Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/23/19
Area Forecast Discussion
National Weather Service Houston/Galveston TX
946 PM CST Fri Feb 22 2019
.UPDATE...
Longwave upper-middle level trough digging down into Arizona this
evening will be placing Texas in the more diffulent region of the
southern branch jet through Saturday afternoon. As this trough
axis tilts out and lifts northeast into the western Plains
overnight, the surface reflection will be one of lee cyclogenesis
that will aid in drawing the region`s quasi-stationary/warm
frontal boundary, and subsequently highly moist (low 70F Td) air,
further north. Mucky weather will persist downstream of the
eastward-advancing cold front that will be reaching Central Texas
around sunrise Saturday. 60 to low 70F dew point air overspreading
most of the CWA may allow for the further expansion of dense fog.
A Dense Fog Advisory is in effect for the nearshore, bay, coastal
and eastern CWA this evening. Western visibilites are already
beginning to fall to around a mile or below this hour so this
Advisory may likely expand westward by Midnight tonight.
Low to mid 50s across the far northwestern CWA, or northwest of
the near stationary/warm front with all communities south of this
boundary remaining in their current average middle to upper 60s.
The cold front will cross the CWA tomorrow morning during the
daytime hours. With the region falling under the right rear
entrance quadrant of the jet mid to late Saturday morning, along
with mid-layer cooling brought on by the vicinity upper trough
axis, this will create near 6C sfc-3km lapse rates and keep the
threat for early day thunderstorms alive. There may be enough
late morning mid-layer cooling to weaken cap in tandem with upper
diffulence to produce strong to severe thunderstorms across the
northeastern CWA. SPC has the southwestern 2/3rds of the forecast
area under a Marginal risk with Slight risk just clipping eastern
Trinity and Polk Counties. The good news is that this frontal
passage will quickly scour out any remaining dense fog, cirrus
remains by the close of business tomorrow. Saturday MaxTs will
average in the upper 60s to lower 70s. Cold air advection brought
on by moderate north winds, with mainly clear overnight skies,
will have many interior locations falling into the low to mid 40s
/ lower 50s along the coast Sunday morning. 31
&&
.PREV DISCUSSION... /ISSUED 605 PM CST Fri Feb 22 2019/
AVIATION...
LIFR ceilings and fog will persist overnight and into the morning
hours Saturday. There could be some brief improvement near any
isolated light/moderate showers overnight, but that won`t be the
norm and isn`t indicated in the TAFs. Cold front and associated
band of shra & embedded tsra should push thru se Tx from northwest
(CLL) to se (GLS) between 13-19Z. Ceilings should gradually lift
into VFR territory a few hours after the front passes and rains
end. Look for wind gusts 15-25kt out of the wnw behind the front.
47
&&
PREV DISCUSSION... /ISSUED 322 PM CST Fri Feb 22 2019/
SHORT TERM [Tonight Through Sunday Night]...
Latest mesoanalysis shows the warm front has moved inland
basically from north of Palacios to Houston HOU to north of
Beaumont. T/Td are in the 70s south of the front as we can confirm
here at the office. North of the front temperatures are still in
the 60s to 50s in the Brazos valley. Temperatures may drop a
little bit tonight but largely remain steady. If anything
temperatures may increase a bit as the warm front moves more north
after midnight tonight.
There will continue to be chances of showers and maybe an
isolated thunderstorm. Jet streak and vorticity max seen on water
vapor imagery has move into the area but any convection with it is
located north of the area towards the Arklatex. There is a thin
band of showers from College Station down to Victoria but this
activity should not develop much more than it has. AMDAR airplane
soundings show capping at 800-700mb and 700mb temperatures are
pushing 8C-10C based of this an RAP mesoanalysis data. Cap should
hold overnight going into tomorrow morning.
Upper level trough over the southern Rockies should rotate east
into the Plains by mid day Saturday. Surface low should deepen
near the upper low and push a Pacific cold front into the area.
Largely this means there will not be much of a temperature
difference, but the airmass will be significantly drier. WRF model
runs agree with a broken line of convection moving along the
front from 12Z to 18Z Saturday. A few storms could be strong but
given the capping, it will be a battle for significant deep
convection to develop. SPC has most of the area in a marginal risk
and this looks on track. Greatest threat will be east and
northeast of the area. Storms could still produce gusty winds,
lightning and brief heavy rainfall. While soils are rather moist,
flooding should not be a concern with storms moving through the
area quickly.
Front should be of the coast and east of the area by 18Z to 21Z
based on WRF model runs along with the NAM/GFS. Airmass should be
much drier and should cool off overnight. Low temperatures Sunday
should be in the 40s most areas with a nice warm up into the 60s
for high temperatures Sunday. Overpeck
LONG TERM [Monday Through Friday]...
Moisture return looks to set up once again Monday night into
Tuesday. Forecast will keep an increase in rain chances for the
Tuesday time period. Beyond Tuesday all of the models really
struggle with finding a common solution. Best chance of rain next
week does look to be on Tuesday, but depending upon the model,
there could be some low end rain chances for much of the week
after Tuesday. Right now think the ensemble/blended model approach
looks to be best course of action for the forecast. Usually the
models have had a least some consistency with only some slight
timing problems, but lately that has not been the case. Overpeck
&&
MARINE... Will be keeping the Marine Dense Fog Advisory in place
for the bays and nearshore waters through 9AM Sat morning. Some
brief periods of slightly improved visibilities are possible the
rest of this after- noon, but should fall once again this
evening/overnight. This Advisory may be extended a couple of
hours tomorrow morning...depending on the timing of the next cold
front. Per the models...the front is expected to reach the coast
around noon (Sat), with scattered showers and isolated
thunderstorms along/ahead of it. Moderate/strong N to NW winds in
the wake of the front will help clear the fog out of the marine
areas late Sat afternoon/early evening. SCEC flags could also be
posted very briefly over the coastal waters Sat night. How- ever,
with the surface high building in quickly over the region, we will
likely see winds decreasing once again by Sun morning.
Winds will turn easterly late Sunday and slowly strengthen Mon/Tues
as the fetch deepens. As a result, tide levels are forecast to rise
to around 2.5 ft above MLLW. Will have to watch for possible run-up
issues from mid-week on. Otherwise, unsettled weather should return
to the coastal waters Tues along with onshore winds. 41
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 52 69 41 64 41 / 40 80 0 0 0
Houston (IAH) 64 73 47 67 45 / 30 80 0 0 0
Galveston (GLS) 64 73 55 65 53 / 20 70 0 0 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Dense Fog Advisory until 10 AM CST Saturday for the following
zones: Brazoria Islands...Chambers...Coastal Brazoria...
Coastal Galveston...Coastal Harris...Coastal Jackson...
Coastal Matagorda...Galveston Island and Bolivar
Peninsula...Houston...Matagorda Islands...Montgomery...
Northern Liberty...Polk...San Jacinto...Southern Liberty...
Trinity...Walker.
GM...Dense Fog Advisory until 10 AM CST Saturday for the following
zones: Galveston Bay...Matagorda Bay.
Dense Fog Advisory until noon CST Saturday 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.
&&
$$
Discussion...31/47