Thursday, January 29, 2009
Nor'easter Anyone???
Could this be our first Nor'easter of the season? I feel it is pretty safe to say that we will see a nor'easter Monday night into Tuesday for this coming week, but there is one big question. Who is getting the snow and how much will they get? This may seem like a classic question, but the models have sent this storm all over the maps. I hope that by Sunday night some of my concerns are addressed by the model runs. Plan for an in depth discussion and possibly the weather blog's first podcast sometime this weekend.
Monday, January 26, 2009
Messy Winter Storm Coming!
Good evening everyone. We have a very interesting weather situation unfolding during the course of the day tomorrow through Wednesday for the State College area (and rest of Northeast). And of course, this winter storm system will not be clear-cut at all (just like every other one this season). Yet again, Central PA will not see JUST snow with this event as a change to sleet/frz rn for some portions of the area seems likely. So, let's take a look at what is currently going on:
Above is the current surface weather map for the US (courtesy of the HPC division of NOAA). We have a nice dome of 1036mb High pressure moving over the plains currently. This will move through the northern part of the country tonight and tomorrow bringing fresh cold air with it. To the south, in 4 corners region, lies the storm that will move NE tomorrow and bring snow with it.
The problem with the forecast (as always) is how much warm air gets brought into the upper levels of the atmosphere. We will have fresh cold air at the surface but the High pressure system will be moving out into the Atlantic during the day on Wednesday. This is not a great set-up for a major snowstorm. However, there is still a lot of potential here and certainly the possibility of a satisfying storm for the State College area.
The models have finally trended together and are close on a solution. They are not in total agreement but they are a whole lot closer than a day or 2 days ago. We'll take a look at the GFS, NAM/WRF, and the CMC (using the 12z runs for continuity...and the fact that the 18z runs are not the greatest).
12z GFS (for KUNV): Moderate snow develops after midnight on Tuesday night as the LOW moves through TN. Thicknesses are 539 dm which is barely cold enough to support snow BUT the 850 mb temps are nicely below freezing at -4.9 degrees C. As the snow intensifies toward daybreak on Wednesday, warm air is making an intrusion in the upper levels and thicknesses go up to 540 dm which is right on the border for snow (850 mb temps are borderline but still below freezing). The LOW is now over Norther VA and exits over Cape May during the afternoon on Wed. We get about .7o inches of QPF from this run which would be just over 7" of snow if it remained all snow. What concerns me is the placement of the 850 mb LOW. It goes over Northwestern PA and you don't want to be on the S side of the 850 mb LOW if you want to get the best snows. This tells me that the GFS says we will go over to sleet for a bit even though thicknesses remain marginal. Verbatim, the GFS gives us 4-8" (probably more on the 4/5" range with sleet mixing in).
12z NAM/WRF (for KUNV): The NAM is a bit slower than the GFS and brings precip in around daybreak (or a bit before) on Wednesday. The overall idea of the NAM is very similar to the GFS except the LOW tracks a bit further North which ends up giving us a little more warm air to deal with. Thicknesses climb to 541 at one point during the storm and the NAM even shows the surface warming to 32.1 degrees F. I find this hard to believe giving the good cold air damming situation and the fresh cold air we will be getting tomorrow. I'm confident that we will never get above freezing at the surface. Basically, the NAM wants to through a mostly sleet storm at us with about 1-3" of snow on the front end. As usual, the NAM is wetter with .90 inches of QPF. I think this is a bit overdone (although we do have a nice SW flow).
12z CMC (for KUNV): The CMC is the furthest north of the 3 models and tracks the LOW through KY, WV, over Allentown PA, and over Boston. As such, we REALLY warm the mid-levels of the atmosphere and go to sleet and most likely freezing rain for a lot of the storm. Storm QPF totals look about the same as the GFS.
My thinking: I'm going to go with a blend of the GFS and NAM and lean a bit more toward the GFS at this point. I think the NAM is too overdone with the QPF (it usually is) and I also think it gets rid of the cold air too quickly (also another bias of the model). The GFS to me has been the most consistent all along for this storm and in addition, the SREF ensemble mean leans toward the GFS as well.
Bottom line: Snow will develop around or a bit after midnight on Tuesday night and continue until about mid afternoon on Wednesday. We will definitely start off as all snow and probably pick up a quick 2-4" inches before any change over occurs. I DO think KUNV will go to sleet for a time and cut down on accumulations. I hope I'm wrong but it's hard for me to buy into all snow with the track of the 850 mb low. Around daybreak I think KUNV changes to a mix of snow and sleet and we pick up about 1-3" of that mess. And as the system moves out maybe and inch or two of snow. So, in the end, my call is for 4-7" of snow/sleet accumulation in State College. Best guess amount is 5".
Have a good night!
PS For those in the NYC area. I think NW of I-287 will see about 3-6". Far NW NJ and the Poconos will see 4-8" (local 10" in the Poconos). And NYC itself will see about 2-4" (mostly at the beginning of the storm).
Above is the current surface weather map for the US (courtesy of the HPC division of NOAA). We have a nice dome of 1036mb High pressure moving over the plains currently. This will move through the northern part of the country tonight and tomorrow bringing fresh cold air with it. To the south, in 4 corners region, lies the storm that will move NE tomorrow and bring snow with it.The problem with the forecast (as always) is how much warm air gets brought into the upper levels of the atmosphere. We will have fresh cold air at the surface but the High pressure system will be moving out into the Atlantic during the day on Wednesday. This is not a great set-up for a major snowstorm. However, there is still a lot of potential here and certainly the possibility of a satisfying storm for the State College area.
The models have finally trended together and are close on a solution. They are not in total agreement but they are a whole lot closer than a day or 2 days ago. We'll take a look at the GFS, NAM/WRF, and the CMC (using the 12z runs for continuity...and the fact that the 18z runs are not the greatest).
12z GFS (for KUNV): Moderate snow develops after midnight on Tuesday night as the LOW moves through TN. Thicknesses are 539 dm which is barely cold enough to support snow BUT the 850 mb temps are nicely below freezing at -4.9 degrees C. As the snow intensifies toward daybreak on Wednesday, warm air is making an intrusion in the upper levels and thicknesses go up to 540 dm which is right on the border for snow (850 mb temps are borderline but still below freezing). The LOW is now over Norther VA and exits over Cape May during the afternoon on Wed. We get about .7o inches of QPF from this run which would be just over 7" of snow if it remained all snow. What concerns me is the placement of the 850 mb LOW. It goes over Northwestern PA and you don't want to be on the S side of the 850 mb LOW if you want to get the best snows. This tells me that the GFS says we will go over to sleet for a bit even though thicknesses remain marginal. Verbatim, the GFS gives us 4-8" (probably more on the 4/5" range with sleet mixing in).
850mb Heights 48 HR Forecast (HPC/NOAA)
12z NAM/WRF (for KUNV): The NAM is a bit slower than the GFS and brings precip in around daybreak (or a bit before) on Wednesday. The overall idea of the NAM is very similar to the GFS except the LOW tracks a bit further North which ends up giving us a little more warm air to deal with. Thicknesses climb to 541 at one point during the storm and the NAM even shows the surface warming to 32.1 degrees F. I find this hard to believe giving the good cold air damming situation and the fresh cold air we will be getting tomorrow. I'm confident that we will never get above freezing at the surface. Basically, the NAM wants to through a mostly sleet storm at us with about 1-3" of snow on the front end. As usual, the NAM is wetter with .90 inches of QPF. I think this is a bit overdone (although we do have a nice SW flow).6 Hr Precip/850mb Temps 54hr Prog NAM (HPC/NOAA)
12z CMC (for KUNV): The CMC is the furthest north of the 3 models and tracks the LOW through KY, WV, over Allentown PA, and over Boston. As such, we REALLY warm the mid-levels of the atmosphere and go to sleet and most likely freezing rain for a lot of the storm. Storm QPF totals look about the same as the GFS.
My thinking: I'm going to go with a blend of the GFS and NAM and lean a bit more toward the GFS at this point. I think the NAM is too overdone with the QPF (it usually is) and I also think it gets rid of the cold air too quickly (also another bias of the model). The GFS to me has been the most consistent all along for this storm and in addition, the SREF ensemble mean leans toward the GFS as well.
Bottom line: Snow will develop around or a bit after midnight on Tuesday night and continue until about mid afternoon on Wednesday. We will definitely start off as all snow and probably pick up a quick 2-4" inches before any change over occurs. I DO think KUNV will go to sleet for a time and cut down on accumulations. I hope I'm wrong but it's hard for me to buy into all snow with the track of the 850 mb low. Around daybreak I think KUNV changes to a mix of snow and sleet and we pick up about 1-3" of that mess. And as the system moves out maybe and inch or two of snow. So, in the end, my call is for 4-7" of snow/sleet accumulation in State College. Best guess amount is 5".
Have a good night!
PS For those in the NYC area. I think NW of I-287 will see about 3-6". Far NW NJ and the Poconos will see 4-8" (local 10" in the Poconos). And NYC itself will see about 2-4" (mostly at the beginning of the storm).
Thursday, January 8, 2009
Winter Storm on the Way!
I hope everyone had a great holiday season and New Year! I know I did! I had the opportunity to travel to Pasadena, CA and the Rose Bowl with the Penn State Blue Band. It was an awesome experience. Now on to the weather.
We have certainly had our share of sleet storms and wintry mix in State College this winter. We seem to have trouble getting a good 4-8" all snow event. Each time we have moisture coming our way, the LO has come to close to the area and we end up with warm air intruding in the upper levels while Cold Air Damming (CAD) in our area remains strong at the surface. Result: SLEET. Well, this drought may be about to end on Friday night and Saturday!
Currently, we have a nice dome of cold air (-10 degrees C at 850mb) moving over our area. We will then see the southern and northern jet streams partially phase and create a nice area of LO pressure over the Southern Ohio Valley on late Friday. The LO will move East through VA on Saturday and off the DE and NJ coast by early Sunday morning. There is fairly good agreement among the models at the current time with the latest (0z) NAM coming into line with the 12z and 18z GFS runs. Below is the 54 hr NAM from the 0z suite:
At this point, it looks like the cold air will hold strong and the track of the LO will be far enough south for KUNV to remain all snow. The 850mb LO is a little to close for comfort but soundings show all snow at this point.
Overall, I am extremely confident about this storm system being a good snow event for a line 50 miles either side of I-80 through PA and NJ. As an early call, I'm going to forecast 3-6" for that area with localized amounts in the 6-8" range. The NAM usually overdoes precip and I don't like it's ~.75 QPF. Yes this system has southern stream moisture with it, but I can't see that much liquid. I like the GFS's QPF output a lot better. .5 inches and a little greater seems much more reasonable.
I hope the 0z run of the GFS doesn't through a curveball into the equation. The only outlier is the Euro which is usually better in longer range situations anyway. So, for now, I like my early forecast and think KUNV will remain all snow (the NWS even had a Winter Storm Watch out early this afternoon). Precip should end at state college before midnight on Saturday night.
Have a good one everyone!
We have certainly had our share of sleet storms and wintry mix in State College this winter. We seem to have trouble getting a good 4-8" all snow event. Each time we have moisture coming our way, the LO has come to close to the area and we end up with warm air intruding in the upper levels while Cold Air Damming (CAD) in our area remains strong at the surface. Result: SLEET. Well, this drought may be about to end on Friday night and Saturday!
Currently, we have a nice dome of cold air (-10 degrees C at 850mb) moving over our area. We will then see the southern and northern jet streams partially phase and create a nice area of LO pressure over the Southern Ohio Valley on late Friday. The LO will move East through VA on Saturday and off the DE and NJ coast by early Sunday morning. There is fairly good agreement among the models at the current time with the latest (0z) NAM coming into line with the 12z and 18z GFS runs. Below is the 54 hr NAM from the 0z suite:
At this point, it looks like the cold air will hold strong and the track of the LO will be far enough south for KUNV to remain all snow. The 850mb LO is a little to close for comfort but soundings show all snow at this point.
Overall, I am extremely confident about this storm system being a good snow event for a line 50 miles either side of I-80 through PA and NJ. As an early call, I'm going to forecast 3-6" for that area with localized amounts in the 6-8" range. The NAM usually overdoes precip and I don't like it's ~.75 QPF. Yes this system has southern stream moisture with it, but I can't see that much liquid. I like the GFS's QPF output a lot better. .5 inches and a little greater seems much more reasonable.
I hope the 0z run of the GFS doesn't through a curveball into the equation. The only outlier is the Euro which is usually better in longer range situations anyway. So, for now, I like my early forecast and think KUNV will remain all snow (the NWS even had a Winter Storm Watch out early this afternoon). Precip should end at state college before midnight on Saturday night.
Have a good one everyone!
Subscribe to:
Posts (Atom)
Posts
