December 2017: End Of The Year Weather

General Weather Discussions and Analysis

Re: December 2017: Pattern Change/Much Colder Weather Possib

Postby DoctorMu » Mon Dec 04, 2017 10:24 pm

GFS modifies the colder air by Friday, while the Ensemble and Canadian hold onto the cold a little longer with reinforcing shots. If the GEM/Canadian is correct, we'd have our first freeze this weekend. We'll see.


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Last edited by DoctorMu on Mon Dec 04, 2017 11:53 pm, edited 1 time in total.
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Re: December 2017: Pattern Change/Much Colder Weather Possib

Postby DoctorMu » Mon Dec 04, 2017 10:29 pm

Overrun and wetness may be prolonged. Gusty winds after the front passage - classic Blue Norther.

Area Forecast Discussion
National Weather Service Houston/Galveston TX
725 PM CST Mon Dec 4 2017

.AVIATION...
Showers departing the area to the east and have cleared the area
TAF sites. Band of MVFR ceilings in the wake of the showers with
VFR conditions elsewhere. Large shield of CI spreading over the
area tonight from the west and this will overtop the developing ST
deck tonight ahead of the cold front. Rain chances looking fairly
low through 09z then increasing with the approaching cold front.
MVFR ceilings and some patches of fog will impact the area. Timing
of the front still keeps it on track for CLL around 12z/IAH
15z/GLS 18z. Will be carrying a mix of SHRA/TSRA along the frontal
boundary with at least scattered coverage and probably more like
widespread as it closes in on the IAH/HOU area. Winds of course
crank around to the north and gusty and will persist that way
through Wednesday. Upglide will keep a thick cloud deck in place
over the area Tuesday afternoon-Wednesday morning with abundant
omega. Have reintroduced rain after 03z Wednesday for IAH.

.PREV DISCUSSION... /ISSUED 257 PM CST Mon Dec 4 2017/

DISCUSSION...
Scattered showers and thunderstorms continue to develop and move
across SE TX this afternoon. The disturbance responsible for
today`s activity will push east of the region between 00-02z and
there should be a lull in precipitation from mid to late evening.
Still some subtle timing differences with an approaching cold
front. Not sure how cold to take KCLL tonight as the front could
arrive after 12z. Shorter term guidance is a bit faster and leaned
toward a slightly faster fropa. The front will trigger scattered
showers and storms but some of the short term guidance is backing
off on PoPs. Will continue to carry likely PoPs but the speed of
the front and benign instability parameters should preclude strong
storms or heavy rain. Temperatures will fall behind the front and
most of the region will be in the 50`s by Tuesday afternoon. Could
be some spotty light rain in the wake of the front Tuesday
afternoon but dry air beneath clouds will likely evaporate any
residual precip.

Models are in good agreement that a series of weak disturbances
will cross the state late Tuesday night through Wednesday night.
Fcst soundings show saturation above 7000 feet and sub cloud layer
is not quite as dry as advertised the last couple of days. The
combination of weak isentropic upglide, the weak disturbances and
subtle forcing by another surge of cooler air will provide the
area with a good chance of light rain late Tuesday night through
early Thursday. Will carry likely PoPs Tues night into Weds night.
The area of precipitation will gradually push south through the
period with drier air filtering into the region drying out the
northern zones and eventually drying out the southern zones on
Thursday. The clouds and precip will keep temps cool on Wednesday
and high temperatures will struggle to warm into the lower 50`s.

Clearing skies are expected Thursday night as high pressure moves
into West Texas. A slight warming trend will ensue on Friday as a
weak SW sfc flow develops. A weak cold front will cross the area
on Saturday. Moisture will not have a chance to return ahead of
the front, so conditions are expected to remain dry. Some cirrus
will scoot across the region Sunday into Monday with a gradual
warming trend. 43
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Re: December 2017: Pattern Change/Much Colder Weather Possib

Postby CrashTestDummy » Mon Dec 04, 2017 10:33 pm

Noooooooooooooooooooooooooo!

I’m home alone this week. Can’t be having to move plants around and covering others!!
Gene Beaird,
Pearland, Texas

"You can learn a lot from a Dummy."
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Re: December 2017: Pattern Change/Much Colder Weather Possib

Postby Ounce » Tue Dec 05, 2017 5:09 am

CrashTestDummy wrote:Noooooooooooooooooooooooooo!

I’m home alone this week. Can’t be having to move plants around and covering others!!


Tell those plants, "Suck it up, buttercup!" See if that'll work.
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Re: December 2017: Pattern Change/Much Colder Weather Possib

Postby Ounce » Tue Dec 05, 2017 5:14 am

000
FXUS64 KHGX 051003
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
403 AM CST Tue Dec 5 2017

.DISCUSSION...

Yesterday there was a tweet that jokingly referred to yesterday as
the last day of summer for us, and in some ways, it`s hard to say
that`s wrong. A cold front will sweep through the area today,
bringing a line of showers and storms with it. Considerably colder
and drier air will surge in on gusty northerly winds behind the
front. However, the drier air will be shallow enough that lingering
rain will likely continue Wednesday and into Thursday before turning
dry into at least early next week. Except for very near the coast,
which may reach the mid-70s before the front chops things down, our
warm temperatures of recent days are done. Much, perhaps all of the
area will fail to reach 50 degrees tomorrow, and we may not see 60
degrees again until Saturday. Look for only a few spots in the
coastal southwest to breach 70 early next week. Low temperatures
don`t look to see widespread freezing temperatures, but there`s
pretty good confidence in consistent lows in the 30s and 40s. We
should be on the lookout for lows that may fall below the 32 degree
mark in our northernmost areas late this week into the weekend. For
reference, "normal" temperatures this time of year in the area are
lows in the middle 40s and highs approaching 70.

.NEAR TERM [Through Today]...

As of 3am, the cold front is just on our doorstep, marked in both
surface obs by a sharp change in winds and drop in dewpoint, and on
radar by a broken line of showers and an embedded thunderstorm or
two. Though forecast soundings show a marginally favorable
environment for severe weather, it seems a threat unlikely to
develop for most of the area if it hasn`t already. The exception
might be very near the coast, as some heating could juice up the
atmosphere before the front sweeps through, potentially rejuvenating
the line some. It still seems like a stretch (indeed, aforementioned
forecast soundings are not impressed, likely as they also build in a
bit of a cap as well ahead of the front), but I suppose it`s not out
of the picture. And, as it seems around this area, I might suspect
that if we beat the odds and see severe, brief tornadoes would be
the primary threat with high wet bulb zeroes and modest DCAPE, but
sufficient amounts of low level shear and helicity.

Look for a sharp dive in temps and dewpoints, while we see a brief
lull in precip behind the front this afternoon and early evening.
Winds will become northerly and increasing in strength and gustiness
through the afternoon. For the interior portions of the area, that
means our high temperature for the day has already happened. Near
the coast, we may see temps rise back towards the mid-70s late this
morning to give us our high temps, and then the front will chop
things down.


.SHORT TERM [Tonight Through Thursday]...

Gusty northerly winds will continue through the night. For the large
majority of the area, they`ll stay low enough that a wind advisory
seems unnecessary. However, it`s a different story very near the
Gulf, so don`t be surprised if one pops up later today for some/all
of the coastal counties. Would expect the strongest winds to occur
on Galveston Island, with a favorable fetch of winds just east of
north that will maximize wind speeds that rides all the way across
Trinity Bay and Galveston Bay.

After the earlier mentioned brief lull in rain chances in the
immediate passage of the the front, eventually we`ll see broader
isentropic lift kick back in with sufficient clearance by the front.
This will bring continued potential for rain through Wednesday and
possibly even into Thursday, until a secondary surge/front dries the
column sufficiently to end rain chances. Before it does so, however,
we may see rain intensity briefly pick up in a narrow band thanks to
frontogenesis occurring on that surge of colder temps aloft.

Something that stands out in forecast soundings for this period -
the low level cold, dry air underneath saturated mid/upper levels
means lots of evaporation before any rain hits the ground. This will
certainly reduce the intensity of any rain, so while confidence in
having rain is high, so is the confidence that rain is likely to be
light. Additionally, this is going to result in (potentially
significant) evaporative cooling. Though the wet bulb trace in
forecast soundings at the surface are above freezing, there looks to
be a surprisingly deep layer at or below 0C. It`s reminiscent of a
similar setup last winter in which brief amounts of sleet were
reported all the way into Houston, and it`s so, so tempting to put a
slight chance for sleet in the weather grids in this time period.
Will hold off for now, but think a few random sleet pellets are at
least possible in this timeframe.


.LONG TERM [Thursday Night Through Tuesday]...

The long term is relatively boring compared to the rest of the
forecast period. Moisture is scoured out of the column, keeping the
weather dry. Temperatures will begin quite chilly and only warm
slowly, perhaps reaching seasonal averages sometime early next week.
Once the base of the mid-level trough rotates through Friday,
northwest flow will establish and prevail through the end of the
forecast period with an amplified ridge-west, trough-east pattern.
Early next week we could see a shortwave trough back winds aloft
slightly to more westerly and potentially bring in a dry front. But
really, the impacts on sensible weather are likely to be small/nil.
Some change may exist beyond the forecast period, but there is wide
spread in the guidance, so confidence in how any change may play out
is low, and may ultimately have only small impacts on sensible
weather.

&&

.AVIATION [06Z TAF Issuance]...

Well mixed moist atmosphere up through 800mb across the area this
evening and has led to MVFR ceilings across the northern areas DWH
northward and a mix of VFR/MVFR southward. Cold front should arrive
at CLL around 12z/IAH-16Z/GLS-18Z. SHRA should be fairly widespread
along the boundary with a few thunderstorms mixed in though the
profile only shows about 300-900 CAPE topped off by a strong
subsidence inversion around 500mb. Precip should taper off post
frontal within a few hours but a vigorous s/w and very favorable jet
should crank up the isentropic lifting with deep overcast layer and
periods of rain Tuesday night throughout Wednesday night and even
Thursday morning. A very cold rain likely Wednesday and Thursday.
Possibly some inflight aircraft icing issues Wednesday night and
Thursday. 45

&&

.MARINE...

A strong cold front will move across the coastal waters this
afternoon through early this evening. Strong offshore winds and
rough seas that develop behind the front will continue for the next
several days. The bays and nearshore waters are under a small craft
advisory, and the offshore waters are under a gale watch. Periods of
rain with embedded showers and thunderstorms can be expected today,
and good rain chances will persist tonight through late Thursday or
early Friday. Weakening winds and lowering seas can be expected
toward the end of the week and over the weekend. 42

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL) 61 40 46 39 53 / 60 40 80 60 30
Houston (IAH) 70 44 47 41 53 / 70 50 80 60 30
Galveston (GLS) 73 48 51 45 55 / 70 70 80 60 50

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...Small Craft Advisory from 3 PM this afternoon to 6 PM CST
Wednesday for the following zones: Coastal waters from
Freeport to the Matagorda Ship Channel out 20 NM...Coastal
waters from High Island to Freeport out 20 NM...Galveston
Bay...Matagorda Bay.

Gale Watch from Wednesday morning through Wednesday afternoon
for the following zones: Waters from Freeport to the
Matagorda Ship Channel from 20 to 60 NM...Waters from High
Island to Freeport from 20 to 60 NM.

Small Craft Advisory from 3 PM this afternoon to 6 AM CST
Wednesday for the following zones: Waters from Freeport to
the Matagorda Ship Channel from 20 to 60 NM...Waters from
High Island to Freeport from 20 to 60 NM.


&&

$$

NEAR TERM...Luchs
SHORT TERM...Luchs
LONG TERM...Luchs
AVIATION...45
MARINE...42
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Re: December 2017: Pattern Change/Much Colder Weather Possib

Postby Katdaddy » Tue Dec 05, 2017 6:38 am

A big weather change is on the way as the cold front is approaching SE TX this morning and will move off the coast later this afternoon. Expect some scattered showers and a few thunderstorms as the front moves across SE TX. Much cooler weather in its wake with highs around 50 for tomorrow and periods of light rain through Thursday night.
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Re: December 2017: Pattern Change/Much Colder Weather Possib

Postby tireman4 » Tue Dec 05, 2017 9:02 am

000
FXUS64 KHGX 051147
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
547 AM CST Tue Dec 5 2017

.AVIATION...
Cold front will move across the TAF sites this morning through early
this afternoon. Winds will shift to the north behind the front and
become gusty. SHRA and possible TSRA can be expected during the day.
There could be a break late this afternoon through this evening before
the area sees rising RA/SHRA coverage during the overnight hours and
on throughout the day tomorrow. MVFR ceilings should prevail for most
of the time with lowering levels possible during the day tomorrow.
42
&&
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Re: December 2017: Pattern Change/Much Colder Weather Possib

Postby tireman4 » Tue Dec 05, 2017 9:03 am

Interesting bit of wording in the disco this morning..


It`s reminiscent of a
similar setup last winter in which brief amounts of sleet were
reported all the way into Houston, and it`s so, so tempting to put a
slight chance for sleet in the weather grids in this time period.
Will hold off for now, but think a few random sleet pellets are at
least possible in this timeframe.
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Re: December 2017: Pattern Change/Much Colder Weather Possib

Postby snowman65 » Tue Dec 05, 2017 9:50 am

Even with this incoming strong front, so far it looks like my prediction of 33 on Oct 29 will still hold as the coldest day this season, at least here in Orange. Don't think this front will break that. I said that 33 on Oct 29 could be the coldest day we see all season...that would be something.... :D
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Re: December 2017: Pattern Change/Much Colder Weather Possib

Postby Ounce » Tue Dec 05, 2017 10:30 am

The front has cleared the Woodlands. Still summertime in Spring (no pun intended).
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