Thundersnow12 Posted February 1, 2011 Share Posted February 1, 2011 AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 651 AM CST TUE FEB 1 2011 DISCUSSION 419 AM CST STORM STUFF (TODAY THROUGH WEDNESDAY)... GORGEOUS/CLASSIC MID LATITUDE CYCLONE IS DEVELOPING OVER THE SOUTHERN PLAINS THIS MORNING...WITH BLOSSOMING (PARDON THE PUN) BAROCLINIC LEAF ON SATELLITE IMAGERY. RAPIDLY EXPANDING WARM CONVEYOR BELT WITH REGIONAL WSR-88D MOSAIC SHOWING LARGE AREA OF MODERATE TO HEAVY PRECIPITATION WITH EMBEDDED THUNDERSTORMS SPREADING FROM OKLAHOMA AND ARKANSAS INTO SOUTHERN MISSOURI EARLY THIS MORNING. AS CYCLONE CONTINUES TO LIFT NORTHEASTWARD OUT OF THE SOUTHERN PLAINS TODAY LOOK FOR CONTINUED EXPANSION OF THE MODERATE TO HEAVY PRECIPITATION WITH THE WARM CONVEYOR BELT TO BEGIN SPREADING INTO SOUTHERN PORTIONS OF THE CWA BY AS EARLY AS LATE MORNING...AND UP TO THE WISCONSIN BORDER BY MID AFTERNOON. GIVEN THE EXPECTED EARLIER ARRIVAL TIMES OF THE SNOWFALL...HAVE ADJUSTED THE START TIME OF THE BLIZZARD WARNING TO 11 AM SOUTHERN COUNTIES TO BETTER COINCIDE WITH THE EXPECTED DETERIORATING CONDITIONS. PART ONE (ASSUMING THE PIDDLY SNOW WE SAW OVERNIGHT WAS PART ZERO) OF THE STORM SHOULD BE LARGELY DRIVEN BY INTENSE WARM AIR ADVECTION/ISENTROPIC ASCENT. SNOWFALL WILL LIKELY BECOME HEAVY AT TIMES WITH SIGNIFICANT SNOWFALL EXPECTED TO HAVE ACCUMULATED ALREADY BY MID EVENING. CERTAINLY POSSIBLE THAT WE COULD SEE A BIT OF A WANING IN THE INTENSITY OF THE SNOWFALL FOR A TIME THIS EVENING BEFORE RAMPING BACK UP BIG TIME LATE EVENING/OVERNIGHT WHEN PART TWO STARTS. PART TWO OF THE STORM WILL BE WITH INTENSIFYING TROWAL/DEFORMATION ZONE TONIGHT. UPWARD VERTICAL VELOCITIES ARE FORECAST TO BE ALMOST OFF THE CHARTS TONIGHT AS UPPER TROUGH CLOSES OFF INTO A NEGATIVELY TILTED CLOSED/COMPACT MID LEVEL LOW AS IT LIFTS NORTHEAST TOWARD SOUTHERN LAKE MICHIGAN BY EARLY WEDNESDAY MORNING. ALL INDICATIONS ARE THAT VERY INTENSE SNOWFALL WILL DEVELOP WITHIN THE DEFORMATION BAND WITH TREMENDOUSLY STRONG UPPER LEVEL DIFLUENCE AND DIVERGENCE AHEAD OF THE DEEPENING CYCLONE. FORECAST SOUNDINGS SUGGEST THAT VERY STEEP MID LEVEL LAPSE (NEARING 8C/KM) ASSOCIATED WITH THE VERY COLD TEMPS ALOFT WILL PROVIDE FOR SUFFICIENT INSTABILITY FOR EMBEDDED THUNDERSTORMS TO DEVELOP WITHIN THE TROWAL...LEADING TO LOCALLY ENHANCED SNOWFALL TOTALS. IN FACT...SEVERAL MODELS SUGGEST THAT MUCAPES OF 100-200 J/KG WILL DEVELOP WHICH MEANS WE COULD ACTUALLY SEE UPRIGHT CONVECTION DEVELOP. MODELS IN GOOD AGREEMENT ON THE TRACK OF THE 700MB LOW...WHICH POINTS TOWARD THE HEAVIEST BAND OF SNOW LINING UP FROM SOUTHWESTERN CWA NORTHEAST TO CHICAGO OR THE SOUTHERN SUBURBS. HAVING SAID THAT...THE CONVECTIVE POTENTIAL TONIGHT REALLY THROWS A WRENCH INTO PIN-POINTING THE EXACT LOCATION OF WHERE THE HEAVIEST SNOW BAND WILL END UP SETTING UP. IN FACT...SNOWFALL TOTALS WILL LIKELY BE QUITE VARIABLE GIVEN NOT ONLY THE CONVECTIVE POTENTIAL BUT THE INHERENT DIFFICULTY IN MEASURING SEVERELY DRIFTED SNOWFALL. QUITE POSSIBLE THAT THE BLOW-ABILITY OF THE SNOWFALL MAY BE SOMEWHAT LIMITED BY HOW HEAVY/WET IT WILL BE...BUT TOO HARD TO SAY AND WITH VSBYS FROM WIND WHIPPED FALLING SNOW LIKELY TO BE SEVERELY REDUCED BLIZZARD WARNING LOOKS RIGHT ON TARGET. WITH 500MB/700MB LOW FORECAST TO TRACK FROM NEAR UIN TO AROUND GYY AM QUITE CONCERNED THAT MID LEVEL DRY INTRUSION COULD RAP INTO THE SOUTHEASTERN 1/3 TO 1/2 OF THE CWA...CUTTING SNOWFALL OFF BY OVERNIGHT TONIGHT WITH A CHANGE TO SLEET POSSIBLE BEFORE FLOPPING OVER TO FREEZING DRIZZLE. THIS IS GOING TO HAVE TO BE MORE OF A NOWCAST ISSUE AND ONLY CHANGE TO GOING FORECAST WAS TO INTRODUCE SLEET INTO THE GRIDS LATE TONIGHT FAR SOUTHERN COUNTIES. FINALLY...HAVE UPGRADED TO A LAKESHORE FLOOD WARNING FOR ILLINOIS LAKE SHORE COUNTIES. INTENSE NORTHEAST WINDS WILL RESULT IN WAVES BUILDING TO 14-18FT WITH OCCASIONAL WAVES UP TO 25FT. THIS VERY LARGE WAVES ARE EXPECTED TO BATTER/BEAT/SHRED ANY PANCAKE ICE THAT IS ALONG THE SHORE AND ALLOW THE VERY LARGE WAVES TO RESULT IN COASTAL FLOODING. LAKE WATER LEVELS ARE RUNNING 6-12 INCHES BELOW AVERAGE...HOWEVER WITH 15FT+ WAVES THIS SHOULD BE OF LITTLE CONSEQUENCE. IN ADDITION TO COASTAL FLOODING...THE INTENSE WINDS WILL RESULT IN HEAVY FREEZING SPRAY RIGHT NEAR THE LAKE COATING EVERYTHING WITH A LAYER OF ICE. Link to comment Share on other sites More sharing options...
snowstormcanuck Posted February 1, 2011 Share Posted February 1, 2011 Negative. This thing will likely occlude than stall--similar to the Northern Plains bomb before tracking eastward. lol, when then that's good news. Not really seeing it in the models though. They seem to blasting their precip fields east quickly. But I suppose that's a byproduct of them not handling the development of low pressure system itself very well. Link to comment Share on other sites More sharing options...
goknights Posted February 1, 2011 Share Posted February 1, 2011 Just looked at the hrrr man it seems to push the precip north in hurry today. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 1, 2011 Share Posted February 1, 2011 lol, when then that's good news. Not really seeing it in the models though. They seem to blasting their precip fields east quickly. But I suppose that's a byproduct of them not handling the development of low pressure system itself very well. NCEP guidance is in epic fail mode, yes. Hopefully 12Z will catch on--doubt they will tho. RGEM is doing pretty decent as is high res WRF guidance. As you have been reading don't bother with the NCEP guidance and what they show. DVN laid it out nice in their disco. Link to comment Share on other sites More sharing options...
A-L-E-K Posted February 1, 2011 Share Posted February 1, 2011 I've been reading this a lot from members. To me it seems if the low occludes faster it'll promote a transfer to the coast faster, thus reducing the duration of deformation zone precipitation over an area. It will be hard to transfer too fast from that far west of the coast me thinks. Just hoping i can avoid the dryslot that LOT hints at. I think i'm safe but who knows Link to comment Share on other sites More sharing options...
MJO812 Posted February 1, 2011 Share Posted February 1, 2011 Hey guys, good luck with this monster storm. It should be really fun for a lot of places. Does anyone have any webcam sites?. Thanks a lot and enjoy. I found 1 but I want to see how other places are doing. http://www.cubworld.com/category/a_cubworld_cam/ Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 1, 2011 Share Posted February 1, 2011 not that I'm worried yet about the dry slot here but this thing would have to start moving a bit more east at this point or it would come close to here.. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 1, 2011 Share Posted February 1, 2011 Repasting the disco from DVN because it is too epic. They said it better than I. AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL704 AM CST TUE FEB 1 2011.UPDATE... VERIFICATION AT 12Z INDICATES STORM SYSTEM IS RAPIDLY INTENSIFYING AT A RATE AS FAST OR FASTER THAN PROJECTIONS. COMPARING DATA...PLUS USING NUMEROUS TECHNIQUES SUGGESTS THE SYSTEM MAY NOT ONLY BE STRONGER...BUT COULD OCCLUDE OR WRAP UP MORE THAN PLANNED BACK TOWARD OUR AREA. IF THIS OCCURS...THIS COULD RESULT IN EVEN HIGHERSNOW TOTALS...SNOW-FALL RATES AND POSSIBLE THUNDER-SNOW OVER ATLEAST THE SOUTHEAST PORTIONS OF THE AREA. IT ALSO MAY RESULT INSLIGHTLY HIGHER WIND SPEEDS FOR MORE SEVERE BLIZZARD CONDITIONS.THIS RISK SHOULD BE CONFIRMED IN THE NEXT 3 TO 6 HOURS.NO CHANGES ARE PLANNED...BUT INDICATIONS CLEARLY SUPPORT THIS WILLNOT ONLY BE A MAJOR STORM OF NEAR HISTORIC PROPORTIONS...BUT MAYBE A BIT STRONGER FOR AT LEAST OUR SE 1/2 LOCATIONS THAN IS CURRENTLYFORECASTED.INDIVIDUALS SHOULD MONITOR THIS SITUATION FOR POSSIBLE UPDATES ONTHIS POTENTIALLY DANGEROUS SITUATION. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted February 1, 2011 Share Posted February 1, 2011 So an earlier occluding low could cause colder temperatures to wrap around in the lower Ohio Valley, maybe leading to less freezing rain but more snow? Link to comment Share on other sites More sharing options...
A-L-E-K Posted February 1, 2011 Share Posted February 1, 2011 not that I'm worried yet about the dry slot here but this thing would have to start moving a bit more east at this point or it would come close to here.. I think the dryslut will be making an appearance in LOTs area, just hope we can keep it south of I88. latest hi-res arw and nmm drop close to 2" here. Link to comment Share on other sites More sharing options...
goknights Posted February 1, 2011 Share Posted February 1, 2011 Intial look at NAM says it is still too weak. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 1, 2011 Share Posted February 1, 2011 If anyone wants an idea of what to expect HRRR is actually pretty close. It has been doing quite well this storm. Link to comment Share on other sites More sharing options...
snowstormcanuck Posted February 1, 2011 Share Posted February 1, 2011 It will be hard to transfer too fast from that far west of the coast me thinks. Just hoping i can avoid the dryslot that LOT hints at. I think i'm safe but who knows I would have thought so too but the sfc low kind of has the E-W enlongated look to it, like it's on a conveyor belt. RGEM which is apparently handling the system best has a 995 just SE of SPI at 6z Wed. 24 hours later it's off the coast of the Canadian Maritimes. Seems a little different then the octobomb situation where the low just sat and spun. But I'll take b_i's word over the RGEM. Link to comment Share on other sites More sharing options...
A-L-E-K Posted February 1, 2011 Share Posted February 1, 2011 If anyone wants an idea of what to expect HRRR is actually pretty close. It has been doing quite well this storm. how far up into northern illinois you think the dryslot gets, i80, i88? Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 1, 2011 Share Posted February 1, 2011 If anyone wants an idea of what to expect HRRR is actually pretty close. It has been doing quite well this storm. you think the dry slot will stay south of I-88 here? keep Alek, Chi storm, and myself in check lol Link to comment Share on other sites More sharing options...
MadTown Posted February 1, 2011 Share Posted February 1, 2011 lake effect snow shower in oregon wi....seriously didn'tthink i woulod EVER say that Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 1, 2011 Share Posted February 1, 2011 I would have thought so too but the sfc low kind of has the E-W enlongated look to it, like it's on a conveyor belt. RGEM which is apparently handling the system best has a 995 just SE of SPI at 6z Wed. 24 hours later it's off the coast of the Canadian Maritimes. Seems a little different then the octobomb situation where the low just sat and spun. But I'll take b_i's word over the RGEM. I meant the northern plains blizzard--not octobomb. My mistake on wording. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 1, 2011 Share Posted February 1, 2011 how far up into northern illinois you think the dryslot gets, i80, i88? haha and we both ask him at the same time Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 1, 2011 Share Posted February 1, 2011 you think the dry slot will stay south of I-88 here? keep Alek, Chi storm, and myself in check lol FOr now yeah--I don't think it will get that far--but I am going to keep an eye on HRRR. It is catching on to trends nicely. Link to comment Share on other sites More sharing options...
River Card Posted February 1, 2011 Share Posted February 1, 2011 First time ever Chicago and St Louis in a blizzard warning at the same time? It is indeed the very first blizzard warning ever issued for the STL metropolitan area. Definently one for the record books. The snow totals were upped in STL to 14-19 inches. Incredible storm, the low has dipped to under 1000mb as well. One for the record books. Link to comment Share on other sites More sharing options...
A-L-E-K Posted February 1, 2011 Share Posted February 1, 2011 haha and we both ask him at the same time it's the million dollar quesiton, you have to gamble with the slots to get the big payoff. Link to comment Share on other sites More sharing options...
snowstormcanuck Posted February 1, 2011 Share Posted February 1, 2011 I meant the northern plains blizzard--not octobomb. My mistake on wording. Well, either or. It seems like this is a bit different due to its speed, at least going by what the RGEM depicts verbatim. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 1, 2011 Share Posted February 1, 2011 NAM 12Z through 6 hours is an improvement but still too weak. Link to comment Share on other sites More sharing options...
snowstormcanuck Posted February 1, 2011 Share Posted February 1, 2011 Man has the NCEP site been slow lately. Wanna attribute it to weenie indulgence but I think it was happening before this storm even popped up on our radar screens. Link to comment Share on other sites More sharing options...
csnavywx Posted February 1, 2011 Share Posted February 1, 2011 I know I've been ragging on the NAM pretty hard here, but I don't think NWP was truly meant/expected to handle situations like this (recall the last two that did this). They certainly hinted pretty well, but the 1-in-50 year beast is typically something that will run away from NWP since our parameterizations are certainly "breakable" at this level. Having said that, some of the meso-guidance is doing a pretty bang-up job so far. Link to comment Share on other sites More sharing options...
Northern_IN_Wx Posted February 1, 2011 Share Posted February 1, 2011 I'm sticking with my 8-10" of heavy snow IMBY...maybe 1-2" out of the weakening deformation band tomorrow. And I fully agree with all of Baroclinic's comments and think the dry slot easily makes it this far north. Chicago is going to get absolutely crushed. Enjoy! Link to comment Share on other sites More sharing options...
A-L-E-K Posted February 1, 2011 Share Posted February 1, 2011 FOr now yeah--I don't think it will get that far--but I am going to keep an eye on HRRR. It is catching on to trends nicely. Nice to hear, sounds like that door is still open but any stay should be prolonged and the pre dry slot hit will be intense. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 1, 2011 Share Posted February 1, 2011 HPC 12Z surface analysis has it down to 998. http://www.hpc.ncep.noaa.gov/sfc/lrgnamsfcwbg.gif Link to comment Share on other sites More sharing options...
A-L-E-K Posted February 1, 2011 Share Posted February 1, 2011 looks like our low is tanking out already. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 1, 2011 Share Posted February 1, 2011 I know I've been ragging on the NAM pretty hard here, but I don't think NWP was truly meant/expected to handle situations like this (recall the last two that did this). They certainly hinted pretty well, but the 1-in-50 year beast is typically something that will run away from NWP since our parameterizations are certainly "breakable" at this level. Having said that, some of the meso-guidance is doing a pretty bang-up job so far. Glad we didn't budge when we saw the cruddy 0Z stuff. I knew this had potential to go positive feedback bust with the convective driven pressure falls and extreme jet coupling aloft--but even I didn't think it would bomb this fast. Link to comment Share on other sites More sharing options...
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