Skip to comments.Washington/Batimore Heavy Snow Forecast...
Posted on 02/14/2003 2:15:54 PM PST by 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.
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.
Also, this is an "Area Forecast Discussion" which is readable by the public, but really isn't intended for the public, hence the technical terminology.
In case you're wondering, computer models really don't output a snow amount, they output an amount of liquid water equivalent.
It's very tricky to convert that back into a snow depth, since it's very sensitive to temperature, etc. The MINIMUM baseline for a wet snow is about 10 to 1...10 inches of snow to 1 inch of rain. It's often 15 to 1 to 20 to 1.
Thus the ETA's 2.00" for DC is actually something like 20 to 40 inches of snow.
ETA can sometimes inflate precip amounts, though.
I met a quite old guy the other day with a heavy European accent. While shooting the breeze, he said he had no computer, but had "worked on them 50 years ago when they were the size of a large room"....
It was cute when he said, "They only had 40K, but...OHHHHHH!!!! The math and everything they could squeeze out of that 40K!!"
Har! I moved back to Pennsylvania this year and brought my new wife, the mountain woman, back with me. I warned her about the difference between East Coast cold and Colorado cold. So of course we get the worst winter since 1994. She's a believer now.
My wife and I are praying for you guys - we lived in the mountains west of Denver and were always worried about a fire up there. Colorado hasn't had a four-year drought before, but you've got one now. Hope for some late-season snow and some good rains in May...
4-6 inches tonight.
There's enough cold air in place to make sure this is an all-snow event. I remember the big dump in 1996 that they are talking about, it put down 30 inches in the Philly area - and the temps were down in the teens. This air mass isn't much warmer, and since it's February instead of early January, there will be more energy to the south for this storm to tap into.
Yeppurs. I'm taking work home with me this weekend, because I don't expect to make it into work on Monday from what the forecast is saying.
was hoping to meet the FReepers in NYC for cocktails after the demo tomorrow ...
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