December 2017: End Of The Year Weather

[redneckweather]

So no '83 or '89 type cold? This was probably the 50th time it has been mentioned in the last 10 years and once again, not going to happen, not even close actually. Kind of silly for that to be mentioned every single time an Arctic front shows up in the models 2 weeks out. lol I'm hoping it stays all rain! This airmass will not be deep enough to produce snow so keep the ice away.

[TexasMetBlake]

Yea looking like only rain here. Even if we do get to below freezing at the surface with such a potent warm nose everything would most likely come down as rain. Opposite setup of the other week where above the surface was all below freezing. Looking more and more likely that the Christmas eve/23rd time frame is going to be cold with rain with temps struggling to get out of the 40s. Now if moisture can stick around longer until Christmas or after, another reinforcing shot of cold air could make things more interesting. Keep an eye out though, especially the further north you are. Looks like it could be difficult for traveling, especially to the DFW area.

I bet it struggles to get out of the 30s. Currently for the Friday-Monday time frame I have highs around 40F. We'll see.

[TexasMetBlake]

So no '83 or '89 type cold? This was probably the 50th time it has been mentioned in the last 10 years and once again, not going to happen, not even close actually. Kind of silly for that to be mentioned every single time an Arctic front shows up in the models 2 weeks out. lol I'm hoping it stays all rain! This airmass will not be deep enough to produce snow so keep the ice away.

No, I'm not seeing anything nearly that cold. Those were superlative events guys. There's a reason we only see single digits two or three times per *century*. A few model runs back I was seeing a 1047+ high nose into Texas. That would give us a devastating freeze but haven't seen that size high in a while on the models.

[stormlover]

5 days away still and we are model hugging, yesterday euro makes it interesting and now we are saying it’s looking like rain, we won’t know till Thursday what’s going to happen

[Texaspirate11]

NWS disco yesterday said it would be a "warm and gross rain"...have no idea what it means but they mention RAIN...not anything else..so far

[BlueJay]

"Warm and gross rain" ... Oh the weather outside is frightful!

[Andrew]

Chances of "warm rain" even in a loosly subjective manner has a low chance of happening. Cold rain is much more likely.

[harp]

It's just as well. Nobody wants an ice storm and that's what this event would have been. Too much warm air aloft for anything but freezing rain from what I read.

[srainhoutx]

Way too much volatility (model flip flopping from run to run including the ECMWF) leads to a highly uncertain forecast with significant bust potential is why it is important to wait until at least mid next week before biting off on any reasonable solution regarding next week. The Saturday morning briefing from Jeff explains this very well...

Active weather period will usher in nearly daily changes in the weather over the next week.

Today-Tonight:
A strong upper level storm system will move into and across TX tonight. A surface low will form along the middle TX coast today and move generally ENE/NE up the coast. Latest guidance appears to keep this feature right along the coast or slightly offshore which should also keep the warm front near the coast or offshore. This will keep a moist and unstable air mass likely across the Gulf waters this evening although the warm front may approach the coast from Freeport to High Island. Most areas will be within the cold sector of this system with ENE/NE surface winds draining cold air out of NE Louisiana as the surface low moves up the coast so temperatures will only slowly warm today as the warm front attempts to push northward.

Expect numerous showers and thunderstorms late this afternoon into tonight as lift increases over the region. Severe threat including tornadoes looks to remain offshore although would not rule out an isolated severe storm as far north as the first tier coastal counties. Moisture levels will be high enough for heavy rainfall, but the speed of the system should negate any widespread flooding threat.

Monday-Tuesday:
Moisture axis will be pushed south on Sunday behind departing storm system, but as winds turn back to the south on Monday expect this moisture axis to push back inland as another storm system approaches from the west. Will go with rain chances again Monday into Tuesday under a warm air advection pattern and increasing lift. Dewpoints rising into the 60’s may result in sea fog formation over the colder nearshore waters…so a period of foggy wet weather appears to store for the area. Temperatures will be on the warm and muggy side Monday-Thursday.

Late Week-Next Weekend:

Let’s start with forecast confidence is not high from Thursday into next weekend.

Upper air pattern over the US will undergo amplification with deep layer ridging building along the US west coast deep into NW Canada and even the arctic circle. This will dislodge a cold arctic air mass and send it southward into the US by the middle of next week. Arctic boundary will arrive in TX on Thursday and likely cross SE TX early Friday. High temperatures will certainly be ahead of this boundary with rapidly falling temperatures Friday into the 40’s and eventually the upper 30’s (NW areas). The confidence in this arctic front making it off the coast sometime on Friday is fairly high along with a colder air mass moving into the region.

Next question then becomes how cold does the surface layer become. Arctic air masses tend to be very shallow in nature (sometimes only a feet thousand feet thick) with much warmer air above the surface cold dome. If moisture were to be in place for next weekend, the shallow nature of the cold air does NOT support snow or sleet. A shallow cold layer near the surface would tend to support freezing rain if and only if the surface temperature is at or below freezing…33 means a very cold rain and 31 would mean freezing rain. At this time the incoming air mass does not appear, at least initially, to be cold enough at the surface to result in freezing rain over much of SE TX. Freezing line may end up over portions of the I-35 corridor by Friday evening (22nd) and a bit southward by the morning of the 23rd. There is very little room for wet bulb cooling of the air mass since model cross sections show a fairly saturated air column over much of the state and surface temperatures and dewpoints are fairly close.

While the surface temperatures are one issue, the other issue is the handling of an upper level low which may dig into the SW US and how much moisture it will bring up and over the surface cold dome. While early, there is some degree of confidence that this upper level feature will form over the SW US by late week and provide a good amount of moisture over the state.

As with any winter weather event in TX, confidence is low as many times such events hinge on 1-2 degree differences in the temperatures which 5-6 days out is impossible to forecast. Run to run model variability continues to be poor which does not lend much confidence in any particular solution actually happening

Key Messages:

1) Significantly colder air mass will likely arrive next Friday and last through the holiday weekend

2) It is too early to determine how cold the air mass will be or if any freezing precipitation will occur over any portions of SE TX

3) Residents traveling to central and N TX late next week/weekend should monitor forecasts closely

[TexasMetBlake]

Well the 12z GFS was certainly an eyebrow raiser. 1058 mb high dropping into the northern plains. Winter weather more robust and widespread across Texas. Still coming in...let's see what happens.

[harp]

Can you let this Louisiana boy know how far east it spreads? Thank you.

[srainhoutx]

Can you let this Louisiana boy know how far east it spreads? Thank you.

If the 12Z GFS is correct, you SE Louisiana folks may see freezing temperatures (near hard freeze criteria) just West of New Orleans and along and N of the I-10 Corridor on the 27th and 28th. Blake and I were just discussing how long a duration the 12Z GFS suggests the cold air stick around. If the GFS is correct the coldest air in the Northern Hemisphere will be situated over most of North America.

[harp]

Can you let this Louisiana boy know how far east it spreads? Thank you.

If the 12Z GFS is correct, you SE Louisiana folks may see freezing temperatures (near hard freeze criteria) just West of New Orleans and along and N of the I-10 Corridor on the 27th and 28th. Blake and I were just discussing how long a duration the 12Z GFS suggests the cold air stick around. If the GFS is correct the coldest air in the Northern Hemisphere will be situated over most of North America.

Thank you so much for the response. My next question would be will this be dry, or do we have any ice issues?

[snowman65]

Are there chances that the frozen stuff could still work its way further south to golden triangle?

[stormlover]

We will know by wed, right now looks like cold rain

[TexasMetBlake]

12z Euro is in and I don't see too many differences right off the bat. I do see it's pretty cold the day after Christmas but still only showing highs in the mid 40s the days before and on Christmas. Nothing that is Earth shattering. It keeps all precip liquid as well.

12z GFS is comparable to the Euro in showing highs in the mid Saturday, Sunday and Christmas Day. It does bring the rain/ice/snow line fairly close to College Station but that's about it. All rain here locally.

Model watching continues.

[MontgomeryCoWx]

Depending on the next few model runs, the story that could emerge would be how cold it’s going to get on Christmas and after moreso than a Winter Storm. If the EPS verified, we would go into the deep freeze as our source region would shift to the brutally cold Central Canadian plains.

[Heat Miser]

So no '83 or '89 type cold? This was probably the 50th time it has been mentioned in the last 10 years and once again, not going to happen, not even close actually. Kind of silly for that to be mentioned every single time an Arctic front shows up in the models 2 weeks out. lol I'm hoping it stays all rain! This airmass will not be deep enough to produce snow so keep the ice away.

Winner, winner chicken dinner. You read these forums long enough and inevitably, almost every winter, there's talk of 83 coming our way. People who hope for 83 are somewhat silly to me. As was mentioned before, some in the Houston area are still living in tents. 83 was as miserable as it gets. In fact think of the flooding from Harvey only this time it comes from within your house. I can think of no reason, none, to wish for or hope for that type of cold to come our way. We don't need nor want it. And, in the unlikely event we get an ice storm, who in the world would want that nightmare? There will be hundreds of vehicle accidents, power lines down, killed vegetation, just not good at all.
Hey, an interesting and rare snow fall, bring it. Pipe busting cold or dangerous ice, stay away.

[DoctorMu]

After Christmas record approaching cold is in the Hill Country on multiple models. Hard freeze in College Station, possibly Houston. It's not unusual for a potent arctic front to appear in our region just after Christmas.

Right now the coldest air is timed after the cold front pushes through. Ice storm in the Hill Country still possible. Cold rain for SE Texas...still a LONG way to go before higher confidence.

[TexasMetBlake]

From HGX's AFD:

.EXTENDED DISCUSSION /THE WEEKEND BEFORE CHRISTMAS/...
Speculation continues about the forecast for the weekend before
Christmas. CIPS Extended Analogs have shown a consistent signal
for sub-freezing temperatures to reach at least parts of Southeast
Texas sometime during the December 24 through December 26
timeframe... and this increases confidence that the region will
see a spell of much below normal temperatures around Christmas.
What remains more uncertain though is when this cold air will
actually reach the region. This airmass looks to originate over
western/northwestern Canada before being dislodged southward
towards the Great Plains as a disturbance now near the Bering
Strait also dives south. These polar airmasses tend to be very
shallow by the time they reach Texas, which means that model
guidance can struggle with when the coldest temperatures arrive
behind the initial cold front. This is because the airmass behind
the front moves moreso from propagation due to density differences
at the surface than forcing from higher up in the atmosphere. The
medium range guidance that was inspected today continues to shows
signs of that struggle with the deterministic GFS/European not
bringing in sub-freezing surface temperatures until Christmas and
the Canadian, well, doesn`t bring them into the region at all.

This is further compounded by the signal that at least a weak
over-running regime sets up across the region behind the front.
This over-running, where more warm, moist air is lifted over the
colder, shallow post-frontal air, looks to produce periods of
light to moderate precipitation across the region over the weekend
before Christmas and into Christmas week. Not only is the timing
for arrival of colder temperatures in question, but whether or not
the atmosphere will be precipitating when they arrive is too.

So what do we know?
- It will be colder than normal the weekend before Christmas into
the beginning of next week.
- Winter weather could certainly be possible... but several
things have to come together for that to be the case.
- It is too early to determine impacts, if any.
- Model guidance is still in poor agreement on what will actually
happen in that portion of the forecast. This makes forecast
confidence low.
- Forecast confidence probably won`t begin to increase until the
middle of next week when the disturbance near Alaska begins to
dislodge our next round of colder air.