Texas Winter 2017-2018

[Theepicman116]

NWS Fort Worth this morning

Early Next Week...
A strong upper low will drop southeast out of Manitoba and swing
across the Great Lakes on Monday, dislodging another cold Canadian
airmass and sending it south through the Plains. This cold air
will arrive in the form of another arctic front late Monday.
Return flow will occur for a brief period ahead of the front,
allowing temperatures to climb into the 50s on Monday.
Temperatures will then drop quickly Monday afternoon and evening
in the cold post-frontal airmass.

An upper trough axis extending from the Great Lakes low southwest
through the Southern Plains will move southeast across North and
Central Texas Monday night. This will generate a period of decent
upglide above the cold frontal layer. The latest guidance is
indicating that moisture and lift will be sufficient for
precipitation Monday night into Tuesday. Model soundings appear
cold enough for a transition from rain to snow, with possibly a
quick shot of freezing rain or sleet prior to the entire column
falling below freezing. The 00Z run of the ECMWF is the most
aggressive model with regard to the development wintry
precipitation Monday night-Tuesday. Will not be as bold as this
model solution, but have expanded the rain/freezing rain/snow
possibilities to include areas from the I-20 corridor to most of
Central Texas. At this time, due to the limited moisture
available, it appears that precipitation and associated
accumulations would be light. We will still need to monitor this
system closely as it appears the airmass will be plenty cold
regardless of how much moisture is present.

[orangeblood]

oh what irony after yesterday's debacle from the FTW office..."accumulations appear to be light". This looks like the storm of the century compared to yesterday's event

[Cpv17]

Usually if it’s 4 days out and we’re already talking about the chance of it snowing then that should bode well imo. Heck, no one knew College Station would get 5” of snow back in early December till it actually started happening. So for it to be this bullish on snow chances this far out, maybe that’s a really good thing.

[weatherdude1108]

Most interesting part of the afternoon AFD just issued by NWSFO Austin/San Antonio:

The focus then shifts to Monday night into Tuesday. An upper level
shortwave rotating through the larger trough sends another surge of
arctic air south with the cold front moving into the Hill Country
around midnight Monday night and the remainder of South Central Texas
overnight into early Tuesday morning. Isentropic lift rapidly
develops over the frontal surface as moisture levels increase
further. Rain should begin overspreading the region from north to
south beginning on Monday evening. Models differ slightly on the
timing and intensity of the freezing temperatures Tuesday morning,
with the 12z Euro showing colder temperatures than the 12z GFS, but
both models show surface temperatures falling below freezing Tuesday
morning across the Hill Country and our northern counties with the
freezing line extending southward to roughly a Rocksprings to San
Antonio to Gonzales line by noon on Tuesday. In regards to
precipitation type, the GFS shows a warm layer aloft, suggesting a
transition to freezing rain or sleet for areas where surface
temperatures drop to or below freezing. The Euro shows an entire
sub freezing temperature profile for the northern counties,
suggesting the possibility of snow at these locations. At this point,
think freezing rain or sleet is more likely than snow. Temperatures
will not warm up much, if at all, on Tuesday afternoon. It is quite
possible temperatures in parts of the Hill Country and Central Texas
never rise above freezing, maintaining a chance for wintry
precipitation through the afternoon. Isentropic lift shuts off as a
slightly drier airmass filters in, ending the precipitation by
Tuesday night. Accumulated rainfall at this point is uncertain. The
12z GFS is much wetter than the 12z Euro. GFS ensemble mean shows up
to half an inch of QPF, with the Euro maintaining much less amounts.
At the present moment, WPC shows up to about a quarter of an inch.
Any possible icing amounts are even more uncertain, especially given
the fact that we are still about 3 and half days out from the event.
The primary question will be how much moisture remains in place after
surface temperatures drop below freezing.

Yeah, I just read that. It "could" get interesting around here. Talk here at work of maybe an "ice day" Tuesday, or beyond the way it reads dropping below freezing during day Tuesday. Basically, we're all hoping for an "ice day" or two. We did not have any ice days last year.

[wxman57]

I have a question for you. Back when it snowed in SETX in early December, what were you saying 4-5 days before it happened?

You can go back to around page 32 of this thread and look. The Tuesday before (3 days out), only the Canadian model was indicating any snow in Houston. I said it's possible, but I wasn't buying it yet. By the next day, 48-60 hrs out, the GFS and Euro had come into agreement that the air aloft would, indeed, be cold enough for snow. I was posting skew-t diagrams saying that the projected upper air profile supported snow, not freezing rain and sleet as was being discussed on TV weathercasts. It looked like a snow event, to me.

Tomorrow will be 3 days out. Sunday is 2 days out. I suspect that we should have a much better idea by Sunday's 12Z model runs. For now, I do think that the DFW area has a good shot at some snow - perhaps down to Waco. However, this airmass currently isn't looking as cold aloft over SE TX as the one Dec. 8th.

Here's a sounding I posted on Wednesday, Dec. 6th. The 12Z GFS clearly showed a snow sounding - all the precip was forming in below-freezing air:
http://wxman57.com/images/GFSSounding.JPG

Here's a shot of my front yard on the morning of the 8th.
http://wxman57.com/images/Snow-Front.JPG

[Texas Snow]

NWS Fort Worth

Early Next Week...
A strong upper low will drop southeast out of Manitoba and swing
across the Great Lakes on Monday, dislodging another cold Canadian
airmass and sending it south through the Plains. This cold air
will arrive in the form of another arctic front late Monday.
Return flow will occur for a brief period ahead of the front,
allowing temperatures to climb into the 50s on Monday.
Temperatures will then drop quickly Monday afternoon and evening
in the cold post-frontal airmass.

An upper trough axis extending from the Great Lakes low southwest
through the Southern Plains will move southeast across North and
Central Texas Monday night. This will generate a period of decent
upglide above the cold frontal layer. The latest guidance is
indicating that moisture and lift will be sufficient for
precipitation Monday night into Tuesday. Model soundings appear
cold enough for a transition from rain to snow, with possibly a
quick shot of freezing rain or sleet prior to the entire column
falling below freezing. The 00Z run of the ECMWF is the most
aggressive model with regard to the development wintry
precipitation Monday night-Tuesday. Will not be as bold as this
model solution, but have expanded the rain/freezing rain/snow
possibilities to include areas from the I-20 corridor to most of
Central Texas. At this time, due to the limited moisture
available, it appears that precipitation and associated
accumulations would be light. We will still need to monitor this
system closely as it appears the airmass will be plenty cold
regardless of how much moisture is present.

That is from this MORNING'S Fort Worth AFD. Afternoon not out just yet.

[Ntxw]

I have a question for you. Back when it snowed in SETX in early December, what were you saying 4-5 days before it happened?

You can go back to around page 32 of this thread and look. The Tuesday before (3 days out), only the Canadian model was indicating any snow in Houston. I said it's possible, but I wasn't buying it yet. By the next day, 48-60 hrs out, the GFS and Euro had come into agreement that the air aloft would, indeed, be cold enough for snow. I was posting skew-t diagrams saying that the projected upper air profile supported snow, not freezing rain and sleet as was being discussed on TV weathercasts. It looked like a snow event, to me.

Tomorrow will be 3 days out. Sunday is 2 days out. I suspect that we should have a much better idea by Sunday's 12Z model runs. For now, I do think that the DFW area has a good shot at some snow - perhaps down to Waco. However, this airmass currently isn't looking as cold aloft over SE TX as the one Dec. 8th.

Here's a sounding I posted on Wednesday, Dec. 6th. The 12Z GFS clearly showed a snow sounding - all the precip was forming in below-freezing air:
http://wxman57.com/images/GFSSounding.JPG

Here's a shot of my front yard on the morning of the 8th.
http://wxman57.com/images/Snow-Front.JPG

That you did good sir! It's always a tough buy for snow along I-10 until it's actually happening! Funny you mention the Canadian being the trend setter there too. That was one of the coldest aloft events I have seen for the southern half of Texas in a long time. There is no 500mb ULL to cool the column in this case you are correct. Dependency on the surface cold to really drive which is usually a good sign of sleet and freezing rain ending as snow. The further north you are the more likely you will be deeper into the cold air in column, but there is moisture issues.

The trendy word for this event is upglide, isentropic lift. That's what we have to bank on.

[Texas Snow]

Now the afternoon Fort Worth Discussion is out. Interesting.

".LONG TERM...
The upper level pattern will remain amplified on Saturday with a
ridge across the western U.S. and a trough in the east. This will
keep it mostly clear and dry across the state but still cool with
highs ranging from the upper 30s near the Red River to the middle
40s in the south. Lows Saturday night will bottom out once again
in the 20s.

The shallow cold air will finally start to modify on Sunday as the
Gulf opens up in response to a developing surface trough across
the Northern and Central Plains. This will bring warmer and more
humid air to the region with afternoon highs Sunday from the
middle 40s to the middle 50s and lows Sunday night in the 30s.

Low level warm/moist advection will continue on Monday ahead of
the approaching surface trough and cold front. The cold front
should enter North Texas Monday afternoon, but most locations
will reach the peak heating hours of the day prior to its arrival,
so afternoon highs will warm into the 50s to around 60.

Sharply falling temperatures are expected Monday evening with
gusty northerly winds. The ECMWF, Canadian and GFS solutions all
develop precipitation behind the front Monday night which should
initially start out as a cold rain. However, all models linger
some precipitation into the late evening and overnight hours when
surface temperatures will be well below freezing. The big question
is how much precipitation will be in the subfreezing air and how
deep will the cold air be. Since this event is still several days
out, we will not get too detailed on weather type and transition
times, but we will keep the possibility of a winter mix Monday
night in all zones with the best chances across the southern half
of the region. Since there is good model consistency on timing and
QPF, we have decided to increase PoPs in all zones. It is way too
early to anticipate impacts, but if the models verify there would
most likely be some type of accumulations.

Some light winter precipitation will be possible through the
morning hours Tuesday across the southern zones until
dry/subsident air moves in on the back side of the departing upper
trough. Tuesday will be a rather cold day with afternoon highs
struggling to get above freezing.

Clearing skies and decreasing northerly winds Tuesday night will
result in overnight lows in the teens and 20s.

A slow warmup is expected the second half of next week with
southerly winds returning by Thursday ahead of another upper
trough. There is some model disagreement regarding precipitation
on Thursday, so for now we will keep a dry forecast."

[TheProfessor]

Well, I just experienced some insanely fast sleet accumulations. Even with warm temps the last 3 days plus rain it only took 10 minutes of moderate sleet to make the sidewalks slick. I think campus forgot to treat the sidewalks(or it isn't working for the first time ever) I haven't ever seen the sidewalks so slick there.

[Cpv17]

A couple days ago my TWC app had a high for me in Wharton in the mid 50’s for next Tuesday. Now it has a high in the mid 30’s for me with a 50% chance of showers and freezing rain

[Ntxw]

18z GFS is basically a carbon copy of the 12z run

[weatherdude1108]

An inch of snow in DFW, Austin, and northern burbs of SA?

[Ntxw]

Well, I just experienced some insanely fast sleet accumulations. Even with warm temps the last 3 days plus rain it only took 10 minutes of moderate sleet to make the sidewalks slick. I think campus forgot to treat the sidewalks(or it isn't working for the first time ever) I haven't ever seen the sidewalks so slick there.

Once you get below 30, doesn't really matter how warm it was. The warm temps and ground thing only works at 31-33. I've seen snow fall and melt at 32F after days below freezing, yet after 70F stick hard in the 20s.

[Cpv17]

18z GFS is basically a carbon copy of the 12z run

Just a tad bit warmer. 1-2 degrees.

[Ntxw]

Here is the last 5 run trends of the GFS for Monday evening



Here it is for the thick of it in DFW overnight 5 runs



The more it trends north, the better the quality of moisture return it is seeing

[Lagreeneyes03]

Oh Lord..the TV Meteorologists in DFW are saying 60 percent chance of sleet and snow Mon Night..and staying cold Tuesday. So..this means starting now HIDE YOUR KIDS HIDE YOUR WIFE! The grocery stores are going to be a madhouse. Unusual that they tout this 4 days out.

[TeamPlayersBlue]

I think GFS temps are wrong. Could be 5-10 degrees off, but i'm thinking at best we get a sleet storm/ice here in Houston.

[Cpv17]

12z GFS vs 18z

[Ntxw]

It's probably off by ~5 degrees. For snow, keep your eyes on 850mb temps. You want to be near or below 0C for snow.

GFS too has near 20mph winds and gusts higher for DFW Mon night/Tuesday morning with snow and +/-25F.

[goCoogs]

At least for Houston it seems if they tout it this far out nothing happens. Usually has to be within 48 hours if snow get forecasted at all. Often it's only an 18 hour advance warning. That's why I like this board so much. It keeps me posted on what may or may not be coming.