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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

                            
000
FXUS64 KHGX 151204
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
604 AM CST Fri Feb 15 2019

.DISCUSSION [12Z TAF ISSUANCE]...

Areas of fog have been affecting TAF sites on and off overnight 
and early this morning, resulting in periods of IFR to LIFR 
conditions. Fog is expected to dissipate after 15Z with vis and 
cigs improving, resulting in VFR conditions during the morning and
afternoon hours. Fog can be expected to develop again this 
evening through early Saturday morning across the most of the TAF 
sites, resulting in periods of IFR to LIFR. The heaviest potential
for areas of dense fog looks to occur across KGLS and KLBX due to
sea fog developing and spreading into the coastal regions. Light S
to SW winds will prevail today, becoming N Saturday morning. 

&&

.PREV DISCUSSION... /ISSUED 456 AM CST Fri Feb 15 2019/ 

DISCUSSION...
Ridging over the eastern Gulf and weak surface low pressure
centered near Abilene keeping light south and southwesterly flow
in place over the area. Dewpoints have climbed into the upper 50s
across the region and even with the cirrus overhead have gotten
fairly widespread light fog with visibilities of 1-5 miles. At
times visibility has dropped to 1/4-1/2 mile though primarily over
the southwest areas where the cirrus hasn't been as prevalent.
Showing up nicely in the Nighttime Microphysics RGB all the way
down into HBV/NQI area of the Coastal Bend/South Texas. Stratus
also getting more widespread along the Upper Texas Coast. The
onshore flow will continue today and continue to boost the
moisture in the lower levels. Cold front stalled near the Red 
River this morning starts sliding south this afternoon and should
move into SETX after 6 pm. The cool air is shallow but should
probably sag all the way down to the Highway 59 corridor by 6 am
Saturday. This evening sea fog should develop and spread over the
nearshore waters and up into the Bays. Could start earlier near
Matagorda Bay this afternoon but not very confident of that
occurrence. Expect that cloud cover will become common in the 
coming days with the frontal boundary and fog to work with which
feeds back into the high temperatures this weekend. The models
have a broad range of highs and have favored the warmer highs
Saturday with greater confidence of warmer SW flow at 850 and the
shallow nature of the cold front. The sea fog should linger
through Sunday morning. A reinforcing push of marginally cooler
and drier Pacific air noses in Sunday and should reach the coast
in the early afternoon probably pushing the fog out into the Gulf
waters (may end up with dense sea fog in the far coastal waters).
Rain chances this weekend are fairly low across the north in the
20-30 percent range...though closer to the coast the rain chances
look more favorable where isentropic lift could produce some rain.
Monday looks to be cool and overcast with light rain possible
through mid morning...then rain chance ramp up and as ripple up
through the state on the fast subtropical/polar jet merger.
Instability increases and have introduced thunderstorms to the
coastal/southeast areas and out into the Gulf Thursday afternoon.
Some brief heavier downpours possible as 850 flow become more
perpendicular to the frontal boundary and moisture increases in
the lower levels. Tuesday should be wet and cloudy and have bumped
up rain chances but these could easily end up being closer to 100
pops with intermittent rain and embedded showers. Wednesday we
start drying out at least briefly as front edges further out into
the Gulf and drier 850 flow develops. This could well be short
lived as the overall broad upper trough over the SW U.S. remains 
in place and the front could develop a wave as another s/w arrives
in the subtropical jet. So confidence in the forecast drops 
quickly for Wednesday and Thursday as the key features haven't 
been sampled yet by observation over the Pacific. 45

MARINE... 

Light onshore flow is expected to prevail across the bays and Gulf 
waters through Saturday night. Patchy to dense areas of sea fog 
could develop over the bays and nearshore waters this evening 
through Saturday as onshore flow persists and transports warm and 
moist air mass over the waters. Model guidance continues to suggest 
winds shifting to the east Sunday as a cold front moves close to the 
coastal region and stalls. Winds should increase Sunday evening 
through Monday morning as the pressure gradient tightens over the 
waters and relax by Tuesday morning. SCA/SCEC will likely be 
required Sunday night and Monday. A coastal low develops over the 
Lower Texas coast Tuesday and moves into the local waters Tuesday 
through Wednesday morning which will increase shower and isolated 
thunderstorm activity. NNE wind flow prevails Tuesday evening 
through the end of the week. 24

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      82  53  72  57  69 /   0   0   0  20  30 
Houston (IAH)              80  59  76  61  73 /   0   0  10  20  40 
Galveston (GLS)            67  61  68  61  67 /   0  10  10  20  40 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Dense Fog Advisory until 9 AM CST this morning for the following 
     zones: Austin...Chambers...Coastal Brazoria...Coastal 
     Galveston...Coastal Harris...Coastal Jackson...Coastal 
     Matagorda...Colorado...Fort Bend...Grimes...Houston...
     Inland Brazoria...Inland Galveston...Inland Harris...Inland 
     Jackson...Inland Matagorda...Montgomery...Northern 
     Liberty...Polk...San Jacinto...Southern Liberty...Trinity...
     Walker...Waller...Wharton.

GM...NONE.
&&

$$

Discussion...45
Aviation/Marine...24