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Lake Effect Snow, sub-zero temps, frozen pipes....what could be better?





AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
647 AM EST MON JAN 21 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 508 AM EST MON JAN 21 2013

00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW DEEP UPR TROF OVER E AND CENTRAL NAMERICA DOWNSTREAM OF HI AMPLITUDE RDG OFF THE W COAST. COLDEST AIRMASS OF THE SEASON HAS FLOODED INTO THE UPR LKS IN THE NW LLVL FLOW WITH H85 TEMPS AS LO AS -25C OVER THE WRN CWA. 00Z H85 TEMP WAS AS LO AS -30C AT YPL. THE PASSAGE OF THIS COLD AIRMASS OVER THE RELATIVELY WARM WATERS OF LK SUP HAS RESULTED IN NMRS LK EFFECT SHSN. BUT LLVL FLOW HAS BACKED TO MORE WNW IN ADVANCE OF NEXT SHRTWV DROPPING SEWD THRU NW ONTARIO TOWARD ISLE ROYALE. IN CONCERT WITH NEAR SFC WSW WIND ENHANCED BY LAND BREEZE FLOW OF SUB ZERO TEMPS TOWARD WARMER LK SUP...THIS WSHFT IS CONFINING THE BULK OF THE LES TO AREAS OVER THE W MAINLY N OF THE PORCUPINE MTNS THRU THE KEWEENAW AND TO AREAS NEAR LK SUP E OF PICTURED ROCKS LAKESHORE. ONE IMPACT OF THE VERY COLD AIRMASS IS THE DGZ HAS NEARLY DISAPPEARED AT LEAST OVER THE W...RESULTING IN VERY FINE SN FLAKES THAT EFFICIENTLY REDUCE THE VSBY WHILE LIMITING SN ACCUMS. SKIES ARE GENERALLY CLR-PCLDY OVER AREAS TO THE S OF THE LES...WHICH HAS ALLOWED TEMPS TO FALL BLO ZERO. THE WIND CHILL EARLY THIS MRNG HAS DROPPED AS LO AS -25F AT IWD. TO THE NW...THERE IS AN AREA OF CLDS ASSOCIATED WITH THE DIGGING SHRTWV AND FAIRLY DEEP MSTR DEPICTED ON THE 00Z YPL RAOB. THERE ARE EVEN SOME REPORTS OF -SN IN ONTARIO JUST N OF THE MN BORDER DESPITE PWATS OF 0.06 INCH REPORTED AT INL/YPL.

TODAY...AS SHRTWV/ACCOMPANYING DEEP LYR QVECTOR CNVGC/MSTR JUST TO THE NW DIG SEWD ACROSS THE CWA THIS MRNG...EXPECT LES INTENSITY TO INCRS SOMEWHAT WHILE NEAR -30C H85 TEMPS ARE DRAWN INTO WRN UPR MI. ALTHOUGH DEEPENING CONVECTIVE DEPTH/MSTR TO ABV 10K FT AS SHOWN ON FCST SDNGS WOULD NORMALLY BE A CONCERN FOR VERY HEAVY LES...NEAR ABSENCE OF DGZ WITH SUCH COLD H85 TEMPS INDICATES SN FLAKES WL BE VERY SMALL...ESPECIALLY OVER THE W WITH SHORTER FETCH/LESS MODIFICATION OF THE COLD/DRY AIRMASS. ONE ADVANTAGE FOR HEAVIER SHSN WOULD BE INCRSG LLVL CNVGC. SINCE THE LLVL FLOW WL VEER MORE TO THE NW WITH PASSAGE OF SHRTWV...EXPECT LES BANDS TO DRIFT BACK TO THE S. THIS VEERING FLOW OFF THE SFC WL LIKELY RESULT IN SHARPER LLVL CNVGC OVER THE W BTWN LAND BREEZE FLOWS OFF WI/INTERIOR WRN UPR MI AND OVER THE E WITH THESE FLOWS OFF CNTRL UPR MI AND SE ONTARIO/ERN UPR MI. GENERAL CONSENSUS OF HIER RES MODELS SHOWS THE BACK CHC FOR THE SHARPER CNVGC WL BE OVER THE W FM THE PORCUPINE MTNS TO NEAR TWIN LAKES IN CNTRL HOUGHTON COUNTY AND IN AREAS E OF MUNISING AND AS FAR S AS ABOUT HIGHWAY M-28. THESE HI RES MODELS ALL SHOW THE SHARPEST CNVGC/HIER QPF OVER THE ERN CWA...AND SOME INDICATE THE HEAVIER SHSN WL PUSH FARTHER INLAND THAN M-28. ON THE OTHER HAND...SOME OF THE MODELS INDICATE A LK INDUCED VORTEX MAY DVLP NEAR GRAND MARAIS AND LIMIT THE INLAND SPREAD OF THE SHSN. AS FOR SN AMOUNTS...OLD LES CHART INDICATES SN FALL OF 5-9 INCHES/12 HRS GIVEN EXPECTED CONDITIONS. BUT RECENT EXPERIENCE SUGS THE NEAR ABSENCE OF DGZ CUTS THESE TOTALS BY ABOUT HALF. WITH SHARPER LLVL CNVGC/MORE LK MODERATION THAT WOULD MAINTAIN HIER LLVL TEMPS MORE CONDUCIVE TO BIGGER SN FLAKES...BEST CHC TO GET THE HIER LES CHART FCST NUMBERS WOULD BE OVER THE ERN CWA. GOING LES WRNG FOR THIS AREA APPEARS ON TRACK. IF THE SN BANDS IMPACT SRN SCHOOLCRAFT COUNTY AS SOME OF THE HIER RES MODELS SHOW...AN ADVY MIGHT BE NECESSARY FOR THAT AREA. BUT GIVEN UNCERTAINTY ON THIS SCENARIO...HELD OFF FOR NOW. CURRENT WINTER WX ADVYS OVER THE W ALSO SEEM WELL PLACED. WITH H85 TEMPS FCST TO FALL AT LEAST CLOSE TO -30C THRU THE DAY...EXPECT SFC TEMPS OVER MUCH OF THE W TO REMAIN BLO ZERO. ALTHOUGH WIND CHILLS AT MOST PLACES EXCEPT FOR IWD ARE UNDER ADVY CRITERIA...ARRIVAL OF COLDER AIR/INCRSG WINDS WITH LLVL DESTABILIZATION JUSTIFIES CONTINUING ADVYS OVER THE INTERIOR W HALF EVEN IF THERE IS MORE LK MODERATION WITH VEERING LLVL FLOW. THESE WINDS WL ALSO AID BLSN/REDUCING VSBYS AND JUSTIFY HEADLINES EVEN IF SN AMOUNTS ARE SUB HEADLINE.

TNGT...WITH DNVA/LARGER SCALE SUBSIDENCE IN THE WAKE OF DEPARTING SHRTWV THAT BEGINS THIS AFTN...EXPECT CONVECTIVE LYR/MSTR DEPTH TO SLOWLY SINK. H925 WINDS ARE ALSO FCST TO VEER A BIT MORE TOWARD THE NW...SO SHSN OVER THE W MIGHT SINK TOWARD IWD. CONSIDERING THE AGREEMENT ON THE MODELS SHOWING HIER QPF OVER IWD WITH THIS VEERING FLOW...OPTED TO INCLUDE GOGEBIC COUNTY IN WINTER WX ADVY IN LIEU OF JUST THE WIND CHILL HEADLINE. ALTHOUGH H85 TEMPS FCST AS LO AS -30C OVER PORTIONS OF THE W INDICATE WELL BLO ZERO LO TEMPS...TENDED TO BUMP UP FCST MIN TEMPS A FEW DEGREES WITH MORE LK MODERATION IN VEERED FLOW. BUT STILL EXPECT WIND CHILLS AS LO AS -25F TO -35F WITH CAD MAINTAINING SOME MIXING...SO MAINTAINED GOING WIND CHILL ADVYS. SHARPEST LLVL CNVGC/SOME LK MODERATION OF ARCTIC CHILL REMAINS OVER THE E. GOING LK EFFECT SN WRNG THRU 12Z TUE IN THAT AREA LOOKS ON TRACK.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 508 AM EST MON JAN 21 2013

AT 12Z TUE...THE COLDEST 850MB TEMPS AS LOW AS -32C WILL BE OVER THE CWA...BUT WILL PUSH E THROUGH THE DAY AS THE UPPER TROUGH OVER MUCH OF THE CONUS SHIFTS SLOWLY E. WITH A SFC RIDGE PUSHING IN FROM THE SW AND A LAKE INDUCED SFC TROUGH STRETCHING INTO ERN LAKE SUPERIOR FROM THE SE...WINDS WILL BE OUT OF THE NW WITH RESULTING NW WIND LES. THESE COLD TEMPS WILL KEEP HIGHS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO...BUT WITH THE PRESSURE GRADIENT RELAXING THROUGH THE DAY...WIND CHILL HEADLINES WILL NOT BE NEEDED AFTER THE MORNING OURS TUE.

TUE NIGHT WILL BE QUITE COLD WITH LOWS TO -2 OVER MUCH OF INTERIOR WRN UPPER MI...BUT WINDS WILL BE LIGHT SO AT THIS POINT WIND CHILL HEADLINES DO NOT APPEAR TO BE NECESSARY. A SHORTWAVE TROUGH WILL APPROACH THE CWA WED NIGHT AND MOVE THROUGH ON WED...BUT ANY SYNOPTIC PRECIP WILL REMAIN OUT OF THE CWA. THE SHORTWAVE WILL ACT TO ENHANCE THE SFC TROUGHING OVER LAKE SUPERIOR /POSSIBLY INTO A WEAK LOW OVER THE ERN LAKE/...WHICH MODELS INDICATE WOULD CAUSE LOW LEVEL WINDS TO BECOME MORE WLY AND CYCLONIC OVER MUCH OF LAKE SUPERIOR. IF THE WINDS DO ALIGN AS INDICATED...A MORE DOMINANT LES BAND WOULD PROBABLY RESULT OVER THE KEWEENAW AND POSSIBLY INTO THE FAR NERN CWA /FAR NRN ALGER AND LUCE COUNTIES/. 850MB TEMPS TUE NIGHT LOOK TO BE IN THE -20C TO -25C RANGE...SO SNOW TO LIQUID RATIOS SHOULD BE A BIT BETTER THAN WHAT WE HAVE SEEN IN THE LAST DAY OR SO WITH THE REALLY COLD TEMPS OVER THE CWA. COULD SEE SEVERAL INCHES OF SNOW IN THE IMPACTED AREAS IF THESE DETAILS COME TOGETHER.

LOW LEVEL WINDS BECOME MORE NWLY ON WED AS THE SHORTWAVE PASSES. CONDITIONS WILL BE MORE THAN SUFFICIENT FOR MODERATE TO POSSIBLY HEAVY LES GIVEN LAKE INDUCED EQUILIBRIUM LEVELS OVER 10KFT PER MODEL SOUNDINGS.

CONDITIONS WILL BECOME INCREASINGLY HOSTILE FOR LES WED NIGHT AS A SFC RIDGE MOVES IN FROM THE NW...SO WILL HAVE DECREASING POPS INTO THU. MODELS DISAGREE MORE ON A SHORTWAVE POSSIBLY MOVING S OF THE CWA THU INTO THU NIGHT...BUT CHANCE POPS NEAR LAKE SUPERIOR AS IS IN THE GOING FORECAST SEEM REASONABLE SO WILL LEAVE THAT IDEA IN THERE. 850MB TEMPS WARM INTO THE NEGATIVE TEENS BY LATE THU AS THE UPPER TROUGH PUSHES FARTHER TO THE E. MODELS AGREE WITH BRINGING ANOTHER SHORTWAVE THROUGH ON FRI...BUT DISAGREE ON THE STRENGTH. AGAIN...CHANCE POPS AT LEAST IN NW WIND SNOWBELTS SEEMS REASONABLE FOR FRI. UPPER AND SFC RIDGING PUSHES IN FROM THE W THROUGH THE REST OF THE FORECAST PERIOD...WITH WARMING LOW LEVEL TEMPS...DECREASING CHANCES FOR LES AND NO MAJOR SYSTEM EXPECTED TO MOVE THROUGH. SIMPLY USED A CONSENSUS OF MODELS FOR THIS TIME PERIOD AND FOCUSED MORE ON THE SHORTER TERM ISSUES.