Detailed Model Analysis

[Extremeweatherguy]

AFM..do you think there is a chance of sleet or frz. rain in Houston out of this? (Since it looks like the chance of snow is greatly decreasing) or do you think this will be an all rain event? How cold do you think it gets here next week? Should we expect freezing weather regardless of precipitation?

[JenyEliza]

AFM, after reading your take on the GLS-AUS slice ... looks like I'll keep my snowplow in the garage.

Yeah...that might be wise. I was gonna break the snowmobile out myself but I'm gonna pass. What ticks me off is my 6 year old hear the dread "S" word on the news last night...he hears everything...and now won't listen to dad who keeps telling him it ain't happening. He's still mad because we didn't DRIVE up to College Station a couple of weeks ago when they were getting flurries.

LOL. Why not? It's only about 90 miles straight shot up TX6 from 290.

I have a 4 (almost 5) year old nephew in the CLL area. They could have played together and had a ball.

[Air Force Met]

AFM..do you think there is a chance of sleet or frz. rain in Houston out of this? (Since it looks like the chance of snow is greatly decreasing) or do you think this will be an all rain event? How cold do you think it gets here next week? Should we expect freezing weather regardless of precipitation?

All rain. As I've been saying...I don't see the cold air. By cold air...I mean cold air I mean air cold enough to cause freezing/frozen precip. I don't think we will see temps below freezing. I think my original forecast of highs in the low 40's might even be in harms way because the precip is coming through at night now and we will be clearing...allowing for some solar insolation. Originally I believed this would begin in the day...and finish in evening...so maybe highs in mid-upper 40's.

Still wish I knew what was going on with the RH's though. That can cool temps by a couple of degrees C.

[Extremeweatherguy]

what I find interesting is that the on air met on Channel 11 just showed a high of 38 next Tuesday with a "wintry mix possible". The NWS is not even showing it nearly that cold...I wonder why the on air mets are being so bold with this?

[PTrackerLA]

We aren't even forecasted to get below freezing for the next 7 days. If the air was really cold enough for frozen precip I'd expect to see lows forecasted in at least the upper 20's for early next week (currently lows are forecasted to be in the mid 30's). As AFM said, it's simply not going to be cold enough.

[Air Force Met]

what I find interesting is that the on air met on Channel 11 just showed a high of 38 next Tuesday with a "wintry mix possible". The NWS is not even showing it nearly that cold...I wonder why the on air mets are being so bold with this?

Well...the local guys are calling for a slight chance of snow now from just southeast of a CLL-Huntsville line...which is close to my CLL-LFK line. Sfc temps are still above freezing or near there...so maybe some flurries in that area. Given the 20% chance of rain they are forecasting...and the fact teh GFS is putting down almost an inch over the southern counties...I don't think they are buying the GFS yet.

[Air Force Met]

00Z - 12Z side by side...


20/00Z
500mb ridging more to east at 00Z and stronger. Weaker at 12Z and further west. System digging down into southwest is stronger.

20/12Z
Southern 500MB shortwave is slower than at 00Z and is deeper. Ridging out west is weaker on 12Z run.

21/00Z
Hudson Bay vortex is more to the east at 12Z. Ridging over NW Canada not near as strong as it was on 00Z run. At 00Z, shortwave was progressive, at 12Z an upper low is beginning to take shape over BIg Bend area. At sfc, precip further west and heavier due to deepening of system.

21/06Z
Upper low at 500 now located over Del Rio...where 00Z run had a weak short wave near Austin. Precip heavier along coast. Coastal low forming near Corpus.

21/12Z
ON 00z run, shortwave was though houston at this time, now it's a deep closed low over southwest TX. SFC low east of BRO, south of GLS.

By 22/00Z the upper low is still over south Texas...near VCT and it hangs around slowely moving eastward until it is kicked out late Thursday.

The big change is the ridge is no longer there to pull the air straight down like it was a few days ago. 2 days ago...there was enough ridging to tap some cold air that would send some of it this way...but not anymore. That's why the 540 line is all the way up neat IL.

[gboudx]

AFM, have you read the San Angelo AFD this afternoon? Is this close to what you are thinking?

[Air Force Met]

AFM, have you read the San Angelo AFD this afternoon? Is this close to what you are thinking?

ARCTIC HIGH PRESSURE BUILDING SOUTH INTO NORTHERN CANADA TODAY WITH
TEMPS OF -20 TO -30. THE SFC HIGH OF 1040+ WILL BUILD SOUTH INTO THE
NORTHERN PLAINS THIS WEEKEND AND THEN THE ARCTIC AIRMASS WILL BUILD
ACROSS TEXAS MONDAY NIGHT THROUGH TUESDAY NIGHT.

Agree with that.

THIS AIRMASS WILL
NOT BE AS COLD AS THE ARCTIC COLD AIR EVENT OF DEC 8-9.

Agree with that...

HOWEVER...LOOKS LIKE THERE WILL BE PLENTY OF MOISTURE FOR THIS ARCTIC AIRMASS TO WORK ON.

Agree with that...

THE 12Z GFS MODEL IS ADVERTISING STRONG UPWARD
VERTICAL MOTION...JET STREAM DYNAMICS AND ISENTROPIC LIFT FOR
MONDAY NIGHT AND TUESDAY. USING...THE TOP-DOWN APPROACH FOR MODELS
SOUNDINGS INDICATE PCPN TYPE AS MOSTLY SNOW ACROSS CWFA FOR MONDAY
NIGHT AND TUESDAY.

I agree with that...especially for them out there.

AS EVENT GETS CLOSER THERE IS A POSSIBILITY OF PL AND FZRA ACROSS THE SOUTHEAST CWFA...MAINLY ALONG I-10...AS WARM LAYER MAY SHOW UP JUST ABOVE SHALLOW ARCTIC AIRMASS.

This is that warm layer I was talking about earlier. It's a few thousand feet thick.

[Johnny]

What do you have for us this morning AFM?

Again I have been looking at the temperatures in Norhthern Canada and they are colder than they were at this time yesterday. Eureka in the territory of Nanavut is now at -40 and Shepard Bay is now sitting at -44.

[Air Force Met]

What do you have for us this morning AFM?

Again I have been looking at the temperatures in Norhthern Canada and they are colder than they were at this time yesterday. Eureka in the territory of Nanavut is now at -40 and Shepard Bay is now sitting at -44.

Here are a few maps...

http://weather.unisys.com/surface/previ ... _na-1.html

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_030m.gif

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_048m.gif

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_072m.gif

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_096m.gif

I think with this kind of upper air pattern that cold air gets sent into eastern Canada and the NEUS with some of it getting tapped. That's why the EURO is trending colder...it's tapping a little more of it than the GFS. The troughing with the EURO is back more under the high which is over Alberta at 500MB than on the GFS...thus sending a little more cold air down on the 19th. The EURO is thus advertising a much deeper trof across the south at 500MB than the GFS.

Compair the two...same valid time:





By Tuesday night...the reason for the cold air is clearer. The 500mb trof on the EURO is deep with flow coming down from Canada...while on the GFS the trof is hanging back and the flow is zonal over Texas. So...it seems it's not really that much about how the models are handling the cold air...but how they are handling the 500mb trof that brings the cold air....and that will be the player.

[Johnny]

More good analysis to digest. It seems like your tone on this has leveled off a little bit....kind of stuck in the middle now huh? With these maps you just provided at least that is how I feel.

[Air Force Met]

More good analysis to digest. It seems like your tone on this has leveled off a little bit....kind of stuck in the middle now huh? With these maps you just provided at least that is how I feel.

I think I'm still about the same. AUS-CLL-LFK for ice line. High in the low-mid 40's for Houston and rain.

[Johnny]

I think this event will end up like the Valentine's snow of 2004. I took my family up to Centerville Friday night to try and put us in some snow. I woke up right before daylight and it was lightly snowing but their was already about a quarter of an inch of snow on the ground. Not much but enough me and the kids to enjoy. That was a very fun mini road trip. In Conroe all we had was a cold rain as did the Houston metro area. Just one time I would like to just sit on my front porch and watch the snow come down. If it snows just off to the north or northwest of us next week, the family and I will take off again.

[gboudx]

I didn't live in the Dallas area in Feb 2004, but didn't Dallas get some snow then?

[Johnny]

Yes, they had a pretty good snowfall out of that system...3 to 6 inches I believe. I don't think Dallas will get that kind of snow. I was just referring to the wintery precipitation line. I think it will be similar to the Valentines Day event in 2004.

[Extremeweatherguy]

just wanted to let u know that sleet is mixing with the rain in north Houston right now (and it was not even expected)!!! If this is happening right now (when it was not forecast)...then that makes me think that we could see even worse next week!

[Johnny]

I've got a little sleet myself about 15 miles northwest of The Woodlands.

[Johnny]

Looking up in Canada, that cold air that was pooled up in northern Canada is now dropping staight southward into the southern territories.....specifically, Manitoba and Saskatchewan.


http://www.weatherunderground.com/globa ... ature.html