Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 131726
AFDDLH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
1226 PM CDT SUN APR 13 2014

.UPDATE...
ISSUED AT 954 AM CDT SUN APR 13 2014

ADDED OCCASIONAL FLURRIES LATE THIS MORNING TO SECTIONS OF THE
ARROWHEAD AND GOT RID OF MENTION OF EARLY MORNING FOG TO THE
FORECAST. OTHERWISE...NO MAJOR CHANGES MADE TO THE FORECAST.

&&

.SYNOPSIS...
ISSUED AT 245 AM CDT SUN APR 13 2014

A SOMEWHAT BUSY SFC PRESS PATTERN EXISTS OVER THE CWA EARLY THIS
MORNING. THE PRIMARY BAROCLINIC ZONE IS LOCATED SOUTH OF THE REGION AND
ID ASSOCIATED WITH THE SRN PLAINS SFC LOW/ELONGATED TROUGH
STRETCHING INTO SRN WISC/MICHIGAN. AS UPPER FLOW AMPLIFIES OVER CTRL
CANADA..AN INVERTED SFC TROUGH HAS DEVELOPED AS ADVERTISED FROM SRN
BDRY NORTH INTO A WEAK SFC WAVE OVER NWRN ONTARIO. A WELL DEFINED
LOW LVL THETAE RIBBON ALONG WITH A DISTINCT WIND SHIFT IS
ACCOMPANYING THIS FEATURE. GUSTY WINDS DEVELOP BEHIND THE BDRY AS
SFC PGF IS INCREASING QUICKLY. SPOTTY PRECIP IS OCCURRING ALONG THE
BORDERLAND AT THIS HOUR. IN BETWEEN THE TWO SYSTEMS A RELATIVE
BENIGN LOW LVL WIND PATTERN... COMBINED WITH VERY LOW COND PRESS
DEFICITS IN THE BDRY LYR... HAS ALLOWED LOCALLY DENSE FOG/AND LITE
PRECIP TO LINGER NEAR THE TWIN PORTS AND ALONG THE NORTH SHORE OF
LAKE SUPERIOR.

&&

.SHORT TERM...(TODAY...TONIGHT...MONDAY)
ISSUED AT 245 AM CDT SUN APR 13 2014

TODAY...EARLY MORNING FOG/DRIZZLE/CLOUDS WILL BEGIN TO DECREASE BY
MID MORNING AS WIND SHIFT ASSOCIATED WITH SFC BDRY PUSHES INTO THE
CWA. A DEEPENING OF THE COLD AIR ADVECTION WILL PRODUCE INCREASINGLY
GUSTY WINDS AS MOMENTUM TRANSFER IS FAVORED WITHIN A PROGRESSIVELY
MORE UNIDIRECTIONAL FLOW IN THE MIXING LAYER. MID LVL FLOW WILL
CONTINUE TO BACK OVER NRN PLAINS AND THIS MAY ALLOW NRN FRINGE OF
PRECIP FROM PLAINS SYSTEM TO EDGE INTO SERN CWA. MULTI MDL QPF
SUPPORTS THIS IDEA. MAX TEMPS BLO CLIMO WITH CAA AND ABUNDANCE OF
CLOUDY COVER. FCST 925/850 LAPSE RATES SUGGEST SOME ADDITIONAL
INSTABILITY CU MAY BE FAVORED OVER NRN/ERN CWA IN THE AFTN HRS.

TONIGHT...MID LVL TROF AMPLIFIES OVER WRN MN AS SFC HIGH PRESSURE
BUILDS EAST OVER THE REGION. PRECIP WILL END AS SNOW OVER SERN CWA
HOWEVER AT THIS TIME DO NOT ANTICIPATE ANY SIG ACCUMULATION. SREF
PLUMES AT KPBH SHOW CONSIDERABLE SPREAD WITH MEAN NEAR AN INCH.

TOMORROW...MAIN STORY TOMORROW WILL BE THE PROGRESSION OF THE MID
LVL TROF OVER THE CWA WITH A CORRESPONDING INCREASE IN LOW LVL LAPSE
RATES. MDLS ARE SKIMPY ON PRECIP HOWEVER GIVEN THE MAGNITUDE OF
THE UPPER FEATURE AND THE TIME OF YEAR WOULD SUSPECT THAT
INSTABILITY SNOW SHOWERS MAY DEVELOP. MAIN LIMITING FACTOR
MAY BE LACK OF SUFFICIENT MOISTURE AND TREND TOWARDS INCREASING
SUBSIDENCE INVERSION DURING THE DAY. WELL MIXED BDRY LAYER LOOKS
LIKELY AS FCST MIXING LAYER HEIGHT REACHES 6K TO 7K FT DURING THE
DAY. THIS SHOULD PROMOTE GUSTY WINDS ONCE AGAIN IN MANY AREAS. MAX
TEMPS EVEN LOWER THAN SUNDAY DUE TO A DROP OF ABOUT 4C TO 6C WITHIN
THE FCST 925/85H LAYER.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT  245 AM CDT SUN APR 13 2014

THE PERIOD WILL BE UNSETTLED...WITH A CHANCE FOR SOME SIGNIFICANT
SNOW MID WEEK. MOST OF THE WEEK WILL ALSO BE COLDER THAN NORMAL.

A LONG WAVE UPPER TROUGH AXIS WILL SHIFT EAST OF THE NORTHLAND
MONDAY NIGHT INTO TUESDAY WITH MOST AREAS DRY. THERE MAY BE SOME
SNOW SHOWERS THAT LINGER OVER THE ARROWHEAD AND ALONG THE SOUTH
SHORE MONDAY NIGHT...BUT ANY ACCUMULATION LOOKS TO BE LIGHT.

EMPHASIS DURING THIS PERIOD WILL BE ON A CHANCE FOR SNOW LATE
TUESDAY NIGHT INTO WEDNESDAY NIGHT. THERE CONTINUES TO BE SOME
SIGNIFICANT DIFFERENCES WITH THIS SYSTEM...WITH THE GFS QUITE A BIT
FASTER BRINGING IN THE SNOW TUESDAY NIGHT. THE ECMWF AND NAM ARE IN
A BIG BETTER AGREEMENT ON A SLOWER PROGRESSION. THE MODELS ARE IN
AGREEMENT IN DEVELOPING AN AREA OF LOW PRESSURE IN A BAROCLINIC ZONE
THAT WILL RESIDE OVER THE REGION. AT THIS TIME...MUCH OF THE REGION
LOOKS TO BE COLD ENOUGH TO RECEIVE SNOW. SEVERAL INCHES OF SNOW LOOK
LIKELY WITH THIS SYSTEM...BUT THERE STILL IS QUITE A BIT OF
UNCERTAINTY IN WHERE AND HOW MUCH WILL FALL AT ANY GIVEN LOCATION.
THERE SHOULD BE SOME DECENT FGEN THAT IS ASSOCIATED WITH THIS SYSTEM
AS WELL...AND COULD PROVIDE SOME ENHANCED BANDS OF SNOWFALL.

BOTH THE GFS/ECMWF AGREE ON DIMINISHING THE CHANCE FOR SNOW QUITE A
BIT WEDNESDAY NIGHT. HOWEVER...THE GFS DOES HAVE A MUCH STRONGER
UPPER WAVE OVER THE DAKOTAS/MINNESOTA THURSDAY MORNING...THEN
DEVELOPS IT INTO AN UPPER LOW OVER MINNESOTA FRIDAY. THE ECMWF IS
MORE PROGRESSIVE AND DOES NOT HAVE NEARLY THE AMOUNT OF PRECIP
FRIDAY/FRIDAY NIGHT THAT THE GFS SUGGESTS WILL OCCUR OVER THE
EASTERN HALF OF THE NORTHLAND. WE HAVE LOW CONFIDENCE IN THE
FORECAST DETAILS BEYOND WEDNESDAY.

MOST OF THE PERIOD WILL FEATURE BELOW NORMAL TEMPERATURES...WITH
THEM RISING LATE IN THE PERIOD TOWARD NORMAL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1226 PM CDT SUN APR 13 2014

MVFR CIGS WILL GRADUALLY GIVE WAY TO VFR CIGS. THE EXCEPTION WILL
BE AT HYR WHERE MVFR CIGS WILL PERSIST UNTIL 14Z/14 WHEN SYSTEM TO
THE SOUTH MOVES FAR ENOUGH AWAY TO ALLOW CIGS TO IMPROVE TO VFR.
HAVE A VCSH MENTION AT HYR FROM 01Z TO 09Z AS PCPN BUBBLES UP FROM
THE SYSTEM TO THE SOUTH.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  38  21  31  16 /   0  10  20  10
INL  35  15  27   9 /  10  10  20  10
BRD  39  22  34  16 /   0   0  10  10
HYR  41  23  34  11 /  10  10  20  10
ASX  41  24  32  15 /  10  10  20  10

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...NONE.
&&

$$

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






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