Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/25/19
Area Forecast Discussion
National Weather Service Houston/Galveston TX
739 PM CDT Thu Oct 24 2019
.AVIATION...
The cold front is passing across the I-35 corridor this hour...
scattered convection will be beginning in the Brazos River Valley
by 9 PM. Scattered showers with isolated storms will be feeding up
into the front as it moves into southeastern Texas through the
early Friday morning hours. Numerous showers and thunderstorms
will be coming across all of the terminals from between 06 and
12Z. The front will be clearing the coast around sunrise with a
strong northerly wind in its wake. Light precipitation may linger
behind the frontal passage and impact more southern hubs through
the early afternoon hours tomorrow. High end IFR to low end MVFR
ceilings will persist from around 8 through 19-20Z tomorrow...eroding
from west to east through the day. Inland north to northwest
winds will range in the 10 to 20 knot range with higher gusts...20
to 25 knots along the coast through the daytime hours. 31
&&
.PREV DISCUSSION... /ISSUED 328 PM CDT Thu Oct 24 2019/
SHORT TERM [Tonight through Tomorrow Night]...
Cold front is making progress south but still pushing through
central TX with the front trailing back to the NE towards north TX
and southeast OK. Moisture continues to increase through the
boundary layer. AMDAR sounding from a 17Z flight showed a shallow
layer of moisture in the boundary layer which will need to modify
greatly in the next 6 to 12 hours to support thunderstorm
activity. Given moisture transport at 925mb to 850mb, that should
happen resulting in an environment supporting thunderstorm
activity. Environmental parameters do not support severe
convection, but a strong storms could form and most likely those
will be capable of heavy rainfall tonight.
Short term hi-res guidance seems to have a good handle on frontal
timing reaching College Station around 9PM to midnight, Houston area
around 3AM to 7AM and then off the coast after 7-8AM. Line of storms
will accompany cold front as mentioned before with linear forcing.
With that in mind 0-3km shear may be something to monitor for QLCS
mesovortex formation but lack of overall instability and surging
cold pool may limit this kind of wind threat. SPC has marginal risk
for the Brazos valley so there is at least a threat for strong
storms approaching severe levels. We do need to monitor for heavy
rainfall since there will be increasing moisture with increased
forcing overnight. HREF and other hi-res guidance show a range of
rainfall amounts. Overall think a good 1-2 inches of rain will be
possible tonight but as we know there could be an isolated 3-5
inches. Looking at probability based guidance from HREF and WPC, it
looks like there are two areas of concern for these higher amounts.
The first area looks to be towards central Texas into the Brazos
valley from 9PM to 3AM tonight. Bryan/College Station could
certainly stand to take the rainfall with drought conditions so it
is unclear how much of a flood threat exists. The second area will
be along the coast from Brazoria/Galveston/Chambers and maybe
southern Harris. Harris County will be on the edge of any higher
rainfall amounts. Basic timing for this rainfall will be midnight
to 6AM Friday. Again we are looking at isolated higher amounts for
these areas based on latest hi-res guidance which may change
depending upon ongoing trends.
Upper level trough over New Mexico will be slow to push east and
possibly reach Oklahoma by 00Z Saturday. This does place some
favorable jet stream dynamics over the area with the right entrance
region causing lift. We may get continued cloud cover through the
day with light rain/showers off and on through the day. With that in
mind, decided to lower max temperatures for tomorrow. Just after
midnight tonight, temperatures could be in the 70s and then drop
into the 50s behind the front. Cloud cover and cold advection could
keep temperatures in the 50s most of the day. We will also have some
windy conditions, but may only reach wind advisory criteria along
the coast. With that in mind, we will have a small craft advisory
for the coastal waters for conditions behind the front. There are
even strong southeast winds ahead of the front which are causing
elevated tide levels. These tide levels should drop back down with
the passing of the cold front. Overpeck
&&
LONG TERM [Saturday through Thursday]...
Mild/dry weather to prevail over the weekend with high pressure
lingering across the area. High temperatures will be in the 70s
with lows in the 50s. The main issues for the extended forecast
should continue to be the evolution of the next upper trof (and
closed low) from the west. GFS is still running faster/slightly
drier than the other global models with these 12Z runs...and it
should be interesting to how it plays out. For now not going to
make any major changes with the grids. 41
MARINE...
Did issue the Small Craft Advisory for all the marine waters for
the expected post-frontal winds tomorrow/tomorrow night. But for
now, the SCA for the offshore waters remain in effect tonight. A
brief period of light winds will be possible late tonight...just
ahead of the cold front. The current projection of timing has it
at the coast between 2AM to 4AM, over the Gulf waters by sunrise.
41
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 50 56 46 69 46 / 100 40 10 0 0
Houston (IAH) 58 59 50 69 51 / 90 40 20 10 0
Galveston (GLS) 64 66 55 68 60 / 100 70 20 10 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Coastal Flood Advisory until 4 AM CDT Friday for the following
zones: Brazoria Islands...Coastal Galveston...Coastal
Harris...Galveston Island and Bolivar Peninsula...Matagorda
Islands.
GM...Small Craft Advisory from 7 AM to 10 PM CDT Friday for the
following zones: Galveston Bay...Matagorda Bay.
SMALL CRAFT SHOULD EXERCISE CAUTION from Friday evening through
Saturday morning for the following zones: Galveston Bay...
Matagorda Bay.
Small Craft Advisory from 7 AM Friday to 7 AM CDT 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...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 7 AM CDT Friday 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 4 AM CDT Friday 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 from 4 AM to 7 AM CDT Friday
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.
&&
$$
Discussion...42
Aviation/Marine...31