December 2017: End Of The Year Weather

[snowman65]

Surely ONE of those will be right......surely

[srainhoutx]

Timing is everything down here in SE Texas. The guidance continues to indicate lift increasing Thursday afternoon as a potent disturbance embedded in the cold trough including the arrival of another shot of colder air aloft and at the surface arrive from N Texas Thursday afternoon/evening. Lift is looking a bit stronger than we have been seeing in the guidance near and above 600mb suggesting some bright banding returns on the radar scope may be possible Thursday night into early Friday. The $64,000 question will be is there any precipitation left as the Artic Air arrives or will the surface be too dry? Time will tell and as always, these wintry type episodes are unusually hard to forecast in our Region.

[TexasBreeze]

NWS adds sleet mix into area zone forecasts.

[sau27]

Interested to see this next AFD

[mcheer23]

400 PM CST Wed Dec 6 2017

.DISCUSSION...
The main issue for the next day or two will be the possibility of
a mix of sleet or light snow with the periods of light rain. So
far this afternoon there has been quite a bit of isentropic lift
across Southeast Texas under a strong upper level jet. There
have been reports of ice pellets (otherwise known as sleet) mixed
in with the rain just to the north of the forecast area.

The main issue for tonight through Thursday will be the
possibility of a mix of sleet or light snow with the areas of
light rain. Forecast soundings from both the NAMBufr and GFSBufr
have profiles that give this possibility. With the surface
temperatures fairly warm, do not think there will be a chance of
any freezing at the surface. The current thinking is that any mix
of snow/sleet with the rain will end toward midday Thursday. Also
think that the best chances will be along and north of Interstate
10.

The main upper level trough will move across the area Friday.
Expect the rain area to diminish from north to south throughout
Thursday night and Friday morning. Given the forecast sounding
profiles there will continue to be a chance for light snow or
sleety to mix with the rain at times. However, given the
uncertainty of timing and how far south the cold air aloft will
be, decided to not mention this possibility in the forecast at
this time (for Thursday night and Friday morning). Will reassess
this possibility later tonight.

In the far northern counties where rain chances are the lowest (10
percent or less), the morning low temperatures on Friday morning
could reach down into the upper 20s. Think this possibility is
greatest from along and north of a line from Madisonville to
Groveton. Freezing temperatures are possible mainly north of metro
Houston Friday morning. Rain chances will be mainly along the
coast Friday morning. With clearing skies, temperatures during the
day on Friday will reach up to around 50 degrees.

The main issue following Friday will be cold overnight
temperatures over the weekend. However, most areas will probably
be just above freezing both mornings. A northwesterly flow will be
overhead of the forecast area and a cold front looks to move
through the area late Monday; although, this front will be remain
dry. A slow warming trend is expected during the first half of
next week.

40

&&

.MARINE...
Look for the NE/N winds to increase in strength the next 12-36 hours
as the pressure gradient tightens. Though elevated, winds at the
offshore rigs have been gusting to 30-40 knots today and expect a
further upward bump overnight and Thurs. Went ahead and hoisted a
Gale Warning in the 20-60nm group starting at midnight. Closer to
the coast, will let the SCA`s ride for now but`ll be keeping a close
eye on the 0-20nm group for a possible upgrade. 47

[srainhoutx]

Wednesday evening briefing from Jeff:

Winter Storm will move across TX through early Friday.

Periods of rain mixed with sleet and snow possible tonight and again Thursday night/Friday morning.

Cold surface high pressure has built southward over the region with temperatures hovering in the low 40’s much of the day. Rainfall coverage has been plentiful today, but amounts have been generally light. Will focus on the potential for P-type transition tonight and again on Thursday night and any possible accumulations.

Tonight:
Widespread light rainfall will continue through the night as moisture overruns the cold surface dome. Surface temperatures will slowly fall into the upper 30’s overnight and some slight cooling of the air column could result in some sleet or snow mixed in with the rainfall north of I-10. Since surface temperatures ae expected to remain well above freezing any sleet/snow would melt on contact with the warm ground.

Thursday:
Expect mostly light rainfall through the day, but a strong upper level trough will approach the region Thursday afternoon with large scale lift developing. Near the surface a surge of drier air will be advecting into the region from the NNE and this will likely result in the rain shield sagging southward during the day and gradually ending from the north to the south by the afternoon hours. Will keep temperatures in the 40’s again on Thursday.

Thursday night/Friday AM:

Forecast becomes highly complicated as all winter weather events are in this part of the state. Strong trough approaches the region spring strong lift over the area. Moisture profiles are marginal, but maybe a little wetter than expected yesterday. Temperature profiles are also marginal, but better than tonight so the potential for a rain/sleet/snow mixture is slightly better on Thursday evening into Friday morning. Much will depend on how dry the surface layer becomes and if any precipitation can actually reach the ground. Think the best chances for this will be along the coast and toward Matagorda Bay. Also to be noted is some weak instability in the mid levels which can sometimes result in meso scale banding in these sort of winter weather setups that can locally enhance precipitation rates and cool the air column…we do not have a lot of experience with this down here, but snow events in 2004 and 2009 both had these fingerprints. Appears the best chances for rain mixed with sleet and snow will be along the coast and then across the coastal bend region where models are more aggressive with moisture. Not sure the thermal profiles will be as favorable as shown…meaning there may be more rain…but the trend today has been in all guidance for a higher threat of mixed precipitation especially down SW.

Other aspect that will come into play Friday morning is low temperatures which could reach freezing over portions of the area. Think the best area likely to see freezing temps. or below is along and N of HWY 105, but this is also to likely be the region with the least precipitation if any at all. Where precipitation is the heaviest (south of I-10) surface temperatures will likely remain above freezing. However should any locally enhanced snow/sleet develop then local cooling of the surface temperature toward freezing is possible and this could result in some ability of accumulation.

Overall at this time the factors involved appear to be just slightly enough out of phase to preclude widespread winter precipitation or accumulation over the region, but something that will need to be watched closely on Thursday as the parameters all come into play over the area and model trends become reality

[jasons2k]

The snow/sleet may be a fun novelty, but other than that I'm freezing my butt off and miss the warm weather already!! Brrrr it's chilly!! I hope I'm not covering plants tomorrow night - that's no fun in the windy cold either. Hey but at least we are getting some rain - I will gladly take that!!

[DoctorMu]

Snow in Sonora and the cold keeps over performing. A refrigerated, wet column up through the tropo...tomorrow could be interesting nowcasting.

[Katdaddy]

Some areas of SE TX may see some sleet and perhaps a snow flurry or two this morning with a repeat again tomorrow morning closer to the coast. Clearing skies arrive Friday with lots of sun and highs in the low 60s for the weekend.

[wxman57]

I think that there's an excellent chance that coastal counties will see snowflakes tonight. However, a warm ground combined with temps above freezing won't allow it to hang around long. It could accumulate briefly on cars and some grassy surfaces, but streets should remain above freezing and free of any ice.

We're discussing requesting the U of H send up a balloon around noon today to sample the air aloft and determine if there is, indeed, no warm tongue up there.

[Heat Miser]

That's about all i''d like to see really. Having to drive back and forth over the causeway to work daily, no ice or accumulation will be just fine.

[srainhoutx]

A couple of interesting features we are seeing this morning. Outbound aircraft from IAH and HOU indicate the freezing level is down to around 2500 feet and is slowly falling closer to the surface (was at 5000 around midnight and 3500 feet around 3 AM). Water vapor imagery suggests the strong vort max (upper air disturbance) is dropping through New Mexico at the tail end of the cold upper trough and that feature should increase lift as it enters West Texas and cross the State today into tonight. HGX is a bit concerned that the freezing line at the surface may creep close to the Northern/North Western and Western suburbs tonight and those elevated bridges may see some minor icing issues tomorrow morning. They indent to re evaluate this potential today and may need to issue some sort of Advisories later today for tonight as additional data becomes available. The Urban Areas appear to be too warm for any wintry precip issues at this time.

[wxman57]

One thing I keep seeing on TV is that we could have some sleet, POSSIBLY mixed with a few snowflakes. However, the vertical profile is definitely not one that could produce sleet (unless all the models are incorrect). Sleet requires a shallow layer of freezing air near the surface, with warmer (above-freezing) temps in the precip column. However, according to the GFS, NAM, and WRF, at no time today is the precip column above freezing. This points to a potential snow event, not sleet.

As I left the house in SW Houston this morning, I’m fairly sure that I saw something that wasn’t rain mixed in with the raindrops. It didn’t look like flakes, but it was much larger than the raindrops and it didn’t fall straight down. I think it was graupel or partially melted snowflakes.

Take a look at the projected vertical profiles for late this evening. They’re not much different from the current profile (a bit colder aloft). There is no above-freezing air anywhere near the precip column. That said, temps above freezing at the surface would not allow for any accumulations except for on cars and briefly on the grass. No travel issues. Streets should stay well above-freezing in most areas from TX to LA.

[srainhoutx]

Also for those wondering, that secondary shot of Artic Air is heading S out of North Texas. The front has passed Dallas and Abilene.

[srainhoutx]

NWS Corpus Christi reports rain/snow line dropping S/SE across their far Northern CWA. Expect a transition to snow across Cotulla/La Salle County over the next 30 minutes.

[redneckweather]

As the atmosphere is getting right for some snow flurries, right on cue the moisture shield is fading southward out of Montgomery County. Shocker.

[stormlover]

models always struggle down here with these kind of events, I mean so we shall see what happens.

[tireman4]

Meanwhile, our neighbors to the West are really dealing with issues (fires). The same buckle in the jetstream that is bringing us potential fun is really reeking havoc on California...

[davidiowx]

As the atmosphere is getting right for some snow flurries, right on cue the moisture shield is fading southward out of Montgomery County. Shocker.

There is supposed to be a low that develops later this afternoon/evening that should provide lift for more precipitation.

[wxman57]

As the atmosphere is getting right for some snow flurries, right on cue the moisture shield is fading southward out of Montgomery County. Shocker.

There is supposed to be a low that develops later this afternoon/evening that should provide lift for more precipitation.

Yes, the main mid-level trough is predicted to move across tonight, spawning a low along the front in the NW Gulf off the TX coast. Classic setup for frozen precip, as long as all the models are correct in predicting that the precip column will be in sub-freezing air.