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Feb. 8-12 Model Discussion Part III


beanskip

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ILM's disco..

valid 12:30 today...

first current Obs..

48.5 °F Scattered Clouds

Windchill:44 °F

Humidity:80%Dew Point:43 °F

Wind:11.2 mph from the ENE

Wind Gust:12.1 mph

Pressure:30.20 in (Steady)

Near term /through tonight/...

as of 10 am Wednesday...sprawling high pressure covers almost the

entire Continental United States within and east of The Rockies. The

main center is over Colorado...but a ridge axis extending across

into the Chesapeake Bay has a secondary high near Norfolk this

morning. Northeast flow south of this ridge axis is modifying as it

crosses the warm Gulf Stream waters offshore...and this has already

led to falling pressures and the development of clouds offshore.

The 12z chs sounding confirmed the 06z NAM and GFS forecasts in the

lowest 4000 feet or so. At mhx this morning's sounding was a few

degrees cooler than forecast within the 2500-4000 feet layer. We have

made only a few tweaks to forecast highs today...expecting highs

near 50 along and north of U.S. Highway 76...with lower 50s the

south. The onshore flow crossing the very chilly nearshore waters

will probably hold the beach temperatures in the 40s today.

Although skies are generally clear at the current time strongly

veering wind profiles with height (indicative of warm advection)

will bring in the stratocumulus deck developing offshore later this

afternoon. Some showers may even try to scoot into the coastal Cape

Fear region late in the day...although we are maintaining only a 20

percent chance within 10-15 miles of the coast toward 5-6 PM. Better

chances of rain will develop after dark.

Below is the previous discussion from 4 am this morning addressing

tonight's forecast...

Lift will increase overnight and Thursday morning as low pressure

develops offshore...and this is well represented in Omega fields.

Initially the column will only be supportive of liquid rain with

warm nose around 5 degree c. However... as frontogenesis intensifies

across the area and rate of precipitation intensifies...cooling the

column further...eventually the column will be supportive of a rain

and snow mix with all snow across the northern zones. A changeover

to all snow is possible across western zones as well. The rate at

which the column cools will be vitally important in determining how

much snow accumulates. This system will not be a prolific

precipitation maker and with some of the moisture being utilized to

saturate the column and some of it falling as rain...there may not

be much left to fall as accumulating snow.

At this time we are thinking the rain will begin to mix with snow

from northwest to southeast after 04-06z with a changeover to all snow most likely

across Robeson...Bladen and portions of Pender County after 09-10z.

There may be a heavier burst of snow across these areas which may

result in amounts up to 1 inch. However...should the changeover

occur sooner...then amounts perhaps closer to two inches will be

possible across these areas. Therefore the National Weather Service

has issued a Winter Storm Watch for late tonight and Thursday morning for

Robeson...Bladen and Pender counties. Rain will mix with and perhaps

briefly changeover to all snow across Marlboro...Darlington...

Dillon...Columbus...Florence... Williamsburg and Marion counties. In

these areas...the mix with and in some cases changeover to all snow

should be later. Since the column is expected to only be supportive

of accumulating snow for a very short duration...any snow

accumulations will be held to less than an inch.

Elsewhere...rain may briefly mix with snow across New

Hanover...Brunswick...Horry and Georgetown counties where no snow

accumulations are expected. The precipitation is expected to come to

an end by midday Thursday. After 12-13z...the light precipitation will

transition from snow to a rain and snow mix inland and from a rain

and snow mix to all rain at the coast.

Temperatures will become critical tonight and are expected to fall

to or just below freezing across most of the area after midnight.

Bridges and overpasses will be especially susceptible to icing very

late tonight and during the morning commute on Thursday. Nearer to the

coast...temperatures should stay above freezing.

&&

Short term /Thursday through Friday night/...

as of 4 am Wednesday...precipitation will be ongoing at the start of the

period as low pressure moves off to the northeast. Lingering

precipitation...possibly in the form of snow...will last through the Thursday

morning hours. Based on Thermo profiles precipitation is going to either be

rain...rain/snow...or all snow. NAM forecast soundings suggests all

snow Thursday morning with a change to rain around 15z. The GFS is warmer

and faster to move the precipitation out...a solution in line with the 00z

ECMWF/Canadian. GFS soundings hint at some snow across inland NC

counties with a rain/snow mix for the remainder of the area. Favor

the consensus seen in the latest European model (ecmwf)/Canadian/GFS and the GFS

ensembles...which is also in line with previous forecast...over the

outlying NAM.

In short the **Coasties** Maybe in for a "Surprise" tomorrow?

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Wow, 18z RUC initialized with the 850 zero line almost touching the TN border. The 12z NAM had the freezing line through middle AL/GA at the same time. I think that has to be a positive sign in terms of moisture transport down the road for us.

Edit: Mesoanalysis confirms otherwise. I'm not sure how the RUC get's its initial conditions but they are way off from reality in this case.

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I agree. To put this into perspective, the entire year's avg. snowfall for KATL is only 2" and the median is only 0.9" for the period 1930-2010.

Some recent years:

2001 0.1"

2002 4.6"

2003 Trace

2004 3.0"

2005 0.5"

2006 Trace

2007 0.1"

2008 1.4"

2009 4.2"

2010 6.8"

2011 4.4"+

You can see how much 2009-11 stick out. KATL has received 15.4" for those three years, combined, and 2011, of course, is far from over. Going back to 1880, the only other heavier S/IP three year periods were the 28.9" of 1893-5, the ~22" of 1884-6, the 19.3" of 1982-4, and the 15.9" of 1934-6. After 2009-11's 15.4"+ comes the 14.1" of 1991-3.

I'd go with the snowfall for the winter, and not for the year. Most stations have a "Snow since July 1" to cover this.

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I'd go with the snowfall for the winter, and not for the year. Most stations have a "Snow since July 1" to cover this.

How I present them doesn't matter as far as my point. The point that these numbers show is that a 2" snow in ATL is normally a big deal (near the entire winter's average and ~twice the median), but that the last three winters likely have many spoiled, especially those with short memories.

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How I present them doesn't matter as far as my point. The point that these numbers show is that a 2" snow in ATL is normally a big deal (near the entire winter's average and ~twice the median), but that the last three winters likely have many spoiled, especially those with short memories.

No doubt Larry. I started to post earlier that 3 years ago we would have KILLED for 2.5" of snow, but was afraid I was bantering, but now we talk about 2" of snow is no big deal. LOL :arrowhead:

If we do land some snow out of this, it will have truly been an awesome winter to have 3 good snows.

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Not sure why 3 members are missing, and this 72 hour QPF takes into account some modeled precip on Friday evening making it into eastern NC, but notice how every members is much wetter than the op run over eastern NC

http://raleighwx.americanwx.com/models/gfsensemble/members/12zp72f072.html

However, looking at the partial thicknesse members, show that most areas soutehast of Raleigh are likely rain or a rain/snow mix through 6z

http://raleighwx.americanwx.com/models/gfsensemble/members/12zthickf018.html

So whatever falls through 6z, even including RDU, is likely rain or a rain/snow mix that doesnt accumulate.

The 6z-12z time frame will be a window for accumulating snow per the GFS and that is when the 1-3 or 2-4 it shows could fall. Still think the NE corner of the state will likely see the most in our areas of interest.

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Hi folks -- I'm trolling from DC, but have coworkers in Tupelo today who are suppose to fly out thru Memphis tomorrow morning. They say the local weather people are saying 1-2 inches (and that theyy have ZERO salt/supplies for the road), I see the map above that says 4"-7" -- do you all feel that's much more likely? Thanks for any info!

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How I present them doesn't matter as far as my point. The point that these numbers show is that a 2" snow in ATL is normally a big deal (near the entire winter's average and ~twice the median), but that the last three winters likely have many spoiled, especially those with short memories.

I disagree. If you get two big snows in a winter, one before new years and one after, it counts for two years instead of one season. It's easier to determine snowier winters (and those that aren't) from July 1 instead of Jan 1.

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Hi folks -- I'm trolling from DC, but have coworkers in Tupelo today who are suppose to fly out thru Memphis tomorrow morning. They say the local weather people are saying 1-2 inches (and that theyy have ZERO salt/supplies for the road), I see the map above that says 4"-7" -- do you all feel that's much more likely? Thanks for any info!

http://ww2.tdot.state.tn.us/tsw/smartmap.htm?city=Memphis

looking at the DOT cams now it looks pretty sweet if you like snow...4" is definitely a possibility seeing whats on the ground and the radar to me.

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Not sure why 3 members are missing, and this 72 hour QPF takes into account some modeled precip on Friday evening making it into eastern NC, but notice how every members is much wetter than the op run over eastern NC

http://raleighwx.americanwx.com/models/gfsensemble/members/12zp72f072.html

However, looking at the partial thicknesse members, show that most areas soutehast of Raleigh are likely rain or a rain/snow mix through 6z

http://raleighwx.americanwx.com/models/gfsensemble/members/12zthickf018.html

So whatever falls through 6z, even including RDU, is likely rain or a rain/snow mix that doesnt accumulate.

The 6z-12z time frame will be a window for accumulating snow per the GFS and that is when the 1-3 or 2-4 it shows could fall. Still think the NE corner of the state will likely see the most in our areas of interest.

Good post Allan, I noticed the same thing earlier. All of them are consistent on bringing a first batch through from around 7pm-1am with the general agreement of up to 1/2" centered around New Bern. This is why the ens mean is so wet, because that is added to the second wave coming through between 4am - 10am. P-type nonogram along the 264 corridor is in the Measurable SN with RN category with 1000-850mb thickness in the 1305 range and 850-700mb thick around 1530-1535. South of 264 looks like mostly RN with the first batch, and north of 64 looks like mainly SN. That supports higher overall totals in the NE, and around here uncertainty depending on when we switch over and how much falls as RN. Does not help that the GFS went kind of nuts with precip either, compared to the rest of the guidance, EC being a non-event pretty much.

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That is because Atlanta is pretty much the worst airport in the US on a good day. Snow of any kind is a nightmare there if you are flying.

HA! I think KORD still has that crown.

Total noob questions here:

1) Why is the southern portion of the radar return so spotty? Is that because the low is now over land and is not pulling moisture from the GOM?

2) Also I see a 'finger-like' projection over the TN - KY border. Is seems to be extending. What is the significance of that formation? Is that the energy transfer we were told to expect?

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I disagree. If you get two big snows in a winter, one before new years and one after, it counts for two years instead of one season. It's easier to determine snowier winters (and those that aren't) from July 1 instead of Jan 1.

I don't disagree with you about that although I still think you are going off on a tangent in relation to my point. Both the last three calendar years and the last three winters have been very snowy in relation to longterm averages/median (2.0"/0.9") and much snowier than the prior six winters overall. Also, the 1930-2010 average/median per winter are obviously going to be essentially the same as the 1930-2010 average/median per calendar year (2.0"/0.9"). However, to make you happy, here are the KATL S/IP amounts per winter since 2001-2:

01-02: 4.6"

02-03: Trace

03-04: 3.0"

04-05: 0.5"

05-06: Trace

06-07: 0.1"

07-08: 1.4"

08-09: 4.2"

09-10: 5.3"

10-11: 5.9"+

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Birmingham NWS says our system is "overperforming" to say the least.

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE BIRMINGHAM AL

1215 PM CST WED FEB 9 2011

.UPDATE...WINTER WEATHER DISCUSSION.

&&

.DISCUSSION...

LOOKING AT TRENDS UPSTREAM...AND VARIOUS MESOSCALE CHARTS...I WOULD

BE A BIT MORE COMFORTABLE IF WE UPPED OUR SNOW TOTALS A BIT FOR OUR

NORTHWESTERN COUNTIES. ALTHOUGH THIS IS A QUICK HITTING SYSTEM...

THAT HIT SEEMS TO BE A GOOD HONEST UPPERCUT. THERE MAY NOT BE ANY

LAG AT ALL BETWEEN THE TIME THE STEADY SNOW STARTS FALLING AND THE

TIME IT STARTS ACCUMULATING LATE THIS AFTERNOON INTO THIS EVENING.

IMPRESSIVE SNOWFALL RATES NOTED IN ARKANSAS. AND WHILE I DON`T

NECESSARILY EXPECT THE TOTALS THEY HAVE GOTTEN/ARE GETTING TO BE

EQUALED HERE...I GET A SENSE THAT THE SYSTEM IS OUTPERFORMING

PREVIOUS MODEL SOLUTIONS.

WILL HAVE UPDATED GRAPHICS ON OUR WEBSITE AND A NEW WSW TEXT PRODUCT

OUT WITHIN THE HOUR. THIS UPDATE DOES NOT CHANGE THE WSW AREA AT

ALL...JUST REFINES THE EXPECTED ACCUMULATIONS.

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I disagree. If you get two big snows in a winter, one before new years and one after, it counts for two years instead of one season. It's easier to determine snowier winters (and those that aren't) from July 1 instead of Jan 1.

Why don't you go do your own research your own way and please leave GaWx alone? ;)

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I do not know folks...maybe it's the inner weenie in me, but it appears that the moisture transport is holding up quite well. Cloud deck is thickening around here. Has a good snow look to it . Also, it looks like moisture is streaming in more from the gulf than what was forecasted?

http://www.intellicast.com/National/Radar/Current.aspx?animate=true

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