Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 210428
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1128 PM CDT Mon Mar 20 2017

.UPDATE...
For the most part, the forecast is on track, with only cosmetic
changes to keep things in line with forecast trends. Though
temperatures today fell just a bit shy of highs, requiring a tweak
to evening temp trends earlier, think that with onshore flow, it
will have no real impact on the forecast lows overnight. Indeed,
ended up nudging lows up ever so slightly along the coast as
overnight winds should be a little bit stronger tonight.

Inherited weather forecast brought in patchy fog for much of the
area around sunrise, and with some low level moisture in place
underneath a very dry, subsident cap, this seems reasonable. If
anything, short range guidance this evening suggests the forecast
is too aggressive near the coast, and maybe even inland, as well.
But, given the environment and relatively low impacts, will keep
the patchy fog area conservatively large for now. Think those low,
moist, cool spots that fog easily should manage at least some
ground fog.

Tomorrow, HRRR soundings suggest we come fairly close to breaking
the cap in the mid-afternoon. While intriguing, precipitable water
is between the 25th and 50th percentile (using LCH and CRP as
climatological proxies), and there is precious little CAPE to be
had, even if the cap is defeated as those high morning dewpoints
look to mix out some. All in all, the dry and quite warm forecast
looks solid at this time and seems unlikely to change until the
end of the week.

Luchs

&&


.PREV DISCUSSION... /ISSUED 627 PM CDT Mon Mar 20 2017/

AVIATION...
VFR this evening followed by some late night and early morning cloudiness
and patchy fog. VFR mid-morning through the afternoon tomorrow. 42

PREV DISCUSSION... /ISSUED 334 PM CDT Mon Mar 20 2017/

DISCUSSION...
The flat upper ridge overhead of Southeast Texas will transition
to a more zonal flow with a series of upper troughs moving across
the country late this week through early next week. The main
impact for our weather will be late night/early morning patchy fog
and daytime high temperatures issues through the mid week period,
and followed by rain chances associated with the upper trough
passages Friday and Monday.

With the upper ridge lingering overhead for another couple of
days, the high resolution model guidance suggests at least patchy
shallow ground fog through Wednesday. The "best" chances will be
late tonight and early Tuesday morning over most of the inland
sites. Lingering chances over at least the northeastern counties
will be possible late Tuesday night and early Wednesday morning.

On the other hand, the high pressure aloft will continue to help
provide conditions conducive for daytime temperatures to reach
into the mid 80s Tuesday through Thursday. The potential is best
for mid 80s on Tuesday and Thursday with some locations possibly
reaching into the upper 80s.

Regarding chances for showers and thunderstorms, both the GFS and
ECMWF were looking similar for the location and strength of the
upper level system on Friday as it moves across the Plains. The
GFS had the surface system a bit further to the north than the
ECMWF. Both are showing the potential for a cold front to move
into SE Texas, possibly all the way to the coast. However, any
offshore flow that develops early Saturday will quickly turn back
around to out of the southeast.

On Monday the models differ a bit more on the strength of the
upper level system and the chances for rain. Took a blend of both.

40

MARINE...
Light onshore flow will continue for the bays and coastal waters
through Wednesday, occasionally strengthening to near caution
criteria each night across the offshore waters. Strengthening
onshore flow ahead of an approaching storm system may result in
caution or possibly advisory flags on Thursday and Friday as winds
and seas build. Latest guidance suggests the associated cold front
will stall inland and not make it off the coast. Since this has been
trending this way for the past 24-36 hours, went ahead and adjusted
wind directions to reflect that scenario and kept onshore flow
going through the weekend.  47

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      63  85  64  84  63 /   0   0   0  10  10
Houston (IAH)              65  84  65  85  64 /   0   0   0   0   0
Galveston (GLS)            69  78  68  78  68 /   0   0   0   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

Discussion...25



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