High pressure has briefly built in off the Gulf and should lead to a decrease in rain chances tomorrow in early Tuesday. Another surge of deeper tropical moisture arrives late on Tuesday and should see at least daily chances of heat of the day showers and storms into late week. By next weekend some changes begin to develop as heights once again fall across Texas and a general trough across the Southern Plains to the Texas Gulf Coast sets up. The longer range Outlook suggest this sort of pattern will continue into late August.
The attachment 08122018 CPC Day 8+ Analogs 500hgt_comp_sup610.gif is no longer available
A fly in the ointment is a rather strong Convectively Coupled Kelvin Wave arriving over the Atlantic Basin for the next couple of weeks. My eye is focused near the Bay of Campeche for any spurious tropical mischief that may attempt to spin up in this favorable pattern of rising air across the Gulf and Caribbean.
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Summary...Thunderstorms are increasing in coverage again in
south-central Texas, and this should continue into the early
evening. The storms should initially fill in along the I-35
corridor from the Mexican border to San Antonio, and may expand
further north or northwest with time. Rain rates may reach 2 in/hr
or so with the more organized bands of heavy rain, and this could
produce flash flooding.
Discussion...Convective coverage was on the increase again near
the I-35 corridor in south-central Texas as of 22-23Z. The area
immediately to the southeast of I-35, and to the south of an
outflow boundary stretching from KUVA-KSSF-K3T5, has become quite
hot and unstable with temperatures well into the 90s and dewpoints
in the 70s. A separate outflow boundary was moving north from Deep
South Texas evident as a thin line on GOES-16 visible satellite
and low-level water vapor channels. This sets up the possibility
of a future boundary collision to increase convection, in addition
to the broad S-SE unstable inflow that is currently leading to a
gradual increase in convective coverage as it intercepts the
northern outflow boundary and an existing stationary front.
Therefore, the immediate I-35 corridor is favored for more
concentrated convective activity in the 23-01Z time frame, and may
expand north or northwest later in the evening. General storm
motions were out of the SSW and parallel to the stationary front,
potentially setting up favorable training as convective coverage
increases. Therefore, localized heavy rainfall seems likely, and
flash flooding could develop if this falls in areas more favorable
for flooding (urban areas or locations that have received heavy
rainfall earlier today). Precipitable water values are around 2.0
to 2.1 inches per the latest GPS-PW observations in the area,
which should support heavy rain rates to around 2 in/hr (perhaps
higher on a very local basis).
Area Forecast Discussion
National Weather Service Houston/Galveston TX
934 AM CDT Tue Aug 14 2018
.UPDATE...
Humid start to the morning but per AMDAR soundings drier air
should mix down quickly late this morning. Heat index readings off
to jackrabbit start with 95-98 at many sites already this morning.
These will climb but with the drier air mixing down this afternoon
should top out in the 102-106 degree range at most sites. Isolated
showers nearing the coast but again the dry air aloft appears to
be the limiting factor. Have made some minor tweaks to showers and
isolated in nature. Hazy/dusty conditions still on tap this
afternoon.
Rip current risk statement issued for strong rips today. Red flag
on the beach for rips.
45
Area Forecast Discussion
National Weather Service Houston/Galveston TX
119 PM CDT Tue Aug 14 2018
.AVIATION...
Onshore winds/slightly deeper moisture moving in from the Gulf
producing some widely scattered SHRA over the western portions
of the CWA. May have to include a brief TEMPO or VCSH for LBX/
SGR/CLL later this afternoon. Otherwise...not too many changes
noted with the overall weather pattern the next few days...and
will keep with previous trends of brief MVFR CIGS/VIS over the
northern sites around sunrise. 41
Rain chances are bumped up over the weekend as capping and the ridge ease and a weak trough approaches from the west. After Thursday, clouds and reduced pressing from the ridge should ease temps. down to the low to mid 90s.
Expect daytime 30-40% chance of afternoon t-storms Friday - Monday. Not bad for mid-August.
Area Forecast Discussion
National Weather Service Columbia SC
458 PM EDT Tue Aug 14 2018
.SYNOPSIS...
A weak surface trough will remain stretched near our southern
forecast area through Wednesday, providing a slight chance of
afternoon/evening showers and thunderstorms for that area.
Otherwise, fair and warm with drier air and upper ridging
precluding convective activity. An upper trough and increasing
moisture will provide a return to scattered afternoon/evening
thunderstorms Thursday through the weekend into early next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Main upper low across eastern PA/NY continues to slowly move
off to the east/northeast. Our region remains on the southern
fringes of this low, with weak mid level northwesterly flow over
the region. Precipitable water values are only around 1.2
inches across the Central Midlands and CSRA with dewpoint
temperatures in the lower 60s. In the far eastern portion of the
forecast area, precipitable water is up to around 1.5 inches
with dewpoint temperatures near 70. Regional radar shows showers
and thunderstorms mainly along the coast late this afternoon.
Continued with slight chance pops across the far eastern
portion of the area. Any isolated rainfall activity will
dissipate after sunset this evening. Atmosphere remains
relatively dry through the night, and skies should be mostly
clear. With light winds overnight, cannot rule out brief patchy
fog at the usual locations towards sunrise. Overnight lows
around 70.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Upper ridging, mid level capping, and a dry atmosphere are expected
to preclude significant convection for most areas on Wednesday.
However, surface troughing and the sea breeze, coincident with
better moisture, may provide some activity near the extreme southern
and eastern forecast area. Both the 12Z GFS and NAM also indicate a
weak shortwave moving across the Midlands during the evening and
overnight hours that could fuel a few showers. Yet due to
uncertainty, have kept the forecast dry for the time being.
Precipitation chances increase on Thursday as the ridge weakens and
a trough approaches from the west with increasing moisture. A lee
trough will also develop over the Piedmont, which could be a focus
for convection. Temperatures during this period will be near to
above normal during this period with highs in the low to mid 90s and
overnight lows in the low 70s.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
Weak upper troughiness will be over the region through the weekend
with southwesterly flow bringing moisture into the area. Therefore,
warm conditions and scattered diurnal thunderstorms can be expected
each day. Despite weak ridging Monday, moisture will remain high and
diurnal convection will persist. Similar conditions are likely
Tuesday as another trough deepens over the Great Lakes.
Hmmmm...the global models and ensemble seem to be more enthusiastic in their last run about the last half of next week vs. this weekend for precip, with the exception of the Euro who are quite troughy. We'll see.
What a gorgeous SE Texas summer evening. All that African dust moved out and a comfortable Seabreeze blew through. Check out the Crescent Moon setting...
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Member: National Weather Association
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It blew through here pretty quick, but we still picked up probably 3/4" (guesstimate)
