WxMan1 Posted March 5, 2013 Share Posted March 5, 2013 Wow...very cold 850mb temps on the Euro (relative to GFS and NAM). Assuming the warm BL bias still exists, I can explain away the surface temps being ~2C and go for predominantly or entirely snow with the Euro? Yes. Which definitely should give us pause when looking at the EC verbatim with it's surface temps. The sfc low track, 850 temps, and extrapolation of those temps down to the surface should leave us to believe the p-type would be mainly/predominately snow for DCA. Let's not forget that the strong diabatic cooling via precip rates would drag that colder layer down and lead to a more isothermal profile near 0C in the lowest level, *not* going from -3.3ish at 850 to over 2C at the surface. I noted earlier how at 00Z the 50 EC ensemble members had about 5-7" for DCA and immediate areas, yet not one member was over 9". That's incredible consistency among the EC members, to get that high of a mean without a 10+ member. That really stands out to me. Granted, the EC ends the accumulating snows earlier, which given the transfer offshore may end up happening. This time of year a 4-8" forecast for immediate DC is a good one, because the low and high end are as far apart as you're going to get in terms of impact compared to other snow ranges. 6-10" is also a 4 inch snow range, but 6 isn't as different to 10 impact-wise as 4 is to 8. Go with 4-8 and hope for the best. Like we saw in the central plains the other week, convection will certainly make totals more binary, or unevenly distributed from location to nearby location. Someone posted the soundings from the NAM and GFS earlier...you can see some potential instsbility with that dry punch above the -10C isotherm. That's where you want it. Link to comment Share on other sites More sharing options...
stormtracker Posted March 5, 2013 Author Share Posted March 5, 2013 Here's my benchmark...if we are productive tonight into the early AM...that is, if we go to snow before 4 am or so, I'll feel good. If we have a little drizzle and keep immediately over to snow, I'm popping out the champagne. Link to comment Share on other sites More sharing options...
wxmeddler Posted March 5, 2013 Share Posted March 5, 2013 crap model crap snow map alert 182444_622767804407073_1583914680_n.png That's only half the storm Link to comment Share on other sites More sharing options...
WxUSAF Posted March 5, 2013 Share Posted March 5, 2013 Let's not forget that the strong diabatic cooling via precip rates would drag that colder layer down and lead to a more isothermal profile near 0C in the lowest level, *not* going from -3.3ish at 850 to over 2C at the surface. Great post. Euro is showing something like ~6-7C difference between the cold 850mb temps which is not far off the moist adiabatic lapse rate of ~8-9C for a surface temp of around 0C. With heavy precip, the profile should be closer to isothermal as you say. Link to comment Share on other sites More sharing options...
Bob Chill Posted March 5, 2013 Share Posted March 5, 2013 Here's my benchmark...if we are productive tonight into the early AM...that is, if we go to snow before 4 am or so, I'll feel good. If we have a little drizzle and keep immediately over to snow, I'm popping out the champagne. For people aob 500' in elevation near the cities one of the keys will be how much can fall and how long can it hang on before trouble comes. Once mixing starts you know the column overhead is in obvious trouble and it will take time to get things right again. One of the nerveracking parts of nowcasting. Things can go either way for us. I don't think anyone can say with any confidence that they are sure what's going to happen. The later mixing can hold off the better (obviously). I hope the transition and probably lull going from heavier waa to heavier ccb is quick and clean and not drawn out and dirty. Link to comment Share on other sites More sharing options...
griteater Posted March 5, 2013 Share Posted March 5, 2013 Yes. Which definitely should give us pause when looking at the EC verbatim with it's surface temps. The sfc low track, 850 temps, and extrapolation of those temps down to the surface should leave us to believe the p-type would be mainly/predominately snow for DCA. Let's not forget that the strong diabatic cooling via precip rates would drag that colder layer down and lead to a more isothermal profile near 0C in the lowest level, *not* going from -3.3ish at 850 to over 2C at the surface. I noted earlier how at 00Z the 50 EC ensemble members had about 5-7" for DCA and immediate areas, yet not one member was over 9". That's incredible consistency among the EC members, to get that high of a mean without a 10+ member. That really stands out to me. Granted, the EC ends the accumulating snows earlier, which given the transfer offshore may end up happening. This time of year a 4-8" forecast for immediate DC is a good one, because the low and high end are as far apart as you're going to get in terms of impact compared to other snow ranges. 6-10" is also a 4 inch snow range, but 6 isn't as different to 10 impact-wise as 4 is to 8. Go with 4-8 and hope for the best. Like we saw in the central plains the other week, convection will certainly make totals more binary, or unevenly distributed from location to nearby location. Someone posted the soundings from the NAM and GFS earlier...you can see some potential instsbility with that dry punch above the -10C isotherm. That's where you want it. Great post and reasoning. Agree with the 4-8 call for immediate DC. Question: regarding the dry punch above -10c...what exactly do you want to see there? Is it a case where you want to see just a touch of drying there for increased instability, but you still want to keep the -10 to -20 layer saturated with respect to ice? Link to comment Share on other sites More sharing options...
Deck Pic Posted March 5, 2013 Share Posted March 5, 2013 18z RAP is encouraging...gets the heavy stuff in here quickly after it starts...thermals on the RAP are unreliable but suggests the diciest time would be around 3-4am..so if we can through that maybe we are ok Link to comment Share on other sites More sharing options...
thesnowsknows Posted March 5, 2013 Share Posted March 5, 2013 I liked the CWG post on analogs the other day. What worries me about it is that history says this will be a big storm but DC will get the short end of the stick. Obv I'm thinking Commutaggedon in particular. But selfishly I'm curious about whether that analog should be extrapolated to just the immediate city, or anything inside the beltway. This is my first time living in DC (Chevy Chase to be exact, grew up in Ellicott City), and I'm used to that EC elevation just west of Baltimore where we KILLED in pretty much every storm as relative to DC or even Bmore. Link to comment Share on other sites More sharing options...
ravensrule Posted March 5, 2013 Share Posted March 5, 2013 Sref's look drier, still about 1.5 in DC and looks like 1.25 BWI. Link to comment Share on other sites More sharing options...
ravensrule Posted March 5, 2013 Share Posted March 5, 2013 Link to comment Share on other sites More sharing options...
clueless Posted March 5, 2013 Share Posted March 5, 2013 So after 3 to 4 am time slot does DCA go to rain? Or expecting all snow from that point? Also do you think this will wrap up quicker as per Euro? Link to comment Share on other sites More sharing options...
thesnowsknows Posted March 5, 2013 Share Posted March 5, 2013 Haven't seen the Euro maps obv but everything else very consistent with precip gradients, hold the totals. Banding very consistently in NOVA. Hopefully that can jump east just a tad but history says that that's just not gonna happen. Link to comment Share on other sites More sharing options...
MN Transplant Posted March 5, 2013 Share Posted March 5, 2013 18z RAP is encouraging...gets the heavy stuff in here quickly after it starts...thermals on the RAP are unreliable but suggests the diciest time would be around 3-4am..so if we can through that maybe we are ok I like that the first wave through cools us down, and then we are set by midnight. Would love to see it play out like that. Link to comment Share on other sites More sharing options...
Deck Pic Posted March 5, 2013 Share Posted March 5, 2013 Sref's look drier, still about 1.5 in DC and looks like 1.25 BWI. it's cold and a bomb..precip ends at like 5am..lol Link to comment Share on other sites More sharing options...
Deck Pic Posted March 5, 2013 Share Posted March 5, 2013 Link to comment Share on other sites More sharing options...
ravensrule Posted March 5, 2013 Share Posted March 5, 2013 it's cold and a bomb..precip ends at like 5am..lol As in 5 A.M tomorrow morning?. Link to comment Share on other sites More sharing options...
Bob Chill Posted March 5, 2013 Share Posted March 5, 2013 So after 3 to 4 am time slot does DCA go to rain? Or expecting all snow from that point? Also do you think this will wrap up quicker as per Euro? rap is showing saturated with marginal snow sounding at midnight in dc. Couple hours in the wee morning look to be rain mix. By 6am or so everything looks good. Last available sounding @ 7am looks really good. It's pretty wet on the model too. shows dc w/ .6 by 7am. Winwxluver already needs a snorkle. precip looks way overdone imo. Nasty band sets up over md to pa border. not sure I buy that either. Link to comment Share on other sites More sharing options...
Ian Posted March 5, 2013 Share Posted March 5, 2013 lwx pulling back Link to comment Share on other sites More sharing options...
Fozz Posted March 5, 2013 Share Posted March 5, 2013 rap is showing saturated with marginal snow sounding at midnight in dc. Couple hours in the wee morning look to be rain mix. By 6am or so everything looks good. Last available sounding @ 7am looks really good. It's pretty wet on the model too. shows dc w/ .6 by 7am. Winwxluver already needs a snorkle. precip looks way overdone imo. Nasty band sets up over md to pa border. not sure I buy that either. Geography/climo does favor good bands setting up in that area, it tends to happen in northern MD (especially psuhoffman land) Link to comment Share on other sites More sharing options...
Fozz Posted March 5, 2013 Share Posted March 5, 2013 lwx pulling back StormTotalSnowRange.png Much more realistic IMO. Looks like the Euro. Link to comment Share on other sites More sharing options...
mitchnick Posted March 5, 2013 Share Posted March 5, 2013 yeah, SREFs are much colder than any other run actually gets the -4C 850 line down to BWI tonight with the heavy precip Link to comment Share on other sites More sharing options...
ravensrule Posted March 5, 2013 Share Posted March 5, 2013 lwx pulling back StormTotalSnowRange.png This is auto generated though, is it not?. Link to comment Share on other sites More sharing options...
MN Transplant Posted March 5, 2013 Share Posted March 5, 2013 it's cold and a bomb..precip ends at like 5am..lol NAMs colder than the RAP. Barely any rain even with the initial band. Link to comment Share on other sites More sharing options...
Ian Posted March 5, 2013 Share Posted March 5, 2013 This is auto generated though, is it not?. i think it's based off the zones Link to comment Share on other sites More sharing options...
Bob Chill Posted March 5, 2013 Share Posted March 5, 2013 Geography/climo does favor good bands setting up in that area, it tends to happen in northern MD (especially psuhoffman land) agreed. I just thought it was a little early in the day to see that look on sim. Also shows dc like .7+ by 7am too. Thats seems awful high. I shouldn't even be looking at 18hr rap stuff anyways. Link to comment Share on other sites More sharing options...
stormtracker Posted March 5, 2013 Author Share Posted March 5, 2013 This is auto generated though, is it not?. From what I understand it is. Link to comment Share on other sites More sharing options...
Ian Posted March 5, 2013 Share Posted March 5, 2013 warning time!!@ Link to comment Share on other sites More sharing options...
stormtracker Posted March 5, 2013 Author Share Posted March 5, 2013 Weather CHannel running a scroll that the watch is now a warning? Link to comment Share on other sites More sharing options...
onel0126 Posted March 5, 2013 Share Posted March 5, 2013 WWA for SoMD up. Link to comment Share on other sites More sharing options...
Ian Posted March 5, 2013 Share Posted March 5, 2013 DCZ001-MDZ005>007-009>011-VAZ052>056-060400- /O.UPG.KLWX.WS.A.0004.130305T2300Z-130307T0500Z/ /O.EXB.KLWX.WS.W.0005.130306T0500Z-130307T0800Z/ DISTRICT OF COLUMBIA-CARROLL-NORTHERN BALTIMORE-HARFORD- MONTGOMERY-HOWARD-SOUTHERN BALTIMORE- PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX- ARLINGTON/FALLS CHURCH/ALEXANDRIA-STAFFORD-SPOTSYLVANIA- INCLUDING THE CITIES OF...WASHINGTON...WESTMINSTER... GAITHERSBURG...COLUMBIA...BALTIMORE...MANASSAS...MANASSAS PARK... FAIRFAX...ALEXANDRIA...FALLS CHURCH...FREDERICKSBURG 248 PM EST TUE MAR 5 2013 ...WINTER STORM WARNING IN EFFECT FROM MIDNIGHT TONIGHT TO 3 AM EST THURSDAY... THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS ISSUED A WINTER STORM WARNING FOR SNOW...WHICH IS IN EFFECT FROM MIDNIGHT TONIGHT TO 3 AM EST THURSDAY. THE WINTER STORM WATCH IS NO LONGER IN EFFECT. * PRECIPITATION TYPE...SNOW. * ACCUMULATIONS...4 TO 8 INCHES WITH THE HIGHER AMOUNTS WEST OF INTERSTATE 95. * TIMING...RAIN MIXING WITH AND CHANGING TO WET SNOW FROM SOUTHWEST TO NORTHEAST TONIGHT AND WEDNESDAY MORNING. SNOW MAY BE MODERATE TO HEAVY AT TIMES WEDNESDAY. SNOW TAPERS OFF WEDNESDAY NIGHT. * TEMPERATURES...IN THE MID 30S. Link to comment Share on other sites More sharing options...
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