LocoAko Posted February 11, 2013 Share Posted February 11, 2013 I know there was some discussion in the NE OK/MO thread, but with NW OK looking to take the brunt of this storm, I figured we could have a dedicated thread to it. The models are still displaying some differences, particularly on the SE side of the snow field and how it may affect OKC metro. (For example, the NAM clown maps show 8-10" in northern Cleveland County and <1" in southern Cleveland -- http://wxcaster4.com/nam/CONUS1_ETA212_SFC_ACCUMSNOWFALL_48HR.gif -- so take that FWIW). As per some of wxwatcher91's tweets (available at @splillo), some of the soundings just NW of OKC in the El Reno area are awfully favorable for some heavy snow: In addition, he also noted the frontogenetic forcing implied by the NAM in NW OK for mid-day tomorrow: The current forecast graphic from WFO OUN looks like this, but I wouldn't be surprised to see amounts upped a bit in northwest OK: Current forecast has OKC mixing by tomorrow afternoon and becoming snow after dark. Link to comment Share on other sites More sharing options...
brettjrob Posted February 11, 2013 Share Posted February 11, 2013 Nice to see the GFS move toward the more generous NAM on QPF this morning. The near-surface thermal profiles are rather shaky with this event, and the diurnal timing isn't helping matters. It will be interesting to see whether evaporational cooling can overcome this throughout the area of heavier precip, or if sig accumulations are confined to the N Panhandles and far NW OK. The ECMWF has been adamant all along that 2m temperatures will be above freezing for almost everyone. Link to comment Share on other sites More sharing options...
LocoAko Posted February 11, 2013 Author Share Posted February 11, 2013 Nice to see the GFS move toward the more generous NAM on QPF this morning. The near-surface thermal profiles are rather shaky with this event, and the diurnal timing isn't helping matters. It will be interesting to see whether evaporational cooling can overcome this throughout the area of heavier precip, or if sig accumulations are confined to the N Panhandles and far NW OK. The ECMWF has been adamant all along that 2m temperatures will be above freezing for almost everyone. Yeah, surface temperatures aren't pretty on the ECMWF. Looks sloppy for sure. If only there was surface wet-bulb output for the ECMWF. Link to comment Share on other sites More sharing options...
LocoAko Posted February 11, 2013 Author Share Posted February 11, 2013 Winter Storm Warnings issued by WFO AMA for 6-9 inches in the eastern part of the TX Panhandle with locally higher amounts. Good stuff. Link to comment Share on other sites More sharing options...
LocoAko Posted February 12, 2013 Author Share Posted February 12, 2013 18Z guidance from WxCaster: Link to comment Share on other sites More sharing options...
Chinook Posted February 12, 2013 Share Posted February 12, 2013 That's starting to look like a pretty awesome storm for that area. Link to comment Share on other sites More sharing options...
brettjrob Posted February 12, 2013 Share Posted February 12, 2013 00z NAM forecast soundings show all snow from 15z onward as far S as OUN, which if taken literally would mean we get hammered with 6"+. The RAP isn't even close, with 2m temperatures in the upper 30s even at full saturation in the afternoon. Probably one of the worst shifts you could ever work at the NWS FO tonight. Link to comment Share on other sites More sharing options...
LocoAko Posted February 12, 2013 Author Share Posted February 12, 2013 00z NAM forecast soundings show all snow from 15z onward as far S as OUN, which if taken literally would mean we get hammered with 6"+. The RAP isn't even close, with 2m temperatures in the upper 30s even at full saturation in the afternoon. Probably one of the worst shifts you could ever work at the NWS FO tonight. Oh wow, I hadn't even noticed the change in the thermodynamics - I had only noticed that it slashed precipitation over a wide area (par for the course). Wow. Link to comment Share on other sites More sharing options...
rockchalk83 Posted February 12, 2013 Share Posted February 12, 2013 Can anyone explain why the models have been insistent on keeping the the bulk of the heaviest precipitation in northern Oklahoma? Is this due to the models picking up on the dry boundary layer across Kansas or something else. Link to comment Share on other sites More sharing options...
brettjrob Posted February 12, 2013 Share Posted February 12, 2013 Oh wow, I hadn't even noticed the change in the thermodynamics - I had only noticed that it slashed precipitation over a wide area (par for the course). Wow. The snowfall algorithms on TwisterData and IWM are really stingy, but looking at the soundings, I'm not sure why. The surface temperatures are still shaky right here in Norman, but especially once you get to OKC north and west, the entire column is subfreezing all day on this run. I guess it does have a lot of the QPF between 12z-15z when the entire lowest kilometer is isothermal right at freezing, so ratios may be exceptionally terrible in that case. Link to comment Share on other sites More sharing options...
LocoAko Posted February 12, 2013 Author Share Posted February 12, 2013 Well alrighty, then! Not something you want to have to do 12 hours before the start of an event... Eek. URGENT - WINTER WEATHER MESSAGENATIONAL WEATHER SERVICE NORMAN OK942 PM CST MON FEB 11 2013OKZ008-013-019-020-023>029-035-036-038-TXZ083-121145-/O.EXB.KOUN.WS.A.0001.130212T1300Z-130213T0200Z/KAY-NOBLE-LOGAN-PAYNE-CADDO-CANADIAN-OKLAHOMA-LINCOLN-GRADY-MCCLAIN-CLEVELAND-KIOWA-JACKSON-COMANCHE-HARDEMAN-INCLUDING THE CITIES OF...PONCA CITY...PERRY...GUTHRIE...STILLWATER...ANADARKO...YUKON...EL RENO...MUSTANG...OKLAHOMA CITY...CHANDLER...CHICKASHA...PURCELL...NORMAN...MOORE...HOBART...ALTUS...LAWTON...QUANAH...CHILLICOTHE942 PM CST MON FEB 11 2013...WINTER STORM WATCH IN EFFECT FROM 7 AM CST TUESDAY THROUGHTUESDAY EVENING...THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A WINTER STORMWATCH...WHICH IS IN EFFECT FROM 7 AM CST TUESDAY THROUGH TUESDAYEVENING.* MAIN IMPACT: RAIN IS EXPECTED TO BEGIN IN CENTRAL OKLAHOMA BEFORE SUNRISE TUESDAY MORNING. RAIN IS EXPECTED TO MIX WITH AND CHANGE TO SNOW BEFORE NOON. SNOW ACCUMULATION OF 3 TO 6 INCHES IS POSSIBLE ACROSS CENTRAL OKLAHOMA.* OTHER IMPACTS:SNOW ACCUMULATIONS MAY RESULT IN SLICK AND HAZARDOUS ROADWAYS TUESDAY.PRECAUTIONARY/PREPAREDNESS ACTIONS...KEEP UP WITH THE LATEST WEATHER INFORMATION...ESPECIALLY IF YOUPLAN TO TRAVEL. Link to comment Share on other sites More sharing options...
LocoAko Posted February 12, 2013 Author Share Posted February 12, 2013 In addition, warnings are now up for western Oklahoma for 5-9" of snow. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2013 Share Posted February 12, 2013 Can anyone explain why the models have been insistent on keeping the the bulk of the heaviest precipitation in northern Oklahoma? Is this due to the models picking up on the dry boundary layer across Kansas or something else. Most of the strong moist frontogenesis which will be driving this event is located a bit farther S. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2013 Share Posted February 12, 2013 Based on the isothermal layer and lack of cold air advection early on...going to be one of those classic cases of heaviest precipitation = snow while lighter precip stays rain. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2013 Share Posted February 12, 2013 00z NAM forecast soundings show all snow from 15z onward as far S as OUN, which if taken literally would mean we get hammered with 6"+. The RAP isn't even close, with 2m temperatures in the upper 30s even at full saturation in the afternoon. Probably one of the worst shifts you could ever work at the NWS FO tonight. RAP soundings look suspect to me. Not sure what it is doing, but it is trying to depict a dry adiabatic boundary layer during the heaviest precip within the CCB (if you want to call it a CCB)....doesn't make sense. Link to comment Share on other sites More sharing options...
rockchalk83 Posted February 12, 2013 Share Posted February 12, 2013 Most of the strong moist frontogenesis which will be driving this event is located a bit farther S. So if the frontogenesis was stronger over a larger area, the precip would be able to expand further north, correct? Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2013 Share Posted February 12, 2013 So if the frontogenesis was stronger over a larger area, the precip would be able to expand further north, correct? Well, perhaps. A lot of different things could theoretically allow for precip to spread farther N, but there is a theoretical limit in this scenario based on the split stream flow pattern and horizontal deformation farther N...which will effectively form a rather sharp moisture/precip gradient. If the upper levels were different (less northern stream interference leading to more of a cutoff flow and possibly stronger cyclogenesis), it is possible things could spread farther N. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2013 Share Posted February 12, 2013 00z RGEM: Pretty similar to the NAM overall, not quite as wet though, which is probably closer to reality than the NAM which is outputting widespread areas of greater than 1.00". That said...a narrow band of 1.00" is definitely possible if the upper PV core can intersect the low level front. There should be some pretty stout convective banding tomorrow. Link to comment Share on other sites More sharing options...
brettjrob Posted February 12, 2013 Share Posted February 12, 2013 00z RGEM: Pretty similar to the NAM overall, not quite as wet though, which is probably closer to reality than the NAM which is outputting widespread areas of greater than 1.00". That said...a narrow band of 1.00" is definitely possible if the upper PV core can intersect the low level front. There should be some pretty stout convective banding tomorrow. Re: the convective banding, that's a hallmark of almost every decent snow event we get around here. Inevitably the spatial liquid equivalent distribution is much more banded in a feast-or-famine fashion than model QPF. I don't think the area of 6"+ will be as large as the NAM shows, but someone in OK could jackpot at 10". Link to comment Share on other sites More sharing options...
OKpowdah Posted February 12, 2013 Share Posted February 12, 2013 00z NAM 700mb vertical velocity and streamlines for 18z tomorrow. Beautiful deformation zone, and lift colocated with the frontogenetic circulation Link to comment Share on other sites More sharing options...
OKpowdah Posted February 12, 2013 Share Posted February 12, 2013 Gotta love the HRRR Link to comment Share on other sites More sharing options...
andyhb Posted February 12, 2013 Share Posted February 12, 2013 MESOSCALE DISCUSSION 0154 NWS STORM PREDICTION CENTER NORMAN OK 0344 AM CST TUE FEB 12 2013 AREAS AFFECTED...TX PANHANDLE/WESTERN OK CONCERNING...HEAVY SNOW VALID 120944Z - 121415Z SUMMARY...MODERATE/HEAVY SNOW WILL BECOME INCREASINGLY PREVALENT ACROSS MUCH OF THE TX PANHANDLE INTO WESTERN OK THROUGH THE EARLY/MID MORNING HOURS. SNOWFALL RATES WILL REACH/POTENTIALLY EXCEED 1 IN/HR THROUGH 12Z-15Z...WITH AS MUCH AS 2 IN/HR LOCALIZED RATES POSSIBLE FOR RELATIVELY SHORT DURATIONS. DISCUSSION...OVERNIGHT WATER VAPOR IMAGERY IS INDICATIVE OF AN EAST-NORTHEASTWARD SHIFTING UPPER TROUGH CENTERED OVER SOUTHERN NM/FAR SOUTHWEST TX. THE INFLUENCE OF THIS TROUGH...IN CONJUNCTION WITH WARM ADVECTION AND INCREASINGLY STRONG UPPER DIVERGENCE VIA A STRONG POLAR JET EXIT REGION /100-125 KT AT 300 MB/...WILL CONTRIBUTE TO INCREASING PRECIPITATION RATES/SATURATION AND RESULTANT INCREASINGLY MORE WIDESPREAD MODERATE/HEAVY SNOW THROUGH THE EARLY MORNING HOURS. AS OF 09Z...ZERO/SUB-ZERO SURFACE WET BULB TEMPERATURES ARE PRESENT ACROSS ALL OF THE TX PANHANDLE/PORTIONS OF THE TX SOUTH PLAINS...INTO WESTERN OK AREAS NEAR/NORTH OF I-40. THESE COLDER TEMPERATURES ROUGHLY COINCIDE WITH AREAS ALONG AND NORTH-NORTHWEST OF A SURFACE INVERTED TROUGH/ZONE OF LOW-LEVEL CONFLUENCE THAT ANGLES FROM THE TX SOUTH PLAINS TO EAST-CENTRAL OK. THE ONSET OF STRONGER FORCING FOR ASCENT/PRECIPITATION RATES SHOULD QUICKLY ERODE TEMPERATURE-DEWPOINT SPREADS THAT ARE AS HIGH AS 10-15F AS OF 09Z...GENERALLY BY 12Z ACROSS THE MAJORITY OF THE TX PANHANDLE AND PERHAPS FAR WESTERN OK. WHILE SOME SLEET WILL BE POSSIBLE INITIALLY /ESPECIALLY WITH CONVECTIVE ELEMENTS/...INCREASINGLY MODERATE/HEAVY SNOW WILL BE DOMINANT. CONSEQUENTIAL ASCENT/QUICK SATURATION ASIDE...SNOWFALL RATES WILL LIKELY BE ENHANCED BY CONVECTIVE ELEMENTS AS BAND/S OF HEAVIER PRECIPITATION EVOLVE. ISOLATED-SCATTERED TSTMS ARE READILY OCCURRING AS OF 09Z ACROSS THE TX SOUTH PLAINS INTO NORTHWEST TX. COMBINED WITH INCREASING MID-LEVEL FRONTOGENESIS /800-600 MB/...WEAK UPRIGHT INSTABILITY AND/OR SLANTWISE INSTABILITY ACROSS THE TX PANHANDLE/WESTERN OK WILL LIKELY ENHANCE SNOWFALL RATES TO 1-2 IN/HR THROUGH 12Z-15Z ACROSS THE TX PANHANDLE INTO FAR WESTERN OK. THIS INCLUDES THE POTENTIAL FOR MULTIPLE/CONSOLIDATING HEAVY SNOW BANDS...AS WELL AS THUNDERSNOW. ..GUYER.. 02/12/2013 Link to comment Share on other sites More sharing options...
brettjrob Posted February 12, 2013 Share Posted February 12, 2013 Only a couple more runs of the HRRR before it's taken down for maintenance today, so might as well throw its 09z run into the mix. Current 2m wet bulbs on the Mesonet suggest the real accumulations may stay just W of the metro area. Not sure about that 12-18" bullseye, but ranchers have got to be loving the current radar. I think the bullseye will be in that area, but more on the order of 9-12". Already 6" in Dalhart, after some thundersnow reports from that area overnight. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2013 Share Posted February 12, 2013 Only a couple more runs of the HRRR before it's taken down for maintenance today, so might as well throw its 09z run into the mix. acsnw_t5sfc_f15.png Current 2m wet bulbs on the Mesonet suggest the real accumulations may stay just W of the metro area. Not sure about that 12-18" bullseye, but ranchers have got to be loving the current radar. I think the bullseye will be in that area, but more on the order of 9-12". Already 6" in Dalhart, after some thundersnow reports from that area overnight. Seems reasonable. 12z sounding for Norman depicts an agonizingly high 3400' WBZ height and matches with local radar melting heights. NAM tries to bring in snow by midday, but it will likely be dependent upon convective banding being in the right area at the right time, probably at best mixing to large, wet flakes. Will be interesting to see if Norman can get sufficiently heavy rates to accumulate something. Link to comment Share on other sites More sharing options...
Srain Posted February 12, 2013 Share Posted February 12, 2013 MESOSCALE DISCUSSION 0155 NWS STORM PREDICTION CENTER NORMAN OK 0758 AM CST TUE FEB 12 2013 AREAS AFFECTED...TX PANHANDLE TO WESTERN/NORTH-CENTRAL OK CONCERNING...HEAVY SNOW VALID 121358Z - 121800Z SUMMARY...MODERATE/HEAVY SNOW WILL CONTINUE TO DEVELOP EAST-NORTHEASTWARD FROM THE TX PANHANDLE INTO WESTERN/NORTH-CENTRAL OK THROUGH 18Z. SNOWFALL RATES SHOULD CONTINUE TO REACH 1 IN/HR THROUGH EARLY AFTERNOON...WITH LOCALLY HIGHER RATES POSSIBLE FOR RELATIVELY SHORT DURATIONS. DISCUSSION...IN ASSOCIATION WITH AN EAST-NORTHEAST ADVANCING UPPER TROUGH OVER NM/APPROACHING FAR WEST TX EARLY THIS MORNING...DEEP LAYER ASCENT VIA UPPER JET EXIT REGION/WARM ADVECTION CONTINUES TO CONTRIBUTE TO AN EAST-NORTHEASTWARD DEVELOPMENT OF PRECIPITATION ACROSS FAR NORTH TX/TX PANHANDLE INTO WESTERN/SOUTHERN OK. AS OF 13Z...ZERO/SUB-ZERO SURFACE WET BULB TEMPERATURES ARE EVIDENT ACROSS THE MAJORITY OF THE TX PANHANDLE AND INTO NORTHWEST OK /AREAS NORTH OF I-40/. THESE COLDER TEMPERATURES CONTINUE TO ROUGHLY COINCIDE WITH AREAS THAT ARE ALONG AND NORTH-NORTHWEST OF A WEAK SURFACE INVERTED TROUGH/ZONE OF LOW-LEVEL CONFLUENCE. ALTHOUGH THE 12Z OBSERVED SOUNDING FROM NORMAN WAS INDICATIVE OF AN ABOVE-FREEZING WET BULB PROFILE BELOW 850 MB...THE ONSET OF STRONGER FORCING FOR ASCENT/HIGHER PRECIPITATION RATES AND LOW-LEVEL COLD ADVECTION SHOULD CONTINUE TO LEAD TO A GENERAL WEST TO EAST TRANSITION OF RAIN TO SNOW INTO WEST-CENTRAL/NORTH-CENTRAL OK THROUGH MIDDAY. THIS ASIDE...SOME SLEET WILL BE POSSIBLE WITH PRECIPITATION ONSET AND/OR EXISTING CONVECTIVE ELEMENTS ACROSS SOUTH-CENTRAL OK. DEEP FORCING/SATURATION ASIDE...MID-LEVEL FRONTOGENESIS /800-600 MB/...ALONG WITH WEAK UPRIGHT INSTABILITY AND/OR SLANTWISE INSTABILITY...WILL LIKELY ENHANCE SNOWFALL WITH RATES OF 1+ IN/HR POSSIBLE INTO EARLY AFTERNOON. THIS WILL ESPECIALLY BE THE CASE ACROSS THE EASTERN TX PANHANDLE INTO WEST-CENTRAL OK AND PERHAPS NORTH-CENTRAL OK BY EARLY AFTERNOON. ..GUYER.. 02/12/2013 ATTN...WFO...OUN...LUB...AMA... Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2013 Share Posted February 12, 2013 Twitter image from Sayre, via OUNWCM: Link to comment Share on other sites More sharing options...
LocoAko Posted February 12, 2013 Author Share Posted February 12, 2013 Weather Channel calling for 3-5" today and 1-3" tonight in my Local on the 8s, while the Weather Service has a (much more reasonable, IMO) 1-3" WWA out. Today should be interesting. Link to comment Share on other sites More sharing options...
brettjrob Posted February 12, 2013 Share Posted February 12, 2013 Looks like it's ripping from west-central OK into most of the Panhandles. Local media shows I-40 already snowpacked at Clinton with visibility under 1/4 mi. Also, already light accumulations with snow ongoing as far SE as Piedmont. Link to comment Share on other sites More sharing options...
LocoAko Posted February 12, 2013 Author Share Posted February 12, 2013 KOKC 121452Z 02012KT 5SM -SNRA OVC024 02/M01 A3002 RMK AO2 SNB47 SLP171 P0012 60019 T00221006 53003Snow mixing in at Will Rogers World Airport already. Link to comment Share on other sites More sharing options...
LocoAko Posted February 12, 2013 Author Share Posted February 12, 2013 Also, fun to watch all the mPING reports from OKC/Norman as it slowly transitions across OKC. No shortage of people willing to report here. http://www.nssl.noaa.gov/projects/ping/display/ Link to comment Share on other sites More sharing options...
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