Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 121724
AFDDLH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
1224 PM CDT SAT APR 12 2014

.UPDATE...
ISSUED AT 1107 AM CDT SAT APR 12 2014

THE PCPN IS NO LONGER AS WIDESPREAD AS INTENSE AS IT WAS
PREVIOUSLY FORECAST AND AS EARLIER MODELS HAD INDICATED. AS THE
BAND OF LIGHT PCPN LIFTS INTO THE ARROWHEAD...THIS HAD
IMPLICATIONS ON THE WINTER WEATHER ADVISORY. MOST NEW MODELS RUNS
HAVE BACKED OFF ON PCPN AMOUNTS FOR THE ARROWHEAD. WHILE THE NAM12
WAS STILL BULLISH ON SNOWFALL...IT WAS FAR TOO HIGH FOR THE TWIN
PORTS AREA. I THINK TEMPERATURES ARE JUST TOO WARM...AND THAT THE
NAM12 IS TOO COLD AND EXPECTING MUCH MORE ACCUMULATION THAT WE ARE
SEEING. THE RELATIVELY WARM TEMPERATURES ARE CUTTING DOWN THE
SNOWFALL ACCUMULATIONS BECAUSE THE ROADS ARE ABLE TO MELT MUCH OF
THE SNOW. THE COMBINATION OF THE WARM TEMPERATURES AND CHANGE IN
THE MODELS GAVE ME ENOUGH CONFIDENCE THAT WE ARE NOT GOING TO SEE
THE 2 TO 4 INCHES OF ACCUMULATION OF SNOW ALONG THE NORTH SHORE
THAT WE WERE PREVIOUSLY FORECASTING. I THINK A COUPLE INCHES ARE
POSSIBLE AT MOST. I CANCELLED THE WINTER WEATHER ADVISORY.

&&

.SYNOPSIS...
ISSUED AT 308 AM CDT SAT APR 12 2014

1023MB SFC HIGH IS LOCATED OVER NRN ONTARIO WITH ELONGATED SFC LOW
ACROSS CTRL PLAINS. ALOFT A VERY FAST FLOW STRETCHES FROM NRN
ROCKIES INTO WCTRL WISCONSIN ASSOCIATED WITH 30H JET CORE. AN
ASSOCIATED INCREASE IN LOW LVL JET HAS OCCURRED FROM NEB INTO SERN
SODAK. A FEW LTG STRIKES HAVE DEVELOPED NEAR NOSE OF LLJ ACROSS
ERN SODAK. SPC MESO SHOWS STRONG FRONTOGENESIS IN LOW/MID LVLS
ACROSS ERN SODAK AND SRN MN. 88D SHOWS INCREASING RETURNS ACROSS
SWRN/SRN CWA IN AREA OF SPEED CONVERGENCE AT 85H. THERMAL PROFILES
SUPPORT LIQUID AT THIS TIME BUT WITH TIME EVAPO COOLING AND DIABATIC
COOLING WILL PROMOTE A TRANSITION TO SNOW BY 12Z NEAR TWIN PORTS
AND NORTH.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 308 AM CDT SAT APR 12 2014

TODAY...AN AREA OF STRONG FORCING WILL CROSS THE CWA FROM SW TO NE
BETWEEN 12Z AND 18Z. THE MAIN CHALLENGE IS PTYPE IN THE EARLY
MORNING WHEN QPF SHOULD BE LARGEST. AFTER CONSIDERING SREF
PLUMES...VARIOUS MDL SOUNDINGS....CURRENT BDRY LYR CONDITIONS AND
LATEST RADAR FEEL FAIRLY CONFIDENT THAT RAIN WILL SWITCH TO SNOW
NEAR TWIN PORTS AND ACROSS THE NORTH MN ZONES AS DIABATIC COOLING
RESULTS FROM TOP DOWN SATURATION AND INCREASING OMEGA WITHIN THE
DGZ. AREA OF POTENTIALLY SIG SNOW SHOULD OCCUR NEAR TWIN PORTS
FROM 12Z-15Z...AND AROUND 15Z-18Z OVER ARROWHEAD. PUSHED START
TIME ON ARROWHEAD BACK TO 12Z AS SNOW SHOULD NOT ARRIVE TIL MID
MORNING. TOUGH DECISION ON WHETHER TO ISSUE ADVISORY FOR DLH
VICINITY GIVEN POTENTIAL FOR A QUICK 2 TO 3 INCHES IN A FEW HRS
EARLY THIS MORNING. STILL SOME UNCERTAINTY AS TO HOW MUCH MELTING
OCCURS WITH BDRY LYR TEMPS REMAINING ABOVE ZERO THROUGH THE EVENT.
WILL LEAVE ADVISORY FOR ARROWHEAD ALTHOUGH FAST MOVING NATURE OF
THERMAL LIFT MAY LIMIT AMOUNTS SOMEWHAT. EXPECT TEMPS IN TWIN
PORTS AREA TO LOWER WITH EVAPO COOLING EARLY IN THE DAY AND THEN
CLIMB A DEGREE OR TWO IN THE AFTN HRS. ELSEWHERE WHATEVER BRIEF
BOUT OF  RASN MAY OCCUR...MOST LOCATIONS SHOULD EXPERIENCE RAIN.
INCREASING PGF ACROSS THE REGION SHOULD GIVE INCREASING WINDS NEAR
TWIN PORTS AND ALONG THE NORTH SHORE.

TONIGHT...SOMEWHAT COMPLICATED SFC PRESS PATTERN DEVELOPS AS UPPER
TROF DROPS INTO NORTH DAKOTA OVERNIGHT. AS THIS OCCURS...AN
INVERTED SFC TROUGH DEVELOPS NORTHWARD FROM CTRL PLAINS TROUGH.
THIS TROUGH PUSHES ACROSS THE MN ZONES BY 12Z WITH A SHIFT IN
WINDS TO THE NORTHWEST. PRECIP WILL BE FAVORED ACROSS NWRN CORNER
OF CWA WHERE CONVERGENCE ASSOCIATED WITH A WEAK SFC REFLECTION
COMBINES WITH UPPER DIVERGENCE FROM MID LVL TROF.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 308 AM CDT SAT APR 12 2014

THE EXTENDED PERIOD WILL BE UNSETTLED WITH GREATER THAN AVERAGE
UNCERTAINTY. TEMPERATURES WILL BE BELOW NORMAL AS WELL THROUGH THE
PERIOD.

A LONG WAVE UPPER TROUGH WILL BE MOVING INTO THE CENTRAL
CONUS/CANADA SUNDAY INTO SUNDAY NIGHT. THE TROUGH WILL CONTINUE EAST
THROUGH THE EARLY PART OF NEXT WEEK...WITH MORE TROUGHING DEVELOPING
WEST OF THE REGION THEN PROGRESSING EAST THROUGH THE REST OF THE
WEEK MAKING INTO OUR AREA. A MID WEEK SYSTEM COULD BRING SOME
SIGNIFICANT SNOWFALL TO PORTIONS OF THE NORTHLAND.

MUCH OF THE NORTHLAND SHOULD BE DRY SUNDAY...WITH PORTIONS OF
NORTHWEST WISCONSIN BEING BRUSHED BY A SIGNIFICANT SYSTEM. A
STRONGER SHORTWAVE ASSOCIATED WITH THE MAIN UPPER TROUGH WILL MOVE
THROUGH SUNDAY NIGHT INTO MONDAY...BRINGING A CHANCE FOR MAINLY
LIGHT SNOW SUNDAY NIGHT. WE KEPT SOME POPS FOR SNOW SHOWERS NORTH OR
A RAIN/SNOW MIX SOUTH INTO MONDAY WITH THE UPPER TROUGH STILL OVER
THE AREA AND COLDER TEMPS ALOFT. PRECIPITATION AMOUNTS SUNDAY NIGHT
INTO MONDAY SHOULD BE LIGHT.

A BAROCLINIC ZONE WILL SET UP OVER/NEAR THE NORTHLAND EARLY TO MID
WEEK...WITH AN AREA OF LOW PRESSURE DEVELOPING AND IMPACTING THE
NORTHLAND INTO AT LEAST WEDNESDAY NIGHT AND POSSIBLY INTO THURSDAY.
THE GFS AND ECMWF ARE NOT IN VERY GOOD AGREEMENT WITH THESE FEATURES
WITH THE ECMWF FURTHER NORTH AND PROGRESSIVE WITH THE LOW.
HOWEVER...BOTH WOULD SUGGEST SOME SIGNIFICANT SNOW WILL FALL OVER
PORTIONS OF THE NORTHLAND DURING THE PERIOD FROM TUESDAY NIGHT INTO
AT LEAST WEDNESDAY NIGHT.

DIFFERENCES BETWEEN THE MODELS BECOME EVEN GREATER LATE IN THE WEEK
AS THE GFS HAS A MUCH STRONGER SOUTHERN WAVE IN THE SOUTHERN
PORTIONS OF THE TROUGH VERSUS THE LESS AMPLIFIED ECMWF. THE GFS
KEEPS AN AREA OF LOW PRESSURE OVER THE REGION...WITH SNOW OR RAIN
GOING MUCH LONGER. WE HAVE SOME POPS IN THE FORECAST FOR NOW...BUT
CONFIDENCE IS LOW.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1224 PM CDT SAT APR 12 2014

MVFR CIGS COVER THE TERMINALS WITH IFR AROUND LAKE SUPERIOR.
EXPECT THE MVFR CIGS TO PERSIST THROUGH THE FORECAST. SOME AREAS
OF BR WITH IFR STILL EXPECTED TO BEGIN FORMING AFTER 00Z AND
AFFECT MOST TERMINALS UNTIL 12Z-13Z WHEN SFC WIND SWITCHES TO THE
NW AND BECOMES GUSTY. CIGS WILL BE BACK IN THE MVFR RANGE.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  38  29  39  22 /  70  20  10  20
INL  39  25  37  16 /  50  40  20  20
BRD  52  31  41  22 /  20  10  10  10
HYR  47  31  43  24 /  50  10  20  20
ASX  44  31  41  24 /  90  10  10  20

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...SMALL CRAFT ADVISORY UNTIL 10 PM CDT THIS EVENING FOR LSZ121-
     140>148.

&&

$$

UPDATE...GROCHOCINSKI
SYNOPSIS...CANNON
SHORT TERM...CANNON
LONG TERM...MELDE
AVIATION...GSF






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