Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/30/19
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1038 PM CDT Wed May 29 2019
.UPDATE...
A broken line of showers and storms continues to move eastward
across Texas and towards our area. We do have some amount of
instability available to these storms, but we also find ourselves
underneath a 700 mb thermal ridge, and divorced from more
significant upper troughing. If the line`s cold pool can sustain
low level convergence, we can continue to manage a broken line of
showers and storms, but capping and upper subsidence indicated in
Austin AMDAR soundings, as well as a decreasing moisture gradient
to the east per GOES-East, will not be favorable for line
maintenance.
All in all, continue to keep decent PoPs in place in our far
northwestern edge, but in keeping with a scenario similar to the
HRRR and other CAM guidance, kill things off pretty rapidly from
there. Nearer the coast, do increase PoPs as onshore flow should
result in the development of streamer showers towards dawn.
Later tomorrow, bring PoPs up from both ends, as the upper jet`s
right entrance region comes closer, along with better potential
for forced lift as the cold front shows up on the scene.
&&
.PREV DISCUSSION /Issued 620 PM CDT Wed May 29 2019/...
.SHORT TERM [Tonight Through Friday Night]...
Low pressure was located near the Big Bend region and high
pressure was over the FL panhandle at mid-afternoon. The flow
between these two features has allowed a ribbon of deeper moisture
to develop over the western third of the CWA on a strong onshore
flow. Isolated showers will persist near this corridor of deeper
moisture this evening, however most of SE TX will likely remain
dry through 9 PM or so. A cold front over N TX will slide south
later tonight. This feature will bring scattered showers and
thunderstorms to the area late tonight. PW values will increase to
between 1.80 and 2.00 inches but instability is not terribly
impressive with the best dynamics confined to mainly the northern
third of SE TX. SPC has outlooked the northern third of the
region, roughly north of a Brenham to Huntsville to Trinity line.
If severe weather does develop, the primary severe weather hazard
will be large hail and damaging winds.
On Thursday, the weak cold front will approach I-10 and probably
stall. Low level convergence along the boundary coupled with weak
lift provided by a weak right rear quad of a departing 75 kt jet
should allow scattered showers and storms to develop. Best rain
chances look to occur between 15-21z as PW values increase to
around 1.90 inches and mid level frontogenesis peaks. Cloud cover
and precip should suppress temperatures a bit and will shave a few
degrees from todays high temps for Thursday. Overnight low
temperatures will remain warmer than normal with cloud cover.
Upper level ridging over the western Gulf expands toward the Upper
Texas Coast on Friday. A weak upper level disturbance sliding
over the top of the ridge should generate scattered showers and
thunderstorms. Not sure if increasing subsidence from the ridge or
lift from the short wave will prevail so will go with 30/40 PoPs
for now. 500 hts build as the upper ridge expands and temperatures
will begin to warm back up. Lower 90`s will prevail over the
southern 2/3rds of the CWA with cooler temperatures to the north
closer to the track of the short wave. 43
.LONG TERM [Saturday Through Wednesday]...
Upper ridging will commence a dry period that will dominant the
extended. Southern based mid to upper level ridging with no upper
level support will provide the subsidence required to keep any
precipitation confined to the mesoscale...either early day near
coastal streamer showers or isolated showers along the sea/bay
breeze boundaries. Slight rain chances across the far northern
counties may exist on both Friday and Saturday afternoons to
account for weak shortwave disturbances passing atop the ridge
axis in the ArkLaTex region. Mostly cloudy mornings will evolve
into partially cloudy afternoons...average middle 70 minimum
temperatures with afternoons warming into the lower to middle 90s.
Overall moisture will ebb and flow to as low as 1.2 inches to
near 1.7 inches pwats under southern steering flow. Afternoon dew
points in the lower 70s with ambient lower to middle 90s will
produce near 100 F heat indices. 31
.AVIATION [00Z TAF Issuance]...
Extremely complex forecast ahead for the area. Here is a brief
sketch of what may lie ahead - I expect that tweaks, potentially
even wholesale changes may be needed in future issuances.
Overnight: a line of strong to severe storms will weaken as it
slowly drops towards Southeast Texas. Sketch out a period of VCTS
at CLL and UTS overnight as to when storms - if any - are expected
to arrive. Very conditional threat here, and there may be no
storms at all.
Tomorrow: a cold front drops into the area. Separated from the
best forcing, there is not a lot of confidence in timing or
strength. General idea tonight is that the front will push through
the northern third to half of the area fairly well this morning,
then slow as it nears IAH. It should stall out, and I end the
forecast period with things in the general vicinity of the Houston
terminals. Use PROB30s for now to highlight most likely windows at
this time.
LBX and GLS: Despite the complexity elsewhere, these TAFs are
fairly straightforward as I stall out the front before reaching
here. If the front pushes more towards the coast, more than a
simple VCTS window may be needed.
.MARINE...
Surface high pressure building down for the Southern Plains through
late week will weaken the onshore pressure gradient. Thus, winds
will be on the decline through Friday and seas will accordingly
fall an average 3 to 4 feet by Saturday. Late week minor coastal
wave run up to between 2 to 2.5 feet MLLW and weakened rip currents.
Overall high pressure across the local waters from the weekend on
through mid next week will generally maintain near 10 knot onshore
winds and sub 2 foot significant wave heights. 31
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 74 87 72 87 71 / 50 30 30 40 20
Houston (IAH) 76 89 74 90 74 / 20 60 40 40 20
Galveston (GLS) 79 85 79 87 79 / 30 30 10 20 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 6 AM CDT Thursday 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.
Small Craft Advisory until 11 PM CDT this evening for the
following zones: 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.
SMALL CRAFT SHOULD EXERCISE CAUTION until 6 AM CDT Thursday for
the following zones: 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.
&&
$$
UPDATE...Luchs/Overpeck
SHORT TERM...43
LONG TERM...31
AVIATION...Luchs
MARINE...31