Preview of NWS' New Version of Forecast
This preview is not operational and should not be used for support decisions.

Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

                            
000
FXUS64 KHGX 160540
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1140 PM CST Fri Feb 15 2019

.AVIATION...
Winds will be shifting to the north as a cold front moves across the
area overnight. The front might stall near/along the coast during the
day on Saturday. A mix of higher ceilings up north (maybe staying VFR)
and lower ceilings with a mix of fog closer to the coast (IFR/LIFR)
are anticipated at this time. Conditions could deteriorate late 
Saturday afternoon into Saturday evening as the front moves back to
the north followed by improving conditions late Saturday night and
on into Sunday morning as another cold front moves across the area
and off the coast. Not much forecaster confidence in the 06Z TAFs.
42 
&&

.PREV DISCUSSION... /ISSUED 556 PM CST Fri Feb 15 2019/ 

UPDATE...
Developing sea fog on the Gulf has pushed onto barrier islands early 
this evening. Galveston has reported 1/4-1/2 mile fog recently, and 
webcams in Galveston and along the Southeast Texas coastline do not 
look promising, and fog should hang with us through the night. A 
dense fog advisory has been issued for all of our barrier islands, 
including Galveston Island and the Bolivar Peninsula. 

There is at least some guidance suggesting that the dense sea fog 
may begin to push over coastal portions of the mainland, but there 
is still uncertainty as to how far inland the most dense fog will 
push. Will maintain a watch on the fog's progress, and will add 
coastal areas on the mainland if the fog shows signs of pushing in.

Luchs

PREV DISCUSSION... /ISSUED 403 PM CST Fri Feb 15 2019/ 

DISCUSSION...
Partially cloudy skies with very warm conditions further within 
the interior where there has been just as much sun as cloud cover.
Quite the temperature gradient across the CWA just this hour as it
has hit 80 F in College Station but still remains in the upper 
60s along the coastline where shallow water temperatures hover
around 60 F. While the weekend will remain mostly dry there is
still much challenge to handle in the short term temperature and
fog forecast that centers around an approaching evening cold front.

The next cold front is currently moving through the Texas 
Panhandle and the Red River Valley. After reviewing the current 
synoptic state and model ensemble, it appears the best consensus 
will be to bring this shallow cold air mass/front to our northerly
doorstep around midnight tonight. As the air mass slowly modifies
on its southern trek, it will slow and eventually hang up somewhere
over the southern third of the forecast area tomorrow morning. 
This will create an even greater temperature gradient across the 
region tomorrow afternoon. Post-frontal cold air advection and a 
lower stratus deck created by moisture being trapped under the 
frontal inversion leans the forecast colder than GFS/EURO but not 
as cold as the higher resolution modeling (NAM/WRF). Thus, have 
attempted to split the difference between the extreme solutions 
and have broken tomorrow's temp behavior in geographic thirds from
north to south. If the front does hang up just shy of the coast 
(as is currently progged) then northern tier Tmaxs may struggle to
reach the lower to middle 60s while coastal counties will again 
reach the mean lower to middle 70s. Fog will be tricky as the most
efficient fog development and severity of such will strictly be 
dependent upon the front's eventual resting place. As of now, 
forecasting inland/coastal county patchy fog in the vicinity of 
the stalled boundary and more areawide dense sea fog over the 
bays/nearshore waters from midnight on through the late Saturday 
morning hours. 

Overnight Saturday into Sunday will remain overcast with returning
sea fog issues Sunday morning; minTs in the lower to middle 50s 
up north, lower 60s over the southern third of the forecast area. 
The movement of the associated surface low/shallow Ohio Valley 
upper trough's eastward movement on Sunday during the day will 
allow a secondary northerly push of energy into our area. This 
will aid in pushing the near coastal boundary offshore and ending 
the coastal/marine fog threat. MaxTs will warm within the interior
as Saturday's shallow cold air will modify enough on Sunday to 
allow warming to again produce inland upper 60 to lower 70s/coastal
upper 60s under a more established north flow Sunday afternoon.

The southwesterly deepening of the next western U.S. trough on
Washington's Birthday will place eastern Texas in a isentropic
upglide set-up through mid-week. Warmer, more moist southwesterly
flow atop cooler and drier near surface northeasterlies will keep
early week skies overcast and generate either periods of light,
steady rain or brief showers. The passage of weak disturbances 
within this southwesterly mid-layer steering flow will induce 
periodic bouts of heavy rain and/or rumbles of elevated thunder. 
Other than on the coast or over upper Texas coast Gulf waters 
where storms may better root within the marine layer, thunderstorms
will likely remain elevated and not be an inland issue. Cooler 
conditions will prevail next week with many days registering near 
normal overnight temperatures on either side of 50 F with days 
struggling to make it out of the 50s through mid week. A 
reinforcing mid week front will aid in maintaining this days long 
north to northeast wind. Very minor warming at week's close as 
region may experience more sun, but pleasant at this time next 
week; low to mid 50s in the morning/middle 60s during the afternoon.
31

MARINE... 
Weak low pressure was noted over NE TX this afternoon with a cold 
front extending west across the panhandle. The low will move E-SE 
toward SE TX tonight and drag a cold front south across the state
but there is some uncertainty on far SSE the front will move. At 
this time, it appears the front will stall very close to the coast
and then retreat north as a warm front late Saturday afternoon. 
Global models support this solution as do neighboring offices and 
WPC. If this solution verifies, warm and moist air will continue 
to flow over the cooler shelf waters and sea fog will develop. For
the sake of continuity, have leaned toward this solution.

The NAM and HiRes models support the front reaching the coastal 
waters with a light offshore wind developing. This scenario is 
plausible as pressures over the panhandle are higher than the 
pressures in Deep South Texas. This scenario would bring slightly 
drier air into the coastal waters and limit the threat for sea fog. 
Mariners should keep up with the latest forecast as only a minor 
change in the front's timing or position could yield significant 
impacts.

A stronger cold front will cross the coastal waters late Sunday. 
High pressure will build into the central plains in the wake of the 
front. The pressure gradient will tighten between the high and a 
trough of low pressure over the western Gulf. This will allow a 
moderate to occasionally strong NNE wind for much of the week ahead. 
A SCEC or SCA may be required at times for the much of the coastal 
waters next week. Tide levels will approach 3 feet on Monday afternoon
due to strong NE winds and an unusually high astronomical high tide. 43

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      49  56  56  69  46 /   0   0  20  10  10 
Houston (IAH)              60  69  62  73  51 /  10  10  30  30  20 
Galveston (GLS)            62  67  62  67  56 /  10  20  20  40  20 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Dense Fog Advisory until 9 AM CST Saturday for the following 
     zones: Brazoria Islands...Galveston Island and Bolivar 
     Peninsula...Matagorda Islands.

GM...Dense Fog Advisory until 9 AM 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...Galveston Bay...Matagorda Bay.

&&

$$