Brick Tamland Posted February 15, 2013 Share Posted February 15, 2013 Hey Guys, my first forecast map and discussion. http://www.examiner.com/article/snow-possible-across-southeast-this-weekend Nice. Hope that 3 to 6 inch range drifts more west. Link to comment Share on other sites More sharing options...
GaWx Posted February 15, 2013 Share Posted February 15, 2013 12Z Doctor clown map has 1-2" of snow RDU eastward. No other snow 1"+ on this clown map. Link to comment Share on other sites More sharing options...
Cold Rain Posted February 15, 2013 Share Posted February 15, 2013 Hey Guys, my first forecast map and discussion. http://www.examiner.com/article/snow-possible-across-southeast-this-weekend Good write-up. I think we're all hoping for a continued increase in amounts, but that's a very reasonable map! Link to comment Share on other sites More sharing options...
NCSNOW Posted February 15, 2013 Share Posted February 15, 2013 The new Euro is wetter than the 00z run, although not as wet as the GFS/GGEM. The 0.25 to 0.5 area is across SE Va, eastern NC (Monroe to FAY to RDU to ORF east and south of there), also over upstate SC, most of the rest of Va/NC/SC in the 0.1 to 0.25 range. Eastern Ga in the 0.05 to 0.1 as well as the rain shadow area of the NC northern foothills. You not sweating the old EE rule. Or is it null since we are inside 24 hours. Link to comment Share on other sites More sharing options...
calculus1 Posted February 15, 2013 Share Posted February 15, 2013 Question concerning the GGEM: Is the highlighted area on this map what is being discussed concerning lee trough enhancement? This little circle of precip seems to blossom in the lee of the mountains on both the GGEM and GFS as the rest of the system pulls off to the east. Edit: Sorry, wrong image posted at first. Link to comment Share on other sites More sharing options...
MotoWeatherman Posted February 15, 2013 Share Posted February 15, 2013 Question concerning the GGEM: Is the highlighted area on this map what is being discussed concerning lee trough enhancement? This little circle of precip seems to blossom in the lee of the mountains on both the GGEM and GFS as the rest of the system pulls off to the east. Edit: Sorry, wrong image posted at first. Yes. Link to comment Share on other sites More sharing options...
superjames1992 Posted February 15, 2013 Share Posted February 15, 2013 In typical NC winter storm fashion, it's topping out at around 60 degrees with full sunshine in the day prior to the storm. It's good to see the Euro continue to look a little better, though it may still be playing catch-up (at least I hope so). Link to comment Share on other sites More sharing options...
calculus1 Posted February 15, 2013 Share Posted February 15, 2013 Yes. Thanks for the quick response. Would you (or anyone else) offer me a little meteorology 101 on why this enhancement occurs? Is it a basic upslope effect, but just from the other direction? Typically, we're (piedmont of NC in lee of Apps) downsloped from systems coming from the NW, but since this one is digging from the south do the mountains to our west actually increase precipitation? That's my thoughts on why it might occur, but I wanted someone with more knowledge to verify this. Thanks. Link to comment Share on other sites More sharing options...
superjames1992 Posted February 15, 2013 Share Posted February 15, 2013 58 degrees; a few clouds. Link to comment Share on other sites More sharing options...
GaffneyPeach Posted February 15, 2013 Share Posted February 15, 2013 Oh, how I absolutely adore a strategically placed Lee-Side Trough. Link to comment Share on other sites More sharing options...
MotoWeatherman Posted February 15, 2013 Share Posted February 15, 2013 Thanks for the quick response. Would you (or anyone else) offer me a little meteorology 101 on why this enhancement occurs? Is it a basic upslope effect, but just from the other direction? Typically, we're (piedmont of NC in lee of Apps) downsloped from systems coming from the NW, but since this one is digging from the south do the mountains to our west actually increase precipitation? That's my thoughts on why it might occur, but I wanted someone with more knowledge to verify this. Thanks. Can be for multiple reasons. This site explains pretty well how it can work. Text below is copied from this link... http://www.theweatherprediction.com/habyhints/129/ WHAT IS A LEE-SIDE TROUGH (LOW)? METEOROLOGIST JEFF HABYA lee-side trough (low) is commonly taught as caused by the stretching of a column of air as it descends on the lee-ward side of highly elevated terrain such as the Rocky Mountains. This stretching causes a spin-up of vorticity and a resulting upper level divergence. Lee-side cyclones can intensify over time as they propagate with the upper level flow and can initiate cyclogenesis. A downslope flow will be most intense if the windflow is perpendicular to the mountain range and the winds have a high velocity. Understanding how this produces a low can be complicated by other processes that occur with a downsloping flow. First, a downsloping flow produces adiabatic warming. Air warms at the dry adiabatic lapse rate as it sinks. This should cause temperatures to warm and heights to RISE (thermal expansion). Second, a downsloping wind is associated with stability (RH decreases, downward vertical velocities). How does a trough develop where air is sinking and stabilizing? Theory 1: Mid-level winds which come in contact with elevated terrain suddenly experiences friction. This causes a directional change in the wind speed (ageostrophic flow). Once the air moves on the lee-ward side of the mountains it no longer experiences the friction. The friction over the mountains creates a shortwave that advects with the upper level flow. This creates a lee-side low. Theory 2: Although the sinking air is warming at the dry adiabatic lapse rate on the lee-side, the air is still colder than the air it is replacing (katabatic wind). This creates a lee-side low since a layer of colder air is related to lower heights. Theory 3: Flow over a mountain produces a spin-up of vorticity due to a stretching of air as the lower levels of the atmosphere fall on the lee-side (most common argument). What is troubling, is that I have often noticed lee-side lows with no vorticity showing on the 500-mb model progs and strong downward UVV's. Theory 4: A combination of 2 or more of the previous theories. The most impressive lee-side lows occur when a pre-existing shortwave moves perpendicular over a mountain range. Link to comment Share on other sites More sharing options...
packfan98 Posted February 15, 2013 Share Posted February 15, 2013 12z GFS individual ensembles....tasty! http://raleighwx.americanwx.com/models/gfsensemble/members/12zsnowf042.html Link to comment Share on other sites More sharing options...
JoshM Posted February 15, 2013 Share Posted February 15, 2013 Oh, how I absolutely adore a strategically placed Lee-Side Trough. And I didn't get it anything for Valentines Day!!! I still adore it too, hoping it will give both of us some enhanced snow Link to comment Share on other sites More sharing options...
eyewall Posted February 15, 2013 Share Posted February 15, 2013 I am not so sure a Lee trough is entirely a good thing when it comes to BL issues. Link to comment Share on other sites More sharing options...
strongwxnc Posted February 15, 2013 Share Posted February 15, 2013 12z GFS individual ensembles....tasty! http://raleighwx.americanwx.com/models/gfsensemble/members/12zsnowf042.html Nice. I counted 9 that place some heavy returns back west around snc/sc. Link to comment Share on other sites More sharing options...
calculus1 Posted February 15, 2013 Share Posted February 15, 2013 Can be for multiple reasons. This site explains pretty well how it can work. Text below is copied from this link... http://www.theweatherprediction.com/habyhints/129/ Thanks for that information. Very helpful. I am not so sure a Lee trough is entirely a good thing when it comes to BL issues. I suppose that's due to the adiabatic warming that Moto referenced in the attached article? Downsloping --> Warming. Link to comment Share on other sites More sharing options...
NC Snow Posted February 15, 2013 Share Posted February 15, 2013 12z GFS individual ensembles....tasty! http://raleighwx.americanwx.com/models/gfsensemble/members/12zsnowf042.html Wow!!! Link to comment Share on other sites More sharing options...
GaffneyPeach Posted February 15, 2013 Share Posted February 15, 2013 I am not so sure a Lee trough is entirely a good thing when it comes to BL issues. I said 'strategically' placed. You are correct, however. There are times when it can cause heartbreak. I'm prepared for either....maybe. Link to comment Share on other sites More sharing options...
superjames1992 Posted February 15, 2013 Share Posted February 15, 2013 12z GFS individual ensembles....tasty! http://raleighwx.americanwx.com/models/gfsensemble/members/12zsnowf042.html I knew they would look good from the mean, but those are absolutely fantastic, even out this way. Outside of a few outliers, they all show a significant event over the vast majority of NC/SC. Link to comment Share on other sites More sharing options...
beanskip Posted February 15, 2013 Share Posted February 15, 2013 Comparing 17z RAP to 12z run (something I did with our last non-event which yielded some important clues) I notice is that the 500 mb trough is trending sharper and is tilting less positively. Also, the trend is for the Texas s/w to be weaker and the Plains s/w to be stronger. Link to comment Share on other sites More sharing options...
DopplerWx Posted February 15, 2013 Share Posted February 15, 2013 individual ensembles look great, looks like ill be headed up to chesterfield/darlington tomorrow morning. should be a good spot. eager to see if the nam comes in wetter, if it does all systems are go. if not...there will be a lot of nervous weenies in here, myself included. Link to comment Share on other sites More sharing options...
FLO Posted February 15, 2013 Share Posted February 15, 2013 Sunny and warm in CAE Link to comment Share on other sites More sharing options...
eyewall Posted February 15, 2013 Share Posted February 15, 2013 Well after eating some crow on locking the thread here is my first call: Link to comment Share on other sites More sharing options...
wake4est Posted February 15, 2013 Share Posted February 15, 2013 60, sunny, 10% chance of meteors Link to comment Share on other sites More sharing options...
burgertime Posted February 15, 2013 Share Posted February 15, 2013 Comparing 17z RAP to 12z run (something I did with our last non-event which yielded some important clues) I notice is that the 500 mb trough is trending sharper and is tilting less positively. Also, the trend is for the Texas s/w to be weaker and the Plains s/w to be stronger. 18z looks like it's coming in slightly sharper as well. Link to comment Share on other sites More sharing options...
packfan98 Posted February 15, 2013 Share Posted February 15, 2013 Comparing 17z RAP to 12z run (something I did with our last non-event which yielded some important clues) I notice is that the 500 mb trough is trending sharper and is tilting less positively. Also, the trend is for the Texas s/w to be weaker and the Plains s/w to be stronger. Yeah Skip. I remember you sniffing out a potential problem with that last storm. From what you are saying, this time it looks like you are indicating that this may go more favorably than modeled. Right? Link to comment Share on other sites More sharing options...
mackerel_sky Posted February 15, 2013 Share Posted February 15, 2013 Where is the SC love at? Well after eating some crow on locking the thread here is my first call: Link to comment Share on other sites More sharing options...
mackerel_sky Posted February 15, 2013 Share Posted February 15, 2013 Is sharper better? More negative tilt sooner? 18z looks like it's coming in slightly sharper as well. Link to comment Share on other sites More sharing options...
Pilotwx Posted February 15, 2013 Share Posted February 15, 2013 The WV is making me think we might have a bigger deal as the day goes on. The energy in the plains looks to be diving in a north to south direction and it is farther west. What this may mean is we might have a bigger storm and it may be delayed for a few hours and slower. I don't have a dog in the fight so it really doesn't effect me, but those to the east of the Triad, Char., Columbia, and eastern Ga. thing just got a lot better for you guys in my opinion. http://www.goes.noaa.gov/GSSLOOPS/ecwv.html Link to comment Share on other sites More sharing options...
eyewall Posted February 15, 2013 Share Posted February 15, 2013 Where is the SC love at? Sorry I only have the time to focus on NC which is why I am using that map. Link to comment Share on other sites More sharing options...
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