Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
FXUS64 KHGX 261707
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1207 PM CDT TUE JUL 26 2016
Showers developing along a line from near 66R-HOU-Galveston Bay.
Left over boundary from last night still evident with these storms
and should remain a focus eventually storms will probably expand
away from the boundary and or lift north slowly with development
of seabreeze which may be hampered by cloud cover. Storms should
dissipate by early evening...last hold outs will probably be near
CLL. Very moist atmosphere over the area will likely lead to the
redevelopment of low stratus and/or fog for the northern sites
after midnight. NAM convective feedback lights up by 12z and so am
skeptical of it`s forecast for tomorrow morning but with what
should be weak PVA expect some sort of cluster of storms to
develop around Galveston Bay area and coast and expand westward
into the Metro hubs and coastal sites after 12-14z.
.PREV DISCUSSION... /ISSUED /
Morning rainfall has largely come to an end this morning, with
most rain now over the waters and a handful of showers over land.
This convection has put temperatures well behind their forecast
this morning, so needed to get that back on track. Given how well
we warmed yesterday despite a fair amount of convection, don`t
want to give up on highs in the lower to middle 90s and for now
will just readjust the day`s warming trend.
Morning convection has also worked over the atmosphere fairly well
per mesoanalysis. Unfortunately, his area also happens to be
where the forecast`s highest precip chances were this afternoon.
Chose to slide the axis of highest chances north a bit towards
Conroe - this should put it back in a more unstable airmass, and
any remnant boundaries from this morning could provide a focus for
development of new convection.
PREV DISCUSSION... /ISSUED 656 AM CDT TUE JUL 26 2016/
KCLL/KUTS/KCXO...main concern has been restricted visibility and
VLIFR CIGS as fog has formed from wet grounds due to yesterday`s
rains and favorable radiational cooling. Atmosphere should recover
quickly this morning and could get TSRA to form later this morning
and through the afternoon. Not sure if fog and low CIGS will be
possible again tomorrow morning but will at least hint at
possibility for KCXO.
KIAH/KHOU/KSGR...overall 2 main concerns for Houston terminals.
First is convection that has impacted both KSGR/KHOU this morning
with limiting visibility and MVFR cigs due to heavy rainfall.
Convection seems to be forming on an outflow boundary from
yesterday and may be showing signs of moving farther north due to
outflow from ongoing convection. KIAH is on the edge of fog and
LIFR CIGS that are impacting KCXO. This has made first 6 hrs of
each TAF challenging since there is little guidance on when
visibility and CIGS will improve or when convection may develop.
Convection will be largely dependent upon outflow boundary
collisions and mesoscale interactions. Will keep TAF overly
pessimistic given the uncertainty on conditions. TAFs will be
amended as needed with conditions changing rapidly.
KLBX/KGLS...As has been the case with the Houston terminals,
convection will be the main issue today. Will keep mention of
VCTS/TSRA but timing will be difficult to pinpoint due to
mesoscale interactions. Again TAFs on the pessimistic side and
will likely need to amend as convection evolves.
PREV DISCUSSION... /ISSUED 427 AM CDT TUE JUL 26 2016/
An upper level weakness in the ridge located over the north-
central and northwestern Gulf of Mexico will continue to drift
toward and over the Texas coast today. This weakness will probably
remain overhead through the upcoming weekend. A weak mid level
low was also located just south of the Southeastern Louisiana
coast. Drier air caught up in the circulation around the low over
Mississippi, Alabama, and the Tennessee Valley was endeavoring to
work its way into the far eastern portions of Texas. A better
plume of moisture was seen over the northern and northwestern
portion of the Gulf of Mexico, southern Louisiana, and the Texas
coastal plains -- the RAP analysis indicated PWs in this airmass
were between 2 and 2.3 inches.
The main challenge for today will be thunderstorm coverage and
temperatures. A model consensus has the best rain chances from the
I-10 corridor south to the coast. Went with likely POPS in these
locations and scattered chances elsewhere. With model PWs near
2.4 inches, also included the mention of locally heavy rainfall
this afternoon. Forecast soundings showed weak steering winds and
storm motion may be slow enough for isolated 1 to 2 inch amounts
in the stronger storms. The temperature forecast was quite a
challenge. Yesterday, Wharton received a little over 2 inches of
rainfall but the temperature reached 100 degrees! A better cloud
cover and better coverage of showers and thunderstorms should lead
lower high temperatures today. However, the potential is there for
highs to reach to near 94 over the inland areas.
Wednesday should see slightly less coverage of rain and
thunderstorms, especially toward the coastal areas. The Nam12,
Gfs, and Ecmwf all forecast the highest moisture moving inland
and north throughout the day on Wednesday.
After Wednesday, a model consensus then has a general weakness in
the upper level ridge overhead of Southeast Texas through the end
of the week. However, the models slowly dry out the airmass as the
lower-level ridge builds across the Gulf into the area. Kept a
model consensus of mainly daytime isolated to scattered coverage
through the weekend and into early next week. The lower pressure
aloft should also lead to daytime highs only reaching into the mid
90s beginning on Thursday. This also means that heat indices will
be on the rise again during the late week and weekend period.
Deep moisture remains over the coastal waters this morning and
should continue over much of the area today. Numerous showers and
thunderstorms will be possible starting out this morning over the
upper Texas coast. Thunderstorm activity should spread inland
during the day. Scattered shower and thunderstorm coverage will
slowly decrease on Wednesday as moisture decreases some and the
upper level trough moves west. Winds will pick up early Tuesday
afternoon, as some thermally induced mixing with the low level jet
brings 10-15 kt winds down to the surface and over the coastal
waters. Moderate southerly winds should continue into the weekend.
Seas of 1 to 3 feet will be the norm through the weekend. Tide
levels one half to one foot above normal can be expected as well.
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 94 76 95 76 96 / 50 20 50 20 40
Houston (IAH) 94 76 96 77 97 / 70 30 50 30 40
Galveston (GLS) 89 81 93 83 92 / 60 40 50 30 40