Texas winter wx thread#4 - big changes on the way eventually

Yankeegirl · #221 Postby **Yankeegirl** » Sat Dec 23, 2006 2:39 am

I have never heard a sonic boom.... :roll:

Extremeweatherguy · #222 Postby **Extremeweatherguy** » Sat Dec 23, 2006 8:24 am

Latest NWS forecast calls for clearing by Christmas morning. However, the GFS continues to show the potential for a return of light precip. by Christmas afternoon and evening. It will be interesting to see if this trend continues and if the NWS mentions it/changes the forecast down the road.

Another interesting thing is that the GFS continues to show very cold upper level air (850mb temps. below 0C and 540 thickness line reaching us). Now I am not saying this will mean flurries, but I think there is certainly a chance of at least sleet. We will have to see how this plays out.

Here is a look at hour 66 on the 06z GFS: http://www.nco.ncep.noaa.gov/pmb/nwprod ... _066.shtml

#223 Postby **Air Force Met** » Sat Dec 23, 2006 9:20 am

Extremeweatherguy wrote:Latest NWS forecast calls for clearing by Christmas morning. However, the GFS continues to show the potential for a return of light precip. by Christmas afternoon and evening. It will be interesting to see if this trend continues and if the NWS mentions it/changes the forecast down the road.

Another interesting thing is that the GFS continues to show very cold upper level air (850mb temps. below 0C and 540 thickness line reaching us). Now I am not saying this will mean flurries, but I think there is certainly a chance of at least sleet. We will have to see how this plays out.

Here is a look at hour 66 on the 06z GFS: http://www.nco.ncep.noaa.gov/pmb/nwprod ... _066.shtml

With that profile some sleet is possible on the back side of the low...possible...but not highly probably. Here is the reason:

There is no melt - refreeze layer. To get sleet...you have to have a melt/refreeze layer. You have to have freezing temps aloft...then the snow has to fall through a layer that is above freezing so that the snow melts...but the water doesn't get too warm...then it has to refreeze by falling through a cold layer near the sfc and refreeze. If the WBZ is close to the sfc...whether by the freezing lvl being close to the sfc or really dry air near the sfc...then sleet can make it to the sfc.

However, this is not the case in this temp profile. As I mentioned in a post a while back...this is a classic temp profile...warm at the sfc...cold aloft...no warm layers. That means nothing to thaw the snow and then no cold layers to refreeze it as sleet.

So...looking at profile...it will fall as snow until about 3K-5K feet...encounter the above freezing layer and then melt. At about 2K feet you would probably have some sort of mix in the extreme North part of SE TX...and it would be completely melted by 1500 feet. IN the Houston area...it will melt at about 3000K feet. Hence the Balloon suggestion. :lol:

Also...as far as the thicknesses are concerned: The reason they are so low is the deepness of the 500mb low. It is skewing the values to the low side because the low is very deep. Normally you would expect a lot colder air with 534 thickness values...but since all thickness really is is the 1000mb height - the 500mb height...if you have a really deep 500mb low (about 3-3.5 standard deviations lower than normal for this time of year in this area)...you get really low thickness values...

If that low was moving through at 560 DM...rather than 550 (over houston)...than the thickness would be 544...and not 534...the temps would be still about the same as you would expect...

And we wouldn't be having this conversation... :lol:

Extremeweatherguy · #224 Postby **Extremeweatherguy** » Sat Dec 23, 2006 10:24 am

Hmm..may be I will have to get a balloon and do that then. :lol:

BTW, for those in and around Austin...the NWS out there is now forecasting rain mixed with sleet for tomorrow:

http://www.srh.noaa.gov/forecast/MapCli ... 6&site=hgx
^^Forecast for Plum, TX...east of Austin^^

so don't be surprised if you see some during the day.

Johnny · #225 Postby **Johnny** » Sat Dec 23, 2006 10:36 am

Yep, this one has turned from a good shot at some wintry precip for a good deal of Texas to 'maybe some sleet mix with rain for the hill country'.

AFM, kind of a hard question to answer of course but I'm gonna ask anyway

....do you see any arctic air coming down for us in the next couple of weeks?

double D · #226 Postby **double D** » Sat Dec 23, 2006 10:45 am

Extremeweatherguy wrote:Hmm..may be I will have to get a balloon and do that then.

BTW, for those in and around Austin...the NWS out there is now forecasting rain mixed with sleet for tomorrow:

http://www.srh.noaa.gov/forecast/MapCli ... 6&site=hgx
^^Forecast for Plum, TX...east of Austin^^

so don't be surprised if you see some during the day.

The only reason I think the NWS is keeping a slight chance of sleet/snow in the forecast is becasue of the busy travel weekend. I think if it wasn't so busy then the NWS wouldn't even mention this event at all. It was very descouraging to see the models back way off on the cold air and thats when I knew our hopes for snow was going down hill.

Although with this pattern in place, it stills favors winter weather down the road and I bet we will get several more chances before the winter is over.

wxman22 · #227 Postby **wxman22** » Sat Dec 23, 2006 10:51 am

Even though that forcast is for the Austin NWS area that is still pretty close to are area...

#228 Postby **Air Force Met** » Sat Dec 23, 2006 11:13 am

Johnny wrote:Yep, this one has turned from a good shot at some wintry precip for a good deal of Texas to 'maybe some sleet mix with rain for the hill country'.

AFM, kind of a hard question to answer of course but I'm gonna ask anyway ....do you see any arctic air coming down for us in the next couple of weeks?

I don't see anything on the horizon. That doesn't mean it's not there...but the models aren't resolving it yet. There may be something right after the New Year...but it looks as if a strong souther branch will keep it bottled up.

#229 Postby **Portastorm** » Sat Dec 23, 2006 11:21 am

wxman22 wrote:Even though that forcast is for the Austin NWS area that is still pretty close to are area...

Trust me, I'll be the first to let you all know if sleet pellets are falling in Austin! :lol:

TexasStooge · #230 Postby **TexasStooge** » Sat Dec 23, 2006 11:54 am

The chance of wet snow flurries in North Texas is...(how can I put it)...pending. The NWS placed a chance of flurries on Sunday Night one day, then took that out the next. And again last night, flurries are back in the forecast.

southerngale · #231 Postby **southerngale** » Sat Dec 23, 2006 2:25 pm

And there goes EWG...

Have fun...hope you brought your laptop so you can report back if you see any snow!

JenBayles · #232 Postby **JenBayles** » Sat Dec 23, 2006 2:55 pm

Extreme - bring some back for us when you find that snow! :lol:

Ah well, I'll just have to pull out the pics of our 2004 Christmas Eve snow and enjoy that way.

#233 Postby **gboudx** » Sat Dec 23, 2006 3:40 pm

Honestly, I just don't know what to think. I guess we'll see what happens tomorrow night and Christmas Day.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
217 PM CST SAT DEC 23 2006

...
CHRISTMAS EVE INTO CHRISTMAS DAY WILL SEE SECONDARY WAVE DROP SEWD
ACROSS N/NE PTNS OF N TX AND INTO ARK-LA-TX THRU 18Z(NOON)...ALONG
WITH A REINFORCING COLD FRONT/COLDER AIR. RANDOM SNOW FLURRIES OR
BRIEF SNOW SHOWERS COULD OCCUR ALONG/N OF INTERSTATE 20 LATE
CHRISTMAS EVE THROUGH EARLY CHRISTMAS MORNING. AMPLE MOISTURE WILL
BE LACKING DOWN LOW BEHIND DEPARTING SE TX SYSTEM...SO NOT EXPECTING
ACCUMULATIONS ATTM. OTHERWISE...COLD AND BLUSTERY CONDS ON CHRISTMAS
DAY AS SKIES CLEAR OUT FOR A COLD CHRISTMAS NIGHT.

double D · #234 Postby **double D** » Sat Dec 23, 2006 4:07 pm

The temperature in Fredericksburg has been steady and slowly falling in the mid 40's all day and it is now 3:00pm. It looks like the forcasted high of 58 is going to bust as I don't see temperatures rising anymore today.
To bad the temperature is not 5-10 degrees cooler..... then we would have some heavy snow falling right now. :wink:

JenBayles · #235 Postby **JenBayles** » Sat Dec 23, 2006 9:51 pm

Like my dad (rest his soul) used to say: If my Aunt had b***s she'd be my Uncle... :lol:

TexasSam · #236 Postby **TexasSam** » Sun Dec 24, 2006 5:54 am

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
418 AM CST SUN DEC 24 2006

.DISCUSSION...
LIGHT TO MODERATE RAIN CONTINUES OVER THE REGION THIS MORNING. AT
09Z...SURFACE LOW PRESSURE WAS LOCATED OVER THE GULF...ABOUT 100
MILES EAST OF BROWNSVILLE. PRESSURE DIFFERENCE FROM THE LOW TO THE
COAST IS ABOUT 10 MB...SO BREEZY CONDITIONS THIS MORNING WILL GIVE
WAY TO LIGHTER WINDS AS THE LOW PUSHES EAST. FORECAST IS
COMPLICATED TO SAY THE LEAST. BOTH THE NAM AND GFS CONTINUE TO
FORECAST SATURATION AT 300K...BUT FOR ALL PRACTICAL PURPOSES THE
ISENTROPIC UPGLIDE ENDS BY 18Z. MOISTURE LEVELS ALSO BEGIN TO DROP
YET IT APPEARS THAT DYNAMICAL FORCING FROM A 500 MB LOW CENTER
WILL HELP TO GENERATE PRECIP THROUGH THIS AFTERNOON.
INITIALLY...THOUGHT THAT PRECIP WOULD END THIS EVENING WITH THE
DEPARTURE OF THE UPPER LEVEL SYSTEM...BUT THIS FEATURE WILL REMAIN
CLOSE ENOUGH TO SE TX TO PRODUCE AT LEAST A SLIGHT CHANCE OF
PRECIP TONIGHT. A SECOND S/WV WILL APPROACH THE REGION MONDAY
MORNING WITH AN ADDITIONAL CHANCE OF LIGHT RAIN. ECMWF/NAM AND 00Z
GFS SHOW 850 TEMPS BETWEEN ZERO AND -2 WITH 1000-500 THICKNESS
AROUND 537 DM. FREEZING LEVEL IS BETWEEN 3-4000 FEET...SO THE
PRECIP TYPE WILL PROBABLY BE A MIX OF RAIN AND SLEET. AT THIS
TIME...FEEL THAT FROZEN PRECIP WILL LIKELY MELT BEFORE REACHING
THE SURFACE. NOT CONFIDENT WITH THE THE PRECIP TYPE OR EVEN IF WE
CAN GENERATE PRECIP AT ALL.

Christmas Day: A slight chance of rain and sleet before noon. Partly cloudy, with a high near 55. Windy, with a west wind 5 to 10 mph increasing to between 20 and 25 mph. Winds could gust as high as 30 mph. Chance of precipitation is 20%.

I got to be first for a change! Big smile!

My Sister should be here from Maui Hawaii about 1:30pm and will be here till the 27th. Dang is she ever in for a shock! LOL!

JenBayles · #237 Postby **JenBayles** » Sun Dec 24, 2006 9:49 am

Nice catch Sam! :lol:

#238 Postby **jasons2k** » Sun Dec 24, 2006 10:33 am

I posted some winter weather history stuff in the TX thread in the USA forum. I meant to post it here, sorry. Sometimes I lose track of what's where...

This cold rain is good fire weather - that's for sure

wxman22 · #239 Postby **wxman22** » Sun Dec 24, 2006 10:53 am

The NWS is forcasting SLEET for most of the county warning area in Southeast Texas.......

http://www.srh.noaa.gov/forecast/MapCli ... X&site=HGX

http://www.srh.noaa.gov/forecast/MapCli ... 0&map.y=85

http://www.srh.noaa.gov/forecast/MapCli ... &map.y=141

Even for Downtown

Look at Huntsvills forcast:
http://www.srh.noaa.gov/forecast/MapCli ... 2&map.y=28

#240 Postby **Air Force Met** » Sun Dec 24, 2006 11:01 am

wxman22 wrote:The NWS is forcasting SLEET for most of the county warning area in Southeast Texas.......

http://www.srh.noaa.gov/forecast/MapCli ... X&site=HGX

http://www.srh.noaa.gov/forecast/MapCli ... 0&map.y=85

http://www.srh.noaa.gov/forecast/MapCli ... &map.y=141

Even for Downtown

Look at Huntsvills forcast:
http://www.srh.noaa.gov/forecast/MapCli ... 2&map.y=28

Slight chance...rain/sleet...and in the discussion they think it will melt. However...there is a fundemental problem with this forecast:

There is no thaw-refreeze layer. I think someone at the NWS forgot the winter precip rules. In order to have sleet...you have to have the snow melt into rain...and then refreeze. The temp profiles for tomorrow show that it is below freezing above 3-4K feet and above freezing below that. There is no layer above freezing above the freezing level that would melt the snow and then allow for re-freezing.

I read the disco...and they made the error that some on here have made...they looked at thickness and 850 temps. If you look at a forecast sounding from both the NAM and GFS...there's no re-freeze layer to even produce sleet. So...any precip has to fall as snow until it melts....and then it hits the ground as a cold rain.

Now...if there is a warm layer in there somewhere that the model is not resolving...then it probably will be some sleet mixed in...but right now...the temp profiles show no inversions what-so-ever.

Texas winter wx thread#4 - big changes on the way eventually

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