming northward across the region. These clouds should thicken
shortly following sunrise due to ample low-level moisture, and will
eventually scatter out by late morning. VFR conditions are
expected this afternoon, but MVFR ceilings have the potential to
develop once again tonight.
Mainly a wind forecast for this taf package, to account for gusts
expected later this morning and through this evening. With a
tightening pressure gradient over the region, expect and onshore
flow with wind gusts to range between 23-27 kts this afternoon.
The hgx VAD wind profiler this morning has 20-25 kts right off
the deck. Wind gusts should settle shortly after sunset this
evening, but sustained winds will still remain between 10-15 kts
Previous discussion... /issued 405 am CDT Sat Jun 23 2018/
at 3 am, an area of low pressure was over the extreme western part
of the Texas Panhandle with a trough of low pressure extending
east of the low. The pressure gradient across southeast Texas is fairly
tight and winds have not decoupled. This is providing mixing and
temperatures are not cooling much. The wind is keeping fog from
developing as a low stratus tries to develop. At 850 mb, high
pressure is edging into the area from the east and 850 temps are
between 20-22 c. At 700 mb, an area of high pressure is located
over southeast Texas with 700 mb temperatures at 12 c. 850 temps will again
support high temperatures in the middle 90's today but breezy S-SW
winds could mitigate some of the heating through mixing. Speaking
of mixing, low level moisture should mix more today and allow sfc
dew points to cool a few degrees lower than yesterdays oppressive
values. This should keep heat index values below 108 degrees.
Currently, the heat index values are progged to reach 107 degrees
late this afternoon. A heat advisory may yet be required later
today. Either way, it's going to feel hot and heat safety rules
will again apply.
Winds will not decouple tonight and the additional mixing will
keep low temperatures from falling too much. Low stratus will also
make a return and between the mixing and insulating cloud cover am
not expecting overnight lows to fall much below 80 degrees by
Sunday morning. One caveat, both the hires arw and nmm show an mesoscale convective system
developing over northwest Texas and bring this feature to the southeast. Models
have this feature falling apart before reaching southeast Texas but it's
something to watch for.
Another warm day is expected on Sunday but 850 temps begin to
cool. Soundings profile look dry but the weak cap in place early
during the morning is progged to erode with heating. Will
maintain 20 pops for possible weak sea breeze activity but think
most of the area will remain dry. Rain chances look a bit higher
on Monday as 850 temps cool further and precipitable water values perk back up to
1.95 inches between 21-00z. Convective temps are near 90 which is
reachable. Will maintain 20-30 pops across the County Warning Area for Monday
Upper level ridging will be the dominant feature for the rest of
the week. The upper ridge will gradually shift east through the
week finally taking residence over the Ohio Valley by Friday. The
ridge is closest to the area on Tuesday and think subsidence will
limit rain chances. On Wednesday, southeast Texas will lie on the southern
periphery of the ridge and precipitable water values again reach 1.85 inches by
afternoon and fcst soundings show a weak cap eroding by 21z.
Convective temps are in the lower 90's which is again obtainable.
Will carry a slight chance of shra/tsra for Wed afternoon.
Conditions look similar on Thu/Fri with a slight chance of
afternoon convection and temperatures in the lower to middle 90's.
even with the recent rainy spell and cooler temperatures, the
average temperature for Houston through June 22nd is 84.5 degrees.
This is the ninth warmest June to date. Looking a bit further
back, 2018 is now tied with 2011 as the warmest may 1st through
June 22nd in city history. 43
the pressure gradient should continue to tighten through the
weekend. Small craft should exercise caution in both the bays and
Gulf waters with winds hovering between 15-20 kts, and with gusts at
times between 20-25 kts. Seas will also build and strong rip
currents can be expected again today. Winds and seas begin
diminishing on late Monday as the gradient relaxes.
Preliminary point temps/pops...
College Station (cll) 95 77 94 77 94 / 0 10 10 0 20
Houston (iah) 94 79 93 78 93 / 10 10 20 10 20
Galveston (gls) 88 82 89 82 87 / 10 10 10 10 10
Texas...high rip current risk through this evening for the following
zones: Brazoria islands...Galveston Island and Bolivar
GM...small craft should exercise caution through this evening for the
following zones: coastal waters from Freeport to Matagorda
Ship Channel Texas out 20 nm...coastal waters from High Island
to Freeport Texas out 20 nm...Galveston Bay...Matagorda Bay...
waters from Freeport to Matagorda Ship Channel Texas from 20
to 60 nm...waters from High Island to Freeport Texas from 20
to 60 nm.