GFS shows storm near February 17 in mid-Atlantic

[jimvb]

The 2009 February 6 00Z GFS run shows a storm striking the Mid-Atlantic states on February 17:

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/00/images/gfs_pcp_276s.gif

It also shows another storm striking three days later. The 06Z run shows the Feb 17 storm but considerably weaker, and it shows the Feb 20 storm going farther to the south, in northern Florida.

[Stephanie]

Maybe the snow gates have finally opened for the Mid Atlantic this winter.

[jimvb]

Now look at the 18Z run. It shows THREE storms.

[srainhoutx]

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
227 PM EST SAT FEB 07 2009

VALID 12Z TUE FEB 10 2009 - 12Z SAT FEB 14 2009


GLOBAL GUIDANCE REMAINS CONSISTENT WITH PRIOR RUNS IN SUSTAINING A
MEAN LONGWAVE TROUGH OVER THE WESTERN CONUS THROUGH THE MEDIUM
RANGE PERIOD....DOWNSTREAM OF A MEAN ERN PACIFIC RIDGE ALONG 150W.
STRONG FAST-MOVING PERTURBATIONS WILL ROTATE THROUGH THE BASE OF
THE WRN CONUS TROUGH.

THIS WILL RESULT IN SIGNIFICANT EPISODES OF SENSIBLE
WEATHER...PARTICULARLY ACROSS THE SE QUADRANT OF THE NATION WHERE
THESE PERTURBATIONS WILL INTERCEPT GULF OF MEXICO MOISTURE. TWO
SYS WILL HAVE THE STRONG DYNAMICS FAVORING SEVER WX OVER THE SERN
STATES. ONE OF THESE WILL OCCUR DAYS 4-5...THE OTHER DAY 6 AND 7.
HEAVY RAINFALL WILL ALSO BE A THREAT WITH THE FIRST SYS FROM E TX
INTO THE LOWER GRT LAKES. THE DAY 6-7 SYS ACROSS THE SE WILL
LIKELY HAVE A HEAVY RAIN THREAT FARTHER S IN THE SERN STATES THAN
THE PREVIOUS SYS. THE WEST WILL SEE SOME MDT TO HEAVY PCPN ALONG
THE COAST/COASTAL RANGES...WITH LESSER AMOUNTS INLAND...SN AT
HIGHER ELEVS...IN THE FAVORED OROGRAPHIC LOCALES.

BY MID PERIOD...HIGH LATITUDE BLOCKING ACROSS GREENLAND AND THE
DAVIS STRAIT WILL BEGIN FAVORING THE SUPPRESSION OF 500MB HEIGHTS
OVER THE ERN PORTION OF THE UNITED STATES. HOWEVER THESE POSITIVE
500MB HEIGHTS IN NE CANADA AND GREENLAND WILL HAVE TO BE DUEL FOR
CONTROL OF THE WEATHER OVER THE UNITED STATES WITH THE POSITIVE
HEIGHT ANOMALY IN THE ERN PACIFIC. WHO WILL WIN? WELL...THERE
SEEMS TO BE A GENERAL MODEL/ENSEMBLE CONSENSUS...ESPECIALLY IN THE
GFS...FOR EACH SHORTWAVE MOVING ACROSS THE LOWER 48 IN THE MEDIUM
RANGE TO TRACK A LITTLE FARTHER S THAN ITS PREDECESSOR. I EXPECT
THAT THE DAVIS STRAIT/GREENLAND BLOCKING SHOULD GRADUALLY GAIN
MORE CONTROL OVER THE LONGWAVE PATTERN BY THE END OF THIS MEDIUM
RANGE PERIOD.
FOR DAYS 3-5 TUE-THU...IN OUR UPDATED PRELIMS...WE WENT WITH A
BLEND OF 40% GFS/40% ECMWF/20% EC ENS MEAN. THE ONLY CHANGE WE
MADE IN OUR FINAL 12Z/07 GRAPHICS WAS TO ADJUST THE TRACK OF AN OH
VLY LOW PRES SYS TO THE N SAT DAY 7 FROM WHAT WE SENT OUT IN THE
UPDATED PRELIM. THE NEW 12Z/07 ECMWF HAS THIS SAME IDEA BUT IS
ABOUT 12 HOURS SLOWER WITH THIS DAY 7 SYS THAN THE GFS.

12Z MODELS: THE NEW 12Z/07 GFS IS PRETTY MUCH ON TRACK WITH 00Z/07
DETERMINISTIC GFS/ECMWF CONTINUITY THRU THU DAY 5. FOR DAY
6-7...THE GFS BRINGS AN OUTSIDE SLIDER TOWARDS CA BUT TENDS TO
LOSE THE NEXT UPSTREAM SHORTWAVE ITS CONTINUITY HAD OFF THE
ALASKAN PANHANDLE. THE CANADIAN AND UKMET ARE GENERALLY IN
AGREEMENT WITH THE 12Z/07 GFS WITH THE MAIN SHORTWAVE FEATURES
AFFECTING THE COUNTRY THRU FRI DAY 6...EXCEPT THAT THEY ARE A BIT
LESS THAN HALF A DAY SLOWER WITH THE SHORTWAVES MOVING THRU THE
MEAN TROF OVER THE SWRN STATES THAN CONTINUITY. THE NEW ECMWF IS
IN THE BALL PARK...BEING A BIT SLOWER WITH A SYS AFFECTING THE NE
CONUS DAY 5...BUT TRENDING FARTHER S TOWARDS THE GFS WITH THE
SHORTWAVE DROPPING OFFSHORE DOWN THE W COAST DAYS 6-7. THE MOST
IMPORTANT CHANGE IN THE NEW ECMWF RUN FROM CONTINUITY IS THAT IT
HAS BACKED OFF DIGGING AN OUTLIER TROF SWWD OVER ALASKA DAY 7. A
LOW CONFIDENCE CHANGE INDEED...BUT STILL IN BETTER HARMONY WITH
THE ENSEMBLE PLOTS.

FLOOD

Should the Greenland Blocking set up, the folks in the Mid Atlantic Region may see some impressive snowfalls. With the performance of guidance as of late, it's just a bit too soon to call IMHO. Hope you get your Big Snow Event.

[jimvb]

I don't want any big snow events. I think of these three storms on the 14th, 17th, and the 20th as being like three big bad wolves, or like the three Gorgons Stheno, Euryale, and Medusa. We need Perseus to cut off that Greenland block.

[jimvb]

2009 February 7 18Z now suggests SIX storms after Valentine's Day. Forget Stheno, Euryale, and Medusa. Call it the Valentine's Day Massacre.

[Stephanie]

I haven't looked at the models yet, but I can't help but think that 6 storms HAS TO BE an extreme.

Right now I'm looking at a pond in my backyard from the 6+ inches of snow fall this week that melted. It's like night and day between early yesterday morning and today. Unbelievable!! I have the windows cracked open and the heat off. My backyard thermostat currently says 65 degrees - but it is in the sun.

[Stephanie]

The February 8 0Z and 6Z looks like they've laid off the "Valentine Day" 6 headed monster massacre.

[srainhoutx]

I haven't looked at the models yet, but I can't help but think that 6 storms HAS TO BE an extreme.

Right now I'm looking at a pond in my backyard from the 6+ inches of snow fall this week that melted. It's like night and day between early yesterday morning and today. Unbelievable!! I have the windows cracked open and the heat off. My backyard thermostat currently says 65 degrees - but it is in the sun.

Well Stephanie, the latest GFS guidance suggests warmer and wetter while the ECMWF says colder and drier. This far out and the way model guidance has performed during the 5-10 range this winter, I wouldn't hold my breath. Enjoy the warmer weather.

[Stephanie]

I haven't looked at the models yet, but I can't help but think that 6 storms HAS TO BE an extreme.

Right now I'm looking at a pond in my backyard from the 6+ inches of snow fall this week that melted. It's like night and day between early yesterday morning and today. Unbelievable!! I have the windows cracked open and the heat off. My backyard thermostat currently says 65 degrees - but it is in the sun.

Well Stephanie, the latest GFS guidance suggests warmer and wetter while the ECMWF says colder and drier. This far out and the way model guidance has performed during the 5-10 range this winter, I wouldn't hold my breath. Enjoy the warmer weather.

I'm not.

[jimvb]

I looked at the 2009 Feb 8 18Z GFS. There are now only 3 storms, and a 4th storm has appeared in hour 384. In addition a rainstorm has appeared on the 12th. For central Virginia, the 12th storm looks like rain, the 14th (Medusa) is a borderline case, the 17th (Stheno) is a borderline case, and the 20th storm has moved to the 22nd (Euryale) and looks like rain. The 24th storm looks like it passes too far to the south, but if it strikes, it would be snow. With so many close calls, I am afraid that one might hit with the 0 line too far to the south, giving us a snowstorm.

[Stephanie]

I looked at the 2009 Feb 8 18Z GFS. There are now only 3 storms, and a 4th storm has appeared in hour 384. In addition a rainstorm has appeared on the 12th. For central Virginia, the 12th storm looks like rain, the 14th (Medusa) is a borderline case, the 17th (Stheno) is a borderline case, and the 20th storm has moved to the 22nd (Euryale) and looks like rain. The 24th storm looks like it passes too far to the south, but if it strikes, it would be snow. With so many close calls, I am afraid that one might hit with the 0 line too far to the south, giving us a snowstorm.

You never know. It's entirely possible that one of these will be a snow monster, but there has to be cold air settled in over the area during that whole time period in order for one to be snow. We'll see.