IsentropicLift Posted January 31, 2011 Share Posted January 31, 2011 Mt. Holly says very significant event NW of Philly and over much of NJ. Funny how the action dwindles on this board when Philly proper is on the edge. 000 FXUS61 KPHI 312030 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 330 PM EST MON JAN 31 2011 .SYNOPSIS... -- Changed Discussion --HIGH PRESSURE WILL GRADUALLY MOVE AWAY FROM THE AREA TONIGHT. A DEVELOPING LOW PRESSURE SYSTEM WILL APPROACH FROM THE SOUTHWEST DURING TUESDAY. THIS SYSTEM WILL TRACK OVER OUR REGION ON WEDNESDAY, BRINGING A VARIETY OF WINTER WEATHER. THE LOW PASSES OFF TO THE NORTHEAST FROM WEDNESDAY NIGHT INTO THURSDAY. HIGH PRESSURE BUILDS INTO OUR AREA TO CLOSE OUT THE WORK WEEK. OVER THE WEEKEND, A LOW PRESSURE SYSTEM MAY DEVELOP OFF THE SOUTHEAST COAST. -- End Changed Discussion -- && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... -- Changed Discussion --WARNINGS AND ADVISORIES HAVE BEEN ISSUED WITH THIS PACKAGE. WHILE THERE WILL BE TWO DISTINCT HEAVIER BURSTS OF PRECIPITATION, THE FIRST ONE WILL BRING THE NW HALF OF OUR CWA CLOSE TO WARNING CRITERIA. THERE SHOULD BE A PRECIPITATION LULL, BUT THE FORECAST SOUNDINGS HAVE THE LOOK OF FREEZING DRIZZLE OR DRIZZLE BEFORE THE NEXT BURST COMES ALONG. ALONG THE I95 CORRIDOR, THE FIRST BURST OF PRECIPITATION IS FORECAST TO BE LIGHTER AND THE REASON WE SEGMENTED THE EVENT IN TWO. THE ADVISORY FOR THE SOUTHEASTERN PART OF OUR CWA IS FOR THE POSSIBILITY OF FREEZING RAIN. AS FAR AS THE MODELING GOES, THE TWO MIXED PRECIPITATION EVENTS WE HAD IN JANUARY WERE BEST HANDLED IN OUR CWA THERMALLY SPEAKING BY THE GFS. THE ECMWF HAS BEEN TOO WARM AND THE WRF-NMM TOO ERRATIC, IT WAS TOO WARM ON ONE AND TOO COLD ON THE OTHER. THE WRF-NMM IS THE COLDEST OF ALL THE 12Z MODELS, WHILE THE GFS PLACED SECOND. COLD HIGH PRESSURE MAINTAINED FAIRLY QUIET CONDITIONS THROUGHOUT THE FORECAST AREA THROUGH THE DAY. WITH THIS HIGH NOW RETREATING TO THE NORTH AND A MORE SOUTHERLY FLOW ALOFT SETTING UP ACROSS THE REGION, SOME MID LEVEL CLOUDS HAVE BEEN STREAMING NORTHWARD INTO THE CWA LATE TODAY. MODEL RELATIVE HUMIDITIES SHOW A MARKED INCREASE FROM 0Z TO 6Z TONIGHT, AND WE ANTICIPATE OVERCAST SKIES FOR THE ENTIRE AREA BY THE LATE EVENING HOURS. NOTICEABLE WARM AIR ADVECTION ALOFT WILL BE TAKING PLACE FROM LATE TONIGHT INTO TUESDAY. THE GFS SHOWS 850MB TEMPERATURES STEADILY INCREASING FROM AROUND 6Z THROUGH THE DAYTIME HOURS TUESDAY. PRECIPITATION ASSOCIATED WITH THE WARM ADVECTION WILL MOST LIKELY BEGIN TO OVERSPREAD THE FORECAST AREA FROM SOUTH TO NORTH DURING THE LATE EVENING HOURS. A LOOK AT MODEL SOUNDINGS SHOWS THAT THE COLUMN WILL STILL BE COLD ENOUGH FROM THE MID LEVELS DOWN TO THE SURFACE TO SUPPORT SNOW THROUGH THE OVERNIGHT AND INTO EARLY TUESDAY. AS A RESULT, OUR FORECAST INCLUDES EXPECTED SNOW ACCUMULATIONS OF SEVERAL INCHES ACROSS OUR NORTHERN ZONES THROUGH TUESDAY. FROM AROUND THE PHILADELPHIA AREA EASTWARD TO THE JERSEY COAST, LIGHT SNOW ACCUMULATIONS ARE EXPECTED. FOR THE SOUTHERN ZONES, LITTLE SNOW ACCUMULATION IS ANTICIPATED BY EARLY TUESDAY MORNING. -- End Changed Discussion -- && .SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/... -- Changed Discussion --AS SURFACE TEMPERATURES WARM ACROSS DELAWARE AND INTO THE EASTERN SHORE OF MARYLAND, A CHANGE-OVER FROM SNOW TO RAIN IS EXPECTED DURING THE MORNING HOURS OF TUESDAY. A TRANSITION FROM SNOW TO RAIN IS ALSO EXPECTED IN THIS SAME TIMEFRAME ACROSS SOUTHERN NEW JERSEY. FROM EASTERN PA AND CENTRAL NJ ON NORTHWARD, MODEL SOUNDINGS DEPICT SURFACE AND MID LEVEL TEMPERATURES THAT WOULD SUPPORT SOME AREAS OF LIGHT SNOW DURING TUESDAY MORNING. BY TUESDAY AFTERNOON, THE GFS AND NAM SOUNDINGS SHOW TEMPERATURES ALOFT WARMING WITH SURFACE TEMPS STAYING BELOW FREEZING FROM EASTERN PA INTO CENTRAL NJ. THUS, A GRADUAL MIX OR TRANSITION TO LIGHT SLEET IS ANTICIPATED FOR THESE AREAS DURING TUESDAY AFTERNOON. ACROSS THE AREA, SOME BREAKS OR A LULL IN THE PRECIPITATION FOR A FEW HOURS TUESDAY AFTERNOON IS PROBABLE. THE TRANSITION FROM SNOW TO OTHER PRECIP TYPES ACROSS THE CWA DURING TUESDAY MORNING AND AFTERNOON WILL VARY, AND SOME FREEZING RAIN OR SLEET MAY MIX IN AT TIMES DEPENDING ON THE THERMAL FIELD ABOVE A GIVEN AREA. FROM TUESDAY NIGHT INTO WEDNESDAY, ANOTHER FAIRLY SIGNIFICANT ROUND OF PRECIPITATION IS ANTICIPATED FOR THE CWA AS SURFACE LOW PRESSURE WILL BE MAKING ITS WAY INTO THE OHIO VALLEY BY TUESDAY NIGHT. THIS LOW TRACKS OVER THE FORECAST AREA DURING WEDNESDAY, REACHING THE NEW ENGLAND COASTAL WATERS BY WEDNESDAY NIGHT. DURING THIS TIMEFRAME, THE SYSTEM WILL CONTINUE TO PULL IN WARM AIR ALOFT WHILE COLDER AIR REMAINS AT THE SURFACE. FOR MANY AREAS FROM THE PHL NORTHWEST SUBURBS, CENTRAL NJ AND EASTERN PA ON NORTHWARD, A TRANSITION TO MORE SLEET AND THEN ULTIMATELY FREEZING RAIN IS EXPECTED FROM TUESDAY NIGHT INTO WEDNESDAY MORNING. THE WEDNESDAY MORNING COMMUTE WILL BE HAZARDOUS IN THESE AREAS. BY MID-MORNING ON WEDNESDAY, SURFACE TEMPERATURES WARM ENOUGH THAT A GRADUAL TRANSITION OVER TO RAIN IS ANTICIPATED FROM CENTRAL NJ BACK TOWARD THE PHILADELPHIA AREA. MEANWHILE, THE POTENTIAL REMAINS FOR A SIGNIFICANT ICE EVENT ACROSS NORTHERN NEW JERSEY, THE POCONOS, THE LEHIGH VALLEY AND ALSO THE PHILADELPHIA NORTHWEST SUBURBS FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY AFTERNOON. THE MODELS INDICATE A MORE PERSISTENT NORTHEASTERLY SURFACE WIND HOLDING ON THROUGH THE EVENT FOR THESE AREAS, ESPECIALLY THROUGH THE DAYTIME ON WEDNESDAY. THIS COMBINED WITH A GOOD SNOWPACK ACROSS THE REGION MAY CONTRIBUTE TO SURFACE TEMPERATURES NOT GETTING ABOVE FREEZING ON WEDNESDAY FOR OUR NORTHWEST HALF OF OUR CWA. ICE ACCUMULATIONS OF ONE THIRD TO TWO THIRDS OF AN INCH ARE POSSIBLE FOR THIS AREA. WITH THE LOW PRESSURE SYSTEM QUICKLY TRACKING OFF TO THE NORTHEAST AND NEARING THE NEW ENGLAND COASTAL WATERS BY WEDNESDAY NIGHT, MUCH OF THE PRECIPITATION WILL BE ENDING FROM SOUTH TO NORTH ACROSS THE CWA. COLD HIGH PRESSURE WILL GRADUALLY BUILD IN FROM THE WEST DURING THURSDAY. QUIET WEATHER AND A PARTLY SUNNY DAY IS EXPECTED AS MODEL RELATIVE HUMIDITIES DECREASE SLOWLY THROUGH THURSDAY. A NORTHWESTERLY FLOW WILL ALLOW COLD AIR TO FILTER IN ACROSS THE REGION, AND HIGH TEMPERATURES WILL RANGE FROM THE LOWER 20S IN THE POCONOS TO THE MID 30S IN THE DELMARVA. IN GENERAL THROUGH THE PERIOD, THE NAM MOS GUIDANCE OFFERED A COLDER SOLUTION AS COMPARED TO THE GFS MOS. WANTING TO BE ON THE CONSERVATIVE SIDE WITH RESPECT TO THE COLD AIR AT THE SURFACE AND CONSIDERING THE SUBSTANTIAL SNOWPACK ACROSS MUCH OF THE AREA, A BLEND OF THE NAM MOS AND GFS MOS WAS USED FOR TEMPERATURES. -- End Changed Discussion -- Link to comment Share on other sites More sharing options...
dryslotted Posted January 31, 2011 Share Posted January 31, 2011 Mt. Holly says very significant event NW of Philly and over much of NJ. Funny how the action dwindles on this board when Philly proper is on the edge. I think that those of us who have lived our whole lives S and or E of the city have seen this movie before and it is mostly rain. Hard to get excited over that. Part of it too is the uncertainty of the forecast. There will be more activity when we get to nowcasting time and radar obs analysis. Lastly, it could be that people are actually trying to get some work done as the next few days' productivity will be dicey with school delays/closures. EDIT: there may have been some key suspensions handed out recently too that has (thankfully) cut down on some of the noise. just a theory. Link to comment Share on other sites More sharing options...
GD0815 Posted January 31, 2011 Share Posted January 31, 2011 i sort of agree with this, im in center city philly, and for me this will probably be mostly rain, but not too far away this could be a serious storm. and even us in philly proper should at least be watching it, it wont take much for this to be a significant ice event even here. I am surprised how few posts are on this topic. We are 24 hours away from what could be a very significant event. Obviously not everyone is involved, but it seems like if it is not a heavy deep snow no one cares. In my opinion - heavy ice is more impactful than heavy snow. Heavy snow is an inconvience for a day or so. No power for a day or two or three is more than an inconvienince. If the public is taking the same lack luster approach to this storm - they may be in for a very rude awakening. It could be the media is down playing this too much. I know they are critized and rightfully so for hyping non events, but this one could be a memorable event. If it even has shades of 1994 the public should be making plans NOW.. I was involved in 1994 running almost 15% of our annual fire calls in one night. That was memorable. Maybe this will be mostly just plain rain - but that is not likely. Link to comment Share on other sites More sharing options...
Parsley Posted January 31, 2011 Share Posted January 31, 2011 Do you think montgomery county will see heavy icing just wondering trying to prepare for something. I haven't lived in this house for an ice storm last one the 1994 one i was really young but i remember sledding on solid ice I think we're on the fence with this one. I do think temperatures Wednesday do climb above freezing (sometime around or just after the morning rush) but if that slug of heavy precip. moves in overnight Tuesday with temperatures between 28-31 degrees, it could be a real mess. I'd say I'm concerned, but I would be even more concerned just north of Mont. County. I don't think a whole lot happens late tonight into Tuesday either (the best overrunning appears to be to our north), I'd be shocked if we had over 1" of snow and sleet combined. I've under forecasted snow in the past few events, so I may be wrong again, we'll see. Link to comment Share on other sites More sharing options...
Thunder Road Posted January 31, 2011 Share Posted January 31, 2011 19z HRRR suspiciously backed off on overnight precip. Nothing appreciable through 4am it says. The 17z and 18z runs had 0.5-1" of snow by that time already. Link to comment Share on other sites More sharing options...
Parsley Posted January 31, 2011 Share Posted January 31, 2011 19z HRRR suspiciously backed off on overnight precip. Nothing appreciable through 4am it says. The 17z and 18z runs had 0.5-1" of snow by that time already. This has been sort of the trend today, keeping the heaviest overrunning well north and northeast of SE PA. It may be onto something. With that said, spotty light snow, sleet and freezing drizzle wouldn't be much fun for the morning commute. Link to comment Share on other sites More sharing options...
Chief83 Posted January 31, 2011 Share Posted January 31, 2011 Do you think montgomery county will see heavy icing just wondering trying to prepare for something. I haven't lived in this house for an ice storm last one the 1994 one i was really young but i remember sledding on solid ice I don't know what we (Montgomery County) will get. I expect we will be on the border with possible significant difference between the southeastern part of the county as compared to the northern part. I happen to be in the middle of the county and many storms you go east and south into a non event and go north and west into a winter wonderland. I think at this point no one knows for sure till the event happens. Maybe the line of significance will set up further north or possibly even south. The point of my post was that no one seems to be saying much and I wondered if it was because it was ice as compared to snow. Seems a small snow event has this board buzzing. Link to comment Share on other sites More sharing options...
greg ralls Posted January 31, 2011 Share Posted January 31, 2011 Regarding the relative quiet concerning the ice storm - that part of the event is still over 24 hours away, and there is a good deal of uncertainty about how much freezing rain happens where. Also, while most of us root for big snowstorms (aside from tracking them, I love cross-country skiing), there aren't many who root for a crippling ice storm. Link to comment Share on other sites More sharing options...
Thunder Road Posted January 31, 2011 Share Posted January 31, 2011 18z NAM at KPNE has 0.47" with the 2m temp at 32.0°. I'm still waiting to for the 3-hourly to upload on WxCaster, but wow that could be crippling. Link to comment Share on other sites More sharing options...
Parsley Posted January 31, 2011 Share Posted January 31, 2011 Regarding the relative quiet concerning the ice storm - that part of the event is still over 24 hours away, and there is a good deal of uncertainty about how much freezing rain happens where. Also, while most of us root for big snowstorms (aside from tracking them, I love cross-country skiing), there aren't many who root for a crippling ice storm. Also, to a degree the relative quiet is a good sign (in this regional thread) that people aren't over here posting non-stop wishcasting forecasts (like other regions seem to be doing). More like a wait and see approach over here. Plus, we get "excited" for snow and want to "talk" numbers, etc., when it comes to ice, nothing to get excited about. I think we are all somewhat cautious, but aware of what could happen on this board. Link to comment Share on other sites More sharing options...
Boreal Posted January 31, 2011 Share Posted January 31, 2011 I don't know what we (Montgomery County) will get. I expect we will be on the border with possible significant difference between the southeastern part of the county as compared to the northern part. I happen to be in the middle of the county and many storms you go east and south into a non event and go north and west into a winter wonderland. I think at this point no one knows for sure till the event happens. Maybe the line of significance will set up further north or possibly even south. The point of my post was that no one seems to be saying much and I wondered if it was because it was ice as compared to snow. Seems a small snow event has this board buzzing. Its been quiet all day. Its unnerving. Link to comment Share on other sites More sharing options...
gibson16 Posted January 31, 2011 Share Posted January 31, 2011 I don't know what we (Montgomery County) will get. I expect we will be on the border with possible significant difference between the southeastern part of the county as compared to the northern part. I happen to be in the middle of the county and many storms you go east and south into a non event and go north and west into a winter wonderland. I think at this point no one knows for sure till the event happens. Maybe the line of significance will set up further north or possibly even south. The point of my post was that no one seems to be saying much and I wondered if it was because it was ice as compared to snow. Seems a small snow event has this board buzzing. Yea i understand what you mean im just west of you and from what i've read could be a ton of ice or nothing which is not good considering the news may say nothing and thats not good they should throw out there the possibility of a bad ice storm Link to comment Share on other sites More sharing options...
Parsley Posted January 31, 2011 Share Posted January 31, 2011 18Z RGEM.....vaild 6z Tue-18z Tue Main precip. focused north of SE PA. Looks like up to 0.20" up til that point. Also looks like by 18z the first slug of precipitation has already exited leaving spotty precipitation at most, until the heavy slug moves in later Tuesday night. Link to comment Share on other sites More sharing options...
_AR_ Posted January 31, 2011 Share Posted January 31, 2011 Link to comment Share on other sites More sharing options...
bluehens Posted January 31, 2011 Share Posted January 31, 2011 I think its quiet because for PHL and S&E its going to be really a non-event. Maybe a smidge of frozen on the front end but then heavy rain. I suspect many, like me, are looking towards the weekend event now. i sort of agree with this, im in center city philly, and for me this will probably be mostly rain, but not too far away this could be a serious storm. and even us in philly proper should at least be watching it, it wont take much for this to be a significant ice event even here. Link to comment Share on other sites More sharing options...
PAPPG Posted January 31, 2011 Share Posted January 31, 2011 Does anybody have thoughts on daytime highs reached today, and if they were higher than predicted? Barometer was falling from a early morn high and wondering just how much "cold" air is around. ...Meanwhile, waiting for the Short range models tonite.. Link to comment Share on other sites More sharing options...
White_Mtn_Wx Posted January 31, 2011 Share Posted January 31, 2011 The big question for LNS and RDG on the 18z NAM is the forecasted temp drop between h30 and h36. In RDG the temp drops from 30.0 to 26.6 before the next slug of heavy precip comes in. LNS 31.8 to 28.9. Obviously this time frame will be key but IMO I have a hard time seeing temps dropping after the initial WAA moves through because that almost never happens in this kind of setup. Perhaps the NAM is onto something but I'm doubtful. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 31, 2011 Share Posted January 31, 2011 GFS is rolling, will be telling on if the NAM was up to something or full of sh** Link to comment Share on other sites More sharing options...
JCT777 Posted January 31, 2011 Share Posted January 31, 2011 As others have posted, it looks like very little precip will fall in Philly and the surrounding suburbs prior to the main event on Wednesday (which IMO probably starts around 1 or 2 AM). My forecast for 1 - 3" of snow/sleet for tomorrow looks like it should be cut back to 1/3" to at most 1" of snow/sleet through noon tomorrow with some spotty freezing drizzle for Tuesday afternoon and evening. Regarding the main event, surface temps during the heavier precip will dictate the impact for the Philly area. Certainly, any rain falling before 8 AM with temps below 32 degrees is going to cause a problem. After 8 AM, solar radiation IMO will start to mitigate things even with temps in the 30 to 32 range. I'm thinking the Lehigh Valley on north could see a really bad ice storm during the day on Wednesday...and Philly on south will not have a major icing problem. The area in between is a tough call at this time. Link to comment Share on other sites More sharing options...
rygar Posted January 31, 2011 Share Posted January 31, 2011 Interesting enough, Binghamton office has a snow forecast for their southern zones (2+) well out of whack with the Mt Holly NW (8-10+) zones and Upton West zones. (12-14+) Link to comment Share on other sites More sharing options...
Thunder Road Posted January 31, 2011 Share Posted January 31, 2011 Does anyone have raw data or ice liquid equivalent charts for the RGEM? Do they even exist? Temp profiles are crucial, so I'd like another country's opinion. Link to comment Share on other sites More sharing options...
Parsley Posted January 31, 2011 Share Posted January 31, 2011 Does anybody have thoughts on daytime highs reached today, and if they were higher than predicted? Barometer was falling from a early morn high and wondering just how much "cold" air is around. ...Meanwhile, waiting for the Short range models tonite.. 12z NAM MOS had RDG and ABE between 25-26 this afternoon. Allentown got to about that, Reading made it into the upper 20s. I know we cracked 30 here, which was a degree or two above MOS numbers. Link to comment Share on other sites More sharing options...
_AR_ Posted January 31, 2011 Share Posted January 31, 2011 Honestly a few degrees above forecasted highs today will not matter much with the clear skies and radiational cooling that will occur before the WAA moves in. Link to comment Share on other sites More sharing options...
Parsley Posted January 31, 2011 Share Posted January 31, 2011 Honestly a few degrees above forecasted highs today will not matter much with the clear skies and radiational cooling that will occur before the WAA moves in. Dark clouds have rolled in down here. You're right though, overall #'s were close to guidance today. Link to comment Share on other sites More sharing options...
Thunder Road Posted January 31, 2011 Share Posted January 31, 2011 gulp... Link to comment Share on other sites More sharing options...
Parsley Posted January 31, 2011 Share Posted January 31, 2011 As others have posted, it looks like very little precip will fall in Philly and the surrounding suburbs prior to the main event on Wednesday (which IMO probably starts around 1 or 2 AM). My forecast for 1 - 3" of snow/sleet for tomorrow looks like it should be cut back to 1/3" to at most 1" of snow/sleet through noon tomorrow with some spotty freezing drizzle for Tuesday afternoon and evening. Regarding the main event, surface temps during the heavier precip will dictate the impact for the Philly area. Certainly, any rain falling before 8 AM with temps below 32 degrees is going to cause a problem. After 8 AM, solar radiation IMO will start to mitigate things even with temps in the 30 to 32 range. I'm thinking the Lehigh Valley on north could see a really bad ice storm during the day on Wednesday...and Philly on south will not have a major icing problem. The area in between is a tough call at this time. Excellent point on the solar radiation, 31 or 32 during the day with pouring rain and things "shouldn't" be as bad. I think the morning rush Wednesday is still going to be a mess from about the PA Turnpike northward. Link to comment Share on other sites More sharing options...
Parsley Posted January 31, 2011 Share Posted January 31, 2011 gulp... not a pretty picture. Link to comment Share on other sites More sharing options...
LVblizzard Posted January 31, 2011 Share Posted January 31, 2011 GFS looks colder than 12z. Link to comment Share on other sites More sharing options...
JCT777 Posted January 31, 2011 Share Posted January 31, 2011 I think the morning rush Wednesday is still going to be a mess from about the PA Turnpike northward. Agreed. I think I'll be working from home on Wednesday...as long as I have power. Link to comment Share on other sites More sharing options...
Thunder Road Posted January 31, 2011 Share Posted January 31, 2011 18z GFS a bit colder. HP to our north is slightly stronger than 12z, 1032 contour is closed off, I believe 12z was 1031mb (6z was 1034mb). 2m temps are significantly colder on the 18z than the 12z at hr42 (12z Wed.) because of it. Means the difference between 0.25" of ice and >0.50" ice in Bucks & Montgomery Link to comment Share on other sites More sharing options...
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