Harbourton Posted March 4, 2015 Share Posted March 4, 2015 I thought snow totals were still 4-8? Sorry I tried to delete that post since I didn't realize the context. Link to comment Share on other sites More sharing options...
famartin Posted March 4, 2015 Author Share Posted March 4, 2015 18Z RGEM and NAM Link to comment Share on other sites More sharing options...
shemATC Posted March 4, 2015 Share Posted March 4, 2015 Trying to learn. I can't remember if it's been every storm lately, but it seems like the HRRR comes in WAY drier than the forecast models. Using 1 model example, the RGEM at 6z tomorrow has fairly decent precip levels over all of NJ and up to NE PA, yet the HRRR has a dry slot in NE PA and much lighter precip through NJ. Other hours are similar with HRRR way down in many areas for expect precip amounts. That drier prediction has also been off from what has actually fallen recently.Any reason, or is that just a bias the HRRR has? Link to comment Share on other sites More sharing options...
Violentweatherfan Posted March 4, 2015 Share Posted March 4, 2015 I saw a post in the MA forum mentioning not all of the moisture may not make it over the apps, I know this can be the case with thunderstorms in the spring and summer. Now would this apply with this system as well? Link to comment Share on other sites More sharing options...
RU848789 Posted March 4, 2015 Share Posted March 4, 2015 Surely. Same caveat applies: These are based on my interpretation of the QPF and thermal profiles based on 6-hour time intervals...so there's a little guesswork. MMU ~0.50" as snow EWR ~0.51" as snow BLM ~0.67" as snow It will, at least if you want someone to do you a favor Thanks, Ray! Link to comment Share on other sites More sharing options...
RU848789 Posted March 4, 2015 Share Posted March 4, 2015 Well, if it cools aloft all the way through the column, then you will go from rain to snow. Sleet would mean that a layer of warm air remains aloft, as was expected with this system. However, the most recent guidance has mostly done away with a significant cold layer beneath warmth during the changeover, opting more for an isothermal look as the entire column cools. A small warm layer near 800 mb during changeover may be enough to get some sleet into the mix, but it probably won't last too long. Surface temps only influence whether it makes it to the ground as sleet versus rain... if its saturated and in the 40s, it won't. Usually during changeovers from rain to snow, you can get some sleet when temps fall to the upper 30s. Once the column cools enough it goes to snow, and that is not directly related to the surface temp. Confused yet? Also, in this kind of situation, dynamics can play a role. It's always snow way up in the snow growth region and in snow to rain scenarios (i.e., largely isothermal, at least for the last 5000 feet from 850 mb down to the surface), the key is the integrated time at temperature above freezing (and how far above freezing the column is) that determines if the falling snowflakes melt into raindrops before hitting the surface or not. If the last 5000 feet are at 33F, it'll still be snow, whereas if the last 5000 feet are 36F, it'll be rain - it's the in-between temps and distances the snowflakes fall at those temps that are the grey areas. And if the precip rate is really high, then the cold snowflakes can transport cold air with them down the column, cooling the column and allowing for snow when the surface temp is even a few to several degrees above freezing. I wrote a small treatise, lol, on the kinetics and integral approach to showing how one might calculate whether a warm nose aloft and the temps and distances at those temps below the warm nose would lead to either sleet or freezing rain. If I had gone into meteorology instead of chem eng'g I probably would've written a program to figure this all out - best I can do now is offer qualitative input... Link to comment Share on other sites More sharing options...
Harbourton Posted March 4, 2015 Share Posted March 4, 2015 GEFS is near 9 inches for central Jersey. Link to comment Share on other sites More sharing options...
famartin Posted March 4, 2015 Author Share Posted March 4, 2015 Also, in this kind of situation, dynamics can play a role. It's always snow way up in the snow growth region and in snow to rain scenarios (i.e., largely isothermal, at least for the last 5000 feet from 850 mb down to the surface), the key is the integrated time at temperature above freezing (and how far above freezing the column is) that determines if the falling snowflakes melt into raindrops before hitting the surface or not. If the last 5000 feet are at 33F, it'll still be snow, whereas if the last 5000 feet are 36F, it'll be rain - it's the in-between temps and distances the snowflakes fall at those temps that are the grey areas. And if the precip rate is really high, then the cold snowflakes can transport cold air with them down the column, cooling the column and allowing for snow when the surface temp is even a few to several degrees above freezing. I wrote a small treatise, lol, on the kinetics and integral approach to showing how one might calculate whether a warm nose aloft and the temps and distances at those temps below the warm nose would lead to either sleet or freezing rain. If I had gone into meteorology instead of chem eng'g I probably would've written a program to figure this all out - best I can do now is offer qualitative input... Actually, if the last 5000 feet are at 33 and its saturated, it will be rain at the surface. 5000 feet is a long way for a snowflake and you actually have liquid water droplets at much lower temps than freezing. If its above freezing and saturated, its not hard to melt the flakes as it runs into all those little droplets. However, melting takes energy from the atmosphere, so gradually, assuming no advection, the continued melting of snowflakes would slowly cool the column from 5000 feet on down to the surface to 32, at which point it would snow. The whole "transporting cold air down" is actually mainly based on the heat absorbed from melting snowflakes. Link to comment Share on other sites More sharing options...
famartin Posted March 4, 2015 Author Share Posted March 4, 2015 Here's the 18Z GFS Link to comment Share on other sites More sharing options...
B Dawk 20 Posted March 4, 2015 Share Posted March 4, 2015 Question for those who do this for a living:Is this sounding enough above 0 at 850 to not be snow?http://www.twisterdata.com/index.php?sounding.lat=40.221636&sounding.lon=-75.274024&prog=forecast&model=NAM&grid=221&model_yyyy=2015&model_mm=03&model_dd=04&model_init_hh=18&fhour=12¶meter=PCPIN&level=12&unit=HR&maximize=n&mode=singlemap&sounding=n&output=image&view=large&archive=false&sounding=y&sndclick=y Link to comment Share on other sites More sharing options...
famartin Posted March 4, 2015 Author Share Posted March 4, 2015 Question for those who do this for a living: Is this sounding enough above 0 at 850 to not be snow? http://www.twisterdata.com/index.php?sounding.lat=40.221636&sounding.lon=-75.274024&prog=forecast&model=NAM&grid=221&model_yyyy=2015&model_mm=03&model_dd=04&model_init_hh=18&fhour=12¶meter=PCPIN&level=12&unit=HR&maximize=n&mode=singlemap&sounding=n&output=image&view=large&archive=false&sounding=y&sndclick=y You would at least get some mixing with sleet and frz rain. Also it would depend on rates; lighter precip would be more mixed, heavier would be snowier. Link to comment Share on other sites More sharing options...
tcutter Posted March 4, 2015 Share Posted March 4, 2015 Anyone see the HRRR? Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted March 5, 2015 Share Posted March 5, 2015 Anyone see the HRRR?No Link to comment Share on other sites More sharing options...
Blizzard-on-GFS Posted March 5, 2015 Share Posted March 5, 2015 GEFS is near 9 inches for central Jersey. GEFS is out of its range now. That number is likely skewed by a few individual members throwing out over a foot of snow. Having said that, I think 6-9" is a good call for our area. Link to comment Share on other sites More sharing options...
tcutter Posted March 5, 2015 Share Posted March 5, 2015 No http://weather.graphics/hrrr/2015030421/ne/hrrr_2015030421_ref_ne.gif Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted March 5, 2015 Share Posted March 5, 2015 http://weather.graphics/hrrr/2015030421/ne/hrrr_2015030421_ref_ne.gif Takes a while to change to snow per those maps. Though after it does it looks like a solid several hours of moderate snowfall. Link to comment Share on other sites More sharing options...
_AR_ Posted March 5, 2015 Share Posted March 5, 2015 This looks juicy! Link to comment Share on other sites More sharing options...
tcutter Posted March 5, 2015 Share Posted March 5, 2015 Takes a while to change to snow per those maps. Though after it does it looks like a solid several hours of moderate snowfall. That is only until 7am Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted March 5, 2015 Share Posted March 5, 2015 That is only until 7am Very nice Link to comment Share on other sites More sharing options...
Violentweatherfan Posted March 5, 2015 Share Posted March 5, 2015 ers-wxman1 from the MA forum said there is plenty of moisture to work with coming from two sources "enough to build a rain forest". That was some funny sh*t. Link to comment Share on other sites More sharing options...
tcutter Posted March 5, 2015 Share Posted March 5, 2015 Paul Kocin 4p.m. update..... http://www.hpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=qpfhsd Link to comment Share on other sites More sharing options...
_AR_ Posted March 5, 2015 Share Posted March 5, 2015 notbad.jpg Link to comment Share on other sites More sharing options...
wkd Posted March 5, 2015 Share Posted March 5, 2015 22Z RAP snow accum, thru 11am tomorrow. Just throwing in some junk until next model runs. Link to comment Share on other sites More sharing options...
wkd Posted March 5, 2015 Share Posted March 5, 2015 0Z Nam got snowier. Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted March 5, 2015 Share Posted March 5, 2015 RUC is pretty sweet, has some nice banding. Link to comment Share on other sites More sharing options...
wkd Posted March 5, 2015 Share Posted March 5, 2015 RUC is pretty sweet, has some nice banding. Nice to see someone else is alive. I guess it is time not to worry about the models and start nowcsting. Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted March 5, 2015 Share Posted March 5, 2015 Latest HRRR is a crush job for Southeastern PA: Link to comment Share on other sites More sharing options...
tcutter Posted March 5, 2015 Share Posted March 5, 2015 Latest HRRR is a crush job for Southeastern PA: What is the best short range model? Link to comment Share on other sites More sharing options...
wkd Posted March 5, 2015 Share Posted March 5, 2015 while we're at it. Link to comment Share on other sites More sharing options...
Coltsfan1217 Posted March 5, 2015 Share Posted March 5, 2015 I'm thinking 3-7 inches of snow for western montco. thoughts? Link to comment Share on other sites More sharing options...
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