Snow Threat Sunday-Monday - Middle Atlantic States

By: Pcroton , 12:08 AM GMT on March 14, 2014

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Update Section, March 16, 4PM

Afternoon analysis shows that the earlier model solutions showed the high pressure suppression as too strong and storm impacts have nudged northward through Central NJ.


Updates begin on Post #267







March 16, 8AM

Snow and Ice threatens the Middle Atlantic states while Severe Weather hits the Gulf Coast and Florida.

Updates Posts 228-233





Updates Posts 228-233






Blog Opening, March 13, 9PM

A potential snow storm threat exists for the Middle Atlantic States for Sunday into Monday.






Two pieces of energy will combine over the Southern Plains on Saturday.








Here are the 12Z Models from 3/13 - centered at 96hr time frame - 8AM Monday.





Notice the amount of energy we are dealing with of which the models have resolved strung out along the frontal system. These scenarios frequently change as guidance nears in on the event. It would be unwise to trust any model guidance at this distance. Recently we have been somewhere in the 48 to 72 hour window where guidance has locked in. This would be the Friday 12Z runs or perhaps Saturday 0Z runs.




Recently guidance has been struggling with storm systems due to the pattern changing and the split flow patterns in the 500MB layer. The result is wildly ranging model solutions both individually and as a group. Note how wild the pattern is through the Pacific and Western US/Canada. These multiple stream splits will undoubtedly give the models fits.






What we know is a system will enter the Southern Plains on Saturday bringing the chance of severe weather. How the storm tracks from here is in question at this time.








The HPC appears to be fairly interested in the threat.

HPC guidance through 8AM Monday.











The NAO is once again going to be near neutral timed with yet another storm threat. While we've never gotten the "strong negative NAO" we heard was coming most of the winter (and never did) there was always this little dip that coincided with our storm threats along the upper middle atlantic coast.







Taking a peek at the long term it appears the Pacific features that were driving our cold weather outbreaks has begun to break up.


The dominating North Pacific SST anomaly has been relaxing.







The PNA is heading negative.







Our jet stream will feature quite an amplified yet fast moving pattern resulting in quite the temperature roller coaster. No longer are we locked into a persistently strong East Pacific ridge and thus Eastern trough.









Looking ahead we appear to be remaining on the cool side although not nearly as brutal as before.







Here are your CFS2 Temperature and Precipitation Maps. It appears through at least April we will remain cool.


The weeklies:















April Monthly:






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Quoting 311. doom22015:
We must have a big-time virga thing going here in DC area. For some time, the radar has made it look like we should be getting lotsa snow, but nothing here at ground level. Guess this would be a good time to bring in firewood.
Temp is 40F and barometer is at 30.00 steady. I am ready to see both of those numbers falling!


Temps will drop and precip will increase through the evening and overnight. You could easily start as rain before going over. It's coming though.



Member Since: September 26, 2011 Posts: 73 Comments: 12846
Yeah Max everything has trended north into central NJ now.


NAM was terrible and continues to do poorly with the high's strength. GFS has had this for some time now. NAM's suppressed solutions are tossed - yet even the NAM came north through the day with 18Z looking a lot closer to other guidance.

Here's the latest comparisons of 12Z model runs for the 21Z hour - against the actual 12Z readings.





GFS: 1028MB
Actual: 1028MB
NAM: 1032MB - which is why it was too suppressed.


The high is weakening steadily at 1MB or more per hour. SPC analysis: 2hr changes (over 2mb drop in high)








Larger view.


Member Since: September 26, 2011 Posts: 73 Comments: 12846
We must have a big-time virga thing going here in DC area. For some time, the radar has made it look like we should be getting lotsa snow, but nothing here at ground level. Guess this would be a good time to bring in firewood.
Temp is 40F and barometer is at 30.00 steady. I am ready to see both of those numbers falling!
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I see the snowfall swatch was pushed northwards...




Winter warnings were expanded north as well and advisories north of there including you P
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18Z NAM snowfall:




Compared with earlier? Now it's more in line with other guidance.











12Z GEM Snowfall is out now:




Member Since: September 26, 2011 Posts: 73 Comments: 12846
High is weakening now. This is 20Z. When we hit 21Z we can compare against guidance at 21Z





Low pressure also tracking eastward through MS-AL and not south east to central AL as early day and last nights guidance had shown.

So there will be no SE track followed by NE - it's just East and then NE. It's just one reason why we're seeing a more northerly push along the middle atlantic coast.

The other is the high is clearly much better modeled by the GFS throughout the last 24 hours (as we've done the comparison) while the NAM had it much stronger thus more suppresson (and even the NAM now initializing off of newer readings isn't doing that as much with the high as before).

Therefore guidance "came north".



I will be happy when these maps are updated. They are stuck in 2PM. These boundaries are your suppression lines aloft. As the storm moves north and east so too should these lines.






If you are south of those lines you get moisture transport and lift. North of those lines is sinking air and dry air transport from the north.


They must be on the move because the precipitation is creeping north of the PA border - and you are starting to see that SW-NE latitude gain in the precip develop as well.




Also in the final few frames some echoes are starting to break out in the sinking zone from earlier (old image below:)







Member Since: September 26, 2011 Posts: 73 Comments: 12846
If we do have another snow storm this would be one of D.C's snowiest March's.
Member Since: August 14, 2010 Posts: 10 Comments: 17860
Quoting 305. Pcroton:


Don't forget 2008 I think it was (maybe 07 I dont quite remember). We had 8" of powder and 25F the second week of April here in NJ.



Was that the time when there were leaves on the tree, i know in 1986-1987 early spring there were leaves on the trees and we had a very heavy wet snow at night and was pretty much gone in two days
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Quoting 303. PengSnow:
Washingtonian, i do see something coming(cold air wise) late next week and especially around the 25th to 28th, if that happens we could have some more winter precip to deal with and you could probably say in to early to mid april, I probably haven't see that since the mid 80s.


Don't forget 2008 I think it was (maybe 07 I dont quite remember). We had 8" of powder and 25F the second week of April here in NJ.
Member Since: September 26, 2011 Posts: 73 Comments: 12846
Quoting 301. washingtonian115:
Hey P.Long range models show another visit from our friend the Polar vortex and another storm at that time.I wonder when the pattern will finally break.


Yeah I touched on the reloading pattern earlier in the blog it does look like we're in for another week of cold. Whether or not it times perfect with a storm well we know the drill....and the margin of error for these things is miniscule this time of year.


Enjoy THIS storm while you have it. You're in the jackpot zone I would think.

Member Since: September 26, 2011 Posts: 73 Comments: 12846
Washingtonian, i do see something coming(cold air wise) late next week and especially around the 25th to 28th, if that happens we could have some more winter precip to deal with and you could probably say in to early to mid april, I probably haven't see that since the mid 80s.
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NWS New York NY ‏@NWSNewYorkNY 5m

Bumped snow totals up slightly, Staten Island may see 1" North fringe of precip tough 2 predict. Minor change.


=============





===============================
Afternoon Updates begin Post 267
===============================



.
Member Since: September 26, 2011 Posts: 73 Comments: 12846
Hey P.Long range models show another visit from our friend the Polar vortex and another storm at that time.I wonder when the pattern will finally break.
Member Since: August 14, 2010 Posts: 10 Comments: 17860
And so it begins:



MESOSCALE DISCUSSION 0195
NWS STORM PREDICTION CENTER NORMAN OK
0328 PM CDT SUN MAR 16 2014

AREAS AFFECTED...PORTIONS OF CENTRAL/ERN WV INCLUDING THE
PANHANDLE...CENTRAL/NRN VA...MUCH OF MD...DC

CONCERNING...HEAVY SNOW

VALID 162028Z - 170230Z

SUMMARY...SNOW WILL DEVELOP THROUGH EARLY EVENING WITH RATES OF ONE
INCH/HR DEVELOPING BY...AND ESPECIALLY BEYOND...02Z.

DISCUSSION...A LARGE AREA OF PRECIPITATION CONTINUES TO LIFT NEWD IN
ASSOCIATION WITH ISENTROPIC LIFT AHEAD OF A DE-AMPLIFYING UPPER LOW
OVER THE MID-MS VALLEY. A DIFFUSE SFC LOW...CURRENTLY OVER NERN
MS...WILL MOVE INTO THE SRN APPALACHIANS BY 02Z. RESULTING N/NE
LOW-LEVEL FLOW WILL CONTINUE TO ADVECT VERY DRY AIR INTO THE
DISCUSSION AREA...AND INITIALLY DRY LOWER LEVELS OF THE ATMOSPHERE
WILL COOL/SATURATE WITH TIME ALLOWING FOR SNOW TO BECOME THE
DOMINANT P-TYPE...BECOMING WIDESPREAD DURING THE EVENING HOURS.
LATEST GUIDANCE CONTINUES TO DEPICT A STRENGTHENING BAROCLINIC ZONE
ACROSS THE DISCUSSION AREA THIS EVENING WITHIN CONFLUENT 700 MB
FLOW...WITH DEFORMATION-INDUCED FRONTOGENESIS EXPECTED TO DEVELOP
WITHIN THE 800 MB TO 700 MB LAYER. MESOSCALE BANDING WILL LIKELY
PRODUCE SNOWFALL RATES OF ONE INCH/HR BY...AND ESPECIALLY
BEYOND...02Z.
Member Since: September 26, 2011 Posts: 73 Comments: 12846
Northward ideas are panning out...



Gary Szatkowski ‏@GarySzatkowski 19m

And the 18Z NAM has shifted slightly northward with its precipitation over NJ. Sigh. We've seen this before.


=======================

So the most suppressed model is now putting central NJ into accumulating snows when it had zero before - with that line in central ocean county even for zero.







Member Since: September 26, 2011 Posts: 73 Comments: 12846
Quoting 296. noreasterrrrr:
Maybe I get a cpl inches??


Unfortunately no...the northward progression still leaves you basically seeking that dusting to an inch at this time.
Member Since: September 26, 2011 Posts: 73 Comments: 12846
SREF MEAN Output - Add both 12 hour blocks for a total.





SREF Plumes






Member Since: September 26, 2011 Posts: 73 Comments: 12846
Maybe I get a cpl inches??
Member Since: February 2, 2014 Posts: 0 Comments: 620
Quoting 293. Pcroton:
Here are the new HPC graphics ending 8AM Monday - yes, ending 8AM Monday when the storm will still be ongoing at least for several more hours in NJ/DE

WOW
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Quoting 290. PengSnow:
So do you seen a route 80 moisture shield with heaver precip in SE PA?


Quoting 291. Pcroton:



I think I-80 may be too far north to ask for.



And well, looking at HPC graphics, it looks like the 1" accumulation line is roughly I-80.

Member Since: September 26, 2011 Posts: 73 Comments: 12846
Here are the new HPC graphics ending 8AM Monday - yes, ending 8AM Monday when the storm will still be ongoing at least for several more hours in NJ/DE








50th Percentile Accumulation:




Maximum Worst Case 90%:


Member Since: September 26, 2011 Posts: 73 Comments: 12846
We appear to have a dispute!


Gary Szatkowski ‏@GarySzatkowski 24m
@NWS_MountHolly bump up in snow amounts looks prudent in that context. We'll find out very soon what happens.

Steven DiMartino ‏@nynjpaweather 17m
Anyone that wants to know why the NWS increased totals, ask them. I'm at a lose to find an answer. @garyszatkowski @nws_mountholly


Gary Szatkowski ‏@GarySzatkowski 7m
@nynjpaweather Stop acting shocked, Steve. WPC guidance is perfectly clear. Discussions coming shortly.


=================

With what we've watched this afternoon I'd be inclined to agree with Gary's change in thinking.

Now what do we watch for? What we see in the above posts and watch and see if those suppressing factors at 850/700MB do in fact move north and east placing us south of the boundary and within the moisture transport. We will see the evidence on the radar imagery within the swath outlined where sinking air is clearly present. We would begin to see echoes breaking out more as well as moving into the region from the south as the boundary potentially lifts northward.



Member Since: September 26, 2011 Posts: 73 Comments: 12846
Quoting 290. PengSnow:
So do you seen a route 80 moisture shield with heaver precip in SE PA?


I like the path that Mount Holly paints with the precipitation now. I don't think we can draw a west to east line on this system as once you get to say central PA/MD it's going to arc more NE. Whether or not they need to up 1 contour is the next question that will unfold during the evening.

State College will probably have to adjust it's eastern contours to meet the arcing contour Mt Holly has put in.


I think I-80 may be too far north to ask for.
Member Since: September 26, 2011 Posts: 73 Comments: 12846
So do you seen a route 80 moisture shield with heaver precip in SE PA?
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So what has happened here?


The boundary the low was following in Arkansas this morning had been pointing ESE and thus the low track was forecast to do this. That boundary surged northward and now points ENE - so the low will not be dipping SE and then turning NE - it's just coming NE. That puts the low further north over it's trek to the coastline.

More importantly the high pressure system has been consistently modeled too strong, even on the GFS at times, and analysis shows this (we compared a few times in the past page or two of the blog) and each new model run is seeing this and "correcting".


These two situations have opened the door for moisture transport further north into the region and therefore the heavy snow band forecast south of DC is now over DC - and your moisture cutoff in southern NJ is now into central NJ.

Member Since: September 26, 2011 Posts: 73 Comments: 12846
Quoting 286. evsnds:
Welp, there goes my travel plans. Damn you P why do you bring snow with you everywhere you go!


LMAO sorry.


And there's the DC correction northward that Wash just posted.


Member Since: September 26, 2011 Posts: 73 Comments: 12846
Quoting 283. wxgeek723:
Still concerned about dry air interfering with this system.


It will but it's more about the sinking air at the 700 and 850mb levels that concern me.





See, the radar doesnt cut off at the PA line because of dry air outright - as it is sinking air that dries out instead.

So what is causing that sinking air?








I want to see those border areas push north of us.

As the storm moves north and east we should begin to see those boundaries on the 850/700 levels also push north and east.

Then as they do we get into the moisture flow and can potentially see the region outlined below fill in on radar.



Member Since: September 26, 2011 Posts: 73 Comments: 12846
Welp, there goes my travel plans. Damn you P why do you bring snow with you everywhere you go!
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Member Since: August 14, 2010 Posts: 10 Comments: 17860
Quoting 264. doom22015:
Well crapuweather has dialed us back in the DC area from 3-6 to 2-4, and I can't see why, based on the model runs. Unless the 12z runs have shifted and are way more suppressed.


Watching all the guidance versus analysis I would ignore the overly suppressed solutions. They (well, NAM really) just does not fit what we see.


I will say DC having the heaviest snow band in southern regions is wrong.

I think DC gets the good stuff.



Member Since: September 26, 2011 Posts: 73 Comments: 12846
Still concerned about dry air interfering with this system.
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I went from an HWO of under an inch to a WWA of 2-4".

If trends on imagery hold true to our discussion and thinking expect a minor bump upwards later today.

Member Since: September 26, 2011 Posts: 73 Comments: 12846
And there ya go... so what we see in the imagery today is legitimate.



Member Since: September 26, 2011 Posts: 73 Comments: 12846
<-140317T1600Z/
NEW CASTLE-CECIL-KENT MD-SALEM-GLOUCESTER-CAMDEN-OCEAN-CUMBERLAND-ATLANT IC-COASTAL ATLANTIC-COASTAL OCEAN-SOUTHEASTERN BURLINGTON-INCLUDING THE CITIES OF...WILMINGTON...ELKTON...CHESTERTOWN...
PENNSVILLE...GLASSBORO...CAMDEN...CHERRY HILL...JACKSON...MILLVILLE...HAMMONTON...ATLANTIC CITY...LONG BEACH ISLAND...WHARTON STATE FOREST
244 PM EDT SUN MAR 16 2014

...WINTER STORM WARNING IN EFFECT FROM 8 PM THIS EVENING TO NOON EDT MONDAY...

* ACCUMULATIONS...SNOW ACCUMULATION OF 4 TO 6 INCHES.

A bit of a departure from Gary's thinking just a few hours ago.

Wow that was quick. I guess confidence is high
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Yeah, maybe too early, but by 6pm, i would assume to a have a better thought. Btw, i do see some 12+ totals in parts of WV, VA and MD,,,,,,,,,,,WOW not bad for Mid March for those areas.
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Surprise surprise...Mount Holly has upgraded South Jersey to Winter Storm Warnings

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
244 PM EDT SUN MAR 16 2014

DEZ001-MDZ008-012-NJZ016>018-020>022-025>027-1703 00-
/O.UPG.KPHI.WW.Y.0015.140317T0000Z-140317T1600Z/
/O.EXA.KPHI.WS.W.0008.140317T0000Z-140317T1600Z/
NEW CASTLE-CECIL-KENT MD-SALEM-GLOUCESTER-CAMDEN-OCEAN-CUMBERLAND-ATLANT IC-COASTAL ATLANTIC-COASTAL OCEAN-SOUTHEASTERN BURLINGTON-INCLUDING THE CITIES OF...WILMINGTON...ELKTON...CHESTERTOWN...
PENNSVILLE...GLASSBORO...CAMDEN...CHERRY HILL...JACKSON...MILLVILLE...HAMMONTON...ATLANTIC CITY...LONG BEACH ISLAND...WHARTON STATE FOREST
244 PM EDT SUN MAR 16 2014

...WINTER STORM WARNING IN EFFECT FROM 8 PM THIS EVENING TO NOON EDT MONDAY...

* ACCUMULATIONS...SNOW ACCUMULATION OF 4 TO 6 INCHES.

A bit of a departure from Gary's thinking just a few hours ago.
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Quoting 275. PengSnow:
P,
As of this morning for my area, i thought we would be are the far Northern edge, I now think that edge will push to almost interstate 80 in Western PA, I do see a more extreme northern push into your area. If that is the cases you would expect WW or WSW to happen for of a more north-north east track.


If that were the case, I would expect to get 2-4 or 3-5 in SWPA. I might be way off, but it sure looks like it. For your area it would be 4-7 or so.

But i do see that there will be a very sharp cut off, do you see the same thing or am way to far north in my observations???



I see the same thing at this time as well, Peng.

Of course we have to see it evolve but it looks like a good chance it's heading this way.

When you look at how the NAM has mishandled the high pressure - the feature that will suppress development of the shield northward - and the GFS has nailed this feature --- then how/why would one follow the NAM and not the GFS?

I think it's a little early to confirm that from your area to central NJ can now see 3-5" (or something of that nature above the trace-2" idea) but it sure does look promising.

Member Since: September 26, 2011 Posts: 73 Comments: 12846
Something to watch as we head towards evening is the dry and sinking air north of the PA border that is evident on radar and the culprits are found on the 700MB (first image) and 850MB (second image) wind maps.







For now that area from the southern PA/OH borders north to the faint signatures on radar in the northern ends of the state are not filling in due to that sinking dry air.

However as the storm system moves NE - these moisture transport features at 850 and 700 move north and east. Do they eject the moisture starving windflow over the southern half of OH and PA and allow the radar echoes to begin to fill in?


Member Since: September 26, 2011 Posts: 73 Comments: 12846
P,
As of this morning for my area, i thought we would be are the far Northern edge, I now think that edge will push to almost interstate 80 in Western PA, I do see a more extreme northern push into your area. If that is the cases you would expect WW or WSW to happen for of a more north-north east track.


If that were the case, I would expect to get 2-4 or 3-5 in SWPA. I might be way off, but it sure looks like it. For your area it would be 4-7 or so.

But i do see that there will be a very sharp cut off, do you see the same thing or am way to far north in my observations???
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I went and did the 12Z comparison as well anyway. GFS still wins both in shape/presentation of the high and the strength.





The other thing to remember is we're not too worried about physical low track - we're more battling how the models are depicting the northward extent of the precipitation shield.

The NAM has the high too strong - consistently through it's runs - and has a very sharp QPF cutoff which the other models don't feature as much.

It's an outlier. It was an outlier when it was far north and putting out 20" totals. It became an outlier when it went far south with 20" totals. Still an outlier.

And the important feature, the suppressing high, has been consitently improperly rendered in shape and strength on the NAM.

It just makes me want to discard it in favor of the GFS based on that.



Member Since: September 26, 2011 Posts: 73 Comments: 12846
The boundary the low was going to track ESE along has moved northward. This is why the low is in northern most MS and not heading ESE at this time.


Surface:






Earlier: Note the ESE boundary stretching out from the low. Then look above.



Member Since: September 26, 2011 Posts: 73 Comments: 12846
Quoting 269. evsnds:
Looks like you're in for a nice surprise, P!

Then again, both the GFS and NAM have been flipflopping north and south nearly every model run, I'm not really sure which one to trust. GFS seems like it's a bit too far north unless that high that's going to be over the great lakes is rapidly weakening.

I think where the NAM has it for the 12z run is spot on.


The NAM has consistently had the high pressure too strong.

Check posts 237 and 270 to see the comparison.


Can't really get a bead on the 12Z runs yet - not enough has evolved since their inception to really compare. Will do that later this evening.

Yet the NAM did come further north and I think it's just too bone dry on it's northern end - it's the only model that far south with the northern extent of the precip shield.

Member Since: September 26, 2011 Posts: 73 Comments: 12846
Quoting 269. evsnds:
Looks like you're in for a nice surprise, P!


It is entirely possible.

Radar isn't too exciting toeing the PA/MD border right now but there will be a northern moisture surge later tonight as the low turns NE.

Member Since: September 26, 2011 Posts: 73 Comments: 12846
All the 12Z runs pushed north.

NAM is a lone southern outlier if you focus in on Central NJ.

It's funny not knowing what I am going to get here. Still firmly in the 0-5" range if you include all guidance.

I still notice that feature is in central Wisconsin. I also notice the heavier WV signatures have risen up to northern PA/NYC on the map.









The low doesn't quite appear to be where they wanted it to be with that southern dip.








Sure looks like the GFS has been handling the system best. Yet another NAM-GFS-Analysis comparison:



Member Since: September 26, 2011 Posts: 73 Comments: 12846
Looks like you're in for a nice surprise, P!

Then again, both the GFS and NAM have been flipflopping north and south nearly every model run, I'm not really sure which one to trust. GFS seems like it's a bit too far north unless that high that's going to be over the great lakes is rapidly weakening.

I think where the NAM has it for the 12z run is spot on.
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CMC/EURO 12Z



Member Since: September 26, 2011 Posts: 73 Comments: 12846
12Z GFS/NAM










Member Since: September 26, 2011 Posts: 73 Comments: 12846
Quoting 263. HeavySnow:
Water poochie want some snow? Come visit your MIL and stop by my March Igloo, which will be up by tomorrow afternoon hopefully!


I wanna see some pics, california-snow!
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WU is saying 5-8, which seems much more plausible. And NWS is saying 3-6.
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Well crapuweather has dialed us back in the DC area from 3-6 to 2-4, and I can't see why, based on the model runs. Unless the 12z runs have shifted and are way more suppressed.
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Water poochie want some snow? Come visit your MIL and stop by my March Igloo, which will be up by tomorrow afternoon hopefully!
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About Pcroton

Located in Monmouth County in central NJ. Watching the weather from North Carolina to Maine.