cyclone77 Posted February 27, 2011 Share Posted February 27, 2011 I think a lot depends on where the convection blows up in Kansas. The 4km WRF had a lot more elevated convection firing in central and northern Kansas later today, with very little surface based convection further south. The RUC/HRRR seem to blow up more surface based convection further south over southeast Kansas in the warm sector, with much less elevated stuff further north. I think a lot will depend on where this initial convection initiates. Link to comment Share on other sites More sharing options...
wisconsinwx Posted February 27, 2011 Share Posted February 27, 2011 I think a lot depends on where the convection blows up in Kansas. The 4km WRF had a lot more elevated convection firing in central and northern Kansas later today, with very little surface based convection further south. The RUC/HRRR seem to blow up more surface based convection further south over southeast Kansas in the warm sector, with much less elevated stuff further north. I think a lot will depend on where this initial convection initiates. I assume the former would produce more snow and sleet/freezing rain in the cold sector? Link to comment Share on other sites More sharing options...
ILSNOW Posted February 27, 2011 Share Posted February 27, 2011 KLOT aviation doesnt appear to be impressed TIMING OF THIS TRANSITION WILL BE TOUGH TO PIN DOWN BUT EXPECT A CHANGE TO FZRA AND/OR SLEET THEN TO SLEET AND SNOW BEFORE GOING TO ALL SNOW AS PRECIP ENDS MONDAY MORNING. HAVE BETTER CONFIDENCE IN TRANSITION AT RFD WITH THINGS BECOMING MORE DIFFICULT TOWARDS DPA/MDW/ORD WHICH WILL BE CLOSER TO THRESHOLDS FOR DIFFERENT PRECIP TYPES. WINDS WILL TURN TO THE NORTH OVERNIGHT HELPING COLDER AIR TO FILL IN BUT WILL ALSO HELP TO BRING DRIER AIR. THERE IS THE POTENTIAL FOR SEVERAL INCHES OF SNOW ACCUMULATION AT RFD WITH AN INCH OR TWO LOOKING REASONABLE AT DPA AND ORD AND LESS AT MDW AND GYY. Link to comment Share on other sites More sharing options...
csnavywx Posted February 27, 2011 Share Posted February 27, 2011 SVR out in the Bloomington area for quarter size hail. Nice. Amazing how well the 4km WRF picked up on that. Link to comment Share on other sites More sharing options...
cyclone77 Posted February 27, 2011 Share Posted February 27, 2011 I assume the former would produce more snow and sleet/freezing rain in the cold sector? Well, it seems that there's a lot less elevated convection north of the front the more surface based convection there is early on. If you look at the 12z 4km WRF, it goes crazy with lots of elevated stuff over central and northern Kansas, and that moves northeastward up into much of Iowa. The RUC/HRRR focus much more on the more surface based storms over southeastern Kansas, and changes the whole evolution of the precip in the cold sector. Just an observation on some of the main differences in how these models differ. Link to comment Share on other sites More sharing options...
Chicago Storm Posted February 27, 2011 Author Share Posted February 27, 2011 Well, it seems that there's a lot less elevated convection north of the front the more surface based convection there is early on. If you look at the 12z 4km WRF, it goes crazy with lots of elevated stuff over central and northern Kansas, and that moves northeastward up into much of Iowa. The RUC/HRRR focus much more on the more surface based storms over southeastern Kansas, and changes the whole evolution of the precip in the cold sector. Just an observation on some of the main differences in how these models differ. It looks like that elevated convection is just starting to develop across South-Central Kansas...so we'll see how things progress. Link to comment Share on other sites More sharing options...
csnavywx Posted February 27, 2011 Share Posted February 27, 2011 I think a lot depends on where the convection blows up in Kansas. The 4km WRF had a lot more elevated convection firing in central and northern Kansas later today, with very little surface based convection further south. The RUC/HRRR seem to blow up more surface based convection further south over southeast Kansas in the warm sector, with much less elevated stuff further north. I think a lot will depend on where this initial convection initiates. Pretty stout cap to the south of the boundary. Some convection is firing off along and to the north of the boundary already in S. Central and Central Kansas, right when and where the 4km WRF had it initiating, so as far as the initial stages are concerned (the central IL and srn Kansas convection), it is spot on. Link to comment Share on other sites More sharing options...
cyclone77 Posted February 27, 2011 Share Posted February 27, 2011 It looks like that elevated convection is just starting to develop across South-Central Kansas...so we'll see how things progress. Yep. The brand new HRRR just coming in looks even more south with the cold sector precip. What it's doing is developing large clusters of thunderstorms/MCS that parade along and just north of the boundary. There is very little if any stratiform precip further north into the cold sector. I hope it's wrong, or we will see very little of anything from here points northwest. Link to comment Share on other sites More sharing options...
cyclone77 Posted February 27, 2011 Share Posted February 27, 2011 Pretty stout cap to the south of the boundary. Some convection is firing off along and to the north of the boundary already in S. Central and Central Kansas, right when and where the 4km WRF had it initiating, so as far as the initial stages are concerned (the central IL and srn Kansas convection), it is spot on. Yeah it really nailed the central IL convection this morning. It's going to be interesting to see how it does the rest of the way. Link to comment Share on other sites More sharing options...
MadTown Posted February 27, 2011 Share Posted February 27, 2011 looks like a 30% chance of snow here tonight..hard to believe how far nw this thing was to were it is headed now Link to comment Share on other sites More sharing options...
csnavywx Posted February 27, 2011 Share Posted February 27, 2011 Just to calm down some of the panic on the rapidly changing precip amounts coming from the models: This is typical with convective events. Each of the models handle convection somewhat differently, depending on their resolution and parameterizations. Make no mistake that a lot of the precipitation from this event will be convective-related, with a smaller component from synoptic forcing. Models do fairly well with broad synoptic lift and the QPF associated with it, but can often fail miserably when convection is involved. Now, having said this... there's already ample evidence from the radar and satellite that the WRF has a great handle on what's currently going on. It picked up on the IL convection (which is indicative of instability spreading into that region), and has the Kansas convection growing upscale into that destabilizing environment. This makes sense given all of the soundings coming out from south of the warm front this morning (most of which displayed rather extreme mid-level lapse rates and a stout EML). Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 27, 2011 Share Posted February 27, 2011 Just to calm down some of the panic on the rapidly changing precip amounts coming from the models: This is typical with convective events. Each of the models handle convection somewhat differently, depending on their resolution and parameterizations. Make no mistake that a lot of the precipitation from this event will be convective-related, with a smaller component from synoptic forcing. Models do fairly well with broad synoptic lift and the QPF associated with it, but can often fail miserably when convection is involved. Now, having said this... there's already ample evidence from the radar and satellite that the WRF has a great handle on what's currently going on. It picked up on the IL convection (which is indicative of instability spreading into that region), and has the Kansas convection growing upscale into that destabilizing environment. This makes sense given all of the soundings coming out from south of the warm front this morning (most of which displayed rather extreme mid-level lapse rates and a stout EML). through-the-roof! Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 27, 2011 Share Posted February 27, 2011 18z NAM continues the trend south. Link to comment Share on other sites More sharing options...
cyclone77 Posted February 27, 2011 Share Posted February 27, 2011 18z NAM continues the trend south. Yep. Still looks okay for Chicago for now, but the trend is not our friend. Starting to look like a non event for the QC. Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2011 Share Posted February 27, 2011 Looks like there could be some small hail with those cells near Kankakee. Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2011 Share Posted February 27, 2011 PRELIMINARY LOCAL STORM REPORT NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 206 PM CST SUN FEB 27 2011 .TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON .DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE. ..REMARKS.. 0205 PM HAIL 20 S VALPARAISO 41.19N 87.05W 02/27/2011 E0.25 INCH JASPER IN TRAINED SPOTTER LITTLE BIGGER THAN PEA SIZE HAIL COVERING THE GROUND. Link to comment Share on other sites More sharing options...
turtlehurricane Posted February 27, 2011 Share Posted February 27, 2011 Probably won't melt much either, so it counts as frozen precip accumulation in my eyes. Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2011 Share Posted February 27, 2011 18z RUC valid 6z has a pretty classic freezing rain sounding at ORD. Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2011 Share Posted February 27, 2011 18z NAM really cut back on snow amounts in that band. Link to comment Share on other sites More sharing options...
turtlehurricane Posted February 27, 2011 Share Posted February 27, 2011 Becoming hard to ignore the MCS and associated MCV in Kansas. It's gonna be a big player down the road for everyone, and the global models never handle this sort of thing right. The main thing I'm wondering about is if the squall moves north over the stable layer. I think this is very possible over northern MO and into IA, and that would cause a nice hydraulic jump, and powerful winds like a derecho. Of course, we'll see how far north this goes before it totally falls apart from lack of instability. Link to comment Share on other sites More sharing options...
Chicago Storm Posted February 27, 2011 Author Share Posted February 27, 2011 Becoming hard to ignore the MCS and associated MCV in Kansas. It's gonna be a big player down the road for everyone, and the global models never handle this sort of thing right. The main thing I'm wondering about is if the squall moves north over the stable layer. I think this is very possible over northern MO and into IA, and that would cause a nice hydraulic jump, and powerful winds like a derecho. Of course, we'll see how far north this goes before it totally falls apart from lack of instability. If the 12z SPC WRF is correct, this will be visiting the Chicago area later. Link to comment Share on other sites More sharing options...
turtlehurricane Posted February 27, 2011 Share Posted February 27, 2011 If the 12z SPC WRF is correct, this will be visiting the Chicago area later. It would appear to be on a track to give northern IL and southern WI some action. Extreme shear developing at the triple point of the MCV now, 100+ kt. Temps approaching 70 on the warm side of it, and they're in the 30s on the cold side! This thing is a monster and isn't just gonna disappear. Link to comment Share on other sites More sharing options...
BeastFromTheEast Posted February 27, 2011 Share Posted February 27, 2011 LOT updated their grid forecasts with 3-5 inches now in the forecast for Lake/Mchenry counties... Link to comment Share on other sites More sharing options...
Chicago Storm Posted February 27, 2011 Author Share Posted February 27, 2011 DVN: TONIGHT...NOWCAST TOOLS SUPPORT AREAS OF RAIN TO SPREAD ACROSS SOUTH 1/3 TO 1/2 SECTIONS BETWEEN 6 AND 10 PM. STRONG EVAPORATIVE COOLING TO RESULT IN RAIN BECOMING FREEZING RAIN NORTH OF HIGHWAY 34 IN IOWA BY OR SHORTLY AFTER 01Z. PROGRESSIVE 925-850 FRONT TO RESULT IN SHARP DROP-OFF IN PRECIPITATION WITH AREAS NORTH OF I-80 TO SEE LIGHT OR NO SIGNIFICANT PRECIPITATION. THE EVAPORATIVE COOLING WILL RESULT IN FREEZING RAIN TRANSITIONING OVER TO SLEET WITHIN 3 OR SO HOURS. THIS IS KEY AS IF SLOWER...THEN HIGHER ICE AMOUNTS SUGGESTED OF GREATER THAN .25 INCH. THIS THE MAIN CONCERN TO PASS ON TO EVENING SHIFT. PRECIPITATION TO CHANGE OVER TO SNOW FROM NW TO SE OVERNIGHT AS COLD AIR MOVES IN. THE BANDS OF FREEZING RAIN AND MIXTURE OF SLEET AND FREEZING RAIN TO SLIDE SOUTHEAST LATE EVENING AND OVERNIGHT ARRIVING ALONG IA/MO BORDER NEAR OR SHORTLY BEFORE MIDNIGHT. SNOW AMOUNTS OF HALF INCH TO LOCALLY 2 PLUS INCHES WITH ICE OF .1 TO .2 TENTHS SUGGESTED ALONG AND SOUTH OF I-80. HENCE...WILL HAVE A 2 SECTION WINTER WEATHER ADVISORY FOR I-80 TO JUST NORTH OF HIGHWAY 34 IN IOWA FROM 01-12 Z AND LOCATIONS ALONG AND SOUTH OF HIGHWAY 34 STARTING AT 05Z UNTIL 12Z. NE TO N WINDS WILL INCREASE TO 10 TO 25 MPH. AGAIN...CONCERN IS POSSIBLE NEED TO UPGRADE PART OF ADVISORY TO WARNING FOR HIGHER ICE ACCUMULATIONS...THIS RISK SHOULD BE KNOWN BY 10 PM. Link to comment Share on other sites More sharing options...
BeastFromTheEast Posted February 27, 2011 Share Posted February 27, 2011 Dekalb is in the 3-5 inch zone as well.. Link to comment Share on other sites More sharing options...
turtlehurricane Posted February 27, 2011 Share Posted February 27, 2011 Kansas City is about to get slammed. Currently 37 °F there with heavy fog, obviously a very stable layer near the surface. Here comes some wind action, especially west of KC. Link to comment Share on other sites More sharing options...
Chicago Storm Posted February 27, 2011 Author Share Posted February 27, 2011 Link to comment Share on other sites More sharing options...
BeastFromTheEast Posted February 27, 2011 Share Posted February 27, 2011 I smell an advisory coming soon.. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 27, 2011 Share Posted February 27, 2011 wouldn't be surprised if that band ends up a bit further southeast, we'll see. Link to comment Share on other sites More sharing options...
cyclone77 Posted February 27, 2011 Share Posted February 27, 2011 Our county is surrounded by the WWA. Clearly DVN and LOT are in a bit of disagreement there. Gonna be close, but I think the worst will miss to our southeast. Link to comment Share on other sites More sharing options...
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