Heavy Snow in Minnesota, April 14 to 15, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
1241 PM CDT SUN APR 14 2013

.AVIATION...18Z TAFS

AREA RADARS SHOWED PRECIPITATION WAS MOVING NORTH THROUGH
MINNESOTA/WISCONSIN...AND WAS BECOMING MORE WIDESPREAD. THE NAM
HAS A PRETTY GOOD HANDLE ON THIS...AS DO THE HIGH RES MODELS. WE
EXPECT THE PRECIPITATION TO BEGIN AS SNOW ALL AREAS...THEN IT MAY
BECOME A WINTRY MIX AT KHYR...AND POSSIBLY AT KBRD BRIEFLY. TIMING
IN THE TAFS MAY NEED TO BE ADJUSTED BY AN HOUR OR SO...AND WE'LL
DO THAT AS CONFIDENCE INCREASES FOR AN EXACT STARTING TIME.

VSBYS WILL DROP TO IFR OR LIFR WITHIN AN HOUR OF PRECIP
ONSET...AND AREAS AROUND LAKE SUPERIOR WILL SEE WINDY CONDITIONS
FURTHER REDUCING THE VSBY IN BLOWING SNOW. A DRY SLOT WILL WORK
NORTH LATER THIS EVENING/TONIGHT AND CAUSE THE PRECIP TO DIMINISH
OVER MOST OF THE TAFS. FORECAST SOUNDINGS SHOW TOP DOWN
DRYING...SO SOME SPOTTY DRIZZLE OR FREEZING DRIZZLE IS NOT OUT OF
THE QUESTION. WE DID NOT ADD THAT TO THE TAFS AT THIS TIME...AS
THAT IS MORE OF A SHORT TERM FORECAST ISSUE AND CAN BE ADDRESSED
WITH LATER UPDATES.

WINDS WILL SWITCH FROM EASTERLY TO SOUTHERLY LAT TONIGHT/MONDAY
MORNING...THEN BECOME SOUTHWEST.

&&

.PREV DISCUSSION... /ISSUED 1105 AM CDT SUN APR 14 2013/

UPDATE...

THE FOCUS REMAINS IN THE IMPENDING STORM. BASED ON THE CURRENT
RADAR AND OBSERVATION TRENDS...AND THE LATEST NAM/SREF/HRRR MODEL
GUIDANCE...THIS STORM IS MOVING IN EVEN MORE SLOWLY THAN WHAT THE
NIGHT SHIFT THOUGHT. MUCH OF THE CURRENT PCPN IS ACROSS FAR SE
MINNESOTA AND WC WISCONSIN...AS WELL AS IN NE SOUTH DAKOTA. THERE
IS LITTLE IF ANY PCPN IN BETWEEN THOSE TWO REGIONS. THE HRRR
PICKS UP ON THIS WELL...BUT THEN INDICATES THE AREA IN BETWEEN WILL
SOON FILL IN WITH PCPN WITHIN THE NEXT FEW HOURS. WE ARE STILL
EXPECTING SIMILAR SNOW AND SLEET AMOUNTS...BUT THIS STORM IS
GENERALLY 1 TO 3 HOURS SLOWER AT MOVING INTO THE NORTHLAND. SOME
WARNINGS AND ADVISORIES ACROSS THE FAR SOUTHERN FORECAST AREA HAD
ALREADY BEGAN BY THE TIME I WAS ABLE TO CREATE A NEW FORECAST...SO
I LET THOSE WARNINGS AND ADVISORIES CONTINUE. FOR WARNINGS AND
ADVISORIES FAR NORTH...I DELAYED THE START TIME A BIT...SUCH AS AT
DULUTH THE WARNING NOW BEGINS AT 2 PM. THE ONLY NEW HEADLINES THAT
WERE ISSUED ARE FOR IRON AND ASHLAND COUNTIES. IT LOOKS LIKE THE
INITIAL BAND OF SNOW WILL BRING ABOUT 1 TO 3 INCHES OF WET
SNOW...AS WELL AS SLEET LATER THIS AFTERNOON WHEN THE PCPN
TRANSITIONS TO WINTRY MIXTURE WITH THE WARMING TEMPERATURES.

MUCH OF NORTHERN MINNESOTA HAS ALREADY WARMED TO THE MID TO UPPER
30S LATE THIS MORNING. IT IS POSSIBLE THAT FOR A BRIEF PERIOD
DURING THE ONSET OF PCPN THAT THE PCPN COULD BE LIGHT RAIN BEFORE
THE PCPN THEN TRANSITIONS TO SNOW.

I ALSO INCREASED THE EAST WINDS FOR TODAY. THE WINDS WILL BE
STRONGEST NEAR LAKE SUPERIOR...ESPECIALLY NEAR THE TWIN PORTS. I
KEPT BLOWING SNOW IN THE FORECAST TO EMPHASIZE REDUCED VISIBILITY
FROM THE SNOW AND WIND.

PREV DISCUSSION... /ISSUED 655 AM CDT SUN APR 14 2013/

AVIATION.../12Z TAF ISSUANCE/
CONDITIONS WILL DETERIORATE RAPIDLY AS THE DAY WEARS ON...AS LOW
PRESSURE STRENGTHENS TO THE SOUTH OF THE REGION AND MOVES
NORTHWARD INTO THE CWA. VFR CONDITIONS WILL QUICKLY BECOME
IFR/LIFR AND EVEN POSSIBLY VLIFR IN SPOTS FROM SOUTH TO NORTH.
SNOW WILL COME DOWN HARD AT TIMES...WITH A MIX OF WINTRY WEATHER
POSSIBLE IN NW WI.

PREV DISCUSSION... /ISSUED 401 AM CDT SUN APR 14 2013/

PRECIPITATION SLOWER TO ARRIVE...

SHORT TERM...MID LVL RIDGING HAS ENTERED CWA WITH LIGHT NW FLOW
ALOFT. A FEW PATCHES OF UPPER LVL CLOUDS ARE MAKING THEIR WAY
ACROSS SWRN/WRN CWA EARLY THIS MORNING. WARM ADVECTION REGIME HAS
STRENGTHENED SOUTH AND WEST OF CWA IN RESPONSE TO AMPLIFYING UPPER
TROF/RIDGE OVER CTRL/NRN ROCKIES AND CTRL/NRN PLAINS. PRECIPITATION
HAS MADE ITS WAY INTO SWRN MN IN ASSOCIATION WITH AREA OF 85/70H
FRONTOGENESIS.

TODAY/TONIGHT...MAIN CHANGE IN EXISTING FCST IS TO SLOW DOWN ARRIVAL OF
MAIN PRECIP AREA ASSOCIATED WITH WARM FRONTOGENESIS. THIS NECESSITATED
PUSHING BACK START TIME OF WARNINGS/ADVISORIES ABOUT 3 HRS. IF
CURRENT TRENDS CONTINUE THEN EVEN SLIGHTLY LONGER DELAY IS
FEASIBLE. GENERAL IDEA IS THAT AN AREA OF MDT/STRONG LOW/MID LVL
FRONTOGENESIS WILL ADVECT ACROSS CWA FROM SOUTH TO NORTH FROM THIS
AFTERNOON THROUGH MIDNIGHT. DEEP SATURATION WITH STRONG FORCING
WILL YIELD A QUICK BURST OF MDT TO OCCASIONALLY HEAVY SNOWFALL
PERSISTING 5 TO 8 HRS IN ANY PARTICULAR LOCATION. COMPLICATIONS IN
MEASUREMENT WILL ARISE DUE TO RELATIVELY LOW SLR COMMON THIS TIME
OF YEAR AND COMPACTION OF SNOW AS IT ACCUMULATES. GENERAL QPF
AREAL AVERAGE IS ABOUT .5" TO .75" WITHIN WARM ADVECTION ZONES.
SLR OF 9:1 TO 11:1 YIELDS ABOUT 5 TO 8 IN TOTALS. NORTH SHORE
AMOUNTS MAY BE LOCALLY HEAVIER AS RELATIVELY COLD AIR SUPPLY
PROVIDED BY LAKE SUPERIOR BDRY LYR MAINTAINS DEPTH OF COLD AIR
THROUGHOUT COLUMN. STRONG TERRAIN LIFT WILL AUGMENT FORCING AS
ONSHORE FLOW IS GREATLY INCREASE LATE THIS AFTERNOON INTO THIS
EVENING. SOME CONCERNS ABOUT SLOWER MOVEMENT OF PRECIP SHIELD INTO
CWA AND ITS EFFECT ON BDRY LYR WARMING. THIS MAY RESULT IN EVEN
LOWER ACCUMULATIONS AS INCREASED MELTING OCCURS WITH HIGH WATER
CONTENT IN SNOWFLAKE PRODUCTION. OVERALL HIGHEST CONFIDENCE IN
WARNING CONDITIONS IS OVER NORTH SHORE WHERE VERY STRONG WINDS
COMBINED WITH SNOW WILL PRODUCE VERY POOR TRAVEL CONDITIONS THIS
EVENING. 500M WIND FCST ALONG NORTH SHORE SUGGESTS WINDS MAY
EXCEED 40MPH IN GUSTS AT TIMES THIS EVENING. PTYPE WILL
TRANSITION TO IP/RAIN BLEND OVER WISC ZONES LATE AFTERNOON INTO
EVENING WITH MUCH LOWER ACCUMULATION POTENTIAL. A DRY SLOT MAY
REQUIRE PTYPES/POPS TO BE MODIFIED THIS EVENING AS ICE NUCLEATION
LAYER IS ELIMINATED. DEEP LAYER SATURATION SHOULD COMMENCE ONCE
AGAIN AFTER MIDNIGHT WITH THERMAL PROFILES SUPPORTING TRANSITION
BACK TO SNOW BY MORNING OVER MOST OF CWA.

TOMORROW...SFC/MID LVL LOW WILL CROSS CWA MONDAY WITH RESIDUAL
SNOW OCCURRING. NEXT SHIFT MAY NEED TO INCREASE POPS IN LINE WITH A
HIGH POP/LOW QPF PATTERN AS COLD AIR ALOFT MOVES THROUGH REGION.

EXTENDED...MONDAY NIGHT THROUGH SUNDAY...
THE LOW PRESSURE SYSTEM WILL MOVE QUICKLY TO THE NORTHEAST MONDAY
NIGHT AND TUESDAY...BUT SOME LIGHT SNOW WILL LINGER IN THE WAKE OF
THE SURFACE LOW. TUESDAY WILL GENERALLY BE QUIET BUT IT WILL REMAIN
ON THE COOL SIDE. THE NEXT STORM SYSTEM WILL BEGIN TO MOVE TOWARD
THE REGION ON WEDNESDAY. THERE IS STILL QUITE A BIT OF DISAGREEMENT
CONCERNING THE EVOLUTION OF THIS POTENTIALLY MAJOR SYSTEM. THE
MODELS DIFFER ON SURFACE LOW TRACK...STRENGTH...AND ESPECIALLY QPF.
THE GEM BRINGS SEVERAL INCHES OF QPF...AND ACTUALLY THE GEM AND GFS
DO TRANSITION TO A SIMILAR SOLUTION BY THURSDAY. THE ECMWF CONTINUES
TO HANG ON TO A LOOSER AND MORE MUDDLED SOLUTION WITH NO LARGE SCALE
QPF. IN ALL...THINK THERE IS ENOUGH JUSTIFICATION TO GO WITH A
LIKELY POP AS THE ALL BLEND IS DOING...BUT CONFIDENCE IN ANY
PARTICULAR SOLUTION IS NOT ALL THAT GREAT GIVEN THE DIFFERENCES AND
WIDE SPREAD. IN GENERAL...THINGS QUIET DOWN A BIT OVER THE
WEEKEND... ALTHOUGH THERE ARE BIG DIFFERENCES IN THE GFS/ECMWF.
SHOULD CONTINUE TO BE A COOLER THAN NORMAL TIME PERIOD.

&&

.POINT TEMPS/POPS...
DLH  29  37  26  39 / 100  50  20  10
INL  29  37  25  37 / 100  70  40  20
BRD  29  38  25  39 /  90  50  10  10
HYR  32  40  27  43 / 100  30  10  10
ASX  31  40  28  42 / 100  30  10  10

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...WINTER STORM WARNING UNTIL 7 AM CDT MONDAY FOR MNZ033-034.

     WINTER STORM WARNING UNTIL 7 AM CDT MONDAY FOR MNZ025-026-035-
     037.

     WINTER WEATHER ADVISORY UNTIL 1 AM CDT MONDAY FOR MNZ036-038.

     WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 10 AM CDT
     MONDAY FOR MNZ010>012-018>021.

WI...WINTER WEATHER ADVISORY UNTIL 4 PM CDT THIS AFTERNOON FOR
     WIZ006>009.

     WINTER WEATHER ADVISORY UNTIL 7 PM CDT THIS EVENING FOR WIZ003-
     004.

     WINTER WEATHER ADVISORY UNTIL 7 AM CDT MONDAY FOR WIZ001-002.

LS...GALE WARNING FROM 4 PM THIS AFTERNOON TO 3 AM CDT MONDAY FOR
     LSZ121-140>148.

&&

SHORT TERM...GROCHOCINSKI
AVIATION...MELDE

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE DULUTH MN
1130 AM CDT SUN APR 14 2013

MNZ010>012-018>021-025-026-033>038-WIZ001>004-006>009-151300-
KOOCHICHING-NORTHERN ST. LOUIS-NORTHERN COOK/NORTHERN LAKE-
NORTHERN ITASCA-CENTRAL ST. LOUIS-SOUTHERN LAKE/LAKESHORE-
SOUTHERN COOK/LAKESHORE-NORTHERN CASS-SOUTHERN ITASCA-
SOUTHERN CASS-CROW WING-NORTHERN AITKIN-SOUTHERN AITKIN-
CARLTON/SOUTHERN ST. LOUIS-PINE-DOUGLAS-BAYFIELD-ASHLAND-IRON-
BURNETT-WASHBURN-SAWYER-PRICE-
1130 AM CDT SUN APR 14 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST MINNESOTA AND
NORTHWEST WISCONSIN.

.DAY ONE...TODAY AND TONIGHT

A WINTRY STORM SYSTEM WILL MOVE INTO THE NORTHLAND TODAY. SNOW
WILL SPREAD FROM SOUTHERN MINNESOTA INTO THE BRAINERD LAKE REGION
EARLY THIS AFTERNOON. PRECIPITATION WILL SPREAD INTO NORTHWEST
WISCONSIN AND ACROSS THE REST OF NORTHEAST MINNESOTA THROUGH THIS
AFTERNOON AND INTO THIS EVENING. MUCH OF NORTHEAST MINNESOTA CAN
EXPECT A TOTAL OF ABOUT 4 TO 8 INCHES OF WET AND HEAVY SNOW
THROUGH MONDAY MORNING. LOCAL ACCUMULATIONS MAY EXCEED 8 INCHES
ALONG THE ELEVATED TERRAIN OF THE NORTH SHORE OF LAKE SUPERIOR.
LIGHTER SNOWFALL AMOUNTS WILL OCCUR OVER EAST CENTRAL MINNESOTA
AND NORTHWEST WISCONSIN DUE TO MIXED PRECIPITATION...INCLUDING
SLEET AND RAIN. GUSTY EAST WINDS WILL DEVELOP TODAY. THE WINDS
WILL BE STRONGEST NEAR LAKE SUPERIOR WHERE THE EAST WINDS WILL
INCREASE TO 15 TO 30 MPH WITH GUSTS UP TO 40 MPH. THE VISIBILITY
COULD DROP TO ONE QUARTER MILE OR LESS AT TIMES DURING THE HEAVIER
SNOW BANDS...ESPECIALLY NEAR LAKE SUPERIOR WHERE THE WINDS WILL BE
STRONGEST. PLEASE REFER TO THE LATEST WINTER STORM WARNINGS AND
WEATHER ADVISORIES FOR ADDITIONAL INFORMATION ON PRECIPITATION
TYPES AND AMOUNTS FOR THE NORTHLAND.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

ADDITIONAL LIGHT SNOW IS EXPECTED ACROSS THE NORTHLAND AS AN AREA
OF LOW PRESSURE MOVES THROUGH THE REGION.

ACCUMULATING SNOW IS POSSIBLE WEDNESDAY INTO THURSDAY ACROSS THE
NORTHLAND. THIS IS BASED ON INITIAL ESTIMATES OF A DEVELOPING LOW
PRESSURE SYSTEM TRACKING SOUTH AND EAST OF THE AREA. THIS MAY
CHANGE WITH TIME.

.SPOTTER INFORMATION STATEMENT...

SNOW SPOTTERS ARE ENCOURAGED TO CALL THE NATIONAL WEATHER SERVICE
WITH PERIODIC UPDATES ON THEIR SNOWFALL AMOUNTS...PRECIPITATION
TYPE...AND VISIBILITY.

LSZ121-140>148-151300-
BAYFIELD TO OAK POINT WI-GRAND PORTAGE TO GRAND MARAIS MN-
GRAND MARAIS TO TACONITE HARBOR MN-
TACONITE HARBOR TO SILVER BAY HARBOR MN-
SILVER BAY HARBOR TO TWO HARBORS MN-TWO HARBORS TO DULUTH MN-
DULUTH MN TO PORT WING WI-PORT WING TO SAND ISLAND WI-
SAND ISLAND TO BAYFIELD WI-OAK POINT TO SAXON HARBOR WI-
1130 AM CDT SUN APR 14 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE NEARSHORE WATERS OF
WESTERN LAKE SUPERIOR.

.DAY ONE...TODAY AND TONIGHT

A GALE WARNING HAS BEEN ISSUED FOR LAKE SUPERIOR FOR LATE TODAY
AND TONIGHT DUE TO VERY STRONG EAST TO NORTHEAST WINDS. PLEASE
CHECK THE LATEST MARINE STATEMENTS FOR DETAILS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

WINDS WILL INCREASE SIGNIFICANTLY AND BECOME GUSTY FROM THE
SOUTHWEST MONDAY BEHIND A DEPARTING LOW PRESSURE SYSTEM. HAZARDOUS
WAVES ARE EXPECTED TO BUILD AND A SMALL CRAFT ADVISORY...POSSIBLY
A GALE WARNING...MAY BE REQUIRED. PLEASE CHECK THE LATEST MARINE
FORECAST FOR ADDITIONAL INFORMATION.

GROCHOCINSKI

MORE INFORMATION MAY BE OBTAINED AT THE FOLLOWING WEB ADDRESS:
HTTP://WWW.WEATHER.GOV/DULUTH (ALL LOWER CASE)