Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/21/19
Area Forecast Discussion
National Weather Service Houston/Galveston TX
747 PM CDT Mon May 20 2019
.UPDATE...
Persistent southeast to south winds on tap tonight and will still
be breezy much of the night in the west and southern areas. As the
upper trough approaches expect the winds to shift to a more
southerly direction and then get strong and gusty again Tuesday
morning as the entrance region of the LLJ lifts out.
Given the winds have issued a Coastal flood advisory for the areas
around Matagorda bay and the bay side of Matagorda and Brazoria
counties. For the remainder of coastal areas...barrier island and
areas around Galveston bay have gone to a Coastal Flood Warning.
High tide times tonight between midnight and noon should peak the
highest at 3.5 to 4.2 feet which is going to impact SH 87 near
High Island, Blue Water Highway stretch, Beach Drive in Surfside
and Toddville Road and may reach some of the roads in Jamaica
Beach. Improving conditions after noon but may need it again for
the big high tide cycle Wednesday morning. Swimming in the Gulf
could be hazardous given the strong to very strong rip currents!
Gale watch has been dropped and a Gale Warning has been issued for
the southwestern Gulf waters of the Upper Texas Coast. Gusts of
gale driving this issuance especially during the midnight to 9 am
window. SCA remains in effect elsewhere.
Rain chances tonight look minimal but have increased rain chances
over the southern areas Tuesday morning for very fast moving
streamer showers beneath the stout capping inversion.
Last but not least will probably be issuing a wind advisory for
the 6 am to noon window with sustained winds of 15 to 25 knots and
gusts of 27 to 37 mph.
Oh yeah we started the `tropical` weather season a little early
too. Subtropical storm Andrea has formed and should be primarily a
fish storm and some slight impacts for Bermuda.
45/43
&&
.PREV DISCUSSION... /ISSUED 615 PM CDT Mon May 20 2019/
AVIATION...
MVFR ceilings will develop between 00-03z across area TAF sites as
low level moisture streams into the area beneath a capping
inversion. Winds will remain strong and gusty overnight as the low
level jet remains overhead. The pressure gradient is very tight
with a pressure difference across the state around 20 mb from the
coast toward low pressure over the Big Bend. Have leaned heavily
toward the LAV guidance for wind/wind gusts for this TAF package.
A dry line or weak surface trough will approach the area tomorrow
morning and trigger a line of showers that will weaken as it moves
east. Strong capping should hasten the weakening but could get
some showers especially over western TAF sites. The NAM/GFS
soundings show a saturated profile below 700 mb so would expect
some rain to affect the KCLL/KUTS TAF sites between 15-21z. The
cap will weaken the line as it moves east and confidence in
showers reaching KIAH and KHOU is low at this time. 43
PREV DISCUSSION... /ISSUED 347 PM CDT Mon May 20 2019/
DISCUSSION...
- Strong southerly winds expected tonight into Tuesday resulting
in rough marine conditions, elevated tides for coastal flooding
especially along Gulf facing beaches, and rip currents. A gale
warning may be needed tonight.
- Capping will be an issue as a line of storms moves into the
area. Storms will likely be weakening and probably more likely a
line of showers with a few thunderstorms. This line should slide
to the north and east throughout the day.
NEAR TERM [Through Tonight]...
Strong upper level low over the southern Rockies should should
move into the Plains tonight into Tuesday morning with a negative
tilt. Airmass is quite moist and unstable over SE Texas tonight
going into tomorrow but there is little to no lift for storms to
initiate. 18Z sounding from TAMU/College Station showed no cap
while AMDAR soundings over Houston showed slight capping. They key
here being the fact that there is just no lift for storms this
afternoon and day time heating will not be enough to get a storm
to develop. So for the rest of the night look for a rain free
forecast with humid and windy conditions. This means low
temperatures in the mid/upper 70s.
SHORT TERM [Tuesday Through Wednesday Night]...
HREF and WRF model runs show some resemblance of a squall line
coming into the area. We will need to maintain some higher end
rain chances because it does look like this line moves into the
area however it will be weakening as it does. Areas to the north
and west of Houston have the best chances of storms from late
morning through the early afternoon. The line then falls apart and
shifts east through the afternoon so there should not be too much
activity by the evening hours. SPC maintains a marginal risk of
severe which looks reasonable although all the forcing and lift
will be well north of the area. Possible to get a damaging wind
gusts as storms decay but overall think the severe threat should
be north of the area.
LONG TERM [Thursday Through Monday]...
Upper level ridging builds over the northern Gulf coast and
southeastern states by Thursday morning with deep southerly flow.
Pressure gradient increases over the area so expect more strong
winds for the marine areas and elevated tides. Thursday we might
get a slightly better chance of showers and an isolated storm as a
piece of vorticity rotates around the ridge and allows for enough
lift to squeeze out a storm. Best chance of an isolated storm
looks to the west and southwest of Houston. Overall not too
confidence in getting something as the ridge looks pretty strong.
Upper level ridge continues to build over the northern Gulf over
the weekend into early next week. Forecast will maintain low
thunderstorm chances if any at all and above normal temperatures.
Overpeck
MARINE...
Winds starting to pick up over the coastal waters this afternoon but
are remaining in SCEC criteria at this time. Models are keeping with
strengthening winds and seas this evening/overnight as the
gradient over the state tightens. Sustained onshore winds should
increase to 20-25 knots with gusts to gale force possible from
overnight through early Tues morning. Will leave the Gale Watch in
place for now (for all of the coastal waters) as there is still
uncertainty with where the low level jet will be strongest.
However, the developing strong/gusty SE flow will be enough for
seas to build to 6 to 8 feet nearshore and 8 to 10 feet offshore.
Additionally, this persistent long duration onshore fetch will
help to keep coastal water levels elevated through much of the
rest of the week. Issues with coastal flooding should be
periodic... mainly during times of high tide, when water levels
could range from 3.5-4.0 feet above MLLW. These levels will put
water along the low lying streets of the west end of Galveston
Island and may impact the ferry service between Galveston Island
and the west end of the Bolivar Peninsula. Levels near 4 feet
will also push Galveston Bay water onto such eastern Harris County
roads as Toddville Road in Seabrook, and lower sections of Red
Bluff Road between Bay Area Blvd and Highway 146. At 4 feet above
MLLW roads near/along the western shores of Chambers County will
also be impacted. Beaches from San Luis to Surfside can expect
significant wave run up with sections of Beach Drive and the Blue
Water Highway going under water during high tide times. Swimming
conditions will also remain dangerous as rip currents stay strong.
41
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 75 85 74 90 74 / 10 60 10 10 10
Houston (IAH) 77 88 77 89 76 / 10 30 20 10 10
Galveston (GLS) 78 84 79 84 78 / 10 10 10 10 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Coastal Flood Warning from midnight tonight to noon CDT Tuesday
for the following zones: Brazoria Islands...Chambers...
Coastal Galveston...Coastal Harris...Galveston Island and
Bolivar Peninsula...Matagorda Islands.
Coastal Flood Advisory until midnight CDT tonight for the
following zones: Brazoria Islands...Galveston Island and
Bolivar Peninsula...Matagorda Islands.
Coastal Flood Advisory from noon Tuesday to 1 PM CDT Thursday
for the following zones: Brazoria Islands...Galveston
Island and Bolivar Peninsula...Matagorda Islands.
GM...Small Craft Advisory until 1 PM CDT Thursday for the following
zones: Coastal waters from High Island to Freeport TX out
20 NM...Matagorda Bay...Waters from High Island to Freeport
TX from 20 to 60 NM.
Small Craft Advisory until 7 PM CDT Tuesday for the following
zones: Galveston Bay.
SMALL CRAFT SHOULD EXERCISE CAUTION from Tuesday evening through
Thursday afternoon for the following zones: Galveston Bay.
Small Craft Advisory from 9 AM Tuesday to 1 PM CDT Thursday for
the following zones: Coastal waters from Freeport to
Matagorda Ship Channel TX out 20 NM...Waters from Freeport
to Matagorda Ship Channel TX from 20 to 60 NM.
Gale Warning until 9 AM CDT Tuesday for the following zones:
Coastal waters from Freeport to Matagorda Ship Channel TX
out 20 NM...Waters from Freeport to Matagorda Ship Channel
TX from 20 to 60 NM.
&&
$$
Discussion...45
MARINE/AVIATION...43
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
951 PM CDT Mon May 20 2019
.UPDATE...
Midevening regional radar mosaic and GOES IR imagery showed
extensive thunderstorm coverage extending from west TX through
OK, into southwest MO. South and east of this area, coverage was
isolated, mainly over north central AR, where a lone thunderstorm
was lifting north.
Across the Midsouth, the lower atmosphere remained capped to deep
convection, under the northern periphery of a midlevel height
ridge centered over the northern gulf. AMDAR soundings from
Memphis showed a warm layer just above 700mb, indicative of
subsidence aloft.
Looking toward the overnight periods, 00Z NAM model does not paint
a particular favorable scenario upper level jet position with
respect to organized storm development. As the upper ridge axis
translates east overnight, the chances of shallow layer showers
will increase a bit north and northeast of Memphis, along and north
of a slowly lifting surface warm front. Current forecast has this
handled well. Only minor adjustments to hourly temps and dewpoints
needed at midevening.
PWB
&&
.PREV DISCUSSION... /issued 641 PM CDT Mon May 20 2019/
UPDATE...
Please see aviation discussion below.
PREV DISCUSSION... /issued 343 PM CDT Mon May 20 2019/
DISCUSSION...
A deep trough continues to spin over the Four Corners region this
afternoon with a ridge building over the Gulf of Mexico. A strong
jet max is rounding the base of the trough, helping support
today`s anticipated severe weather outbreak across the Southern
Plains. Farther east, we`ll be dry for the most part this evening,
but there is a potential for some weakening convection to move
out of the Ozarks and into the northwest portion of the CWA after
midnight as the Four Corners trough lifts northeast across the
Central Plains. Slight chance PoPs were included for areas north
of Memphis after 06z.
A few lingering showers will be possible along the KY/MO border
early Tuesday, but most of the area will be warm and dry
throughout the day. A secondary trough will move across the
Southern Plains tomorrow afternoon and evening and will force
ongoing convection to our west into a linear mode. This convection
is expected to approach the MS River around or after 00z. There is
a risk for severe weather, primarily across northeast AR and the
MO Bootheel, with the primary concern being damaging winds.
However, this line will be weakening as it moves into the Mid-
South and shouldn`t pose a significant severe risk for most of
west TN and north MS.
An outflow boundary from this convection is expected to linger
across the CWA on Wednesday and may serve as a focus for
additional development of showers and thunderstorms. However, a
mid-level capping inversion will become an issue as the ridge
over the Gulf builds poleward. PoPs were generally capped at 40%
or so for Wednesday afternoon with precipitation diminishing by
sunset. Temperatures through Wednesday will range from the highs
in the mid/upper 80s to overnight lows in the mid 60s to lower
70s.
The subtropical ridge becomes the dominant factor in our weather
pattern for the remainder of the forecast, with 500mb heights
perhaps building as high as 595dam by the end of the week,
approximately 2 standard deviations above the norm. While an
isolated diurnal shower/thunderstorm will be possible during this
time frame, this ridge will generally suppress convective
development and will result in warming temperatures. Temperatures
will gradually climb into the lower 90s across much of the Mid-
South by late week with overnight lows creeping into the lower
70s. Heat indices will respond in the same manner, reaching into
the mid 90s in some areas Thursday-Sunday.
The global models differ on the timing of a potential pattern
change early next week. The GFS swings another strong trough
across the Plains on Monday, but the ECMWF/GEM maintain ridging
over the central CONUS for at least an additional 24 hours,
pushing any potential for precipitation into the midweek period.
Johnson
&&
.AVIATION...
00Z TAF Cycle
VFR conds through the period. Winds will shift southerly
overnight and remain around 5-9 kts. Gusty south winds will
develop at all sites after 21/15Z as a low pressure system
approaches from the west. Showers and thunderstorms will develop
along a front late tomorrow night.
AC3
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$