Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 210047
AFDDLH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
647 PM CST SAT DEC 20 2014

.UPDATE...
ISSUED AT 647 PM CST SAT DEC 20 2014

WE MADE SOME MINOR CHANGES TO THE GRIDS...MAINLY ADJUSTED TIMING
OF THE PRECIP A BIT THROUGH THE EVENING TO ACCOUNT FOR CURRENT
TRENDS. THE FOG HAS LIFTED AND PRECIP DECREASED EARLY THIS
EVENING...BUT WE EXPECT BOTH TO REDEVELOP OVERNIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 330 PM CST SAT DEC 20 2014

SHORT TERM FOCUS ON FAST MOVING VORT MAX SEEN IN SATELLITE IMAGERY
TRANSLATING EAST OVER NORTH DAKOTA. CURRENT OBS AND VIS SAT SHOW
A WELL DEFINED CLEARING LINE ASSOCIATED WITH THE WAVE THAT IS
PUSHING INTO SOUTH-CENTRAL NORTH DAKOTA. MODELS DO NOT HAVE A GOOD
HANDEL ON THIS DRY SLOT...BUT DO SHOW AN AREA OF LOWER RH THAT
MIGRATES EAST WITH THE VORT MAX. AT THIS TIME...NOT EXPECTING ANY
CLEARING AS RH/PWAT VALUES INCREASE WITH THE EASTWARD PROPAGATION
OF THE WAVE. THE SHORT WAVE WILL TRIGGER SNOW SHOWERS ACROSS MUCH
OF THE NORTHLAND AS IT TRACKS EAST ALONG THE INTERNATIONAL BORDER
LATE TONIGHT THROUGH SUNDAY MORNING. SNOWFALL AMOUNTS WILL
GENERALLY BE LIGHT...ON THE ORDER OF LESS THAN A HALF INCH. THE
EXCEPTION WILL BE ALONG THE BORDERLAND/IRON RANGE AND INTO THE MN
ARROWHEAD REGION WHERE 1 TO 2 INCHES OF SNOW ACCUMULATION IS
POSSIBLE THROUGH SUNDAY AFTN.

TEMPERATURES OVERNIGHT WILL REMAIN STEADY AROUND 30 F DUE TO THE
CLOUDS COVER AND CONTINUED RETURN FLOW. THE MILD CONDITIONS WITH
H85 TEMPS WARMING TO AROUND ZERO WILL ALSO KEEP A SMALL THREAT FOR
FZDZ OVERNIGHT AND INTO SUNDAY. NO ICE ACCUM IS EXPECTED.
HOWEVER...THE MIX OF LIGHT SNOW AND DRIZZLE MAY PRODUCE SLICK
SPOTS ON UNTREATED ROADS AND SIDEWALKS.

ANOTHER WAVE WITH SFC REFLECTION LOW WILL DEEPEN OVER THE DAKOTAS
SUNDAY NIGHT...PUMPING ADDITIONAL MOISTURE INTO THE REGION AND
ALLOWING PWAT VALUES TO INCREASE OVER A HALF INCH...WHICH IS 2 SD
ABOVE NORMAL FOR DEC. PTYPE WILL BE A CONCERN SUNDAY NIGHT AS LOW
LEVELS WARM AROUND/ABOVE FREEZING. FOR NOW HAVE A MENTION OF SNOW
AND DRIZZLE...WITH A FEW INCHES OF SNOWFALL ACCUMULATION ALONG THE
NORTH SHORE OF LAKE SUPERIOR.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 330 PM CST SAT DEC 20 2014

THERE WILL BE A SLOW MOVING LOW PRESSURE SYSTEM OVER THE NORTHERN
PLAINS AND UPPER EARLY THIS UPCOMING WEEK. THIS LOW COULD RESULT IN
SIGNIFICANT SNOWFALL OVER THE NORTHLAND MONDAY THROUGH TUESDAY AS IT
MOVES THROUGH THE REGION. THERE ARE STILL SOME DIFFERENCES ON ITS
TRACK...WITH THE ECMWF BEING THE OUTLIER COMPARED TO THE GFS AND
GEM. OTHER CONCERNS ARE HOW THE RELATIVELY WARM TEMPERATURES IN THE
LOW TO MID 30S...AND RELATIVELY WARM TEMPERATURES ALOFT AROUND 0
DEGREES CELSIUS...WILL AFFECT SNOWFALL TOTALS. THERE COULD BE
MELTING OR PERIODS OF DRIZZLE/RAIN THAT COULD LIMIT SNOWFALL.
ALSO...THE NAM SHOWS A DRY SLOT MOVING THROUGH THE NORTHLAND
TUESDAY...AND ITS LOSS OF SATURATION ALOFT SUGGESTS A LACK OF SNOW
DUE TO THE LOSS OF ICE CRYSTAL SEEDING. ON THE OTHER HAND...THE GFS
KEEPS THE LOW/MID LEVELS WELL SATURATED TUESDAY.

THE BEST CHANCE FOR HEAVIER SNOWS MONDAY AND TUESDAY APPEARS TO BE
THE HIGHER TERRAIN OF THE ARROWHEAD. THERE WILL BE SOUTHERLY TO
EASTERLY FLOW FROM LAKE SUPERIOR THAT SHOULD PROVIDE AMPLE MOISTURE
AND OROGRAPHIC EFFECTS FOR SNOWS TO ACCUMULATE IN THE COLDER HIGHER
TERRAIN. THIS IS WHERE UP TO 6 TO 9 INCHES IS FORECAST. THE REST OF
THE NORTHLAND HAS ABOUT 1 TO 4 INCHES IN THE FORECAST FOR MONDAY AND
TUESDAY...BUT ONCE AGAIN...THERE IS QUITE A BIT OF UNCERTAINTY WITH
THIS BECAUSE OF POTENTIAL MELTING. SNOWFALL COULD BE SIGNIFICANTLY
HIGHER IF THERE IS NOT MUCH MELTING.

THE SYSTEM WILL BEGIN TO MOVE EAST OF THE NORTHLAND DURING THE
MIDDLE OF THE WEEK...AND IS STILL SHOWN TO MERGE WITH A LOW PRESSURE
SYSTEM WHICH WILL LIFT FROM THE SOUTHERN US. THIS LARGE AND COMBINED
LOW PRESSURE SYSTEM WILL DEVELOP SOMEWHERE OVER THE GREAT LAKES
REGION. THERE IS STILL UNCERTAINTY AS TO WHERE THIS LOW WILL
FORM...BUT THE MODELS ARE TRENDING TOWARDS THE CENTRAL GREAT LAKES.
THIS TRACK WOULD SUGGEST LESS OF AN IMPACT TO THE NORTHLAND COMPARED
TO SOME EARLIER MODEL RUNS THAT HAD THE LOWS MERGING CLOSER TO LAKE
SUPERIOR. THE CURRENT TRENDING TRACK WOULD STILL LIKELY BRING LIGHT
SNOW TO PARTS OF THE NORTHLAND...ESPECIALLY THE ARROWHEAD AND NW
WISCONSIN.

COLDER WEATHER WILL RETURN TO THE NORTHLAND DURING THE LATTER HALF
OF THE WEEK IN THE WAKE OF THE PASSING SYSTEM. THE GFS AND ECMWF ARE
SHOWING A COLORADO OR PLAINS LOW LIFTING INTO THE UPPER MIDWEST LATE
IN THE WEEK. THE GFS BRINGS THE ASSOCIATED LIGHT TO MODERATE SNOW
THROUGH THE NORTHLAND. THE ECMWF HAS MORE SUBSTANTIAL PCPN...BUT IT
MAINLY KEEPS IT SOUTH OF THE NORTHLAND. HOWEVER...THE ECMWF DOES
AFFECT NW WISCONSIN.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 542 PM CST SAT DEC 20 2014

IFR/LOW MVFR CONDITIONS WILL PREVAIL THROUGH SUNDAY EVENING WITH
PERIODS OF FREEZING DRIZZLE OR SNOW AND FOG. AN UPPER WAVE WAS
PARTIALLY RESPONSIBLE FOR THE PRECIPITATION OVER THE ARROWHEAD AND
FAR NORTHERN WISCONSIN AND AS IT DEPARTS THIS EVENING SO SHOULD
MUCH OF THE PRECIPITATION. ANOTHER SHORTWAVE SEEN ON WATER VAPOR
OVER NORTH DAKOTA WILL MOVE EAST/NORTHEAST ACROSS NORTHERN
MINNESOTA LATER TONIGHT INTO SUNDAY MORNING. THIS FEATURE WILL SET OFF
ANOTHER PERIOD OF SNOW OR FREEZING DRIZZLE.

BUFR SOUNDINGS SHOW NORTHERN AREAS BECOMING MORE SATURATED WITH
THE WAVE TONIGHT...WHICH SHOULD LEAD TO A BETTER CHANCE FOR SNOW
THAN AREAS FURTHER SOUTH.

LOWER VSBYS IN FOG WILL DEVELOP LATER TONIGHT AS WELL.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  27  32  31  33 /  40  50  50  80
INL  27  32  29  33 /  60  60  20  80
BRD  28  33  32  35 /  30  30  50  80
HYR  27  33  32  36 /  40  40  60  80
ASX  26  35  34  38 /  30  40  60  80

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...WINTER STORM WATCH FROM LATE SUNDAY NIGHT THROUGH TUESDAY
     AFTERNOON FOR MNZ012-020-021.

WI...NONE.
LS...NONE.
&&

$$

UPDATE...MELDE
SHORT TERM...GRANING
AVIATION...MELDE






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