Washington/Batimore Heavy Snow Forecast...

National Weather Service Baltimore/Washington ^ | February 14, 2003

[John H K]

AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 445 PM EST FRI FEB 14 2003

...SHORT TERM...TONIGHT AND SAT...

ROUND ONE OF THIS WEEKEND'S TWO PART WINTER STORM HITS TONIGHT THRU LATE SAT. ACROSS THE FAR N ZONES AND MOUNTAINS...TEMPS WILL BE COOL ENOUGH THRU THE PERIOD THAT ALL SNOW IS EXPECTED. IN THE N SHEN VALLEY...NORTHERN VIRGINIA...AND DC AND S BALT AREAS...TEMPS WILL BE WARM ENOUGH FOR A RAIN/SNOW MIX TONIGHT. MODEL SOUNDINGS SHOW THE POSSIBILITY OF A BRIEF MIX OF SLEET OR FREEZING RAIN BETWEEN DAWN AND 8 AM. MID MORNING SAT...THE PRECIP WILL CHANGE TO ALL SNOW. ACROSS THE CENTRAL SHENANDOAH VALLEY...THE FREDERICKSBURG AREA AND SOUTHERN MARYLAND...PRIMARILY RAIN IN EXPECTED WITH A MIX OF SLEET/SNOW/OR FREEZING RAIN POSSIBLE. THE PRECIPITATION WILL CHANGE OVER TO MAINLY SNOW SOMETIME SAT AFT FROM N TO S. SNOWFALL ACCUMULATIONS WILL BE HIGHEST IN THE N WHERE MAINLY SNOW IS EXPECTED AND LOWEST IN THE S WHERE A SIGNIFICANT PERIOD OF MIX WILL OCCUR. RANGE FOR BOTH PERIODS...2 TO 6 INCHES.

MMARGRAF

LONG TERM (SAT NITE-FRI)

ETA/GFS HAVE TRENDED STRONGER AND SLOWER WITH RESPECT TO THE UPPER TROF THAT WILL BE EJECTING FROM THE PLAINS INTO THE MID-ATL STATES. ETA CLOSES OFF A MID-LVL CENTER BY 06Z MON NEAR PITTSBURG WHILE GFS DOES NOT. PER QPFHSD WILL LEAN MORE TOWARD THE ETA GIVEN IT HAS SOME SUPPORT FROM UKMET AND CANADIAN.

OCASSIONAL -SN EARLY SAT NITE WILL BECOME HEAVIER AS THE NIGHT PROGRESSES AS WAA PATTERN STRENGHTENS IN RESPONSE TO APPROACHING UPPER TROF/HEIGHT FALLS. 12Z ETA SHOWING IMPRESSIVE WAA PATTERN ON SUN WITH STG H85 EASTERLY JET OF 50 KTS FEEDING ATL MOISTURE INTO AN ALREADY JUICY AIR MASS. FCST PW FIELDS ARE OVR 0.8 INS OVR MOST OF THE CWA WITH VALUES EXCEEDING 1.0 IN OVR THE FAR SOUTHERN COUNTIES. ATMOS FROM TOP TO BOTTOM SUPPORTS MOSTLY SNOW ENTIRE CWA. HOWEVER MODELS SOUNDINGS SHOW SOME SLEET COULD GET MIXED IN WITH THE SN BETWEEN 00Z SUN-06Z SUN OVR FAR SRN MD/SPOTSYLVANIA/CHO. ADDED IP TO THOSE AREAS TO MATCH UP WITH SURROUNDING WFOS.

TEMPS ON SUN WILL HOVER AROUND 20 DEGS MOST OF THE DAY WHICH WILL PROBABLY RESULT IN HIGHER THAN NORMAL SNOW TO LIQUID RATIOS. GIVEN STRONG UPSLOPE COMPONENT (H85 50-KT JET)...STRONG 700-500 OMEGAS IN THE SNOW GROWTH REGION AND FVRBL LFQ JET DYNAMICS OF A 100-KT JET SUGGEST HEAVY SNOWFALL RATES THROUGH MUCH OF THE DAY ON SUN. EXTENDED PRECIP A LITTLE BIT LONGER INTO MIDDAY MON AS PER SLOWER TREND IN THE MODELS. ETA GIVING ALMOST 2.0 INS OF LIQUID EQUIVALENT WITH GFS ALMOST HALF OF THAT. BY THE TIME EVERYTHING IS SAID AND DONE WE COULD BE LOOKING AT THE MOST SIG SNOW EVENT IN THE WASHINGTON AREA SINCE EARLY JAN 1996. 10 INS OF SNOW WILL BE A VERY...VERY CONSERVATIVE SNOW TOTAL FOR THE AREA.

REST OF THE EXTENDED...TRENDED TEMPS COLDER GIVEN EXPECTED SNOWPACK. NEXT CHANCE OF PRECIP LOOKS TO BE NEXT FRI. LONG WAYS OUT FROM NOW KEPT IT DRY FOR NOW.

ROSA

[Textide]

Still snowing hard. <1/4 mile visibility at 16 degrees. Hard to tell how much has fallen, but is probably 14-15in.

[Textide]

A guy just came down the street in a four-wheeler through downtown Leesburg dragging another guy sitting on an inner tube.

Pretty funny looking.

[Ligeia]

I ventured out and didn't have any problems, really. Free enterprise and our tax dollars are hard at work both plowing and sanding. I drove out to Great Falls where the snow measures over a foot at this point. It's magnificent! I was so proud of my little SUV as I went toe-to-toe with a Hummer. One poor landscape truck with a blade strapped to the front had misjudged the edge of the asphalt and was in the ditch but all other 4x4s were doing fine. I stopped on the a one-lane bridge that crosses over Difficult Run to see the water freezing into a creek slurpee.

The only problem I had was the ice on the wiper blades. I hope GM has fixed that problem in the past few years. If not, someone in R&D needs to get busy.

It was good to see so many independent trucks out wearing the rust off their capital investment. Everything they plowed is getting recovered at the rate of an inch per hour. Funny thing, schools are out of snow days and Washington's Birthday tomorrow was supposed to be a make up day. Not this year!

[brianl703]

Front-wheel drive and traction control really helps. Traction control is neat, on my car it is capable of cutting back on the throttle and applying the brake to the spinning wheel to transfer power to the other wheel.

Unfortunantly, I'm not going to test it out today...

[brianl703]

People who end up overflowing the toilet do so because they mistakenly assume that the second flush will push the stuff down.

Most toilets will give you a one-flush grace period before they overflow. They also give you a visual indication that the second flush would be ill-advised by the fact that the bowl is excessively full.

[Ligeia]

Traction control is neat

I think I had that on a 197-something or early '80s Chrysler LeBaron. I lived up a steep driveway and when it was slippery with wet leaves, I could feel the wheels grab on the driest spot. I like the 4x4s of today better, though, especially today during the biggest storm of our lifetime, or so says WMAL. It's not supposed to stop snowing until tomorrow afternoon!

[muggs]

Most toilets will give you a one-flush grace period before they overflow. They also give you a visual indication that the second flush would be ill-advised by the fact that the bowl is excessively full.

I would probably be better off if I gave IQ tests to prospective renters instead of running credit/crimminal checks on them.

[muggs]

Of course, if I had to take a spelling test for any reason, I'd be in bad shape.

crimminal = criminal

[brianl703]

Wow, you sure? I don't think the technology existed to make traction control at a reasonable price in the early 80s. (They did, however, have inexpensive technology to make an annoying voice tell you that the door is a jar)

Traction control, at least the type I have in my car, needs ABS to work, as it uses some of the ABS functions to apply the brakes to the spinning wheel.

There's another, cheaper, form of traction control which just cuts fuel to the engine, but it still needs fuel injection (not very common in the early 80s) to work, plus it still needs the wheel speed sensors like ABS uses.

The wheel grabbing phenomenon is pretty normal. In fact, if your wheels were grabbing on the dry pavement, it means they were spinning on the wet leaves, a situation traction control will prevent.

[Ligeia]

I must have had the prehistoric version. ;^)

[brianl703]

Let me describe how traction control works:

Without traction control, in the rain/snow (or even in the dry), if I give it too much gas, the wheels will just spin and I will go nowhere.

With traction control, if I give the it too much gas, the computer will detect that the wheels are spinning and cut back on the throttle with a device connected in-line with the throttle cable to the throttle plate.

The device works by adding slack to the throttle cable, thereby reducing the
amount of throttle opening, which has the same effect as taking one's foot off the gas pedal.

In addition to that, if the traction loss occurs at slower speeds(under 15MPH I think), the computer will also use the ABS pump to apply the brake to whichever wheel is slipping, transferring power to the other wheel. It can apply the brakes only to the wheel that is slipping. It works kind of like a limited slip differential.

It's the same reason that pulling up the parking brake on a rear-wheel drive car while the rear wheel is spinning sometimes works to get you unstuck.

My experimentation has shown that if I floor the gas pedal in the rain, the wheels will slip for a split second, then stop slipping as the traction control takes over.

In fact, if I want to be childish and peel out/screech the tires, I have to turn the traction control off..

[Ligeia]

This is all way too much detailed information for me, but as I was stirring the spaghetti sauce, the term "Posi-traction" came to mind. That's what Chrysler called it then.

[brianl703]

Ok, posi-traction is a limited slip differential. Ford's name for it traction-lok, and my 1988 Mustang 5.0 has it although it's probably lost effectiveness due to mileage with 145,000 miles. When I get the differential gear ratios changed I will get the traction-lok rebuilt at the same time.

Limited slip differentials are very common on rear wheel drive vehicles, but not so common on front wheel drive (I guess the additional weight of the engine over the drive wheels reduces the need for it).

[Jimmy Valentine's brother]

I don't think the technology existed to make traction control at a reasonable price in the early 80s.

It was called positraction most GM cars with big engines had it in the sixties. As Casey Stengel would say, you could look it up.

[brianl703]

Traction control systems incorporate some method for reducing the power produced from the engine to stop the wheels from spinning.

Positraction: Both wheels will spin unless you back off on the throttle

Traction control: will back off on the throttle for you

In fact it is possible to have traction control and positraction on the same car, see any late-model Mustang equipped with traction control.

Traction control and positraction are not the same.