Tuesday, March 13, 2018

Mar. 10 18

Houston, TX radar, during the early morning.


Northwest Houston, TX, during the early morning.
Northwest Houston, TX, during the early afternoon.
Northwest Houston, TX, during the mid-afternoon.
West Houston, TX, during the mid-afternoon.


Locations: Northwest, west, and the heights area of Houston, TX.


Thoughts: The day was mostly cloudy and warm with scattered light to moderate showers in the early and maybe mid-morning.


Area Forecast Discussion 
Issued by NWS Houston/Galveston, TX
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000
FXUS64 KHGX 110335
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
935 PM CST Sat Mar 10 2018

.UPDATE...
A quiet night for the radar...high cloudiness up north and low
overcast across the coastal counties. A tight enough western
corridor pressure gradient to maintain higher south winds out
west but overall onshore flow will weaken past midnight. Interior
mid to upper 60 F dew point air/lower 70 F dew point coastal air
mass will be moist enough to mention early Sunday morning fog.
Areas of thicker (sea?) fog and low overcast will plague the
coastal counties while...further inland where winds will stay up a
bit longer...areas of patchy fog may develop just downstream of
an approaching cold front. Mid-level dry air with a stout 850-950
mb capping layer should be enough to hold any precipitation
chances to slight/low end probabilities through tomorrow morning.
Low QPF with the higher probs for primarily showers to focus
across the northeastern and central eastern counties through 18Z
Sunday. The cold front is timed to travel across the northern tier
counties shortly after sunrise...through the metro area shortly
after noon...and be off the coast by late afternoon. Model guidance
does want to focus some late morning and afternoon post-frontal
light precipitation along the mid level front mainly over the
(east) central CWA. If the surface boundary does race out away
from the mid-level front then a brief period of rain with isolated
(elevated) thunder is possible during the day tomorrow. Expecting
any frontal or post-frontal activity to not make much of a mark.
Moderate to occasionally strong northerlies in the front`s late
Sunday-early Monday wake will introduce short term marine advisory
flags. The next several days (for what is Spring Break for many)
look to be absolutely beautiful! Mainly clear skies with cool
evenings (40s) and mild days (60s) under light north breezes. 31

&&

.PREV DISCUSSION... /ISSUED 543 PM CST Sat Mar 10 2018/

AVIATION...
Expect stratus to fill back in overnight. Most TAF sites should
ceilings transition to low MVFR or IFR between 2-7z (we`re already
there at the coast with some 4-6sm vsbys in sea fog too). Look
for a continued downward trend into sunrise. Cold front should be
making it into northern parts of se Tx around mid-morning and off
the coast early in the afternoon. North winds will increase and
become gusty a few hours after the initial windshift. We could
see some sct areas of frontal rain as well but overall impacts
should be negligible considering ceilings should be lifting and
the precip, if any, should be fairly light. 47

&&

PREV DISCUSSION... /ISSUED 341 PM CST Sat Mar 10 2018/
Main feature of the forecast period will be on the impending cold
front, with some rain chances into Sunday, as well as cooler and
drier weather for at least the first half of the week. Weather
will continue to remain quiet into next weekend, but as winds
eventually turn to be onshore again, we`ll begin to gradually warm
and see moisture increase. As it does, we may see the return of
at least some low shower chances.

NEAR TERM [Through Tonight]...
After a fairly cloudy morning, the sun has broken through across
the area, with mostly fair weather cumulus dotting the sky. A
smattering of clouds around Galveston Bay and in the offshore
waters look to have a little more vertical growth, confirmed by a
bit more of a greenish hue in the Day Cloud Phase RGB. Radar
reveals that the only showers are out over the offshore waters of
the Gulf.

We can expect more of the same for the rest of the afternoon,
which means warm temperatures across the area. But, from there, we
should expect clouds to return overnight. We should stay dry
through the evening, but as the cold front approaches overnight,
rain chances in the north will start to increase. In the meantime,
closer to the coast, the pressure gradient may relax enough to
allow for some fog to form. Taking kind of a middle path here with
patchy fog - if the winds don`t drop off at all, we`ll stay clear.
But if for some reason we are able to go calm, there`s enough
moisture that some could see the fog get pretty dense. Since I`m
not expecting the gradient to go that slack, we`ll stick with the
patchy fog here.

SHORT TERM [Sunday Through Monday Night]...
The cold front cometh! Its time of arrival seems to be slowing by
the day, but it should still enter the area and pass through
College Station to Crockett(ish) around or just after dawn. Look
for it to reach the coast towards mid-day and push farther
offshore through the afternoon. The best rain chances are likely
going to be in the northeast, where it`ll be down with H-T-P
(Houston, Trinity, and Polk counties). As you head southeast,
those chances will dwindle as the best vorticity advection remains
to our northeast, and much of the area is in more of a subsident
region relative to the upper jet. It`s a little messy and not
super clear cut, so we may manage for something to defeat the cap,
but it`s clearly not as supportive of rain there as to the north
and northeast of the metro.

Sunday afternoon may be...interesting. Though the front is through
the area at the surface, progged precipitable water remains around
or above 1.25 inches. Now, add onto that the arrival of the
trailing 850 front, and we might be in a spot to pick up some
post-frontal rain showers. Looking at some forecast soundings,
there`s even a bit of lingering instability aloft, so a strike or
two of thunder isn`t even out of the question. Did undercut
guidance some, as there may be question of the vertical
distribution of moisture relative to what may be lifted over the
frontal surface, but it seems reasonable for some precip to be
generated here.

From Sunday night through Monday night, the story is the influx of
cooler and drier air. After temperatures have been in the 70s and
80s, look for a return of the 60s on Monday (which will carry
through mid- week). And, with dewpoints dropping into the mid-
30s, cool spots way up north might see overnight lows reach or
even briefly dip below 40 degrees one more time.

LONG TERM [Tuesday Through Saturday]...
Cooler and drier weather dominates through the mid-week as high
pressure slowly drops from the Central Plains into the Deep South.
The sunnier skies will likely mean slowly warming temperatures,
but 60s for highs will be the rule until the late week.

Onshore flow doesn`t look to really resume until Wednesday night
or Thursday, which will be what really gets us going back into the
70s or low 80s for the weekend. It will also pump up dewpoints and
general column moisture. The details obviously depend on your
favorite model, but there`s general consensus that along with the
increased moisture, passing shortwave troughs should help support
at least some lighter rain showers towards the end of the week.
Rather than chase the folly of timing super-specifically, I
spread relatively low rain chances from Thursday into the weekend.
There`s a little variation in some attempt to suss out the most
likely times, but it`s probably not worth getting too attached to
specifics at this range. 25

&&

MARINE...
Moist onshore flow in the 10-15 knot range should continue
tonight with a cold front marching down to the coast Sunday close
to noon. In the meantime expect some light fog/haze and seas of
3-5 feet. After the front pushes through Sunday winds gradually
ramp up in 2-4 hours after the frontal passage and SCA conditions
look to occur Sunday after 5 pm. Seas should build to 8-9 feet
offshore by early Monday morning. Winds slowly coming down Monday
evening/Tuesday morning and SCA should drop off with winds
diminishing and turning to the northeast. High pressure traverses
the area Wednesday with onshore flow strengthening Wednesday night
through Thursday noon. Showers and possibly thunderstorms
developing over the coastal waters late Thursday as an upper level
disturbance passes overhead. 45

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      64  69  43  61  40 /  10  20  10   0   0
Houston (IAH)              67  75  47  63  43 /  10  30  10   0   0
Galveston (GLS)            69  72  53  62  51 /  10  20  10   0   0

&&

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

$$

Discussion...31/47

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