FXUS63 KDLH 280544 AAB
AFDDLH
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DULUTH MN
1144 PM CST FRI NOV 27 2009
.AVIATION...06Z TAF ISSUANCE...
BRISK WRLY FLOW ALOFT IS MAINTAINING A STEADY PROGRESSION OF
MID/HIGH LEVEL CLOUDS ACROSS CWA. A WEAK SFC WAVE WILL PUSH
ACROSS THE REGION OVERNIGHT WITH LITTLE EFFECT AS MOISTURE
CONVERGENCE IS LIMITED. COND PRESS DEFICIT FCST FROM NAM12/RUC13
SUGGEST A BRIEF PERIOD OF MVFR CEILINGS MAY OCCUR NEAR KBRD AFTER
10Z SATURDAY. CONFIDENCE NOT HIGH AT THIS POINT GIVEN LACK OF ANY
DEVELOPMENT AT THIS HOUR UPSTREAM.
&&
.PREV DISCUSSION... /ISSUED 940 PM CST FRI NOV 27 2009/
UPDATE...CURRENT GRIDS/ZFP IN GOOD SHAPE. WEAK SFC
WAVE...REFLECTION OF MID LVL SHORTWAVE..IS PUSHING INTO WRN EDGE OF
CWA. LIMITED FORCING AVAILABLE WITH WEAK BLYR CONVERGENCE
ALONG WINDSHIFT AXIS AND UPPER JET CORE NORTH OF AREA . COND
PRESS DEFICITS INDICATE ANY SIGNIFICANT SATURATION OF ATMOSPHERIC
COLUMN OVERNIGHT WILL BE CONFINED TO MID LVLS. AN AREA OF LOWER
CLOUDS MAY EVENTUALLY DEVELOP ACROSS NW WISC AFTER 10Z WHEN
DEFICITS LOWER TO 10/20MB AND WEAK OMEGA ADVECTS OVERHEAD.
PREV DISCUSSION... /ISSUED 540 PM CST FRI NOV 27 2009/
AVIATION...00Z TAF ISSUANCE...
A WEAK SFC LOW ASSOCIATED WITH AN UPPER DISTURBANCE WILL CROSS THE
AREA OVERNIGHT. VARYING AMOUNTS OF MID/HIGH LVL CLOUDS
ARE ANTICIPATED OVER THIS FCST PERIOD. NAM12 COND PRESS DEFICITS
INDICATE AN AREA OF MVFR CEILINGS MAY DEVELOP AFTER 9Z NEAR
KDLH/KHYR TERMINALS...AND LINGER UNTIL LATE MORNING. RUC13/GFS DEFICITS
REMAIN HIGHER SO WILL NOT INCLUDE ANY MVFR AT THIS POINT. WILL
NEED TO ADD LATER IF SATURATION APPEARS TO BE DEVELOPING LATER
THIS EVENING.
PREV DISCUSSION... /ISSUED 313 PM CST FRI NOV 27 2009/
DISCUSSION...
FAIRLY CALM AND QUIET ACROSS THE CWA WITH WARM AIR ADVECTION MID AND
UPPER CLOUDS MOVING THROUGH. A FEW LOWER CLOUDS WERE FOUND ALONG
THE NORTH SHORE...WITH THICKER MID CLOUD COVERAGE OVER THE
ARROWHEAD AND ADJACENT SOUTHERN CANADA...WHERE PROGRESSIVE WEAK
IMPULSES ARE TRAVERSING A FLATTENING UPPER RIDGE TO OUR WEST. IT
LOOKED...AND MAY HAVE FELT WARMER THAN IT WAS OUTSIDE WITH WELCOME
SUNSHINE EARLIER IN THE DAY. THE NORTHLAND CURRENTLY REMAINS IN
BETWEEN HIGH PRESSURE EXTENDING THROUGH WISCONSIN TO CENTRAL LAKE
SUPERIOR. THIS HIGH HAS MADE LITTLE EASTWARD PROGRESS
TODAY...WHILE LOW PRESSURE OVER THE DAKOTAS HAS ENTERED THE NW
CORNER OF MN...RESULTING IN 1-2 MB 3HR PRESSURE FALLS OVER OUR MN
ZONES.
THE SURFACE LOW TO THE WEST WILL WEAKEN AND SINK SOUTH
TONIGHT...WITH THE TROUGH AXIS PASSING OVER THE CWA OVERNIGHT.
WINDS WILL WEAKEN AND THEN BECOME NNW ON SATURDAY...THOUGH THE
MAIN COLD AIR ADVECTION PUSH WILL NOT COME UNTIL SUNDAY.
MEANWHILE SATURDAY...ANOTHER PROGRESSIVE UPPER LEVEL DISTURBANCE
CURRENTLY ENTERING WESTERN ALBERTA WILL PASS THROUGH SOUTHERN
CANADA DURING THE DAY. THEREFORE WILL CONTINUE THE MID AND UPPER
LEVEL CLOUD COVER.
MODELS AGREE THAT THIS DISTURBANCE WILL ENTER NW MN SATURDAY
NIGHT. THERE IS A VERY WEAK SURFACE LOW REFLECTION WITH THIS
FEATURE...MAINLY NORTH OF THE BORDER...WHICH IS WHERE THE BEST
FORCING WILL BE. THIS WAVE THEN QUICKLY DIVES SE THROUGH THE AREA
ON SUNDAY..PUSHING OFF INTO NW WISC DURING THE AFTERNOON. WHILE
THE MODELS HAVE BEEN FAIRLY CONSISTENT WITH THE TRACK OF THIS
FEATURE...THE LATEST GFS/GEM AND GFS ENSEMBLES ARE MORE BULLISH
WITH THE SOUTHERN EXTENT OF LIGHT QPF...COMING IN LINE WITH 12Z
ECMWF. THE NAM KEEPS MOST OF THE MOISTURE PRECIP IN THE NORTHERN
TIER...WITH THE SREF SPLITTING THE DIFFERENCE THOUGH GENERALLY
CLOSER TO THE NAM. WEAK FRONTOGENESIS WILL AID IN UPPER LEVEL
WAVE TO RING OUT SNOW SHOWERS IN A NARROW RIBBON OF DEEPER LAYER
SATURATION. FLURRIES WILL BE SEEN ELSEWHERE. WE HAVE ADDED POPS TO
MOST OF THE CWA...ALTHOUGH HIGHER POPS...IN THE CHANCE
CATEGORY...WILL BE NORTH OF DULUTH AND ALSO ALONG THE SOUTH
SHORE...WHERE LAKE ENHANCEMENT WILL OCCUR SUNDAY.
LONG TERM...SUNDAY NIGHT THROUGH FRIDAY..
THERE IS SOME AGREEMENT BETWEEN THE VARIOUS MEDIUM TO LONGER RANGE
DETERMINISTIC AND ENSEMBLE RUNS TODAY TOWARD COLDER TEMPS NEXT
WEEK..BUT OVERALL DETAILS OF HOW WE GET THERE ARE SIGNIFICANTLY
DIFFERENT. THUS..CONFIDENCE IN THE FORECAST FOR NEXT WEEK IS BELOW
NORMAL.
ALMOST ALL GUIDANCE GENERALLY AGREES THAT A TRANSITION TO
COLDER TEMPS IS ON THE WAY WITH THE INITIAL SHORT-LIVED SHOT
SUNDAY-MONDAY..AND THEN A SECOND STRONGER..AND MORE LONG LIVED PUSH
OF ARCTIC AIR SOMETIME AROUND MID-WEEK. A PROGRESSIVE WARM ADVECTION
PATTERN WILL SET UP MONDAY/MONDAY NIGHT MAY RESULT IN A SHORT
PERIOD OF LIGHT SNOW. A SECOND AND STRONGER SHORT WAVE TROF IS
EXPECTED TO DIVE SEWD FROM CANADA INTO THE WRN LAKES REGION TUE
NIGHT/WED..BUT THERE IS QUITE A BIT OF UNCERTAINTY ON THE TIMING
AND EVENTUAL PLACEMENT OF THE STRONGEST FORCING. WE HAVE CONFINED
POPS FOR BOTH OF THESE WAVE ACROSS THE NRN THIRD TO HALF OF THE
DULUTH CWA..WTH THE HIGHEST POPS ALONG THE CANADIAN BORDER. COLDER
TEMPS CLOSER TO NORMALS FOR LATE NOV/EARLY DEC APPEAR ON TAP AFTER
THE PASSAGE OF THE MID WEEK WAVE AS A MORE SUBSTANTIAL COLD FRONT
WILL ACCOMPANY ITS PASSAGE. THERE APPEARS TO BE AT LEAST SOME
CHANCE OF SOME LIGHT SNOW TOWARD THE END OF NEXT WEEK..BUT THE
LATEST ECMWF SEEMS TO HAVE COME MORE IN LINE OF THE MORE
PROGRESSIVE GFS SOLN FOR THE PAST COUPLE DAYS. DESPITE PERHAPS THE
COLDEST AIRMASS OF THE YOUNG WINTER SEASON SO FAR..THE LACK OF
SNOW COVER BOTH ACROSS OUR AREA AND ALSO UPSTREAM ACROSS MUCH OF
SOUTHERN CANADA IS EXPECTED TO TEMPER THE COLD..AND WE HAVE NOT
GONE TOO TERRIBLY COLD FOR THE WED-FRI TIME PERIOD WITH THIS
ISSUANCE.
AS IS TYPICAL FOR THIS TIME OF YEAR..ANY COLD AIRMASS WILL PROMPT A
CHANCE OF LAKE EFFECT SNOW SHOWERS WITH LK SUPERIOR WATER TEMPS
STILL IN THE LOWER TO MID 40S. WE HAVE INCLUDED A MENTION OF LAKE
EFFECT SNOW FOR THE SOUTH SHORE SUNDAY NIGHT..AND AGAIN
WED-THUR..AND ALSO OVER THE MN ARROWHEAD AND NORTH SHORE WITH S/SE
RETURN FLOW LATER TUESDAY AND TUESDAY NIGHT.
AVIATION...18Z TAF ISSUANCE...VFR CONDITIONS THROUGH THE PERIOD WITH
INCREASING CIRRUS/CIRROSTRATUS. SOME PATCHY FOG IS POSSIBLE AT
KHYR...BUT CONFIDENCE LOW AT THIS TIME TO INCLUDE IN THE TAF. A
FEW MID LEVEL CLOUDS WILL RIDE ALONG THE INTERNATIONAL BORDER WITH
DISTURBANCES PASSING THROUGH SOUTHERN MANITOBA AND ONTARIO. WIND
WILL BECOME LIGHT AND VARIABLE OVERNIGHT AND THEN BECOME MORE NNW
ON SATURDAY AFTER A WEAK TROUGH PASSAGE. WINDS ARE NOT EXPECTED TO
GET TOO STRONG...AS MAIN CAA PUSH WILL OCCUR AFTER THE CURRENT TAF
PERIOD.
&&
.POINT TEMPS/POPS...
DLH 26 37 27 33 / 0 10 20 20
INL 20 35 25 29 / 10 10 30 10
BRD 26 40 28 34 / 0 10 20 10
HYR 25 42 26 34 / 0 10 20 20
ASX 23 41 28 37 / 0 10 30 30
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...NONE.
&&
$$
CANNON/CANNON/CANNON
