OceanStWx Posted December 9, 2012 Share Posted December 9, 2012 So in theory, Some of these qpf totals could be underdone then? That would be my biggest concern with our current forecast package. It's not like the models that are pushing 2" QPF have no support for it. Link to comment Share on other sites More sharing options...
powderfreak Posted December 9, 2012 Author Share Posted December 9, 2012 The 18z NAM continues with the idea of some backside snows up this way... I know it is the NAM but it is within 48 hours so it may have a clue. H85 temps were 0C across northern VT at H+33...then drops to southern VT at H+36 with some left over moisture and a slight upslope signature as the system moves away. Wonder if we can pull 1-3" off at the end. Link to comment Share on other sites More sharing options...
dryslot Posted December 9, 2012 Share Posted December 9, 2012 Looking at radar over the Mid west the convection is quite impressive so that would make sense here for the increase in qpf Link to comment Share on other sites More sharing options...
dryslot Posted December 9, 2012 Share Posted December 9, 2012 We are radiating temps down here to as well as we are down to 33.4F from 42.6F @ 2:57 pm today Link to comment Share on other sites More sharing options...
dendrite Posted December 9, 2012 Share Posted December 9, 2012 The 18z NAM really has a good burst of snow/sleet into NH/ME... It sneaks in some pockets of 0.35-0.5" QPF with H85s of like -2C to -4C. Not sure what above that looks, but I'm guessing that's a pretty good 3 hour burst of snow/sleet for the northern half of NH, and it continues in the next panel in western Maine. Wonder if some spots start pulling out some solid 1"/hr snows for a bit prior to changeover. It warms up pretty quickly above 850. Meanwhile... upstairs on the dynamic tropopause you can see the anticyclone PV anomaly growing and bulging north on the GFS. Here is the 12z initialization and 24 hour forecast. The strengthening gradient ahead of the cyclonic PV anomaly over the GL is helping strengthen the jet streak and in turn you're able to crank up the QG forcing over the area more broadly. Yeah...pretty strong QG forcing over the region tonight into tomorrow. Link to comment Share on other sites More sharing options...
CT Rain Posted December 9, 2012 Share Posted December 9, 2012 For people interested in what Chris was talking about there are some really good articles out there about why PV thinking can be useful in an operational sense. As he mentioned PV anomalies that develop in the troposphere can modulate the wind flow... in this case the PV anomaly that develops from the convection in the south can actually strengthen the LLJ to the east thanks to the circulation that forms. All of this is also impacted by the QG response from the strengthening storm from the northwest. So there is always a lot to see from a PV perspective Link to comment Share on other sites More sharing options...
CT Rain Posted December 9, 2012 Share Posted December 9, 2012 It warms up pretty quickly above 850. Yeah...pretty strong QG forcing over the region tonight into tomorrow. The new moisture flux maps are pretty cool too. Link to comment Share on other sites More sharing options...
ctsnowstorm628 Posted December 9, 2012 Share Posted December 9, 2012 The 18z NAM continues with the idea of some backside snows up this way... I know it is the NAM but it is within 48 hours so it may have a clue. H85 temps were 0C across northern VT at H+33...then drops to southern VT at H+36 with some left over moisture and a slight upslope signature as the system moves away. Wonder if we can pull 1-3" off at the end. It'll be a snow profile by 6z tomorrow, but most guidance holds the precip back longer than I think it will. We will see. 1-2" seems pretty decent for now. Link to comment Share on other sites More sharing options...
OceanStWx Posted December 9, 2012 Share Posted December 9, 2012 We are radiating temps down here to as well as we are down to 33.4F from 42.6F @ 2:57 pm today This cirrus isn't going to factor in too much at all. Already dipping into the low 20s just north of the border. Link to comment Share on other sites More sharing options...
OceanStWx Posted December 9, 2012 Share Posted December 9, 2012 For people interested in what Chris was talking about there are some really good articles out there about why PV thinking can be useful in an operational sense. As he mentioned PV anomalies that develop in the troposphere can modulate the wind flow... in this case the PV anomaly that develops from the convection in the south can actually strengthen the LLJ to the east thanks to the circulation that forms. All of this is also impacted by the QG response from the strengthening storm from the northwest. So there is always a lot to see from a PV perspective Thank you for the LLJ mention, I don't know why I couldn't get that out while I was fumbling around that description. To highlight that further, here is the NAM 925 wind anomalies valid at 03z (same time as the cross section I posted). Notice the +2 to +3 SD v wind anomaly (southerly flow) east of the Mississippi. There is the response to the internal PV anomaly. Link to comment Share on other sites More sharing options...
dryslot Posted December 9, 2012 Share Posted December 9, 2012 This cirrus isn't going to factor in too much at all. Already dipping into the low 20s just north of the border. Yeah cirrus is not going to prevent the fall in temps, Wet bulb is down to 27.5F here Link to comment Share on other sites More sharing options...
ctsnowstorm628 Posted December 9, 2012 Share Posted December 9, 2012 29/23 here at LSC...winds NW at 3kts. Link to comment Share on other sites More sharing options...
CT Rain Posted December 9, 2012 Share Posted December 9, 2012 Thank you for the LLJ mention, I don't know why I couldn't get that out while I was fumbling around that description. To highlight that further, here is the NAM 925 wind anomalies valid at 03z (same time as the cross section I posted). Notice the +2 to +3 SD v wind anomaly (southerly flow) east of the Mississippi. There is the response to the internal PV anomaly. I wish cross sections like the one you posted from AWIPS or more model output with PV displayed was available online. There's a lot of great stuff now with PV on the DT which is awesome... but it's still a challenge to diagnose PV anomalies in the troposphere. Link to comment Share on other sites More sharing options...
OceanStWx Posted December 9, 2012 Share Posted December 9, 2012 I wish cross sections like the one you posted from AWIPS or more model output with PV displayed was available online. There's a lot of great stuff now with PV on the DT which is awesome... but it's still a challenge to diagnose PV anomalies in the troposphere. Even then, the PV stuff related to the tropopause that we can see in AWIPS is really only good for the American models. The Euro and GEM either don't get shipped to AWIPS or just don't have the variables available. Link to comment Share on other sites More sharing options...
CT Rain Posted December 9, 2012 Share Posted December 9, 2012 Even then, the PV stuff related to the tropopause that we can see in AWIPS is really only good for the American models. The Euro and GEM either don't get shipped to AWIPS or just don't have the variables available. Oh really? That's too bad. There's some good stuff here: http://meteocentre.com/models/explorateur.php?mod=ukmet&run=12&stn=DT&hh=048&map=na&stn2=PNM&runb=12&mod2=ukmet&hh2=048&comp=1&fixhh=1〈=en Link to comment Share on other sites More sharing options...
OceanStWx Posted December 9, 2012 Share Posted December 9, 2012 Oh really? That's too bad. There's some good stuff here: http://meteocentre.c...fixhh=1〈=en I have a couple great procedures I've created that I would love to be able to use with the foreign centers output, but thanks for this link. At least I can get a sense at what our neighbors to the north have. Link to comment Share on other sites More sharing options...
powderfreak Posted December 9, 2012 Author Share Posted December 9, 2012 28/23 at 6pm... solidly below freezing wet bulb. Link to comment Share on other sites More sharing options...
weatherMA Posted December 9, 2012 Share Posted December 9, 2012 34.9/25.8 Link to comment Share on other sites More sharing options...
dryslot Posted December 9, 2012 Share Posted December 9, 2012 Down to 30.0F here, Wet bulb at 25.0F, Won't be a problem with wintery precip here Link to comment Share on other sites More sharing options...
OceanStWx Posted December 10, 2012 Share Posted December 10, 2012 I just kicked out an AFD update, but this image highlights some of my concern for the northern end of the WWA areas in Maine. A couple of highlights, this is our local WRF sfc winds at 15z tomorrow. Notice what is going on over the waters. A circulation has developed off of PWM (winds have even kicked around to N there). If this wave forms along the warm front (not uncommon with this type of event) there is going to be a greater area of subfreezing temps in the interior. Given that scenario and the QPF concerns, could envision a need to expand warnings south (either winter storm or ice storm) to cover possibly KLEW to KWVL. Of course, this is if QPF doesn't overwhelm the low level cold with diabatic heating. Never a dull moment with FZRA. Link to comment Share on other sites More sharing options...
OceanStWx Posted December 10, 2012 Share Posted December 10, 2012 More FZRA fodder. A little Hysplit backwards trajectory from 18z tomorrow using the latest NAM near KRUM. The air at 100 m is originating from northern Maine (cold, high pressure). The air at 1500 m on the other hand is originating over Mississippi. We were also messing around with ensembles of air at 100 m for KAUG at 18z tomorrow (so basically multiples runs to see where air is most often originating from). It was roughly 2/3 to 1/3 members originating in the St. Lawrence Valley (where temps were in the low teens for highs). Link to comment Share on other sites More sharing options...
dendrite Posted December 10, 2012 Share Posted December 10, 2012 heh...cool to see some HYSPLIT trajectories again. I don't think I've played around much with those since air quality. Link to comment Share on other sites More sharing options...
OceanStWx Posted December 10, 2012 Share Posted December 10, 2012 heh...cool to see some HYSPLIT trajectories again. I don't think I've played around much with those since air quality. I have more Here is the KAUG ensemble for 1500 m at 15z. Just about classic for FZRA. Deep South origin, that is force sharply up over the cold dome at the last minute. Link to comment Share on other sites More sharing options...
ctsnowstorm628 Posted December 10, 2012 Share Posted December 10, 2012 I have more Here is the KAUG ensemble for 1500 m at 15z. Just about classic for FZRA. Deep South origin, that is force sharply up over the cold dome at the last minute. I know you're focused on GYX's region, but what are your thoughts for the adjacent NEK of VT? Good stuff btw! Link to comment Share on other sites More sharing options...
OceanStWx Posted December 10, 2012 Share Posted December 10, 2012 I know you're focused on GYX's region, but what are your thoughts for the adjacent NEK of VT? Good stuff btw! Pretty similar to Coos, obviously. I think the warm air will flood the Connecticut Valley mid morning or so tomorrow, but places like Essex County and parts of Caledonia could hang on to the low level cold a little longer. One of those situations where you could see KHIE jump into the mid 30s, while it's 29 in parts of Essex. Link to comment Share on other sites More sharing options...
OceanStWx Posted December 10, 2012 Share Posted December 10, 2012 Just peeked at HPC WWD grids, they've got 0.50" to 0.75" ice for basically KIZG to KLEW tonight/tomorrow, with a 70% chance of 0.25" or greater in that same area. That's using a 12z NAM thermal field and model consensus QPF. Sounds pretty reasonable other than I would shift that area east 25 to 50 miles. Link to comment Share on other sites More sharing options...
ctsnowstorm628 Posted December 10, 2012 Share Posted December 10, 2012 Pretty similar to Coos, obviously. I think the warm air will flood the Connecticut Valley mid morning or so tomorrow, but places like Essex County and parts of Caledonia could hang on to the low level cold a little longer. One of those situations where you could see KHIE jump into the mid 30s, while it's 29 in parts of Essex. Yeah, that's what I have been thinking. Been very busy with my junior core so I haven't had much time to look at stuff this afternoon. Yeah I've been advertising a flip to RA from ZR around 14z here at 1k in Lyndonville during our VTrans forecasting. We were discussing the mesoscale features of this in the Passumpsic vs. CT Valley and how it may take valley locales north of 1V4 a bit longer than 1V4 itself (maybe 15z vs 12z). Thing is, during that timeframe, precip could be coming down pretty good...so it may be the difference between 0.10" and 0.25" of accretion, especially just off the valley floor. Link to comment Share on other sites More sharing options...
OceanStWx Posted December 10, 2012 Share Posted December 10, 2012 Yeah, that's what I have been thinking. Been very busy with my junior core so I haven't had much time to look at stuff this afternoon. Yeah I've been advertising a flip to RA from ZR around 14z here at 1k in Lyndonville during our VTrans forecasting. We were discussing the mesoscale features of this in the Passumpsic vs. CT Valley and how it may take valley locales north of 1V4 a bit longer than 1V4 itself (maybe 15z vs 12z). Thing is, during that timeframe, precip could be coming down pretty good...so it may be the difference between 0.10" and 0.25" of accretion, especially just off the valley floor. That sounds pretty reasonable to me, matches our grids pretty well on the overlap area with BTV. The next data set I want to see is the 21z SREF, to see if it continues the trend of increasing ZR probs. Link to comment Share on other sites More sharing options...
ctsnowstorm628 Posted December 10, 2012 Share Posted December 10, 2012 That sounds pretty reasonable to me, matches our grids pretty well on the overlap area with BTV. The next data set I want to see is the 21z SREF, to see if it continues the trend of increasing ZR probs. Yeah definitely. ZR probs are quite high out your way...could be quite an event in Oxford county. My colleague here has a cottage in Norway, Me. Good spot at the base of the foothills. Link to comment Share on other sites More sharing options...
OceanStWx Posted December 10, 2012 Share Posted December 10, 2012 Yeah definitely. ZR probs are quite high out your way...could be quite an event in Oxford county. My colleague here has a cottage in Norway, Me. Good spot at the base of the foothills. I think those 1000-1500 ft foothills from about Norway to Belgrade Lakes could see some serious ice. A few of those northeast facing slopes will see warning criteria I think. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.