Chicago WX Posted November 23, 2010 Share Posted November 23, 2010 I'm curious to see what our surface temps will actually be when precip gets here. We struggled to get out of the 30's during the day with a lot of sun so it makes you wonder. Low level trajectories will be E/SE and gradually becoming more southerly so it will only be a matter of time, but I could see a period of several hours where it's sort of borderline in the low/mid 30's. Gut feeling is that we will be just cold enough to start out with something wintry...we'll see. Yeah, plus one would think the colder we get overnight will help a little in keeping temps in check a bit for tomorrow afternoon. Link to comment Share on other sites More sharing options...
Powerball Posted November 23, 2010 Author Share Posted November 23, 2010 I'm curious to see what our surface temps will actually be when precip gets here. We struggled to get out of the 30's during the day with a lot of sun so it makes you wonder. Low level trajectories will be E/SE and gradually becoming more southerly so it will only be a matter of time, but I could see a period of several hours where it's sort of borderline in the low/mid 30's. Gut feeling is that we will be just cold enough to start out with something wintry...we'll see. Apples & oranges. Today we had strong cold air advection to overrule whatever daytime mixing took place Tomorrow will be a different story since we'll be under a warm air advection regime (sun or no sun). I'm not really expecting anything wintry to start south of I-80 (or south of I-94 for that matter). Link to comment Share on other sites More sharing options...
Chicago WX Posted November 23, 2010 Share Posted November 23, 2010 Apples & oranges. Today we had strong cold air advection to overrule whatever daytime mixing took place Tomorrow will be a different story since we'll be under a warm air advection regime (sun or no sun). I'm not really expecting anything wintry to start south of I-80 (or south of I-94 for that matter). Eh, the real strong push of WAA will be later tomorrow evening/overnight. Hoosier has a point and past instances to back up his assertion. It'll be short-lived even if it happens...but we'll see. Link to comment Share on other sites More sharing options...
Hoosier Posted November 23, 2010 Share Posted November 23, 2010 Apples & oranges. Today we had strong cold air advection to overrule whatever daytime mixing took place Tomorrow will be a different story since we'll be under a warm air advection regime (sun or no sun). I'm not really expecting anything wintry to start south of I-80 (or south of I-94 for that matter). I'm well aware of the WAA, but it isn't extreme to start out with. Plus we will have the easterly flow (or slightly south of due east) in the low levels which will try to keep things cooler. Link to comment Share on other sites More sharing options...
Stebo Posted November 23, 2010 Share Posted November 23, 2010 I'm well aware of the WAA, but it isn't extreme to start out with. Plus we will have the easterly flow (or slightly south of due east) in the low levels which will try to keep things cooler. Yeah I'm with you on this, even more so up this way that things could initially start out wintry. Link to comment Share on other sites More sharing options...
Hoosier Posted November 24, 2010 Share Posted November 24, 2010 Yeah I'm with you on this, even more so up this way that things could initially start out wintry. 31 here, about on track. Should be able to get down well into the 20's with some good radiational cooling. Gotta be careful to not read too much into temps when there are good radiating setups like this...they can change quickly. I can't help but think that mos is too warm though with temps around 40 here tomorrow. Maybe toward evening, especially late but I have a hard time envisioning it happening before then. Link to comment Share on other sites More sharing options...
Stebo Posted November 24, 2010 Share Posted November 24, 2010 31 here, about on track. Should be able to get down well into the 20's with some good radiational cooling. Gotta be careful to not read too much into temps when there are good radiating setups like this...they can change quickly. I can't help but think that mos is too warm though with temps around 40 here tomorrow. Maybe toward evening, especially late but I have a hard time envisioning it happening before then. Yeah WAA >>> all, we been down that road many times, but I think like you said the trajectories early will be of an Easterly component which isn't the best for WAA. Link to comment Share on other sites More sharing options...
Chicago WX Posted November 24, 2010 Share Posted November 24, 2010 Looks like the 0z NAM has taken a little jog to the east/or is quicker with the last piece. Through 54 hours, it has a stripe of 4"+ total amounts of rainfall to central IN. Take that drought! Link to comment Share on other sites More sharing options...
BowMeHunter Posted November 24, 2010 Share Posted November 24, 2010 12-18" for Buckeye this time on the SV snow map. Link to comment Share on other sites More sharing options...
Hoosier Posted November 24, 2010 Share Posted November 24, 2010 Looks like the 0z NAM has taken a little jog to the east/or is quicker with the last piece. Through 54 hours, it has a stripe of 4"+ total amounts of rainfall to central IN. Take that drought! Riding a fine line but we should make out decently with precip. Link to comment Share on other sites More sharing options...
Chicago WX Posted November 24, 2010 Share Posted November 24, 2010 12-18" for Buckeye this time on the SV snow map. Congrats CMH. Link to comment Share on other sites More sharing options...
Hoosier Posted November 24, 2010 Share Posted November 24, 2010 12-18" for Buckeye this time on the SV snow map. lol...what in the world is that thing using to calculate snow. Link to comment Share on other sites More sharing options...
Chicago WX Posted November 24, 2010 Share Posted November 24, 2010 Riding a fine line but we should make out decently with precip. Still looks good for an inch or so for us. South of us is going to bank real nicely. Link to comment Share on other sites More sharing options...
Hoosier Posted November 24, 2010 Share Posted November 24, 2010 Still looks good for an inch or so for us. South of us is going to bank real nicely. yes What temp does KTIM have right now? Link to comment Share on other sites More sharing options...
Chicago WX Posted November 24, 2010 Share Posted November 24, 2010 yes What temp does KTIM have right now? 29.2º Link to comment Share on other sites More sharing options...
Chicago WX Posted November 24, 2010 Share Posted November 24, 2010 0z GFS has 4"+ rainfall amounts as well...east-central Indiana into central Ohio. And Hoosier, I got 28º right now. Link to comment Share on other sites More sharing options...
cyclone77 Posted November 24, 2010 Share Posted November 24, 2010 Congrats Chicago? Link to comment Share on other sites More sharing options...
BowMeHunter Posted November 24, 2010 Share Posted November 24, 2010 Def looks intriguing for some backside snows to the east/se of here. Gotta say that first week of dec in goofy land looks potentially nice, too. Link to comment Share on other sites More sharing options...
trapperman Posted November 24, 2010 Share Posted November 24, 2010 Are we in the time frame where I could possibly trust the NAM? Suggests convectively enhanced snow for the Twin Cities. If this happens MPX's forecast is going to bust deeper. 4-6"??? I'll take it... GFS says 2"... heck I'd take that... Link to comment Share on other sites More sharing options...
baroclinic_instability Posted November 24, 2010 Share Posted November 24, 2010 Are we in the time frame where I could possibly trust the NAM? Suggests convectively enhanced snow for the Twin Cities. If this happens MPX's forecast is going to bust deeper. 4-6"??? I'll take it... GFS says 2"... heck I'd take that... 4-6" seems unlikely with the wet now and relatively quick mid level dry slot. Seems about 3-4 hours of moderate maybe heavy snow north end cities (starting sleet/wet snow south end) followed by a mix of light snow and perhaps freezing drizzle with the lingering low level moisture after 22-0Z. Believe it or not, I think the NAM is slightly better on timing than GFS...NAM is too slow, GFS too fast and they continue to converge, I think it will be faster than current Nam by a tad but will end up being closer to 0z NAM timing for Twin Cities than GFS timing. Link to comment Share on other sites More sharing options...
trapperman Posted November 24, 2010 Share Posted November 24, 2010 4-6" seems unlikely with the west now and relatively quick mid level dry slot. Seems about 3-4 hours of moderate maybe heavy snow north end cities (starting sleet/wet snow south end) followed by a mix of light snow and perhaps freezing drizzle with the lingering low level moisture after 22-0Z. Believe it or not, I think the NAM is slightly better on timing than GFS...NAM is too slow, GFS too fast and they continue to converge, I think it will be faster than current Nam by a tad but will end up being closer to 0z NAM timing for Twin Cities than GFS timing. :guitar: Forgive my enthusiasm. I went from depression expecting another ice/sleet/rain event to a little bit of elation... perhaps it's just the Leinies... Link to comment Share on other sites More sharing options...
michsnowfreak Posted November 24, 2010 Share Posted November 24, 2010 models are starting to hint it may end as snow here as well. If the cold air gets in fast enough, perhaps a decent burst of snow ahead of crashing temps could give us a surprise. Basically IF something materializes could see this as one of those times when the rain changes to a burst of snow, it slushily accumulates, then temps plummet, freezing the slushy snow into white ice as temps quickly tumble into the low 20s. Link to comment Share on other sites More sharing options...
Ajdos Posted November 24, 2010 Share Posted November 24, 2010 models are starting to hint it may end as snow here as well. If the cold air gets in fast enough, perhaps a decent burst of snow ahead of crashing temps could give us a surprise. Basically IF something materializes could see this as one of those times when the rain changes to a burst of snow, it slushily accumulates, then temps plummet, freezing the slushy snow into white ice as temps quickly tumble into the low 20s. Agree, has potential, the snow could be quiet convective, we just need that dynamical cooling to take effect. Link to comment Share on other sites More sharing options...
trapperman Posted November 24, 2010 Share Posted November 24, 2010 Agree, has potential, the snow could be quiet convective, we just need that dynamical cooling to take effect. Can't remember which thread it was, but several on here have wondered if the models haven't been under-doing the amount of cold air with this system, given the ridiculous arctic airmass out west... Link to comment Share on other sites More sharing options...
baroclinic_instability Posted November 24, 2010 Share Posted November 24, 2010 Agree, has potential, the snow could be quiet convective, we just need that dynamical cooling to take effect. "dynamic cooling" isn't a magical process and more often than not numerical models sufficiently model mid/upper level height falls associated with a trough as it propagates. This term is often coined during intense storms which are underforecasted by numerical models. This is important because, if a particular storm system "deepens" stronger than modeled, heights fall at a greater rate and/or deeper than predicted and therefore, from a thermal perspective, a storm may end up being "cooler" than predicted through some portion of the atmospheric column which can be the difference between what was a forecasted rain event and what ends up being a huge snow event. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted November 24, 2010 Share Posted November 24, 2010 In terms of potential convection, instead of looking to determine whether "dynamic cooling takes effect", what one should be looking at is lapse rates. Lapse rates alone will tell you if the profile is conditionally/totally unstable. If you believe a particular model is underestimating the deepening of a particular storm (height falls), then you can "alter" the lapse rates to what you think would be likely under a certain amount of deepening. This can act to enhance an already unstable profile, or it can act to destabilize what was previously a stable profile. Link to comment Share on other sites More sharing options...
Ajdos Posted November 24, 2010 Share Posted November 24, 2010 Can't remember which thread it was, but several on here have wondered if the models haven't been under-doing the amount of cold air with this system, given the ridiculous arctic airmass out west... I know, I'am amazed at the amount of cold air....It's all about nowcasting. Link to comment Share on other sites More sharing options...
Ajdos Posted November 24, 2010 Share Posted November 24, 2010 In terms of potential convection, instead of looking to determine whether "dynamic cooling takes effect", what one should be looking at is lapse rates. Lapse rates alone will tell you if the profile is conditionally/totally unstable. If you believe a particular model is underestimating the deepening of a particular storm (height falls), then you can "alter" the lapse rates to what you think would be likely under a certain amount of deepening. This can act to enhance an already unstable profile, or it can act to destabilize what was previously a stable profile. Thank you for all the information. Link to comment Share on other sites More sharing options...
Ajdos Posted November 24, 2010 Share Posted November 24, 2010 I'am not sure what year, I know it was November, but we had a similar event happen, when colder air was underestimated by the models and we ended up switching from Heavy rain to Heavy snow- it was very convective, we even had thunder-snow. Lasted for a few hours, but got a quick 1-3" and a deep freeze after. Link to comment Share on other sites More sharing options...
Hoosier Posted November 24, 2010 Share Posted November 24, 2010 The RGEM is certainly hinting at some precip type problems at onset down into central IL. Interestingly, the precip trends toward rain as it gets into Indiana on the model, perhaps partially due to diurnal influences/less favorable time of onset? Link to comment Share on other sites More sharing options...
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