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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

FXUS64 KHGX 210549

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1149 PM CST Wed Feb 20 2019

Philosophy remains the same as below on lowering ceilings from 
current southern county mid-level MVFR / northern cirrus to low 
end MVFR to high end IFR within the next 8-10 hours. As an 
offshore warm front nears the coast and creeps onshore through 
tomorrow afternoon, expect an increase in early Thursday rain. 
More persistent early rain will likely taper off through the 
afternoon to either drizzle or very light showers. As the sun sets
tomorrow and the near surface layer cools and condenses, forecast
calls for afternoon IFR to fall another category to LIFR by this 
time tomorrow night. Easterly breezes within this late week warm 
air advection pattern. 31


.PREV DISCUSSION... /ISSUED 856 PM CST Wed Feb 20 2019/ 

Clouds have begun to increase across Southeast Texas this evening
with a scattered to broken deck under 10000 feet moving inland 
from the coast (partly associated with developing isentropic lift)
and some cirrus moving into the area from the southwest (associated
with the deep southwest flow aloft). Expect to see an increase in 
rain coverage overnight off the coast with activity possibly edging
inland before sunrise. The better rain chances come during the day
tomorrow and last until the passage of a cold front on Saturday 
morning.  42 

PREV DISCUSSION... /ISSUED 625 PM CST Wed Feb 20 2019/ 

After a day of VFR per mainly SKC inland conditions, the region 
will again fall into low flight categories within the next 12 to 
15 hours. In a repeat performance from a few days ago, nearshore 
pressure will begin to lower and develop a near coastal trough 
through Friday. A warm front will move onshore beginning tomorrow 
afternoon. So, this TAF package has VFR conditions through the 
evening hours with a deterioration/falling categories from around
midnight tonight on through the morning hours from the coast 
northward. This evening's cloud deck hugging the coast will fall 
to MVFR to high-end IFR through the early overnight Thursday 
morning hours with light precipitation (mainly drizzle with 
occasional showers). Ceilings will fall into IFR territory shortly
after sunrise tomorrow around metro, around noon further north. 
Moderate confidence for areawide IFR to possible LIFR by tomorrow 
night with drizzle and/or VCSH during the morning daytime hours 
into the early afternoon. A persistent northeast wind of around 10
knots can be expected through the majority of the period. 31

PREV DISCUSSION... /ISSUED 353 PM CST Wed Feb 20 2019/ 

NEAR TERM [Through Tonight]...

I see skies of blue and clouds of white which visible satellite 
imagery show are moving out of the area off the Gulf coast. 
Surface analysis has weak high pressure over Texas providing light
northerly winds and drier air with dewpoints in the 30s/40s. 
Hopefully everyone can get outside for fresh air this evening. 
Overnight we are expecting cloud cover to increase after midnight 
going into Thursday morning. Once again we will have an isentropic
lift situation over the frontal boundary and the formation of a 
coastal trough off the Gulf coast by Thursday morning.

SHORT TERM [Thursday Through Friday Night]...

Clouds cover increases Thursday and remains in place through the 
end of the week as we continue with isentropic lift and warm air 
advection. Warm front does push north early Friday with dewpoints 
getting up into the 60s. This should support the development of 
sea fog as early as Thursday night depending upon the strength of 
moisture advection. Forecast will keep some solid rain chances 
going with a mention of isolated thunderstorms. Upper level trough
really starts to move across the southern Rockies Friday into 
Friday night which will only cause pressure to fall in the plains 
and continued warm air advection with the LLJ increasing into 
Saturday morning. Temperatures due to warm advection could reach 
the 70s under cloud cover and not drop much into Saturday morning 
due to moisture and cloud cover.

LONG TERM [Saturday Through Wednesday]...

Upper level trough finally moves into the Plains with a negative 
tilt. Environment becomes favorable for severe weather Saturday 
north of the area but may have to watch Madison/Houston/Trinity 
counties for a small threat. There is at least a marginal threat 
for severe at the end of day 3 outlook for Saturday morning over 
these northern areas of the forecast area. Main severe threat 
should move over the Arklatex to the Mid-South during the day 
Saturday. Pacific cold front should move through the area during 
the day and see temperatures falling in the late afternoon behind 
it. This will also end any sea fog potential over the bays and 
near shore waters.

High pressure builds into the area Sunday which will allow for 
quiet weather conditions. The day 6 to 8 forecast has no 
consistency whatsoever so sticking closer to ensemble means and 
blends for the forecast. GFS shows a upper level disturbance 
moving across the Plains Tuesday which draws up more moisture and 
increased rain chances. ECMWF remains dry and then brings a front 
into the area next Thursday maybe. GFS on the other hand is 
aggressive with the front bringing it through next Wednesday. I 
really have no good clues but the GFS operational run may be a 
slight outlier compared to other GEFS members. GEFS members seem 
to be clustering in 2 areas with more leaning towards no front.



Winds/seas will continue to decrease this afternoon as high pressure 
builds over the area briefly this evening. As this high lifts off to 
the NE overnight, the return of onshore winds/low-level moisture and 
perhaps some patchy fog/spotty light rain and drizzle is expected to 
begin in earnest once again tonight. While still not too sure on the 
exact starting time of sea fog over the bays/nearshore waters,
conditions should become quite favorable for its development 
sooner than later (especially as previous round of moisture/clouds/rains
has not moved that far away). We could start see conditions start
to go down tomorrow/Thurs morning, but the more significant deterioration
could hold off until Thurs night and early Fri morning. As with 
the previous event, we'll see things improve with the next cold 
front...which is currently progged for Sat afternoon/early 
evening. 41


College Station (CLL)      43  56  51  69  61 /  10  30  40  60  50 
Houston (IAH)              48  58  55  74  67 /  10  50  50  50  40 
Galveston (GLS)            55  62  60  71  66 /  30  50  40  30  20 


     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.