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February 25-27 Winter Storm Part 2


Chicago Storm

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18z NAM text for LAF with the temporary flip to snow (totaling 2.5"). 0.1% chance of happening, but I need to dream.

21 02/26 15Z   32     31      61      21    0.30  0.00    547    549    3.5 -16.5 1002 100 RA    007OVC319    0.0    1.0
24 02/26 18Z   33     32      76      16    0.28  0.00    543    542   -0.8 -18.7  999 100 -SN   008OVC273    2.5    7.6
27 02/26 21Z   34     33      74      14    0.04  0.00    541    538    0.6 -22.7  996 100 -RA   008OVC149    0.0    7.3

NAM trolling us hard. I still wouldn't be surprised if it's not a smooth transition to rain. If only it could stay a little colder...

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Tom Brown of CFTO has assured viewers that Toronto will not be getting the brunt of the storm, with us getting 13cm (5") by the end of the day Wednesday.

 

How'd he do for the Feb 8 storm again? :lol:

 

that being said, his forecast is on the low end, but not unreasonable. And the worst very well may be to our NW so I don't want to slam him too much.

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Here's some encouragement: VPZ lost 5 degrees the last hour (37 at 23z), GYY lost 4 (also 37 last hour).

 

Who knows for sure if that's just the immediate sunset bump or not, but with such a quick fall, it doesn't seem at all out of the question that we sneak below my point&click forecast low of 31.

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Please, for the love of god tell me she didn't mention lake enhancement.

 

Nope just had a map saying it's the projected snow totals. It had KW at 13cm, and there may have been a 12cm just outside of Toronto. Was making dinner and wasn't expecting the map so I didn't get a good look.

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Still concerned about rain mixing in here, though DTX is leaning towards that window as being brief. Looking at ptype maps, we look good for mostly snow, but the cobb is scary as it consistently shows a mix. Anyone know if the cobb has a warm bias?

 

AREA FORECAST DISCUSSIONNATIONAL WEATHER SERVICE DETROIT/PONTIAC MI642 PM EST MON FEB 25 2013.AVIATION...//DISCUSSION...DRY AND STABLE CONDITIONS WILL EXIST ACROSS SOUTHEAST MICHIGANTHROUGH TUESDAY MORNING ENSURING SKIES REMAIN CLEAR BELOW 10K FT.HIGHER CLOUD COVER WILL THICKEN/LOWER THROUGH THIS TIME IN ADVANCEOF A LOW PRESSURE SYSTEM LIFTING OUT OF THE PLAINS.  A DEEP PLUME OFMOISTURE ASSOCIATED WITH THIS SYSTEM WILL SPREAD NORTHWARD ACROSSTHE REGION 20-23Z LATE TUESDAY.  THIS WILL LEAD TO A RAPIDDETERIORATION OF CONDITIONS TO IFR/LIFR IN ACCUMULATING SNOWFALLDURING THAT TIME.  SNOWFALL WILL CONTINUE THROUGH THE EVENING ANDOVERNIGHT HOURS AS THE LOW SLOWLY LIFTS ACROSS THE NORTHERN OHIOVALLEY.  EASTERLY WINDS EMERGING THIS EVENING IN THE WAKE OFDEPARTING HIGH PRESSURE WILL STRENGTHEN ON TUESDAY.  A SLIGHT MIXINGCOMPONENT WILL YIELD SOME 20-25 KNOT GUSTS DURING THE DAY.FOR DTW...PRECIPITATION ARRIVES 20-21Z TUESDAY AFTERNOON.  WINDOWFOR RAIN CONTINUES TO LOOK VERY BRIEF WITH THE INCREASINGPRECIPITATION INTENSITY ENSURING A RAPID CHANGEOVER TO ALL SNOW.A BURST OF MODERATE TO HEAVY WET SNOWFALL WILL TARGET THE EVENINGHOURS...BRINGING A PERIOD OF LIFR AND A QUICK ACCUMULATION OFSEVERAL INCHES DURING THAT TIME. SNOWFALL WILL PERSIST INTOTUESDAY NIGHT...WITH ADDITIONAL ACCUMULATION EXPECTED.//DTW THRESHOLD THREATS...* HIGH CONFIDENCE IN CEILINGS DROPPING BELOW 5000 FEET LATE TUESDAYAFTERNOON.* HIGH CONFIDENCE IN PRECIPITATION TYPE AS SNOW TUESDAY EVENING ANDOVERNIGHT.* MEDIUM CONFIDENCE IN VISIBILITY DROPPING BELOW 1/2SM AT TIMES INSNOW TUESDAY EVENING.&&.PREV DISCUSSION...ISSUED 425 PM EST MON FEB 25 2013SHORT TERM...TONIGHTBIGGEST CHALLENGE IS FORECASTING THE TEMPERATURE DROP EARLY THISEVENING BEFORE HIGH CLOUDS AND LOW LEVEL EASTERLY WINDS BEGIN TORAMP OVERNIGHT. TEMPERATURES THIS AFTERNOON WERE ABLE TO TOP OUTAROUND 40 DEGREES WITH THE LATE FEBRUARY INSOLATION. CURRENT DEW PTSARE HOVERING IN THE LOWER 20S (PROVIDING A NICE BASELINE)...ANDLOOKING AT UPPER TEENS TO MID 20S...WITHIN A COUPLE DEGREES OFLATEST GUIDANCE (MET/MAV/ECM).LONG TERM...TUESDAY THROUGH NEXT SUNDAYTHE DYNAMIC UPPER LEVEL LOW PRESSURE SYSTEM OVER CENTRAL TEXASBOTTOMED INTO THE SUBTROPICAL JET AXIS THIS AFTERNOON. SATELLITEIMAGERY ALONG WITH MODEL DATA SUPPORTS LIFTING THIS ANOMALYNORTHEASTWARD DURING THE NEXT 48 HOURS BEFORE STALLING OUT OVERPORTIONS OF PA/NY/NJ WEDNESDAY EVENING. THE STORM TERM PORTION OFTHE DISCUSSION CENTERS ON THE POTENTIAL WINTER STORM SET TO AFFECTSOUTHEASTERN MICHIGAN LATE TUESDAY AFTERNOON THROUGH WEDNESDAYMORNING.TUESDAY AFTERNOON. A LEAD SPIRAL OF 500MB CYCLONIC VORTICITY ISSHOWN TO LIFT INTO PORTIONS OF FAR SOUTHEASTERN MICHIGAN PRIOR TO18Z TUESDAY. THIS IS A GOOD INDICATOR THAT OPAQUE MID CLOUD WILL BEBLANKETING A GOOD PORTION OF THE CWA BY THE AFTERNOON. IMPORTANT ASIT SHOULD LIMIT THE DIURNAL TEMPERATURE HEATING RESPONSE UNDER THECANOPY AS MAXT OCCUR AHEAD OF THE MIDCLOUDS. THIS IS NON-TRIVIALWITH SURFACE TEMPERATURES TODAY PUSHING 40 DEGREES. THE MAIN BAND OFPRECIPITATION IS EXPECTED TO LIFT ACROSS THE OH/MI STATELINEAT/AROUND 21Z TUESDAY. THIS PRECIPITATION WILL BE FORCED ON THEMIDLEVEL OCCLUDED FRONT LIFTING NORTHWARD AWAY FROM THEMAIN/CONSOLIDATED PV ANOMALY OVER PORTIONS OF SOUTHERN IN/KY (00ZWEDNESDAY). VIRTUALLY ALL MODEL SOUNDINGS SUPPORT MEANINGFULPRECIPITATION AS SNOW FROM THE START. ANY WARM LAYER CENTERED OFFTHE DECK BETWEEN 900-800MB SHOULD RAPIDLY WET BULB DOWN TO THEFREEZING MARK. VARIOUS ALGORITHM TYPE PARAMETERS...INCLUDING MOS ANDSOME OTHERS ARE REALLY STRUGGLING WITH PTYPE DUE TO WARM SFCTEMPS...33-35 DEGREES F. THESE TOOLS SEEM TO BE KEYING OFF SOMEINNOCUOUS WARM LAYERS ALL OF WHICH WILL BE COOLER THAN 3C. LOOKINGTHROUGH THE MODELS IT IS REALLY DIFFICULT TO GET A HANDLE WHERE THEMID 30 DEGREES SURFACE TEMPS ARE COMING FROM AFTER THE START OFPRECIPITATION. DEWPOINTS THIS AFTERNOON FROM WV/PA THROUGH OHIO ANDONTARIO ARE ALL IN THE TEENS TO 20S...A POSITIVE FOR THE ALL SNOWPTYPE. THE BAND WILL LIFT NORTHWARD...DETROIT SOUTHWARD AFTER 2PMEST...NORTHERN BURBS...AFTER 4PM EST...FLINT AND THE TRI CITIESAFTER 6PM.THE MAIN POTENTIAL VORTICITY ANOMALY RESPONSIBLE FOR THIS SYSTEMWILL HAVE CLOSED OFF INTO A BOWLING BALL OVER ARKANSAS BY 12TUESDAY. OUTSIDE OF A LOBE/OR PV FILAMENT ROTATING AROUND THENORTHEAST PERIMETER OF THE ANOMALY BETWEEN 12-15Z...THE SYSTEMWILL BE IN A FILLING MODE. THE AFOREMENTIONED OCCLUSION EMANATINGNORTHEASTWARD WILL BRING GOOD PRECIPITATION RATES IN DURING THELATE AFTERNOON. GIVEN THE SYSTEM IN A MATURE STATE...MOISTUREDEPTH ALONG THIS MAIN BAND WILL BE OUTSTANDING...UPWARDS OF 30 KFTAGL...WITH LOW STATIC STABILITY ABOVE 700MB. SYSTEM RELATIVEISENTROPIC ASCENT WILL BE CENTERED AT ROUGHLY THE 285K SURFACEDURING THE AFTERNOON BEFORE LOWERING DOWN TO AROUND 300K DURINGTHE EVENING. SPECIFIC HUMIDITIES MOISTURE WILL BE APPROXIMATELY 4G/KG SHOWN THROUGHOUT THE COLUMN. PROGGED UVVS ARE SHOWN TO BEHIGH AND WITH EVERYTHING CONSIDERED...1 INCH PER HOUR TYPE SNOWRATES ARE EXPECTED AT THE ONSET. THE REAL QUESTION ANDUNCERTAINTY WILL BE WHAT SORT OF SNOW ACCUMULATING EFFICIENCYWILL BE EXPERIENCED WITH THE SNOWFALL RATES DURING THE LATEAFTERNOON/EVENING. OVERALL DURATION FOR ANY ONE AREA WILL BEROUGHLY 3 TO 4 HOURS. THE CURRENT THINKING IS THAT 1 INCH PER HOURRATES WILL ALLOW THE SNOW TO ACCUMULATE ON THE ROADS. SNOWFALLACCUMULATIONS DURING THE EVENING WITHIN THE BAND ARE EXPECTED TOBE IN THE 2 TO 4 INCH RANGE.ANOTHER MAIN QUESTION MARK MOVING FORWARD IS WHAT SORT OFSECONDARY TROWAL/ISENTROPIC LIFT RESPONSE OCCURS AS THE CLOSED LOWCIRCULATION LIFTS UP AND BRUSHES FAR WESTERN LAKE ERIE 06-12ZWEDNESDAY. THIS IS INTERESTING AS FRONTAL AND UVV FORCING FROM ACONCEPTUAL MODEL STANDPOINT SHOULD AGAIN BECOME MAXIMIZED. THE NWPIS REALLY STRUGGLING WITH THIS. HOWEVER...THERE ARE SIGNS THATTHIS FORCING COULD CAUSE A CONSIDERABLE ATMOSPHERIC RESPONSE. FOREXAMPLE..MODEL SOLUTIONS ARE SHOWING THE DRY SLOT THAT WILL FOLLOWTHE OCCLUDED FRONT TO BEGIN FILLING IN WITH SATURATION.ADDITIONALLY...ECMWF AND NAM ARE BOTH SHOWING QPF BULLSEYES LATE(ECMWF OVER PORTIONS OF NORTHERN OHIO AND THE NAM OVER PORTIONS OFTHE FAR EASTERN CWA OVER ST CLAIR COUNTY/LAKE ST CLAIR).CONFIDENCE REMAINS LOW AT THIS TIME...REGARDING THIS SECONDARYRESPONSE...BUT IF IT WERE TO OCCUR IT WOULD AFFECT PORTIONS OF THEFAR EASTERN CWA. THIS ADDITIONAL 1 TO 3 INCHES COULD PUSH AMOUNTSOVER 6 INCHES. THEREFORE...THE WINTER STORM WATCH WILL BE ALLOWEDTO CONTINUE FOR THE POTENTIAL OF GREATER THAN 6 INCH AMOUNTS.FARTHER NORTH OVER THE SAGINAW VALLEY...PRECIPITATION OCCURRENCE OUTSIDEOF EVENING COMMUTE AND AMOUNTS IN THE 3 TO 5 INCH RANGE FELTPRUDENT TO UPGRADE TO ADVISORY.THE TRANSFER OF ENERGY TO THE EAST COAST WILL PROCEED WEDNESDAYAFTERNOON INTO WEDNESDAY NIGHT RESULTING IN MODEST COASTALCYCLOGENESIS AND A CONTINUED WEAKENING TREND IN LARGE SCALE FORCINGOVER LOWER MICHIGAN. THAT IS A WEAKENING TREND BUT NOT A DISSIPATINGTREND IN SUPPORT FOR SNOW AS THE RESIDUAL MID LEVEL TROWAL ISEXPECTED TO BE PULLED BACK OVER SE MICHIGAN AS THE SYSTEM MOVESAWAY. THAT WILL BRING WEAK SYSTEM RELATIVE ISENTROPIC LIFT BACK INTOPLAY TO AUGMENT DEEP AND STRONGLY CYCLONIC FLOW ON THE WESTERN FLANKOF THE LOW. A GOOD ATLANTIC MOISTURE CONNECTION WILL ALSO REMAININTACT AND FEED SPECIFIC HUMIDITY OF 2-3 G/KG INTO THE REMNANTS OFTHE TROWAL OVER OUR AREA. THAT BEING THE CASE, THERE IS SUPPORT FORTHE INHERITED HIGH POP/LOW ACCUMULATION FORECAST WEDNESDAY AFTERNOONTHROUGH SUNRISE THURSDAY AND LEAN AWAY FROM THE HIGHER QPF NAMSOLUTION. THE MAIN REASON FOR THAT HAS TO DO WITH THE NAMPOSITIONING THE CENTER OF THE UPPER LOW TOO FAR WEST BY WEDNESDAYEVENING CONSIDERING THE ANTICIPATED EAST COAST TRANSITION. MODELCROSS SECTIONS INDICATE THE FARTHER WEST SOLUTION LEAVES THE DOOROPEN FOR LOW STATIC STABILITY PLACED TOO FAR WEST IN THE MID ANDUPPER LEVELS WHICH IS LIKELY LEADING TO FALSELY ENHANCED VERTICALMOTION AND QPF NEARLY A FACTOR OF 2 HIGHER THAN THE OTHER MODELS.THIS WILL BE ESPECIALLY TRUE CONSIDERING LITTLE TO NO LAKEENHANCEMENT DUE TO ICE COVER OVER THE SOUTH THIRD OF LAKE HURON ANDLOW INSTABILITY OVER THE REST OF THE OPEN WATERS. FOR NOW, PREFER TOMAINTAIN THE LIKELY POP AND INCLUDE A SMALL UPWARD ADJUSTMENT TOSNOW ACCUM UNTIL MORE EVIDENCE MATERIALIZES FOR THE FARTHER WESTPOSITION OF THE UPPER LOW.
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Hmmm...that does look to be a least a little south of where the models had it. You always want to not put on the weenie goggles and overreact to something like that but it will be interesting to watch through the evening.

 

Most models have the sfc low going through the MO bootheel. It'll have to be a sharp left turn for that to verify.

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Hmmm...that does look to be a least a little south of where the models had it. You always want to not put on the weenie goggles and overreact to something like that but it will be interesting to watch through the evening.

 

:weenie:

 

One of my friends just texted me and said that she heard we were getting 5" of snow tomorrow. I lol'ed back. Has Chad gone screwy, and calling for more wintry weather?

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