Heavy Snow in Michigan, February 20, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1000 PM EST SAT FEB 19 2005

.UPDATE...

WILL BE UPDATING TO UPGRADE THE WATCH TO A WARNING IN ALL OR MOST
OF THE CWA. 00Z ETA12 AND NGM BOTH MAKE THIS DECISION SEEMINGLY AN
EASY ONE AS STRONG INSENTROPIC LIFTS LEADS TO A PROLONGED PERIOD
OF GOOD VVELS THROUGH A DEEP LAYER. QPF VALUES IN THE 0.50-0.75
FOR THE 5-8 INCH SNOWFALL (WHERE PRECIPITATION IN ALL/MAINLY SNOW)
MATCHES UP NICELY WITH MIXING RATIO VALUES THAT INCREASE IN THE 3
TO 4 G/KG AREA ON AVERAGE DURING HEIGHT OF THE STORM FROM AFTERNOON
INTO THE EVENING. MUCH LIKE 12Z/18Z MODELS...00Z SOLUTIONS SHOW
THAT THE ATMOSPHERE DOES NOT SET UP OPTIMALLY FOR EFFICIENT SNOW
PRODUCTION AS THE -13C TO -17C AREA IS COMPACT/RELATIVELY HIGH UP
AND BEST VVELS ARE FOCUSED IN THE -10C OR MILDER AIR. THAT SAID...
THE LOWER LEVELS...WHERE PRECIPITATION REMAINS PRIMARILY SNOW
ANYWAY...MAY MAKE UP FOR THAT AS SNOWFLAKES ARE ABLE TO AGGREGATE
NICELY & PRECIPITATION RATES WILL LIKELY BE RATHER IMPRESSIVE FOR A
NUMBER OF HOURS WITH SUCH STRONG LIFT.

WATER VAPOR IMAGERY STILL SHOWS A VERY CONVULUTED SERIES OF WAVES
RIDING IN FROM THE PLAINS...AND IT IS HARD TO LATCH ONTO MUCH...
OTHER THAN THE FACT THAT IT IS READILY APPARENT THAT A VERY GOOD
SLUG OF MOISTURE IS GOING TO RIDE NORTHEAST UP OVER COLD DOME IN
PLACE TONIGHT.

AM CONFIDENT ABOUT THE WINTER STORM WARNING FOR MUCH OF THE CWA...
BUT FEEL IT WILL BE A CLOSE CALL IN THE FAR NORTHEAST CWA. LAKE
HURON SHOULD HELP PUSH THIS AREA OVER THE TOP THOUGH AS PERSIST
EAST/SOUTHEAST FLOW ADDS LOW LEVEL MOISTURE TO THE THUMB. BIGGER
QUESTION REMAINS AT THE OHIO BORDER WHERE THE BEST PRECIPITATION
WILL LIFT NORTH OF DURING THE EVENING...AND THE CHANGEOVER MAY GO
ALL THE WAY TO RAIN...LIMITING PROBLEMS DURING THE LAST PART OF
THIS EVENT. THIS IS A VERY DIFFICULT CALL...AND WILL HINGE ON THE
EXACT TRACK OF THE SURFACE LOW...AND HOW FAR NORTH SOUTHEAST WINDS
CAN BRING 32F+ DEGREE BOUNDARY LAYER TEMPERATURES. AT THIS TIME...
FEEL MORE COMFORTABLE ADDING THE SOUTHERNMOST TWO COUNTIES TO THE
WARNING AS WELL. IT SEEMS THAT A SOLID 3 TO 4 INCHES OF SNOW WILL
BE A GOOD BET BY EARLY/MID AFTERNOON...WITH A MIXTURE OF SLEET AND
FREEZING RAIN SETTING UP IN THE LATE AFTERNOON AND EARLY EVENING.
LENGTHEN OF THIS POTENTIALLY ICY PERIOD WILL MAKE/BREAK WARNING
WHEN ALL IS SAID AND DONE.

.AVIATION...

FORECAST GOING DOWN HILL AS WARM AIR ADVECTION SNOW SPREAD INTO THE
REGION QUICKLY ON SUNDAY MORNING...AND PERSIST INTO THE EVENING. IN
THE SOUTH...MODEL SOLUTION FROM 18Z AND NEW RUNS AT 00Z STILL SHOW
A CHANGE TO SLEET/FREEZING RAIN IN THE DTW/DET AREAS IN THE 21Z-00Z
TIMEFRAME...WITH PLENTY OF SNOW BEFORE THAT FROM ABOUT 15Z ON.

&&

.SHORT TERM...ISSUED AT 330 PM EST.

DISORGANIZED STORM SYSTEM OVER THE ROCKIES WITH MULTIPLE SHORTWAVES
NOTED. WITH A LACK OF A WELL DEFINED SHORTWAVE...TOUGH TO GAUGE
EXACTLY WHERE THE SURFACE LOW WILL BE OVER THE CENTRALS PLAINS
TONIGHT. HISTORICALLY...MODELS TEND TO BE TOO FAR NORTH WITH WEAK
SURFACE LOW COMING OUT OF THE ROCKIES. A MORE WELL DEFINED SHORTWAVE
TROUGH IS EXPECTED TO ORGANIZE OVER THE MIDWEST TOMORROW.

EQUALLY IMPORTANT FOR US IS THE STRONG SURFACE HIGH OVER THE
NORTHERN MINNESOTA...WHICH WILL BUILD EAST THROUGH THE NORTHERN
LAKES TONIGHT. THIS HIGH HAS/WILL ALLOW THE SURFACE FRONT TO SINK
SOUTH OF LOWER MICHIGAN...SETTING UP A GOOD OVERRUNNING SITUATION ON
SUNDAY. IT SHOULD BE NOTED THE PRESSURE IS HIGHER THAN FORECASTED BY
12Z ETA/GFS OVER WESTERN GREAT LAKES.

THE PROBLEMS BETWEEN THE MODELS SEEM TO LIE WITH THE CUTOFF LOW OVER
SOUTHERN BRITISH COLUMBIA. HOW FAST DOES A PIECE OF ENERGY EJECT
EASTWARD...AS UKMET/GFS AND ESPECIALLY 12Z CANADIAN INDICATING
PHASING OCCURRING BY SUNDAY EVENING...WHICH TRANSLATES TO A STRONGER
AND FARTHER NORTH SURFACE TRACK...AND THUS MORE WARM AIR.
MEANWHILE...12Z ETA/NGM REMAIN FASTER AND WEAKER WITH THE INITIAL
PSEUDO SOUTHERN STREAM WAVE...AS PHASING DOES NOT REALLY OCCUR.

WITH A SURFACE LOW TRACK ALONG OR JUST SOUTH OF THE MICHIGAN
BORDER...SURFACE TEMPERATURES WOULD BE HARD PRESSED TO RISE ABOVE
FREEZING...AS EASTERLY FLOW FROM ONTARIO WOULD CONTINUE TO ADVECT
LOW LEVEL COLD AIR WITH A STRONG HIGH OVER SOUTHERN QUEBEC.
IT SHOULD BE NOTED 12Z GFS RUN IS 3 MB WEAKER WITH THE SURFACE LOW
BY 6Z MONDAY COMPARED TO PREVIOUS RUN.

CONFIDENCE IS HIGH A GOOD SURGE OF MOISTURE AND WARM ADVECTION WILL
LEAD TO A BURST OF HEAVY PRECIPITATION. UNFORTUNATELY...THE THERMAL
PROFILES REMAIN IN QUESTION. BOTH GFS AND ETA INDICATING GREATER
THAN A HALF AN INCH TO JUST UNDER ONE INCH OF QPF OVER SOUTHEAST
MICHIGAN (EXCEPT ACROSS THE FAR NORTH WHERE THERE IS LESS).

UNTIL I SEE A SIGNIFICANT PIECE OF ENERGY EJECT FROM THE PACIFIC
NORTHWEST/BRITISH COLUMBIA...FAVOR A FARTHER SOUTH AND FLATTER
INITIAL WAVE...WHICH IS ALSO SUPPORTED BY 20KM RUC. EVEN WITH THE
WARMER GFS SOLUTION...SHOULD BE A GOOD BURST OF SNOW BEFORE WE
CHANGEOVER. GFS BUFKIT GUIDANCE AND GFS MOS GUIDANCE WOULD SUGGEST
4-7 INCHES.

WITH THE UNCERTAINTY...AND THE POSSIBILITY OF SIGNIFICANT SNOW
AND/OR ICING...WILL BE ISSUING A WINTER STORM WATCH FOR MUCH OF
SOUTHEAST MICHIGAN. WILL GENERALLY BE MENTIONING 4 TO 8 INCHES
POSSIBLE...WITH LESS AMOUNTS TOWARD OHIO BORDER. OBVIOUSLY...IF THE
PRECIPITATION IS MOSTLY SNOW WE COULD BE ON THE HIGHER
END...OTHERWISE WE WILL HAVE TO SETTLE FOR 3 TO 4 INCHES OF SNOW
WITH A CHANGEOVER TO ICE. GUIDANCE ISSUED BY HPC IS TO TAKE A
COMPROMISE BETWEEN ETA/GFS.

A QUICK GLANCE AT 18Z ETA SHOWS SURFACE LOW TRACK ALONG OR JUST
SOUTH OF THE MICHIGAN BORDER. HOWEVER...A LITTLE CONCERNING IS THE
LACK OF QPF FORECASTED. WILL NOT JUMP SHIP YET WITH PREVIOUS
THINKING...BUT WOULD NOT BE SURPRISED IF WATCH ENDED UP BEING
TRANSITIONED TO A ADVISORY BY MIDNIGHT SHIFT. CANT RECALL TOO MANY
TRUE OVERRUNNING EVENTS WHICH PRODUCE MORE THAN 6 INCHES.

&&

.LONG TERM...MONDAY THROUGH SATURDAY...ISSUED AT 330 PM EST.

MODELS DO AGREE ON SURFACE LOW PULLING AWAY BY DAYBREAK
MONDAY...WITH TROUGH ALSO RETREATING EAST...BUT SUBSEQUENT
RESUMPTION OF TROUGHINESS OR WEAK WAVE SETTLING DOWN INTO AREA FOR
TUESDAY AND TUESDAY NIGHT. AT 500 MB...A VORTICITY LOBE SWINGS
THROUGH MONDAY WITH ANOTHER APPROACHING DURING THE TUESDAY TIME
FRAME.

MODEL SOUNDINGS...BOTH GFS AND NAM...SHOW MOISTURE ALOFT RAPIDLY
PEELING AWAY BY MID DAY OF MONDAY...PROMISING THEN LITTLE IN WAY OF
ICE NUCLEI AVAILABILITY. THUS WILL CONFINE MONDAY PRECIPITATION...
CHANCE POPS AS BEFORE...JUST TO THE MORNING. SOME INCREASE IN DEEPER
MOISTURE AGAIN TUESDAY AND TUESDAY NIGHT AS PER NAM/GFS...SO WILL
INTRODUCE FLURRIES MENTION FOR THOSE PERIODS. LOW LEVEL MOISTURE
WILL CONTINUE PRETTY GOOD THROUGH TUESDAY AND INTO TUESDAY NIGHT.

OMEGA FIELDS IN LOW TO MID LEVELS MONDAY THROUGH TUESDAY GENERALLY
INDICATE WEAK SUBSIDENCE. SOME SLIGHT 850 TO 500 MB QVECTOR
CONVERGENCE TUESDAY AND TUESDAY NIGHT WITH OCCASIONAL DIFFERENTIAL
PVA...WITH SURFACE CONVERGENCE THROUGH THIS TIME FRAME SLIGHT AT
BEST.

FOR REMAINDER OF EXTENDED PERIOD...NOT MUCH CHANGE FROM FORECASTS OF
PAST COUPLE OF DAYS...WILL CONTINUE THE DRY FORECAST. SURFACE HIGH
PRESSURE NOSES IN BY MID WEEK WITH MODEL CONSENSUS THEN INDICATING
HIGH PRESSURE TO PREVAIL THROUGH THE WEEK INTO THE WEEKEND. DGEX
1000 TO 500 MB RELATIVE HUMIDITY FIELDS...06Z RUN...DO NOT GENERALLY
INDICATE MUCH MOISTURE TO WORK WITH INTO THE WEEKEND...WITH 700 MB
OMEGA LIFT AND MODEL QPF ALSO ABSENT. AT 500 MB...SERIES OF NORTHERN
STREAM SHORTWAVE TROUGHS PIVOT ACROSS THE GREAT LAKES INTO THE
LATTER PART OF THE WEEK...WITH SOME MODEL CONSENSUS TOWARD RIDGING
BUILDING IN FRIDAY AND SATURDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

.MI...WINTER STORM WARNING FROM NOON SUNDAY TO 4 AM MONDAY FOR
MIZ047>049-053>055-060>063-068>070-075-076-082-083.
.LAKE HURON...SMALL CRAFT ADVISORY SUNDAY AFTERNOON INTO SUNDAY
NIGHT FROM PORT AUSTIN TO PORT HURON.
.LAKE ST CLAIR...NONE.
.MI WATERS OF LAKE ERIE...NONE.

&&

DEG/SF/DWD

HAZARDOUS WEATHER OUTLOOK FOR SOUTHEAST MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
440 PM EST SAT FEB 19 2005

MIZ053>055-060>063-068>070-201200-
GENESEE-LAPEER-LIVINGSTON-MACOMB-OAKLAND-SAGINAW-SANILAC-SHIAWASSEE-
ST. CLAIR-TUSCOLA-
440 PM EST SAT FEB 19 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF SOUTHEAST MICHIGAN.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

A WINTER STORM WATCH IS IN EFFECT FOR SUNDAY AFTERNOON AND SUNDAY
NIGHT...FOR A COMBINATION OF SNOWFALL AND SOME SLEET AND FREEZING
RAIN. SIGNIFICANT SNOWFALL ACCUMULATIONS ARE EXPECTED. PLEASE REFER
TO THE LATEST URGENT WINTER WEATHER MESSAGE FOR DETAILS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED. HOWEVER...SNOWFALL REPORTS
WOULD BE APPRECIATED ON SUNDAY.

MIZ075-076-082-083-201200-
LENAWEE-MONROE-WASHTENAW-WAYNE-
440 PM EST SAT FEB 19 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR FAR SOUTHEAST MICHIGAN.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

A WINTER STORM WATCH IS IN EFFECT FOR SUNDAY AFTERNOON AND SUNDAY
NIGHT FOR A COMBINATION OF SNOW...SLEET AND FREEZING RAIN. THERE
IS THE POTENTIAL FOR BOTH SIGNIFICANT SNOW AND ICE ACCUMULATIONS.
PLEASE REFER TO THE LATEST URGENT WINTER WEATHER MESSAGE FOR DETAILS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED. HOWEVER...SNOWFALL REPORTS
WOULD BE APPRECIATED ON SUNDAY.

MIZ047>049-201200-
BAY-HURON-MIDLAND-
419 PM EST SAT FEB 19 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FAR NORTHERN AREAS OF SOUTHEAST
MICHIGAN.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

SEVERAL INCHES OF SNOWFALL WILL BE POSSIBLE ACROSS THE REGION SUNDAY
AND SUNDAY NIGHT. IN ADDITION...SNOW MAY CHANGE TO SLEET AND FREEZING
RAIN SUNDAY EVENING. SNOWFALL TOTALS OF 2 TO 6 INCHES ARE EXPECTED
AT THIS TIME.

THIS PRECIPITATION WILL BE THE RESULT OF A LOW PRESSURE SYSTEM
DEVELOPING OVER THE PLAINS TONIGHT. THIS LOW WILL TRACK EAST ACROSS
INDIANA AND OHIO THROUGH SUNDAY NIGHT. SOME UNCERTAINTY STILL EXISTS
ABOUT THE EXACT TRACK OF THIS STORM AND THE TIMING OF ANY CHANGE TO
MIXED PRECIPITATION. UPDATES TO EXPECTED SNOWFALL AND THE LOCATION OF
ANY MIXED PRECIPITATION WILL BE REFINED AS THE STORM APPROACHES.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED. HOWEVER...SNOWFALL REPORTS
WOULD BE APPRECIATED SUNDAY.

LCZ422-423-460-LEZ444-LHZ421-422-441>443-462>464-201200-
LAKE HURON-SAGINAW BAY-LAKE HURON NEARSHORE FROM PORT AUSTIN TO PORT
HURON-ST CLAIR RIVER-LAKE ST CLAIR-DETROIT RIVER-MICHIGAN WATERS OF
LAKE ERIE-
440 PM EST SAT FEB 19 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SAGINAW BAY...SOUTHERN LAKE
HURON...THE ST CLAIR RIVER...LAKE ST CLAIR...THE DETROIT RIVER...AND
THE MICHIGAN WATERS OF LAKE ERIE.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

A SMALL CRAFT ADVISORY IS IN EFFECT SUNDAY AFTERNOON INTO SUNDAY
NIGHT FOR THE NEARSHORE WATERS OF LAKE HURON FROM PORT AUSTIN TO
PORT HURON. PLEASE SEE THE LATEST MARINE FORECASTS FOR DETAILS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED.

GURNEY