Texas Winter 2017-2018

[CaptinCrunch]

It was 26 this morning @ 6am at the house.

[bubba hotep]

Woo hoo!!



Unfortunately, the cold air is very shallow with a thick warm layer up above. I doubt that there is any ice accumulation unless surface temps get down to 30 or below. The rain will probably be too warm for any kind of ice accumulation, even if surface temps fall to 32 in portions of DFW.

[Ntxw]

6z GFS for 6am



Temperatures 8:30am central time

[orangeblood]

NAM did a much better job with the handling of this air mass...coincidentally, the FTW NWS office seems to be discounting this model in their latest discussion. Which by the way, their discussion and thought process seems to be extremely contradictory, highlighted below

.SHORT TERM... /Issued 323 AM CST Mon Feb 5 2018/
/Today and Tonight/

The short term forecast is not an easy one as the models vary
considerably on what may transpire over the next 24-30 hours. As
indicated on the 00Z sounding from Norman, Oklahoma yesterday,
the near-surface cold air behind yesterday`s front only extends up
to about 900 mb. The models are struggling with how to handle
this shallow cold layer and what effects the atmosphere above the
near-surface layer will have on it. Thus, there is a potential
for today and tonight`s weather to noticeably vary from what is in
the forecast.

Area VAD wind profiles are detecting that the winds up to around
850 mb are already veering to the southeast. By daybreak, the
winds in the 925-850 mb layer are expected to become southerly.
This will induce warm air advection above the cool surface layer,
and we will see an expansion of clouds through the morning hours.
Surface winds will also gradually turn to the south as the
surface high slides east of the region. The NAM (along with
similar hi-res guidance that initializes similar to and/or with
the same parameters) is very aggressive in prevailing these low
clouds all day across most of the region. As a result the NAM
forecasts cold temperatures with highs in the 30s and 40s. On the
other side of model guidance, the clouds are pushed east of
Interstate 35 this afternoon as the 850 mb winds transport drier
air above the cloud deck which may help to erode the clouds across
the western half of the region. With the 925 mb winds also
expected to shift to a southwest direction this afternoon, have
sided with the latter solution keeping mostly cloudy skies east of
the I-35 corridor this afternoon but mostly clear skies across
the west. For temperatures, the forecast shows a range from the
mid 60s in the west to lower 50s in the east. Think some breaks in
the cloud deck will allow filtered sun to provide some warming
across the east today, but would not be surprised if some
locations struggle to exit the 40s.

Dewpoints will continue to increase overnight even as surface
winds back to the east in response to a surface low in New Mexico
and an approaching cold front. Once again, the NAM is the outlier
with the front infiltrating our northern counties before daybreak
Tuesday. However, the NAM is known for its better handling of
shallow cold airmasses. For overnight lows, have leaned on a
conservative blend with a range from the mid 30s in the north to
around 50 degrees in the south. Isentropic lift and warm air
advection will likely result in some drizzle and/or light rain
across part of the region late tonight, and have continued with a
20-30% PoP along and east of a Gainesville to Fort Worth to
Goldthwaite line.

JLDunn

&&

.LONG TERM... /Issued 323 AM CST Mon Feb 5 2018/
/Tuesday through Next Monday/

Return flow in advance of a strengthening shortwave trough will
modify temperatures across the southern half of the region Tuesday.
Farther north (from I-20 to the Red River), winds will quickly
back to a more east to northeast direction ahead of another arctic
front. This will keep temperatures on the cold side with highs
likely remaining in the 40s across the northern couple of rows of
counties. The NAM began picking up on this yesterday and is the
cold outlier of all the models. If it were to verify, high
temperatures would remain in the 30s across all but the southern-
most counties. The current thinking is that the NAM is a bit too
aggressive with the cold air. Though the current temperature
forecast is well below the much warmer National Blend, it will
remain somewhere in between it and the NAM, with Tuesday high
temperatures ranging from the mid 40s along the Red River, to low
50s along I-20, to the lower 60s across the south.

Lift will be on the increase Tuesday and Tuesday night as the
shortwave digs southeast across New Mexico and into Northwest
Texas. The front will simultaneously surge south, bringing the
colder air southward once again. There may be some widely
scattered surface-based convection along the boundary where
additional forcing and low-end instability will be present. A
strong storm or two would be possible, with timing being Tuesday
afternoon and the most likely locations across the southeast third
of the forecast area. Severe weather is not expected at this
time. The front should clear all counties during the early
evening hours, and any convection thereafter would be isolated
and elevated above the cold frontal layer.

The next concern is the possibility of wintry precipitation along
the Red River as temperatures fall below freezing. There would be
a brief window for this to occur, as precipitation would be
winding down around the time temperatures drop to and below 32.
Probabilities are low enough to leave it out of the forecast grids
at this time. If future guidance trends colder or keeps moisture
around longer, a few hours of freezing rain may be added to the
Red River and northwestern counties during the midnight to sunrise
timeframe Wednesday.

A couple of cold and dry days are expected Wednesday and Thursday
as the cold front clears the entire state and the shortwave
crosses the Central Gulf Coast region.

An interesting split flow pattern is then progged to develop
Friday through next weekend. A southern stream shortwave will
lift northeast from Mexico across Central Texas, bringing a chance
of showers late Friday through Saturday. This will force the next
front southward to near the I-20 corridor, where it will briefly
become stationary as a stronger shortwave in the northern stream
approaches from the northwest. The front will surge south late
Saturday as the shortwave swings east across the Plains. The GFS
continues to drop this disturbance south and west of the main
flow, partially cutting it off over New Mexico and Arizona. This
would lead to more prolonged post-frontal precipitation Sunday and
Monday. At this time, the more progressive ECMWF will b

[Portastorm]

As much as I would love to believe that 12z NAM snowfall map, it is highly suspect. Both 2m and 850mb temps in my area of the state never go below freezing. Now, it *may* be more accurate for you North Texas folks but not down here.

[bubba hotep]

:uarrow:

As much as I would love to believe that 12z NAM snowfall map, it is highly suspect. Both 2m and 850mb temps in my area of the state never go below freezing. Now, it *may* be more accurate for you North Texas folks but not down here.

Yea, I put the sad news below the image lol:

Unfortunately, the cold air is very shallow with a thick warm layer up above. I doubt that there is any ice accumulation unless surface temps get down to 30 or below. The rain will probably be too warm for any kind of ice accumulation, even if surface temps fall to 32 in portions of DFW.

[srainhoutx]

Model mayhem continues. The 12Z GFS suggests the PV split developing at hour 96 with the SSW event underway by hour 144. The entire 500mb pattern across the Northern Hemisphere is shaken as the tropospheric/stratospheric wind reversal begins in earnest. Extreme caution is warranted when attempting to utilize the various computer schemes until the volatility settles down.

[bubba hotep]

12z GFS continues to show a wet pattern for Texas with a series of systems moving into the SW keeping things unsettled for an extended period of time.

[Ntxw]

12z GFS is a pattern with a lot of running, just doesn't spill the cold with it on this run. As srain mentioned above there has been a lot of volatility. We are getting more westward digging troughs however, as evident from the systems this week

[OKMet83]

Need to watch the trends on the NAM for possible light changeover to frz drizzle late Tom in far Southern OK into the Northern tier counties that hug the Red River (I DO NOT expect travel issues that far south though) ... As far as the extended goes EXTREME volatility showing up 6-10 days out for example last night the GFS showed a ice storm from SE OF OKC Metro down to near the Red River valley the 12z this morning shows highs in the 60s for about that same time period! Hang tight it's not over could be a wild ride of ups and downs..

[wxman57]

Quite a difference in the models for Sun/Mon. GFS says "what front" and has temps reaching the mid to upper 70s Sunday and Monday. Canadian keeps temps in the low 40s all day Sunday with a low in the upper 30s in Houston on Monday.

The German ICON model has lows in the mid 20s Sunday with a high only 31-32 Sunday afternoon. Upper 20s to upper 30s on Monday.

I guess this means that temps on Sunday in Houston will be somewhere between the mid 60s and mid 20s for lows with highs between 32 and 78.

[Ralph's Weather]

Next week's weather is very uncertain, but I do like seeing SW US troughiness on the ensembles of the models. At least we should see some rain and likely a pretty good amount of it. Hope we can get a SW closed low to bring rain and mountain snow to the SW US and Panhandles.

[Ntxw]

Midday and its mostly cloudy and mid 30s at Dfw. Huge temp bust today, kudos nam. 50s looks like a pipe dream

[Brent]

Midday and its mostly cloudy and mid 30s at Dfw. Huge temp bust today, kudos nam. 50s looks like a pipe dream

what a model bust. I was kind of looking forward to the 80 the Euro had.

can we get one of these when theres precip

[bubba hotep]

If clouds mix out this afternoon, then temps will spike. Too bad we don't have any geographical features across N. Texas that can produce a true CAD because this cold air bust would have set the stage perfectly for freezing rain.

[Ntxw]

If clouds mix out this afternoon, then temps will spike. Too bad we don't have any geographical features across N. Texas that can produce a true CAD because this cold air bust would have set the stage perfectly for freezing rain.

GFS had near 0% cloud cover with clouds rolling in tonight. I am sitting outside for lunch and it is mostly cloudy. I-35 is socked in it. West of 35 is best for clearing. This is one of those busts when cold, dense shallow air OP guidances have trouble. Aloft isn't all that cold

[Tejas89]

Too bad we don't have any geographical features across N. Texas that can produce a true CAD because this cold air bust would have set the stage perfectly for freezing rain.

Wait. You would actually like to see freezing rain?

[dhweather]

Quite a difference in the models for Sun/Mon. GFS says "what front" and has temps reaching the mid to upper 70s Sunday and Monday. Canadian keeps temps in the low 40s all day Sunday with a low in the upper 30s in Houston on Monday.

The German ICON model has lows in the mid 20s Sunday with a high only 31-32 Sunday afternoon. Upper 20s to upper 30s on Monday.

I guess this means that temps on Sunday in Houston will be somewhere between the mid 60s and mid 20s for lows with highs between 32 and 78.

Fabulous !!!

[orangeblood]

40 Deg Temp Difference at hr 144 b/w CMC and GFS

[srainhoutx]

The 12Z ECMWF did a complete flip as well. Yesterday the Euro pushed a strong front off the Coast Friday night/early Saturday. Today that front stalls across the Permian Basin and N Texas.