Jan. 20-21 MidAtl/NE Winter Storm OBS, Last Minute Forecasts & OBS Options

[BergenCountyNJ]

Figured I would start it since people said it started snowing in PA

[hckyplayer8]

[Undertakerson]

[attachment=117585:pmsl.gif]



Hard to see but the surface low is currently on the KY/VA border.

http://w1.spc.woc.noaa.gov/exper/mesoanaly...&parm=pmsl#

This post has been edited by Undertakerson: Jan 20 2011, 03:59 PM

[The Day After To...]

Mostly cloudy outside here.

[Undertakerson]

[attachment=117586:sfc_con_pres.gif]

a better visual of SLP

[cheesetaco7]

Updated Taunton map.

[hckyplayer8]

Didn't get much time to look at this one. Though it looks pretty simple (famous last words) In general it has and continues to look like a 2-4 for the local regions I usually forecast with the general upslope regions through WPA and WV getting some higher totals...likely pushing half a foot. Models have obviously trended a tad wetter in the past 24 hours making yesterdays possible higher totals through SE NE, immediate coastal New England down into coastal NJ a pretty good bet as Atlantic moisture gets involved with the deepening low. Don't know how much time I will get on here for the next couple days but I would look for further digging of the Northern branch that leads to lower height anomalies trying to slide Eastward and energy associated with the PV trying to phase and directly influence surface cyclogenesis off the coast of ME. Here totals pushing a foot may be possible if that scenario plays out.

Local Final Totals

IMBY-2-4
Harrisburg-2-4
Lancaster-2-4 *likely low end
York- 2-4 *likely low end
Philly-2-4 *likely low end

This post has been edited by hckyplayer8: Jan 20 2011, 04:07 PM

[dtown]

I'm going to post this here as well:

I don't post much but I think I'll take a shot at nowcasting this storm. I have seen on several sites people mainly in the SE PA and Philly region getting excited for over 4", even 8" of snow with this storm. Using the Accuweather.com water vapor imagery I am going to try and explain why I DO NOT like our chances for those amounts. I'm taking a page from HM here who often says to watch for where the thunderstorms curl up into the cold air for heavy snow and that is the basis for my discussion below.



So let me explain my graphic. I circled in red where storms are firing up in the GOM. This is what some mets are calling a "Gulf Tap". The gulf is definitely being tapped, but what some mets are not realizing is that the moisture will simply not affect areas west of NYC metro.

Now notice that I highlighted the dry slot. this dry slot is creating two distinct separate areas of moisture, one circled in yellow and the other in black. When the GOM moisture curls up into the storm, it will get involved in the area circled in yellow. the dry slot will prevent it from moving up into the black circled area.

The darkest blue line is the current axis of the dry slot. The medium blue line is where this axis should shift to as the storm approaches the coast. Since the GOM moisture will only get into the yellow circled area, and that area is south and east of the dryslot, that places the gulf moisture offshore. In order for that extra "juice" to curl up and enhance snowfall rates over eastern Pa, the dry slot axis would have to look something like the light blue line. The fast east movement of the storm and lack of blocking will prevent that from happening. Therefore the only moisture providing snow for all of PA is the moisture circled in black. Areas in the dry slot will get 2" or less, and based off the latest NAM (which I feel is accurate) Extreme SC PA on the east side of the mountains may be in this zone too. Otherwise, I think we will see a general 2-4" in PA with locally 5/6" in the Poconos.

In NE, the area I circled in red (where it stays all snow) can expect 8-12", with 4-8" between there and NYC.

Accuweather.com water vapor loop

[Undertakerson]

I'm going to post this here as well:

I don't post much but I think I'll take a shot at nowcasting this storm. I have seen on several sites people mainly in the SE PA and Philly region getting excited for over 4", even 8" of snow with this storm. Using the Accuweather.com water vapor imagery I am going to try and explain why I DO NOT like our chances for those amounts. I'm taking a page from HM here who often says to watch for where the thunderstorms curl up into the cold air for heavy snow and that is the basis for my discussion below.



So let me explain my graphic. I circled in red where storms are firing up in the GOM. This is what some mets are calling a "Gulf Tap". The gulf is definitely being tapped, but what some mets are not realizing is that the moisture will simply not affect areas west of NYC metro.

Now notice that I highlighted the dry slot. this dry slot is creating two distinct separate areas of moisture, one circled in yellow and the other in black. When the GOM moisture curls up into the storm, it will get involved in the area circled in yellow. the dry slot will prevent it from moving up into the black circled area.

The darkest blue line is the current axis of the dry slot. The medium blue line is where this axis should shift to as the storm approaches the coast. Since the GOM moisture will only get into the yellow circled area, and that area is south and east of the dryslot, that places the gulf moisture offshore. In order for that extra "juice" to curl up and enhance snowfall rates over eastern Pa, the dry slot axis would have to look something like the light blue line. The fast east movement of the storm and lack of blocking will prevent that from happening. Therefore the only moisture providing snow for all of PA is the moisture circled in black. Areas in the dry slot will get 2" or less, and based off the latest NAM (which I feel is accurate) Extreme SC PA on the east side of the mountains may be in this zone too. Otherwise, I think we will see a general 2-4" in PA with locally 5/6" in the Poconos.

In NE, the area I circled in red (where it stays all snow) can expect 8-12", with 4-8" between there and NYC.

Accuweather.com water vapor loop

Nice disco - one question?

You chose to ignore the tail end of the stream presently defining the tail end of the main moisture feed, why?

Once this translates east, it too would probably tap the GOM and quickly get entrained into the main flow of the approaching storm. It has the support of much more organized LP and should not be discounted IMO

[attachment=117593:5.gif]

[dtown]

Nice disco - one question?

You chose to ignore the tail end of the stream presently defining the tail end of the main moisture feed, why?

Once this translates east, it too would probably tap the GOM and quickly get entrained into the main flow of the approaching storm. It has the support of much more organized LP and should not be discounted IMO

That is a good question, appreciate the response. Models show that area simply fading out as the low in KY/TN takes over. However that is one more thing that should be watched to make sure it goes as planned.

In fact in the few frames after the one I used for that graphic, the western t-storms I circled in red basically disappeared. Have not looked to see what has happened since.

[sw03181]

first guess:
NYC: 3-6
New Haven: 4-8
Hartford: 5-10
Springfield (MA): 5-10
Worcester: 6-12
Providence: 6-12
Boston: 6-12
Hyannis: 2-5

[Undertakerson]

That is a good question, appreciate the response. Models show that area simply fading out as the low in KY/TN takes over. However that is one more thing that should be watched to make sure it goes as planned.

In fact in the few frames after the one I used for that graphic, the western t-storms I circled in red basically disappeared. Have not looked to see what has happened since.

Cool - just wanted to hear your thoughts really. Your points are valid because we kind of saw something similar last storm.

Current SPC Meso's show that wester GOM feeder still providing SOME impetus.

http://w1.spc.woc.noaa.gov/exper/mesoanaly...&parm=pmsl#

I think the T-storms dimished as much due to daytime heating reductions at this hour, as much as any lack of "tapping" abilities.

Like you said, we shall have to watch what develops. I appreciate your open-mindness.

[BoroSnow]

NWS forecast for Washington Boro, PA

Late Afternoon: A slight chance of snow showers. Cloudy, with a high near 33. Calm wind. Chance of precipitation is 20%.

Tonight: Occasional snow, mainly after 7pm. Low around 24. Calm wind becoming north between 6 and 9 mph. Chance of precipitation is 100%. New snow accumulation of 3 to 5 inches possible.

Friday: Cloudy, then gradually becoming mostly sunny, with a high near 29. Breezy, with a west wind between 13 and 22 mph, with gusts as high as 33 mph.

http://forecast.weather.gov/MapClick.php?C...Field2=-76.4339

[Trogdor]

first guess:
NYC: 3-6
New Haven: 4-8
Hartford: 5-10
Springfield (MA): 5-10
Worcester: 6-12
Providence: 6-12
Boston: 6-12
Hyannis: 2-5

With the way trends have gone today, this is the generally accepted and conservative approach. I agree, with a chance of NYC seeing a little better. Also adding LI, should be 4-8, 5-10 possibly...

[ilovethesnow223]

any word on the gfs yet? just curious to see what it showed.

[snow4joe]

Currently 34.2 F here in Brick, NJ and falling. Dew Point is around 20 F.

[Fire/Rescue]

Current conditions here IMBY (20 miles Northeast of Baltimore)

Cloudy skies

Temperature: 39.8
Windchill: 38
Humidity: 59%
Dew Point: 24
Wind: 2 mph from the ESE

This post has been edited by Fire/Rescue: Jan 20 2011, 04:47 PM

[LoveNYCSnow]

GFS has the low tracking over southern PA, really far north

http://www.nco.ncep.noaa.gov/pmb/nwprod/an...fs_ten_012l.gif

its a good thing this storm is pretty weak because if it was a strong a track like that would be a soaker for a lot of people

This post has been edited by LoveNYCSnow: Jan 20 2011, 04:49 PM

[AY FROM CT]

GFS Hour 12

[morpheus27]

With the way trends have gone today, this is the generally accepted and conservative approach. I agree, with a chance of NYC seeing a little better. Also adding LI, should be 4-8, 5-10 possibly...

Any concern over later than expected development restricting those higher totals further north and east?

OBS:

Temp: 30 f
Dewp: 11 f

Overcast


This post has been edited by morpheus27: Jan 20 2011, 04:49 PM