Tuesday, February 6, 2018

Feb. 5 18

Northwest Houston, TX, during the early morning.
Northwest Houston, TX, during the late evening.
Dense Fog Advisory for the Houston, TX area, issued by NOAA during the late night.


Locations: Northwest Houston, TX.


Thoughts: The day stayed cloudy to mostly cloudy. There may have been some light showers in the Houston, TX area, during the late night. It felt a little cool during the late morning and afternoon, and early night. I think it felt cool, during the early and mid-morning and late night.


Area Forecast Discussion 
Issued by NWS Houston/Galveston, TX
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000
FXUS64 KHGX 060300
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
900 PM CST Mon Feb 5 2018

.UPDATE...
A cool and dreary night with lowering clouds...light precipitation
..and areas of fog development. A near-coastal warm front will
work its way northward and into the southern 2/3rds of the forecast
area through tomorrow afternoon. Cool easterly near surface flow
along and behind this front...with mid-level westerly flow atop
the frontal zone creating a steep overnight inversion...will trap
low level moisture and make for continued raw conditions. Gentle
upglide drizzle or periods of light rain/showers along and ahead
of the warm front. Warm and moist air moving over cooler shelf
waters will produce early evening marine fog and to subsequently
advect inland...locally dense fog with visibilites falling to below
and mile at times through late Tuesday morning. Many interior
counties can expect low ceilings and patchy fog with intermittent
light precipitation north of the warm frontal boundary. Model
progs indicate enough instability (near 1k J/kg MU CAPE) with 6 to
7 deg C mid-level lapse rates to promote a mention of elevated
PM thunderstorms. A cooler surface per easterly flow and overcast
will really thwart any surface-based storms. A near 12k freezing
level/10k wet bulb zero height suggests that..."if" efficient wet
bulbing to saturation does occur within the hail growth zone...then
(far interior county) small hail can be expected to fall out of
any isolated strong afternoon thunderstorm. 31

&&

.PREV DISCUSSION... /ISSUED 525 PM CST Mon Feb 5 2018/

AVIATION...
Warm front will be approaching the coast and moving inland tonight
and Tuesday. Expect the typical unfavorable flying conditions that
typically occur in these scenarios. MVFR conditions will
transition to IFR & LIFR as low ceilings, fog, drizzle, -ra
develop and persist across the region. Little improvement is
expected Tuesday. 47

&&

PREV DISCUSSION... /ISSUED 354 PM CST Mon Feb 5 2018/
A relatively active week continues as yesterday`s cold front
pushes back north through the area as a warm front, bringing back
moisture and fog potential. Another cold front pushes through the
area late Tuesday night into Wednesday morning, along with showers
and thunderstorms - hail is a possible threat in the strongest
storms Tuesday night, particularly for points from College Station
and Huntsville northward. Spots well north of Houston look to
fall into the middle 30s Wednesday night/Thursday morning, but
thinking that with clouds only partially breaking behind the
front, freezing temperatures aren`t a significant danger. Another
front awaits us this weekend, and though details continue to be
difficult to nail down, another shot of rain looks likely.

NEAR TERM [Through Tonight]...
Outside of a brief period this morning where the northern/eastern
chunks of the area broke into sun, cloudiness has been the rule
across Southeast Texas. So although a warm front is moving north
across the area, these clouds have largely kept temperatures in
check.

Tonight, look for boundary layer moisture to continue to pump up
with light onshore winds on the warm side of the front. This will
bring a return for fog potential - first over the nearshore
waters, but gradually become possible inland, as well. Where winds
go calm, some dense fog should be possible, but where winds stay
up, mixing should limit the density. Additionally, vertical motion
along with increasing rain chances towards morning will also
inhibit fog formation to some extent. Actually kind of like the
HRRR`s general idea of greatly varying visibilities across the
area. Of course, given the lack of skill in pinpointing such
localized spots of denser fog, will hold at patchy for most, only
going to areas for sea fog.

SHORT TERM [Tuesday Through Wednesday Night]...
The potential for warm sector showers will slowly nudge upwards
through the day Tuesday as the cold front approaches from the
north. Guidance suggests a thunderstorm may be possible with
modest instability developing into the afternoon. Southwest winds
at 850 may provide some capping to diminish that potential, but
those winds aren`t terribly veered, so it may be a beatable cap.
The Euro does hint at this with a couple convective-looking, if
not terribly impressive QPF bullseyes Tuesday afternoon. Given
continued cloudiness expected and our relatively lackluster
heating in similar situations the past couple days, have gone
ahead and taken a whack at highs tomorrow already. Meanwhile, at
the immediate coast, sea fog may continue to encroach on the
shoreline a bit.

Things start to look a little more impressive Tuesday night,
particularly late Tuesday night as the surface front reaches our
area. Despite the loss of sun, we still hang onto a bit of
surface-based CAPE at the coast, and forecast soundings suggest
more elevated CAPE farther inland above the more stable nocturnal
boundary layer with MUCAPEs in excess of 1000 j/kg. Deep layer
shear is sufficient enough to support some organized updrafts, as
well. It`s not a terribly fat instability profile, but the -20C
point is near the maximum area of that CAPE trace, and for what
it`s worth, SHIP is just shy of 1.0, which is near the 75th
percentile for hail up to 1.5 inches. On the other hand, height
falls are relatively negligible (even suggested height rises at
one point?), the upper jet alignment is awkward, and low level
convergence is relatively weak in our area with the 850 front
focused well to the northwest. All in all, I wouldn`t go looking
for quarters and ping pongs to start dropping from the sky, but
the strongest storms will certainly have an environment in which
they could produce hail, and a marginally good one for reaching
that 1 inch severe threshold from points around College Station
and Huntsville northward.

The front shoves through the area Wednesday, most likely entering
from the north in the pre-dawn hours, and reaching the coast
around mid-day or in the early afternoon. This timing on the front
means our diurnal temperature range is likely to to be nigh on
nil, and we may even see temperatures slowly fall through the
afternoon. The 850 front looks to lag behind, which sets us up
for continued elevated thunderstorm potential. But with a slightly
higher wet bulb zero, we may lose the top end potential for
severe hail as convection marches coastward. Still, the strongest
storms seem capable of producing some small hail, and as colder
air aloft starts to move in for the late afternoon and evening,
the SHIP numbers at IAH start to buck up again. WBZ is still a
little high and there may be some question as to whether any
storms will be present at all, so I`d still put the best chance
for severe hail for the north on Tuesday night. But...it`s not
impossible (cue SoYoureSayingTheresAChance.gif ).

LONG TERM [Thursday Through Monday]...
Temperatures will fall through Wednesday night as colder air
moves in, and by early Thursday morning, some spots way up north
(thinking near and north of Crockett) may dip into the middle 30s.
How far we fall up there will depend on just how much clearing we
see. Have been pretty pessimistic with the breaking of clouds,
and so am thinking that will keep freezing temps out of reach.
Also, this push of cold air isn`t terribly strong - with the lack
of rain and some breaks in the clouds allowing filtered sunlight,
highs on Thursday look to match and up north, even exceed
Wednesday`s highs. The NAM suggests a few showers may linger into
Thursday, but have not really bought into that yet, and it appears
drier than when the previous shift noted the potential. So will
follow suit with them and keep PoPs relatively low, but feel more
confident in keeping clouds around, as winds just aloft to the
mid-levels become more onshore, and set up potential isentropic
lift.

The focus then turns to the weekend and the next front. Starting
to get a little jealous of the midnight shift, which always briefs
me on relatively good agreement among the long range models. Then
I get the 12Z set, and the GFS decides to do something wonky.
Today, it tries twice to bring a front into our area and fails,
not succeeding until the end of NEXT week. The Euro has stayed
more consistent, albeit a bit slower, bringing a front through
Sunday morning/mid-day. As far as this forecast goes, I suppose
the impact on sensible weather remains relatively stable. Both
models generate a subtle coastal trough, and that`s enough to
produce rains in the warm sector ahead of the cold front far to
our northwest. Some shortwaves in the mid-level pattern and the
approach of a southern stream jet streak eventually putting us
under the left exit region should support upward motion. With the
GFS progging precipitable water at or above 1.5 inches, we may
want to keep an eye out on precip potential. Indeed, for whatever
reason, the GFS has come into line with the GEFS, and the
ensemble`s envelope has become more moist itself. But, with
another front to go before this one and the GFS showing so little
run to run continuity, will not deign to speculate much on this
right now. Luchs

MARINE...
Fog could develop and become widespread/dense late this afternoon
through tonight and then persist until a strong cold front moves
through the area on Wednesday. Moderate to strong north winds and
rough seas are expected to develop in the wake of the front
Wednesday through Wednesday night, and small craft advisories will
likely be needed. Light to moderate east to southeast winds
return to the area at the end of the week as surface high pressure
moves off to the east. South winds Saturday and Saturday night
can be expected until the next cold front`s arrival on Sunday. 42

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      53  65  47  47  38 /  30  60  70  60  10
Houston (IAH)              56  70  56  56  42 /  30  50  70  80  30
Galveston (GLS)            57  68  58  58  46 /  20  50  40  80  50

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...Dense Fog Advisory until 10 AM CST Tuesday for the following
     zones: Coastal waters from Freeport to the Matagorda Ship
     Channel out 20 NM.

&&

$$

Discussion...31

Hazardous Weather Outlook

Hazardous Weather Outlook
National Weather Service Houston/Galveston TX
358 PM CST Mon Feb 5 2018

TXZ163-164-176>179-195>200-210>213-226-227-062200-
Austin-Brazos-Burleson-Colorado-Fort Bend-Grimes-Harris-Houston-
Liberty-Madison-Montgomery-Polk-San Jacinto-Trinity-Walker-Waller-
Washington-Wharton-
358 PM CST Mon Feb 5 2018

This hazardous weather outlook is for portions of Southeast Texas..

.DAY ONE...This Afternoon and Tonight

A warm front will approach the area tonight. Areas of fog will
develop and could become locally dense reducing visibility to less
than a mile at times.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

A warm front will move through the region early Tuesday.
Scattered showers and thunderstorms will develop Tuesday afternoon
and a few of the stronger storms could produce small hail. A cold
front will trigger more storms on Wednesday and a few of the
stronger storms could again produce small hail. There is a
marginal risk for larger hail on Tuesday night near and north of a
line from College Station to Huntsville.

A potent storm system will approach the area Friday night and
Saturday. This system has the potential to produce locally heavy
rain Saturday morning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.

$$

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