Hoosier Posted February 7, 2012 Share Posted February 7, 2012 My main focus is the southern end of Lake Michigan since I'm most familiar with that area but other areas feel free to join in. Models have been showing a decent shot of cold air this weekend which will lead to the development of lake effect snow. The devil is in the details and we're still a ways out but an early look at this event suggests the potential for significant accumulations. Recent runs of the GFS/Euro are suggesting 850 mb temps approaching -20C at the southern end of the lake which would put delta T values into the 20-23C range. At this time, the long axis fetch and high instability looks favorable for a healthy Jacques de Plume to develop and impact the southern and possibly western shore Friday into Saturday. Steering flow looks like it may shift around which would suggest a transient nature to the band but that is obviously getting way ahead. Link to comment Share on other sites More sharing options...
heavy_wx Posted February 7, 2012 Share Posted February 7, 2012 It looks like there may be a fairly intense band forming sometime Friday evening and lasting into the morning, as a shortwave brings in some synoptic moisture and deepens the moist layer up to around 725 mb according to the 12z GFS bufkit for KSBN. The 850 mb winds do suggest a band oscillating around a general nnw flow. The band will probably continue and weaken into the afternoon on Saturday as the ridge approaches from the west. Areas in north central Indiana and southwest Michigan could get some decent snowfall out of this, especially Friday evening into Saturday morning. Link to comment Share on other sites More sharing options...
Hoosier Posted February 7, 2012 Author Share Posted February 7, 2012 It looks like there may be a fairly intense band forming sometime Friday evening and lasting into the morning, as a shortwave brings in some synoptic moisture and deepens the moist layer up to around 725 mb according to the 12z GFS bufkit for KSBN. The 850 mb winds do suggest a band oscillating around a general nnw flow. The band will probably continue and weaken into the afternoon on Saturday as the ridge approaches from the west. Areas in north central Indiana and southwest Michigan could get some decent snowfall out of this, especially Friday evening into Saturday morning. You think it sets up that far east? This looks like more of a NW IN event to me. Link to comment Share on other sites More sharing options...
Geos Posted February 7, 2012 Share Posted February 7, 2012 I looked at some of the wind flow trajectories and it seemed this could brush the western shoreline. Skilling mentioned it this morning. I think Gary would be in line for some good lake snows. Link to comment Share on other sites More sharing options...
heavy_wx Posted February 7, 2012 Share Posted February 7, 2012 You think it sets up that far east? This looks like more of a NW IN event to me. I think it will be a bit further east initially since the 850 mb shortwave looks like it will be oriented nnw. More northerly flow will probably occur later on during early Saturday morning, which would move the band into northwest Indiana. It all depends on the exact orientation of the shortwave. Link to comment Share on other sites More sharing options...
ValpoVike Posted February 7, 2012 Share Posted February 7, 2012 The way it looks now, it would appear to be a good setup for LaPorte and Porter counties in NW Indiana late Friday thru Sat morning. However 3 days out is an eternity especially for a south end of lake, long fetch event. It doesn't take much of a change in wind profiles to shift LES east at this end of the lake. Link to comment Share on other sites More sharing options...
Hoosier Posted February 8, 2012 Author Share Posted February 8, 2012 00z NAM would favor NW IN and the western shore of IL and southeast WI. Flow weakens with time which could complicate things. Better to wait until the higher res models come into range. Link to comment Share on other sites More sharing options...
KeenerWx Posted February 8, 2012 Share Posted February 8, 2012 00z NAM would favor NW IN and the western shore of IL and southeast WI. Flow weakens with time which could complicate things. Better to wait until the higher res models come into range. If this continues to look promising for NW Indiana, I may have to do a little LES chasing. This winter has been pretty dull, and it would be nice to have some reconciliation. Link to comment Share on other sites More sharing options...
Geos Posted February 8, 2012 Share Posted February 8, 2012 00z NAM would favor NW IN and the western shore of IL and southeast WI. Flow weakens with time which could complicate things. Better to wait until the higher res models come into range. 0z GFS is hinting at that solution as well! Link to comment Share on other sites More sharing options...
Thunder Road Posted February 8, 2012 Share Posted February 8, 2012 The Euro looks like it drives a band into Chicago then rotates it east. What's really nice is 12z Sat when there's a subtle convergence line that basically follows the Lake/Porter line from the lake down to almost Rensselaer. I would call it a classic set-up, except for the fact that I've never experienced a classic LES set-up before... Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 8, 2012 Share Posted February 8, 2012 LOT BESIDES THE COLD...THE REAL FORECAST CONCERN IN THE FRIDAY-SATURDAY PERIOD IS THE POTENTIAL FOR LAKE EFFECT SNOW INTO NORTHEAST IL AND NORTHWEST INDIANA. LAKE SURFACE TO 850 HPA DELTAS INCREASE INTO THE LOW 20S LATE FRIDAY THROUGH SATURDAY MORNING...DURING A PERIOD IN WHICH THE LOW LEVEL WINDS WILL BE NORTH-NORTHEAST DOWN THE FULL FETCH OF THE LAKE. FORECAST SOUNDINGS INDICATE EQUILIBRIUM LEVELS RISING TO NEAR 9000 FT BY 12Z SATURDAY...WITH LAKE INDUCED CAPES OF 400-500 J/KG. THIS WOULD SUGGEST THE POTENTIAL FOR SOME SIGNIFICANT ACCUMULATING LAKE EFFECT FROM FRIDAY AFTERNOON THROUGH SATURDAY MORNING. ONLY LIMITING FACTOR WOULD BE THE VERY DRY ARCTIC AIR SPREADING ACROSS THE WESTERN LAKES...THOUGH THE LONG FETCH WILL LIKELY PROVIDE ENOUGH MOISTURE FLUX TO MAKE UP FOR THE DRYNESS OF THE AIRMASS. WILL BE INTERESTING TO SEE SOME OF THE HIGH RESOLUTION GUIDANCE AS THE FRIDAY-SATURDAY PERIOD APPROACHES. FOR NOW HAVE INCREASED POPS FOR THE LAKESIDE COUNTIES...AND WILL HIGHLIGHT POTENTIAL FOR ACCUMULATING LAKE SNOWS IN THE HAZARDOUS WEATHER OUTLOOK. Link to comment Share on other sites More sharing options...
A-L-E-K Posted February 8, 2012 Share Posted February 8, 2012 potential for 3rd best snow of the year Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 8, 2012 Share Posted February 8, 2012 look at that convergence over the southern end of the lake Link to comment Share on other sites More sharing options...
Hoosier Posted February 8, 2012 Author Share Posted February 8, 2012 IWX LAKE EFFECT EVOLUTION WILL BE THE PRIMARY CONCERN FOR THE FRIDAY/SATURDAY PERIOD. A PERIOD OF FAVORABLE NORTHERLY FETCH BEHIND THIS LOW LEVEL TROUGH AXIS ON FRIDAY WILL BE ACCOMPANIED BY LAKE/850 HPA DELTA TEMPS INCREASING TO AROUND 20 DEG CELSIUS BY FRIDAY EVENING. A LOW LEVEL THERMAL TROUGH WILL LIKELY DEVELOP IN RESPONSE TO THIS COLD AIR ENHANCING MID LAKE CONVERGENCE. GIVEN THIS EXPECTED LOW LEVEL MASS FIELD RESPONSE ALONG WITH INCREASING LAKE INDUCED INSTABILITY...MAINTAINED HIGH RANGE CHANCE POPS FOR THE FRIDAY THROUGH EARLY SATURDAY PERIOD. UNCERTAINTY AT THIS FORECAST DISTANCE WITH EXACT ORIENTATION OF STRONGEST LOW LEVEL CONVERGENCE PRECLUDES LIKELY MENTION. ALSO SOME QUESTION AS TO EXACT EVOLUTION OF SYNOPTIC WIND FIELD WITH INDICATIONS OF SLIGHTLY VEERING LOW LEVEL WINDS TO THE NORTH NORTHEAST BY LATE FRIDAY EVENING IN ASSOCIATION WITH THE PASSAGE OF A SECONDARY UPPER LEVEL VORT MAX TAKING GREATEST POTENTIAL ACROSS FAR NWRN PORTIONS OF THE AREA OR PERHAPS EVEN WEST INTO EXTREME NWRN INDIANA FOR A TIME LATE FRIDAY NIGHT/EARLY SATURDAY. LOW LEVEL WINDS EVENTUALLY TO BACK MORE NORTHWEST ON SATURDAY AS LOW LEVEL ANTICYCLONE FROM THE NORTHERN PLAINS DROPS INTO THE CENTRAL PLAINS. DRYING MID LEVELS AND LOWERING LAKE INDUCED EQUILIBRIUM HEIGHTS SHOULD SUPPORT A GRADUALLY LESSENING LAKE EFFECT THREAT INTO SATURDAY EVENING INTO SWRN LOWER MICHIGAN WHERE HAVE MAINTAINED LOWER CHANCE POPS. Link to comment Share on other sites More sharing options...
Hoosier Posted February 8, 2012 Author Share Posted February 8, 2012 Possible transient nature could cause totals to not get out of hand but at this point I see no obvious reason why the band wouldn't support rates of about 1-2" per hour. Do the math if it were to stall out. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 8, 2012 Share Posted February 8, 2012 12z LSX WRF is interesting, targets eastern/southeastern portions of Cook co. into Lake co with one single band from friday evening into saturday morning but doesn't get that far inland, alteast this run. Link to comment Share on other sites More sharing options...
McDude Posted February 8, 2012 Share Posted February 8, 2012 Skilling just showed a snowfall map through Saturday of 1-2" near the Lake. Obviously LES is more of a wait and see thing, especially around this side of the Lake. Link to comment Share on other sites More sharing options...
Geos Posted February 8, 2012 Share Posted February 8, 2012 Skilling just showed a snowfall map through Saturday of 1-2" near the Lake. Obviously LES is more of a wait and see thing, especially around this side of the Lake. I saw that as well. Nice solid band riding the full length of the lake. 6z NAM was the most promising for NE IL. Looks like the best window is Friday PM and into early Saturday morning. Link to comment Share on other sites More sharing options...
Hoosier Posted February 8, 2012 Author Share Posted February 8, 2012 A model I will be watching is the RGEM. At times it has done surprisingly well with band placement. Link to comment Share on other sites More sharing options...
Chicago Storm Posted February 8, 2012 Share Posted February 8, 2012 NAM would favor areas from up around Evanston, down through southwestern Cook Co, and Lake Co (IN). GYY Link to comment Share on other sites More sharing options...
Geos Posted February 8, 2012 Share Posted February 8, 2012 NAM would favor areas from up around Evanston, down through southwestern Cook Co, and Lake Co (IN). GYY What kind of inversion levels are we looking at? Good as the Christmas lake effect snow of 2010? Link to comment Share on other sites More sharing options...
Chicago Storm Posted February 8, 2012 Share Posted February 8, 2012 What kind of inversion levels are we looking at? Good as the Christmas lake effect snow of 2010? generally 7kft+ Link to comment Share on other sites More sharing options...
Hoosier Posted February 8, 2012 Author Share Posted February 8, 2012 NAM would favor areas from up around Evanston, down through southwestern Cook Co, and Lake Co (IN). GYY Nice omega in the DGZ Link to comment Share on other sites More sharing options...
Hoosier Posted February 8, 2012 Author Share Posted February 8, 2012 IWX afternoon updated PROGGED NORTHERLY LOW LVL TRAJECTORIES AND RAMP UP IN LAKE INDUCED INSTABILITY CONTINUE TO SUPPORT THE POTENTIAL FOR A TYPE 1 LAKE EFFECT SNOW EVENT FRIDAY NIGHT INTO SATURDAY. PERUSAL OF MODEL SOUNDINGS CONTINUE TO SHOW INVERSION HEIGHTS NEAR 750 HPA...LAKE INDUCED CAPE NEAR 500 J/KG...AND 7H DELTA T/S OF 25-27C. ALSO...NAM/GFS 925 HPA PLUME ANALYSIS SUPPORTS THE POTENTIAL FOR AN INTENSE SINGLE BAND GIVEN PREVAILING FLOW NEARLY PARALLEL TO LONG AXIS OF LAKE RESULTING IN AN AREA OF STRONG FRICTIONAL/THERMAL MID LAKE CONVERGENCE. GIVEN THIS...CONFIDENCE IS INCREASING IN AT LEAST A MODERATE LES EVENT WITH STILL SOME DIFFERENCES WRT MOISTURE AND LOW LVL TRAJECTORIES. AREAS IN OUR FA THAT COULD BE IMPACTED BY THIS SINGLE BAND AND POSSIBLE INTENSE RATES APPEARS TO BE MAINLY WEST OF HIGHWAY 31...ACROSS WESTERN LAPORTE/STARKE AND FAR SOUTHWESTERN BERRIEN COUNTIES. IT IS WORTH NOTING THAT SOME GUIDANCE VEERS BOUNDARY LAYER WINDS MORE NORTHEASTERLY FOR A TIME AS LOW LVL RIDGING TRIES TO EDGE EWD INTO THE GREAT LAKES. THIS WOULD KEEP BETTER CHANCES FOR MORE SIGNIFICANT SNOWFALL AMOUNTS JUST WEST OF THE FA INTO LAKE/PORTER COUNTIES IN NW INDIANA. BACKING WINDS AND CRASHING INVERSION HEIGHTS WILL ALLOW THIS BAND TO SHIFT EWD AND FALL APART SATURDAY AFTN INTO SATURDAY EVENING WITH ONLY MINOR ACCUMS ANTICIPATED DURING THIS TIME. Link to comment Share on other sites More sharing options...
Hoosier Posted February 8, 2012 Author Share Posted February 8, 2012 If things don't change much, I'm thinking we may see a lake effect snow watch by tomorrow, at least for Lake and Porter counties. Link to comment Share on other sites More sharing options...
Geos Posted February 8, 2012 Share Posted February 8, 2012 IWX afternoon updated PROGGED NORTHERLY LOW LVL TRAJECTORIES AND RAMP UP IN LAKE INDUCED INSTABILITY CONTINUE TO SUPPORT THE POTENTIAL FOR A TYPE 1 LAKE EFFECT SNOW EVENT FRIDAY NIGHT INTO SATURDAY. PERUSAL OF MODEL SOUNDINGS CONTINUE TO SHOW INVERSION HEIGHTS NEAR 750 HPA...LAKE INDUCED CAPE NEAR 500 J/KG...AND 7H DELTA T/S OF 25-27C. ALSO...NAM/GFS 925 HPA PLUME ANALYSIS SUPPORTS THE POTENTIAL FOR AN INTENSE SINGLE BAND GIVEN PREVAILING FLOW NEARLY PARALLEL TO LONG AXIS OF LAKE RESULTING IN AN AREA OF STRONG FRICTIONAL/THERMAL MID LAKE CONVERGENCE. GIVEN THIS...CONFIDENCE IS INCREASING IN AT LEAST A MODERATE LES EVENT WITH STILL SOME DIFFERENCES WRT MOISTURE AND LOW LVL TRAJECTORIES. AREAS IN OUR FA THAT COULD BE IMPACTED BY THIS SINGLE BAND AND POSSIBLE INTENSE RATES APPEARS TO BE MAINLY WEST OF HIGHWAY 31...ACROSS WESTERN LAPORTE/STARKE AND FAR SOUTHWESTERN BERRIEN COUNTIES. IT IS WORTH NOTING THAT SOME GUIDANCE VEERS BOUNDARY LAYER WINDS MORE NORTHEASTERLY FOR A TIME AS LOW LVL RIDGING TRIES TO EDGE EWD INTO THE GREAT LAKES. THIS WOULD KEEP BETTER CHANCES FOR MORE SIGNIFICANT SNOWFALL AMOUNTS JUST WEST OF THE FA INTO LAKE/PORTER COUNTIES IN NW INDIANA. BACKING WINDS AND CRASHING INVERSION HEIGHTS WILL ALLOW THIS BAND TO SHIFT EWD AND FALL APART SATURDAY AFTN INTO SATURDAY EVENING WITH ONLY MINOR ACCUMS ANTICIPATED DURING THIS TIME. What is type 1 lake effect? I know it can be in a single plume or in multiple bands. Link to comment Share on other sites More sharing options...
Hoosier Posted February 8, 2012 Author Share Posted February 8, 2012 What is type 1 lake effect? I know it can be in a single plume or in multiple bands. There are several types...I think I saw a paper or diagram once but I have no idea where. Link to comment Share on other sites More sharing options...
wisconsinwx Posted February 8, 2012 Share Posted February 8, 2012 It'd be nice if we could get lake effect snow of more than a dusting, but I guess it's just not happening here. We even miss out on lake effect in favor of Chicago it seems. Link to comment Share on other sites More sharing options...
Thunder Road Posted February 8, 2012 Share Posted February 8, 2012 Nice write-up in the afternoon AFD from LOT: WITH MODELS INDICATING 850HPA TEMPERATURES OF -16 TO -18C MOVINGOVER THE SOUTHERN PORTION OF LAKE MI FRIDAY EVENING...FORECAST SOUNDINGS OVER THE LAKE SUGGESTING A CLOUD DEPTH OF AROUND 1.5KM...WINDS BELOW AND THROUGH THE CLOUD BEARING LAYER TAKING ON A SLIGHT EASTERLY COMPONENT BY 00Z SAT AND A BIT MORE OVERNIGHT FRIDAY...A PLUME OF LAKE EFFECT SNOW IS LIKELY TO DEVELOP. INITIALLY THIS PLUME IS EXPECTED TO IMPACT THE AREA FROM THE NORTH SIDE OF CHICAGO SOUTH TO FAR EASTERN WILL CO AND E ACROSS LAKE AND NORTHWESTERN PORTER COUNTIES OF NORTHWEST IN DURING FRIDAY AFTERNOON AND THEN SHIFT MARGINALLY WESTWARD DUE TO THE ABOVE MENTIONED ADDITIONAL VEERING OF THE LOW LEVEL FLOW. THIS WOULD BRING THE THREAT OF LAKE EFFECT SNOWS WESTWARD TO THE LAKESHORE OF LAKE AND NORTHERN COOK COUNTIES...AND SOUTHWARD ALONG/NEAR THE STATE LINE DOWN TO THE KANKAKEE RIVER FOR FRIDAY NIGHT. AS THE LOW LEVEL FLOW BEGINS TO BACK SATURDAY MORNING THE TAIL OF THE LAKE EFFECT PLUME IS EXPECTED TO START SHIFTING BACK EASTWARD ACROSS PORTER CO AND TO FAR SOUTHWEST LOWER MI AND NORTH CENTRAL IN BY EARLY SATURDAY AFTERNOON. DUE TO A SOMEWHAT PROLONGED PERIOD OFF LAKE EFFECT...THE CITY OF CHICAGO COULD SEE SNOWFALL AMOUNTS FROM UP TO 1 INCH NORTH SIDE TO 3 TO 4 INCHES FAR SOUTHEAST SIDE...WITH NORTHERN LAKE AND NORTHWEST PORTER COUNTIES POTENTIALLY SEEING 3 TO 4 INCHES. http://www.crh.noaa.gov/product.php?site=lot&product=AFD&issuedby=lot Link to comment Share on other sites More sharing options...
Hoosier Posted February 8, 2012 Author Share Posted February 8, 2012 Nice write-up in the afternoon AFD from LOT: http://www.crh.noaa....FD&issuedby=lot Too early for amounts if you ask me. Link to comment Share on other sites More sharing options...
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