961
FXUS63 KDLH 210938
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
338 AM CST SAT NOV 21 2009
DISCUSSION
AT THIS TIME...AN AREA OF SHALLOW FOG SURROUNDS AND COVERS PRICE
COUNTY. ISOLATED PATCHES OF FOG...ACROSS OTHER AREAS SOUTH OF
DULUTH...ARE HAVING TROUBLE SPREADING OR BECOMING ESTABLISHED DUE
TO THE DRYNESS OF THE COLUMN...ESPECIALLY ABOVE THE NOCTURNAL
INVERSION. A FOG ADVISORY RATHER THAN A FREEZING FOG ADVISORY HAS
BEEN ISSUED SINCE THE GROUND IS RELATIVELY WARM AND MOST FROST
ACCUMULATION IS RESTRICTED TO SUCH OBJECTS AS ELEVATED DECKS...
BRANCHES AND RAILINGS RATHER THAN ROADS...WALKS...OR EVEN BRIDGES.
DEEP RIDGING OF PACIFIC AIR...BOTH SURFACE AND ALOFT...WILL
MAINTAIN AN AXIS OVER THE CENTRAL LAKES. A PRESSURE GRADIENT TO
THE WEST...OVER OUR AREA...WILL MAINTAIN A BRISK SOUTH FLOW JUST
ABOVE THE SURFACE TODAY AND ESPECIALLY TONIGHT...WHERE A LOW-LEVEL
WIND SHEAR SITUATION COULD DEVELOP. FALLING HEIGHTS ALOFT AND AN
IMBEDDED SURFACE TROUGH WILL WEAKEN THE LOW LEVEL SOUTH FLOW A
LITTLE AND BRING ENOUGH MOISTURE FOR SCATTERED SHOWERS ACROSS THE
AREA SUNDAY.
EXTENDED
SUNDAY NIGHT THROUGH FRIDAY.
THE MODELS BEGIN THE PERIOD IN FAIRLY GOOD AGREEMENT AND THEN
DIVERGE. A COLD FRONT FROM MILLE LACS UP THROUGH DULUTH AND ALONG
THE NORTH SHORE WILL BEGIN TO WASH OUT AS SEEN IN THE WIND
FIELD...BUT THE LOW LEVEL THERMAL GRADIENT LINGERS OVER THE AREA.
A DISTURBANCE WILL RIDE ALONG THE BOUNDARY...TRIGGERING
PRECIPITATION INTO MONDAY MORNING. BEST MOISTURE TRANSPORT/LLJ
ALONG THE NORTH SHORE AND INTO NW WISC. AFTER DISTURBANCE AND
DEPARTING JET CRUISE OFF INTO CANADA AND MERGE WITH THE NORTHERN
STREAM FLOW...THE FRONT THEN MOVES NORTH AS A WARM FRONT AS WIND
FIELD BECOMES MORE SOUTHERLY IN RESPONSE TO A DEEPENING LARGER
AMPLITUDE MID LEVEL LOW PUSHING OUT OF THE NORTHERN ROCKIES INTO
THE CENTRAL PLAINS. POPS WERE INCREASED IN NORTHEAST MINNESOTA
ACCORDINGLY...WITH AN INVERTED TROUGH AXIS THROUGH OUR NW ZONES.
THOUGH MODELS AGREE ON EVOLUTION...SOME SMALL DIFERENCES ARE SEEN
IN PRECIP FIELDS. NW WISC SHOULD DRY OUT FOR A TIME ON MONDAY WITH
DRIER AIR FILTERING IN FROM THE EAST.
MODELS THEN BEGIN TO DIVERGE ON THE SURFACE REFLECTION OF THIS UPPER
LOW AS WELL AS THE UPPER LOW TRACK. GENEARL IDEAS HAVE THE GFS/SREF
BEING THE FASTEST AND THE FURTHEST NORTH...THE NAM AND ECMWF BEING
ON THE SLOWER SIDE...WITH THE GEM IN THE MIDDLE. HAVE GONE CLOSER TO
GEM...THOUGH IT IS INTERESTING OF NOTE THAT THE 0Z ECMWF HAS SPED UP
AND COME FURTHER NORTH. THE GENERAL IDEA THOUGH IS THAT THE PRECIP
WIL LINGER IN NW MINNESOTA ALONG THE INVERTED TROUGH AXIS BEFORE THE
UPPER LOW SWINGS SOUTH AND SHOVES THE SURFACE LOW EAST OF THE AREA.
ON ITS HEELS IS A FAST MOVING CLIPPER THAT THE GFS MOVES THE BEST
FORCING SOUTH...THE ECMWF FURTHER NORTH...WITH BOTH MODELS PUSHING A
COLD FRONT THROUGH. TEMPERATURES DO NOT GET COOL ENOUGH TO SUPPORT A
RAIN/SNOW MIX UNTIL WEDNESDAY...SO WE HAVE REMOVED ANY SNOW MENTION AND
RAISED TEMPS ON TUESDAY. EITHER WAY...CONDITIONS WILL REMAIN
UNSETTLED THROUGH MID-DAY ON THANKSGIVING BEFORE HIGH PRESSURE
BUILDS BACK IN. UPPER LEVEL HEIGHTS AND LOW LEVEL THICKNESSES
RESPOND QUICKLY AS THE UPPER JET BUILDS BACK NORTH OF THE BORDER.
AVIATION
06Z TAF ISSUANCE
VFR CONDITIONS EXCEPT AT KBRD WHERE FOG AND MVFR VSBYS WILL
PERSIST UNTIL 15Z AND KHIB WITH IFR AND FZFG. KHYR IS ON THE BORDER
OF MVFR VSBYS AND FOG. EXPECT KHYR TO DIP TO IFR FROM 09-12Z WITH
DENSE FOG EXPANDING NORTHWARD THROUGH NW WI. KDLH MAY SEE SOME FOG
AS WELL WITH MVFR VSBYS BEFORE 15Z BEFORE CIRRUS MOVES IN.
ANTICIPATE ALL TAF SITES TO BE VFR AFTER 15-16Z WITH CIRRUS AND
INCREASING WINDS.
POINT TEMPS/POPS
DLH 51 36 49 39 / 0 10 30 30
INL 51 31 46 29 / 0 10 30 10
BRD 53 36 51 37 / 0 10 20 30
HYR 54 36 52 40 / 0 10 30 30
ASX 53 37 51 41 / 0 10 30 30
DLH WATCHES/WARNINGS/ADVISORIES
MN...NONE.
WI...DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR WIZ009.
LS...NONE.
EOM/DONOFRIO
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