RaleighWx Posted February 15, 2015 Share Posted February 15, 2015 Looks like NWS in RAH is going to pull trigger on warnings BASED ON THE CURRENT TRACK AND EXPECTED AMOUNTS/HAZARD...WILL GOWITH A WINTER STORM WARNING FOR MOST OR THE PIEDMONT COUNTIES...ANDA WATCH FOR THE REMAINDER OF THE REGION. Link to comment Share on other sites More sharing options...
wxduncan Posted February 15, 2015 Share Posted February 15, 2015 Just Released: Link to comment Share on other sites More sharing options...
SnowDeac Posted February 15, 2015 Share Posted February 15, 2015 GSP must be banking on lower QPF. Most of the I-85 area is below .4, per their most recent maps, and the WSW has the precip ending Monday night. Are any models showing this? Link to comment Share on other sites More sharing options...
griteater Posted February 15, 2015 Share Posted February 15, 2015 Also, I have to throw out the obligatory, take the NAM QPF output with a big grain, unless you love disappointment. Agree CR. I really like the Euro suite with QPF. It is usually more conservative, which is usually a better play. I don't buy the notion of favoring the short term models over it at any time range Link to comment Share on other sites More sharing options...
GaWx Posted February 15, 2015 Share Posted February 15, 2015 I'm fairly confident that areas north of 85/ne of gainesville will get hit pretty good. Especially, the prime elevation of 1500 as is typical. Here though it's razor thin close. gfs says I should as it gets me below freezing before warming back up. If the surface low comes as far north as the nam/gfs it will probably change to rain here after just a few hours as that far north of a low track will cause warming even at 950mb which is the death nail for freezing surface temps. Overall i'm not expecting much unless the models back off on such a far north track which seems unlikely at this point the 18z nam is clearly rain here but it's precip fields seems pretty wacky and seems too slow. Places like atlanta, over toward athens and south seem out of luck for sure at this point though. I really am surprised at how every model is taking the low on a track that far north. Your research you posted on it was great and i sure don't recall ever seeing a surface low take that sort of track either after a wedge as been established. When I look at wind speeds in the boundary layer, they are late turning east/northeast and aren't that strong (10 knots or less through 950mb) so maybe there isn't the usual amount of resistance and that is why the low can move that far north vs what we would expect to happen..which is it being pushed further south around the wedge or it takes the northern alabama/ne tn route. Even if it's unusual and goes against what we would expect to happen it's hard to ignore every single model showing it take this track though so maybe we see something new. That is the thing with cad/wedges..none of them are exactly alike and are always challenging in their own way. It's what makes them so fun Lookout, Thanks. 1) The 18Z NAM actually ticked south a hair (as much as ~25 miles in E GA) fwiw. That in itself is obviously pretty trivial. However, if it were to start ticking further south each six hourly run, I suppose it could add up. I mean 100 miles could make a big difference. 2) Did you see Allan's high resolution 12Z WRF hour 38 (for 9 PM tomorrow) showing widespread ZR from Athens back all of the way to Cartersville? What an outlier! What do you make of it? Is it possible that it is better handing the wedge? I'm surprised not more is being said about it. https://www.americanwx.com/bb/uploads/monthly_02_2015/post-25-0-24750900-1424028442.gif Link to comment Share on other sites More sharing options...
Disc Posted February 15, 2015 Share Posted February 15, 2015 They haven't done their afternoon update yet. It's coming. And just like that, they issued it. Calling for 8-10" http://forecast.weather.gov/showsigwx.php?warnzone=VAZ022&warncounty=VAC770&firewxzone=VAZ022&local_place1=Roanoke%20VA&product1=Winter+Storm+Warning&lat=37.2784&lon=-79.9584#.VOEGgfnF86o Link to comment Share on other sites More sharing options...
calm_days Posted February 15, 2015 Share Posted February 15, 2015 Just want to point out, we are less than 24 hours from onset and, for the U.S. 74 corridor from F. City to CLT, the NAM insists on a crippling ice storm with barely a puff of snow/sleet at the start while the GFS is equally insistent on a 4-6 inch snow changing to sleet and perhaps ZR at the end. #crazy Yes, it is really interesting. regardless of the model guidance, the system track hasn't happened yet; there are a lot of uncommon features interacting. The focus is on the features that models attempt to handle such as layer temps, looking at the actual system there is a lot more going on. I am remembering the early Feb. 2012 system (just a small amount of sleet but lots of snow forecast) and it was very small compared to this one and had a relatively direct path, coming onshore in California and moving to the east, with arctic air moving southeast providing some of the momentum shifts. This one is much stranger! Link to comment Share on other sites More sharing options...
Cold Rain Posted February 15, 2015 Share Posted February 15, 2015 Agree CR. I really like the Euro suite with QPF. It is usually more conservative, which is usually a better play. I don't buy the notion of favoring the short term models over it at any time range It's probably smart to go on the low end of QPF guidance and give a nod to the anomalous air mass in place for temps. That still yields a good winter storm for most. Link to comment Share on other sites More sharing options...
NC_WX10 Posted February 15, 2015 Share Posted February 15, 2015 How is the NWS going with 4-8 inches of nothing but snow for my area? Are they just not believing the low is going North? Link to comment Share on other sites More sharing options...
WxJordan Posted February 15, 2015 Share Posted February 15, 2015 GSP must be banking on lower QPF. Most of the I-85 area is below .4, per their most recent maps, and the WSW has the precip ending Monday night. Are any models showing this? I felt GSP was very conservative with their forecast, and even their discussion mentions precipitation ending Monday evening in the west. I feel like this is too early. Even the most recent NAM has precipitation lasting through early Tuesday morning in western NC, so I feel like the precipitation will not end as quickly. I feel like most areas will receive over .5 of an inch of precipitation from this event. We shall see. Link to comment Share on other sites More sharing options...
Jonathan Posted February 15, 2015 Share Posted February 15, 2015 How is the NWS going with 4-8 inches of nothing but snow for my area? Are they just not believing the low is going North? They do say "with some sleet in North Carolina" Link to comment Share on other sites More sharing options...
NC_WX10 Posted February 15, 2015 Share Posted February 15, 2015 They do say "with some sleet in North Carolina" Yeah I just read it for detail.. Still don't know how we get 4-8. Link to comment Share on other sites More sharing options...
RaleighWx Posted February 15, 2015 Share Posted February 15, 2015 Interesting to see the difference in total qpf from the 4km NAm and the 12km NAM. Higher resolutions perhaps picking up on relative min with the energy transfer? Link to comment Share on other sites More sharing options...
rduwx Posted February 15, 2015 Share Posted February 15, 2015 I've been a little surprised w/ the transfer spot of around Delmarva on some of the models. Once the miller B solution looked like the way to go, I was thinking it'd be somewhere around Myrtle. Link to comment Share on other sites More sharing options...
HKY_WX Posted February 15, 2015 Share Posted February 15, 2015 Just from trial/error you kinda get a feel for how to use the models as they currently are. The NAM can usually do well w/ warm noses but tends to overdo qpf routinely. The GFS/EURO are prob better to use from a QPF standpoint. So for instance I guess a blend of GFS/EURO qpf would give about .7 for RDU and NAM precip type would be probably 60% zr and 40% IP as of now. So we're talking maybe an inch of snow/sleet followed by .3 to .4 glaze. Nothing crippling, but a very solid icestorm. It would take NAM type numbers to get up into the crippling icestorm criteria. Link to comment Share on other sites More sharing options...
Cold Rain Posted February 15, 2015 Share Posted February 15, 2015 Interesting to see the difference in total qpf from the 4km NAm and the 12km NAM. Higher resolutions perhaps picking up on relative min with the energy transfer? Exactly why you don't get tricked into going with high QPF with these types of systems. There's almost always a min around our area. Link to comment Share on other sites More sharing options...
superjames1992 Posted February 15, 2015 Share Posted February 15, 2015 Looks like the 18z RGEM is a little weaker with the surface low and probably a little colder, comparing it to the 06z run. I am only looking at the B&W maps at 12-hr increments, so it is impossible to say how it compares to the 12z run so far. The surface low is also 25-50 miles SE. Link to comment Share on other sites More sharing options...
burrel2 Posted February 15, 2015 Share Posted February 15, 2015 Looks like the 18z RGEM ticked south and weaker with the low pressure... at least compared to the 06z run. Edit: I see Superjames beat me to it.. lol Link to comment Share on other sites More sharing options...
FallsLake Posted February 15, 2015 Share Posted February 15, 2015 Here's the RAH afternoon discussion. We should see the Warning show soon. .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... -- Changed Discussion -- AS OF 333 PM SUNDAY... WINTER STORM POTENTIAL INCREASING FOR LATE MONDAY THROUGH EARLY TUESDAY... MONDAY...ARCTIC HIGH PRESSURE WILL EXTEND ACROSS THE REGION IN THE MORNING. MEANWHILE A /S W INT EH CENTRAL-SOUTHERN PLAINS WILL GENERATE A SURFACE LOW PRESSURE SYSTEM OVER THE LOWER MS VALLEY MONDAY MORNING. WLY FLOW ALOFT WILL ADVECT MID-HIGH LEVEL CLOUDS INTO OUR REGION MONDAY MORNING...THICKENING/LOWER BY EARLY AFTERNOON. THIS CLOUD TREND WILL HAMPER TEMP RECOVERY DURING THE DAY ESPECIALLY ACROSS THE PIEDMONT. AFTER MORNING LOWS IN THE 10-15 DEGREE RANGE ACROSS MOST OF THE AREA...AFTERNOON TEMPS WILL ONLY RECOVER INTO THE UPPER 20S/LOWER 30S ACROSS TEH NORTH AND LOW-MID 30S ACROSS THE SOUTH. AS THE LOW PRESSURE SYSTEM GETS CLOSER MONDAY AFTERNOON...LOW LEVEL FLOW ABOVE THE SURFACE WILL BACK TO A MORE SLY DIRECTION...ADVECTING MOISTURE OFF THE ATLANTIC AND GULF. SINCE COLD AIR CANNOT HOLD AS MUCH MOISTURE AS WARM AIR...AIR MASS WILL QUICKLY SATURATE WITH AREAS OF LIGHT PRECIPITATION BREAKING OUTR ACROSS THE WEST SHORTLY AFTER MID DAY AND MORE SO BY MID-LATE AFTERNOON. DUE TOT HE COLD DRY AIR MASS IN PLACE (SFC DEWPOINTS MONDAY AFTERNOON ONLY IN THE SINGLE DIGITS)...PRECIP SHOULD FALL IN THE FORM OF LIGHT SNOW. DUE TO TE COLD INITIAL CONDITIONS...SNOW SHOULD STICK TO ROAD SURFACES. MONDAY NIGHT...BULK OF PRECIPITATION WILL FALL DURING THIS TIME FRAME WITH MOST OF THE HEAVIER/MOST WIDESPREAD PRECIPITATION FALLING BETWEEN 9 PM AND 5 AM. LOW LEVEL SLY WILL CONTINUE TO STRENGTH AS THE SFC LOW APPROACHES...INCREASING ISENTROPIC UPGLIDE/LIFT IN THIS PART OF THE ATMOSPHERE. ALOFT...CENTRAL NC WILL BE IN THE RIGHT ENTRANCE REGION OF A 150+ JET CROSSING/EXITING OFF THE NORTHERN MID ATLANTIC. THIS ADDED LIFT IN TANDEM WITH THE WAA AT 850MB IN THE LOWER LEVELS SUGGEST THE HIGH POTENTIAL FOR PRECIPITATION MONDAY NIGHT. DUE TO THERMAL PROFILES...EXPECT SWATHS OF WINTRY PRECIP ACROSS CENTRAL NC...BASICALLY VARYING NORTH TO SOUTH. ACROSS THE NORTHERN PIEDMONT INTO FAR NORTHERN COASTAL PLAIN (INCLUDING THE TRIAD REGION...ROXBORO...HENDERSON...ROANOKE RAPIDS...BULK OF PRECIP WILL FALL AS SNOW OR SNOW MIXED WITH SLEET. OVER THE FAR SOUTH INCLUDING WADESBORO...LAURINBURG...FAYETTEVILLE...CLINTON...PRECIP WILL START OUT AS SNOW/SLEET MIXED THEN QUICKLY TRANSITION TO SLEET AND FREEZING RAIN...EVENTUALLY GOING TO ALL FREEZING RAIN OR RAIN. IN BETWEEN...OR ESSENTIALLY NEAR OR SOUTH OF HIGHWAY 64 INCLUDING ALBEMARLE...SANFORD...RALEIGH...ROCKY MOUNT/WILSON ....PRECIP WILL START OUT AS SNOW OR SNOW/SLEET MIXED THEN TRANSITION TO MOSTLY SLEET/FREEZING RAIN MIXED...AND POSSIBLY TO MAINLY FREEZING RAIN. AMOUNTS...EXPECT 2-4 INCHES OF SNOW MIXED WITH SLEET ACROSS BASICALLY THE NORTH HALF OF CENTRAL NC WITH AN INCH OR LESS OF SNOW ACROSS THE SOUTH. THERE IS A POTENTIAL FOR ICE ACCRUAL OF AROUND A QUARTER OF AN INCH ACROSS SECTION OF THE SOUTHERN PIEDMONT...SANDHILLS AND CENTRAL COASTAL PLAIN..BASICALLY SOUTH OF HIGHWAY 64/264...BUT NORTH OF A CLINTON...HOPE MILLS...WADESBORO LINE. IMPORTANT...THIS FORECAST BASED ON A SFC LOW TRACK FROM EASTERN GA...THROUGH NORTHERN SC/EXTREME SE NC TO OFF THE OUTER BANKS MONDAY EVENING-TUESDAY MORNING. IF THE SFC LOW WERE TO TRACK FARTHER NORTH...THE THREAT FOR SIGNIFICANT ICE ACCRUAL WILL SHIFT NORTH INTO THE TRIANGLE AREA AND POSSIBLY THE TRIAD. CONVERSELY...A TRACK FARTHER SOUTH WILL SPELL MORE SNOW THAN SLEET ACROSS THE NORTHERN PIEDMONT LEADING TO HIGHER SNOW TOTALS...AND A SIGNIFICANT ICE EVENT FOR THE FAR SOUTHERN COUNTIES. BASED ON THE CURRENT TRACK AND EXPECTED AMOUNTS/HAZARD...WILL GO WITH A WINTER STORM WARNING FOR MOST OR THE PIEDMONT COUNTIES...AND A WATCH FOR THE REMAINDER OF THE REGION. TUESDAY...BEST LIFT WILL LIFT AWAY FROM OUR REGION EARLY TUESDAY WITH DRIER AIR OVERSPREADING TEH REGION ALOFT FROM THE SW. SHOULD SEE PRECIP TAPER OFF SW-NE BETWEEN 5 AM AND 10AM. IN ITS WAKE EXPECT PARTIAL CLEARING TUESDAY AFTERNOON. ANOTHER S/W WILL APPROACH AND CROSS THE AREA TUESDAY NIGHT. THIS FEATURE APPEASR MOISTURE STARVED AT THE TIME BUT COULD SEE A FEW SNOW FLURRIES...MAINLY ACROSS THE NORTH. -- End Changed Discussion -- && Link to comment Share on other sites More sharing options...
DopplerWx Posted February 15, 2015 Share Posted February 15, 2015 Here's the RAH afternoon discussion. We should see the Warning show soon. && also mentioned the forecast for lows near zero across the area thurs and friday, which can beat record lows set in 1899 if we have any snow/ice cover from this system Link to comment Share on other sites More sharing options...
burrel2 Posted February 15, 2015 Share Posted February 15, 2015 Hey superjames.. Compare 24 and 36hr increments and look at how much flatter the trough is in the plains... this is exactly the trend we need here.. It reflects the 500mb changes at 24hrs by putting the surface low 30 or 40 miles further south in Mississippi and increases the low pressure from 1006 to 1009mb. Link to comment Share on other sites More sharing options...
beanskip Posted February 15, 2015 Share Posted February 15, 2015 Makes sense to me except that 12z GFS was considerably wetter than the 12z or 18z NAM. What's confounding is that the NAM usually picks up on CAD events best, but it is also the warmest at 2m, at least in CLT area. Just from trial/error you kinda get a feel for how to use the models as they currently are. The NAM can usually do well w/ warm noses but tends to overdo qpf routinely. The GFS/EURO are prob better to use from a QPF standpoint. So for instance I guess a blend of GFS/EURO qpf would give about .7 for RDU and NAM precip type would be probably 60% zr and 40% IP as of now. So we're talking maybe an inch of snow/sleet followed by .3 to .4 glaze. Nothing crippling, but a very solid icestorm. It would take NAM type numbers to get up into the crippling icestorm criteria. Link to comment Share on other sites More sharing options...
HKY_WX Posted February 15, 2015 Share Posted February 15, 2015 Makes sense to me except that 12z GFS was considerably wetter than the 12z or 18z NAM. What's confounding is that the NAM usually picks up on CAD events best, but it is also the warmest at 2m, at least in CLT area. No doubt this has been a strange event. I am guessing the discrepancies are due to the sharp nature of the cold front that came in last night. I haven't seen a front w/ this much dry air/wind in a long time. It's pretty unique in that sense. Plus the nature of the front and how it has not penetrated very far south into the deep south. That why there will probably be some really strange cutoff lines over the south side of the CAD tomorrow. Link to comment Share on other sites More sharing options...
beanskip Posted February 15, 2015 Share Posted February 15, 2015 Agree totally with that. Will be fascinating to hold a post-mortem on this and see what factors won out. Would certainly seem that the 18z RGEM's slightly south/weaker low might play to the GFS hand of less of a nose. Or not. If I were in the GSP office, I'd do exactly what they did -- hedge best with all precip types and then try to be nimble late if a clear P-type trend emerges. No doubt this has been a strange event. I am guessing the discrepancies are due to the sharp nature of the cold front that came in last night. I haven't seen a front w/ this much dry air/wind in a long time. It's pretty unique in that sense. Pleus the nature of the front and how it has not penetrated very far south into the deep south. That why there will probably be some really strange cutoff lines over the south side of the CAD tomorrow. Link to comment Share on other sites More sharing options...
burgertime Posted February 15, 2015 Author Share Posted February 15, 2015 Hey superjames.. Compare 24 and 36hr increments and look at how much flatter the trough is in the plains... this is exactly the trend we need here.. It reflects the 500mb changes at 24hrs by putting the surface low 30 or 40 miles further south in Mississippi and increases the low pressure from 1006 to 1009mb. That def. needs to be watched. I still don't see how the low is going to go as far north as every model is showing. I can see the warm nose coming as that always happens but how fast it drops in also seems a little suspicious to me as well. Link to comment Share on other sites More sharing options...
GaWx Posted February 15, 2015 Share Posted February 15, 2015 Hey superjames.. Compare 24 and 36hr increments and look at how much flatter the trough is in the plains... this is exactly the trend we need here.. It reflects the 500mb changes at 24hrs by putting the surface low 30 or 40 miles further south in Mississippi and increases the low pressure from 1006 to 1009mb. Note that the 18Z NAM was as much as 25 miles south of the 12Z NAM for the low's track. Interesting. Could a weaker low and further south track trend be starting? I also noted a slightly stronger NE high on the 18Z NAM vs the 12Z NAM. That would be consistent. May I have the link to the 18Z RGEM, please? Link to comment Share on other sites More sharing options...
PackGrad05 Posted February 15, 2015 Share Posted February 15, 2015 RAH issued warning for 4PM Monday - Noon on Tuesday They say 2-4 inches of snow and sleet possible with ice accrual on top. Link to comment Share on other sites More sharing options...
NGA WINTER Posted February 15, 2015 Share Posted February 15, 2015 That def. needs to be watched. I still don't see how the low is going to go as far north as every model is showing. I can see the warm nose coming as that always happens but how fast it drops in also seems a little suspicious to me as well. Like Larry and lookout have said we need a southern trend. Even 25-50 miles can be big for us Northeast Ga folks. Link to comment Share on other sites More sharing options...
burgertime Posted February 15, 2015 Author Share Posted February 15, 2015 Note that the 18Z NAM was as much as 25 miles south of the 12Z NAM for the low's track. Interesting. Could a weaker low and further south track trend be starting? I also noted a slightly stronger NE high on the 18Z NAM vs the 12Z NAM. That would be consistent. Just my two cents I think we are starting to see that trend and would not be surprised to see until 6z tomorrow morning. My very first post mentioned this. The models keep making moves that go against what this past winter and climo dictate should be happening. Maybe they are starting to come up against the "brick wall" and having to resolve that now. Link to comment Share on other sites More sharing options...
superjames1992 Posted February 15, 2015 Share Posted February 15, 2015 NWS RAH is going with 3-5" for the Triad and surrounding areas in the NW Piedmont. URGENT - WINTER WEATHER MESSAGENATIONAL WEATHER SERVICE RALEIGH NC418 PM EST SUN FEB 15 2015...AN ARCTIC AIRMASS WILL SETTLE OVER THE REGION TODAY SETTINGTHE STAGE FOR A POSSIBLE WINTER STORM LATE MONDAY AND MONDAYNIGHT....ON MONDAY...A LOW PRESSURE SYSTEM WILL DEVELOP OVER THE DEEPSOUTH AND BEGIN TO TRACK TOWARD THE CAROLINAS. PRECIPITATION WILLSPREAD ACROSS THE AREA LATE MONDAY...WITH A WINTRY MIX EXPECTEDACROSS ALL OF CENTRAL NORTH CAROLINA.NCZ007-021>023-038-039-161200-/O.UPG.KRAH.WS.A.0002.150216T2100Z-150217T1700Z//O.NEW.KRAH.WS.W.0001.150216T2100Z-150217T1700Z/PERSON-FORSYTH-GUILFORD-ALAMANCE-DAVIDSON-RANDOLPH-INCLUDING THE CITIES OF...ROXBORO...WINSTON-SALEM...GREENSBORO...HIGH POINT...BURLINGTON...GRAHAM...LEXINGTON...THOMASVILLE...ASHEBORO...ARCHDALE...TRINITY418 PM EST SUN FEB 15 2015...WINTER STORM WARNING IN EFFECT FROM 4 PM MONDAY TO NOON ESTTUESDAY...THE NATIONAL WEATHER SERVICE IN RALEIGH HAS ISSUED A WINTER STORMWARNING FOR SNOW AND SLEET...WHICH IS IN EFFECT FROM 4 PM MONDAYTO NOON EST TUESDAY. THE WINTER STORM WATCH IS NO LONGER INEFFECT.* ACCUMULATIONS...SNOW AND SLEET ACCUMULATION OF 3 TO 5 INCHES.* LOCATIONS...THE NORTHWEST PIEDMONT...INCLUDING THE TRIAD AREA.* HAZARD TYPES...ACCUMULATING SNOW AND SLEET RESULTING IN DANGEROUSTRAVEL CONDITIONS.* TIMING...LATE MONDAY AFTERNOON THROUGH TUESDAY MORNING.* IMPACTS...ROADS WILL QUICKLY BECOME SNOW AND SLEET COVERED ANDTRAVEL WILL BECOME DANGEROUS. ISOLATED TO SCATTERED POWEROUTAGES WILL ALSO BE POSSIBLE.PRECAUTIONARY/PREPAREDNESS ACTIONS...A WINTER STORM WARNING MEANS SIGNIFICANT AMOUNTS OF SNOW ANDSLEET ARE EXPECTED OR OCCURRING. THIS WILL MAKE TRAVEL VERYHAZARDOUS OR IMPOSSIBLE. ONLY TRAVEL IN AN EMERGENCY. IF YOU MUSTTRAVEL...KEEP AN EXTRA FLASHLIGHT... FOOD... BLANKETS... ANDWATER IN YOUR VEHICLE IN CASE OF AN EMERGENCY.&&$ Link to comment Share on other sites More sharing options...
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