JANUARY 2018 - Seasonal WX Week/Pacific Front Saturday

[srainhoutx]

For those in the Golden Triangle and SW Louisiana, NWS Lake Charles will keep the Winter Weather Advisory in affect for this event.

[wxman57]

From Jeff Lindner at Harris County Flood Control:

***Winter Storm Warning issued for SE TX for Tuesday for areas along and N of I-10***

***Winter Weather Advisory remains in effect for areas south of I-10 to the coast***

Hazardous travel is likely to develop across the region on Tuesday during the day

***Unlike other winter weather events this region has experienced in recent years where impacts tend to lessen during the day…impacts with this event will worsen throughout the day on Tuesday into Tuesday evening.***

Discussion:
Arctic boundary is moving into TX this afternoon and will surge into the region overnight and off the coast early Tuesday. Temperatures will rapidly fall to freezing initially over our NW counties and then spread SE during the day reaching the coast by early afternoon. This will result in a rapid change of rain early to freezing rain/sleet/snow across the region during the day on Tuesday.

P-type:
Freezing rain is the likely precipitation type from the coast northward to I-10 where the freezing rain will begin to mix with sleet. North of HWY 105 freezing rain early Tuesday will change to sleet and all snow by Tuesday afternoon.

Accumulation:
Ice accumulation up to .10 of an inch is now likely across the entire region with sleet and snow accumulations N of HWY 105 up to 1-2 inches. Ice accumulations south of I-10 will likely average near .05 of an inch

Accumulations of this magnitude will likely result in hazardous travel developing across the region on Tuesday especially bridges and overpasses. Travel throughout the day on Tuesday will become increasingly difficult especially where bridges and overpasses are encountered.

Decision Support:

• NW of LaGrange to Huntsville: Onset freezing rain 300-400am Tuesday. Ice accumulation up to .10 of an inch, with sleet and snow accumulation of 1-2 inches. Hazardous travel all day

• N of HWY 105: Onset freezing rain 500-700am Tuesday. Ice accumulation up to 10 of an inch. Sleet accumulation likely up to .25 of an inch. Hazardous travel early Tuesday morning

• N of US 59 including metro Houston: Onset freezing rain 800-1000am. Ice Accumulation up to .10 of an inch. Hazardous travel starting mid-morning

• Coastal areas: Onset of freezing rain 1100am-100pm. Ice accumulation up to .05 of an inch. Hazardous travel starting around noon

• Precipitation should gradually end from N to S Tuesday evening, but very cold temperature will maintain icy conditions through mid-morning on Wednesday.


There remains some uncertainty on exactly where any meso scale bands may develop which could produce some locally higher amounts, but feel the current ice accumulation amounts are decent for now. Snow and sleet accumulations depending on how quickly transitions occur could be locally higher under any banding of heavier precipitation

Key Messages:

• Winter Storm Warning in effect along and N of I-10
• Winter Weather Advisory in effect along and S of I-10
• Ice accumulation up to .10 of an inch is likely across much of SE TX on Tuesday
• Sleet and snow accumulations may reach 1-2 inches from Brenham to Livingston
• Travel will become increasingly difficult on Tuesday across the region with bridges and overpasses the most likely to experience ice formation
• Hard freeze likely for portions of the region Wednesday morning with low temperatures into the low and mid 20’s

Jeff Lindner
Director Hydrologic Operations Division/Meteorologist
Harris County Flood Control District

[stormlover]

I think lake Charles will upgrade it jmo

[DoctorMu]

This is real now per Jeff and wxman. I think estimates from my local mets is a bit conservative with a cautionary ****totals are not exact****


But this will be a snow on ice event with falling temps. NOT conductive to driving!


https://twitter.com/KBTXShel/status/953000112950841344



I've also been reading in the models more snow west, not east...hmmmmm...

[Belmer]

I'm getting more worried about the freezing rain impact than anything else. Warm nose is pretty stout and doesn't seem to erode away until the precipitation starts exiting, on the backside, which may result in some quick snowfall. Latest mesoscale models (HRRR/NAM, etc) seem to really be ticking up p-values and the dense cold air coming in a tad quicker than forecasted.

Like stated before, this is going to be quite different than previous winter events we have had in our area. Main event will be late tomorrow morning, worsening through the day into the evening. Glad TxDOT pretreated the roads well ahead of time.

[TexasMetBlake]

Here's the Winter Storm Warning. Those in the Golden Triangle, a Winter Weather Advisory is on the way for the entire area.

[DoctorMu]

Here's the Winter Storm Warning. Those in the Golden Triangle, a Winter Weather Advisory is on the way for the entire area.

Local CLL upgrade in agreement with Jeff Linder:

Shel Winkley @KBTXShel
9m9 minutes ago

WINTER STORM WARNING now in place for the ENTIRE Brazos Valley.

Ice accumulations up to 1/10" and **up to** 1" or 2" of snow possible throughout the area between tonight & midday Tuesday

[wxman57]

I'm thinking that total liquid precip amounts across Houston will not be high, perhaps up to around .25 inch. However, much of this precip may fall when road temperatures on bridges and overpasses are at 32f or colder. This would result in bridges and overpasses getting a glazing of ice by tomorrow late morning. Very dangerous travel conditions tomorrow. Precip could briefly change to snow before ending tomorrow mid afternoon. Watch for a very hard freeze Wednesday (possibly near 20).

[srainhoutx]

For our Neighbors in SE Louisiana...

Area Forecast Discussion
National Weather Service New Orleans LA
334 PM CST Mon Jan 15 2018

.SHORT TERM...
The focus today has been on the short term. Starting out with high
confidence information first. Another strong arctic cold front is
racing south. Behind it a strong 1045 to 1050 mb surface high is
building south across the Great Plains. This is a favorable set up
for very cold air to reach the central Gulf Coast. General cold front
arrival estimates Tuesday are about 6am at MCB... 9am at BTR...
MSY by noon... MS Coast early afternoon. The northerly wind shift
may be slightly earlier. That general timing represents the
stronger winds and when temperatures begin dropping. The north and
west portions of our area will see high temperatures early in the
day. By Wednesday morning low temperatures across northern areas
will be in the upper teens to low 20s, mid 20s elsewhere, and
upper 20s across extreme SE LA. A hard freeze warning will be out
for all but the lower portions of the SE LA coastal parishes
Tuesday night. Wind chill values in the single digits inland and
low teens to the south Tuesday night into Wednesday behind the
front meet criteria for a Wind Chill Advisory areas wide.
Continued strong cold air advection will keep nearly all of the
central Gulf Coast region in the 30s Wednesday.

The 12z runs of the NAM and GFS have a band of QPF a bit further
south into SW MS during the daytime Tuesday than previously
forecast. Precip may begin as sleet or freezing rain then switch to
snow in this area. Light accumulation is possible so therefore will
be adding a Winter Weather Advisory for SW MS and adjacent
Louisiana parishes with this package. Expected snow and sleet
accumulation amounts in the advisory area are a trace to under an
inch. Even very light accumulation of frozen precip on elevated
roads and bridges can have significant travel impact. Thanks to
neighboring offices and WPC for discussion and collaboration today
on this evolving forecast.

Further south moisture dries out along the front and is later onset.
Trace amounts of sleet or freezing rain may be possible in the
early evening to midnight timeframe across the BTR metro and the
Northshore. During the afternoon and early evening further south
any precip across the New Orleans Southshore and MS Coast would be
liquid with temperatures above freezing. Then later in the
evening there is a brief window from about 8pm to midnight where
trace amounts of freezing rain or sleet may be possible across
these southern areas. This is low probability and represented in
the forecast with 20 to 30% POP. Keep up to date with the latest
forecast as information may change. Area wide there will be a
chance for flurries later overnight Tuesday before clouds clear
out.

Improper use of space heaters and home heating techniques are a real
concern during cold weather. Be safety conscious to avoid carbon
monoxide and home fire dangers.

.LONG TERM...
Another very cold night is anticipated Wednesday night into Thursday
morning with low 20s inland and upper 20s further south. A warming
trend will finally occur into the weekend with a slight chance for
showers as southerly flow returns Saturday into Sunday. A better
chance for showers and maybe some thunderstorms as a shortwave
trough crosses the region Sunday into early Monday.

Krautmann

[srainhoutx]

Thanks for posting wxman57. I know you've been busy fielding calls with clients all day.

[unome]

disregard, sry - that was a retweet by CenterPoint but from the 11th


http://www.wrh.noaa.gov/zoa/mwmap2.php?map=zhu
http://www.wrh.noaa.gov/zoa/mwmap2.php? ... =0&limit=2

[don]

Area Forecast Discussion
National Weather Service Houston/Galveston TX
357 PM CST Mon Jan 15 2018

.DISCUSSION...
It is so nice to see temperatures in the mid/upper 60s today. So
wish I could be outside to enjoy instead of bringing the bad news.
What`s that saying? If you don`t like the weather in Texas just
wait 5 minutes? That`s the forecast for tonight/tomorrow. So let`s
get to it.

Currently the arctic cold front is pushing into Red River region
and north Texas. Latest surface obs at 12Z show a 1048-1050mb high
sitting over NE Montana/NW North Dakota. Water vapor imagery shows
that nice closed low over the Great Lakes and broad vorticity
maximum over the Plains swinging southward. Upper air analysis
shows highly amplified pattern with ridge over the western U.S.
driving the polar jet due south over the Plains.

Tuesday...This is probably one of my top 5 toughest most
challenging forecasts to make and one of the toughest forecast
decisions to make. Big thanks to our forecast team collaborating
on this but 12Z models all show very similar trends. Ensembles
like SREF/GEFS seem to be showing something similar.

First thing we saw was temperatures in the boundary layer are
trending colder so we had to trend surface temperatures colder and
sooner than previous forecast. This calls for freezing
temperatures for most of the day on Tuesday with precipitation
falling.

Second the transition of precipitation types looked on track with
a transition Tuesday morning from rain - freezing rain - sleet -
snow. Model soundings from NAM/GFS show this trend. The ECMWF also
showed colder 850MB temps by 18Z Tuesday indicating a similar
trend. There is a fight between the moisture over the frontal
surface and precip falling versus the drier boundary layer air
coming into from the north. This could allow for precip to end
sooner than expected but it will have to overcome quite a bit of
thermodynamic wet bulbing to do it.

Third increase in frontogenetic lift at several levels. GFS/NAM
all show frontogenesis at 925-850mb and 850-700mb layers. There is
also jet stream configuration with the right entrance region over
much of SE Texas and quite a bit of 500-300mb Q vector
convergence supporting large scale lift. These seem to come
together a little bit late but still lift over the area 18Z
Tuesday to 00Z Wednesday. This all suggests possible banded
precipitation and you even see hints of that in the QPF output in
the models. I`m not going to get into a discussion of CSI and
lapse rates but cross sections do show pockets of CSI and steeper
lapse rates in these areas. Frontogenesis will be driving most of
the banding anyway.

Fourth we need to emphasize freezing rain/sleet as the primary
threat for most of the area. Most ice accumulations will be from a
few hundredths to a tenth of an inch. Banding could lead to
higher amounts of ice leading to need a winter storm warning. With
this potential in mind, we decided on a winter storm warning for
areas along and north of Interstate 10. Farther north there could
be a band of snow from Brenham/Conroe/Livingston north with
generally 1 inch of snow possible which would fall on already icy
conditions from freezing rain/sleet prior to snow. There very
well could be some sleet/snow late afternoon/evening in the
Houston area but freezing rain will be the main issues south of
Conroe.

Precipitation should come to an end Tuesday night with low
temperatures Wednesday morning requiring a hard freeze warning. In
the extended forecast there looks to be a chance of rain Friday
with warm air advection. This continues Saturday into Sunday with
another front pushing through Sunday. This time it looks like a
line of showers and a few thunderstorms Sunday. High pressure
builds in with more cold conditions.

Overpeck

[MontgomeryCoWx]

While we are focused on our imminent winter worries, I couldn’t help but notice the large volcanic eruption in the Philippines. Events like this tend to effect weather patterns greatly.

[sau27]

Noticed it will also be quite windy tomorrow. Curious how this is going to impact the speed with which ice accretion begins due to evaporative cooling of surfaces.

[MontgomeryCoWx]

Brazos, Walker and Grimes county schools already closing...

[stormlover]

Rgem is really nice
https://www.tropicaltidbits.com/analysi ... 11518&fh=6

[WeatherDuck]

Hutto ISD in Williamson County announced it will be closed Tuesday.

[DoctorMu]

Texas A&M classes are cancelled tomorrow. That virtually NEVER happens.

[MRG93415]

Waller ISD just announced school closed tomorrow.

[MRG93415]

Cy-Fair just cancelled school. HISD should be next.