433
FXUS63 KDLH 210520
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
1120 PM CST FRI NOV 20 2009
UPDATE
ISSUED A DENSE FOG ADVISORY FOR PRICE COUNTY WI UNTIL
15Z SATURDAY. VSBYS HAVE BEEN HOVERING AROUND 1/4 MI OR LESS AND
NO REAL IMPROVEMENT SEEN UNTIL AFTER SUNRISE.
AVIATION
06Z TAFS.
VFR CONDITIONS EXCEPT AT KBRD WHERE FOG AND MVFR VSBYS WILL PERSIST
UNTIL 15Z. KHYR IS ON THE BORDER OF MVFR VSBYS AND FOG. EXPECT
KHYR TO DIP TO IFR FROM 08-12Z WITH DENSE FOG JUST TO THE E AND
SE. KDLH/KHIB MAY SEE SOME FOG AS WELL WITH MVFR VSBYS BEFORE 15Z.
ANTICIPATE ALL TAF SITES TO BE VFR AFTER 15-16Z.
PREV DISCUSSION
/ISSUED 824 PM CST FRI NOV 20 2009/
UPDATE...SFC RIDGE AXIS MOVING OVERHEAD ATTM. FOG IS FORMING IN
NW WI...MAINLY SE OF HIGHWAY 63. SOME FOG ALSO FORMING IN THE
BRAINERD LAKES REGION OVER TO NORTHERN LAKE MILLE LACS. HAVE ADDED
FOG WORDING IN THESE AREAS. PREVIOUS MIN TEMP FORECAST RANGES
ALREADY BEATEN IN SEVERAL LOCATIONS AND HAVE ADJUSTED DOWNWARD.
CI SHIELD ATTEMPTING TO RIDE THE RIDGE INTO THE FA FROM THE W.
THESE CLOUDS...ALONG WITH WAA...MAY PRECLUDE FOG FROM BECOMING
MORE WIDESPREAD IN THE WESTERN THIRD OF THE FA.
AVIATION...00Z TAFS.
MAINLY VFR CIGS...BUT THE FOG FORMATION FROM RADIATIONAL
COOLING/MOIST GROUND...ESPECIALLY IN NW WI...WORTHY OF MVFR/IFR
VSBYS THROUGH SUNRISE. WAA FROM THE W AND FORECAST SOUNDINGS
INDICATE IT MAY BE TOUGHER TO FORM FOG AT KINL.
PREV DISCUSSION... /ISSUED 316 PM CST FRI NOV 20 2009/
CORRECTED FOR TYPO ERRORS...
DISCUSSION...A PROGRESSIVE PATTERN WITHIN THE MID LVL FLOW WILL
BRING CHANGEABLE WEATHER TO THE REGION OVER THE NEXT SEVERAL DAYS.
HIGH PRESSURE AT THE SFC WILL MOVE ACROSS THE CWA OVERNIGHT.
SHOULD SEE FOG TONIGHT WITH HIGHEST POTENTIAL FOR WIDESPREAD AREAL
COVERAGE/DURATION ACROSS NW WISC WHERE LONGER DECOUPLED BDRY LYR
WILL EXIST. USED AREAS OF FOG TERMINOLOGY IN ERN CWA AND PATCHY
ELSEWHERE. LATEST FCST OF 925 WINDS SUGGEST WARM ADVECTION REGIME
WILL BEGIN WEST OF A CDD-DLH- HINCKLEY LINE AFTER 6Z. HOPEFULLY
THIS MAY MITIGATE EXTENT OF FOG OVER WRN CWA. AS IS THE CASE WITH
MOST FOG POTENTIAL FORECASTS...LATER UPDATES MAY BE NEEDED.
PLEASANT DAY ACROSS THE REGION SATURDAY WITH WARM ADVECTION
PATTERN AND ABOVE NORM TEMPS. 85H MSTR TRANSPORT AXIS LOCATED WEST
OF CWA SATURDAY...WILL TRANSLATE EAST INTO REGION SATURDAY
NIGHT/SUNDAY. EXISTING FCST HAD GOOD SOLUTION REGARDING TIMING OF
LOW STRATUS CLOUD DEVELOPMENT AND POPS. DID NOT CHANGE ALIGNMENT
OF POP GRADIENT SUNDAY ALTHOUGH TREND IS FOR HIGHER POPS TO BE
OVER NW WISC SUNDAY AFTERNOON IN ZONE OF BEST LOW LEVEL THETAE
AXIS. SFC BDRY MOVING INTO THE REGION SUNDAY GETS SOMEWHAT WASHED
OUT IN THE LOW LVL WIND FIELD BUT MAINTAINS WELL DEFINED SIGNAL IN
LOW LVL THERMAL FIELDS. ALTHOUGH SOME WEAK FRONTOGENESIS MAY
DEVELOP LATE SUNDAY INTO MONDAY...OVERALL SYNOPTIC SCALE FORCING
WILL BE LIMITED. AS A RESULT...EXPECT ABUNDANT CLOUDS BUT NOT A
LOT OF PRECIPITATION MONDAY. NAM/EC/GEM FAVOR NWRN PART OF CWA FOR
HIGHER POPS.
EXTENDED...MONDAY NIGHT THROUGH FRIDAY
GFS AND ECMWF ARE STILL IN SIGNIFICANT DISAGREEMENT WITH THE LOW
PRESSURE SYSTEM THAT WILL BE AFFECTING THE REGION THROUGH THURSDAY.
WE FOLLOWED CLOSE TO THE ECMWF SOLUTION...WHICH HAS BEEN
CONSISTENT...AND HAS SUPPORT FROM THE CANADIAN.
THE UPPER LOW IS FORECAST TO TRACK FROM KS...NORTHEAST TOWARD IA ON
WEDNESDAY...WITH A NORTHERN STREAM WAVE ALSO STRENGTHENING AS IT
NEARS MB/OT. THESE UPPER WAVES WILL THEN CONTINUE EAST THURSDAY. AT
THE SURFACE...LOW PRESSURE WILL ACCOMPANY THE UPPER WAVE IS IT MOVES
THROUGH. THE ECMWF IS WARMER THAN THE GFS. PRECIP TYPE WILL BE AN
ISSUE WITH THIS SYSTEM...ESPECIALLY DURING THE OVERNIGHT PERIODS
WHEN BOUNDARY LAYER TEMPS COOL. WE WENT WITH A RAIN/SNOW MIX FOR
SEVERAL OF THE PERIODS BETWEEN MONDAY NIGHT AND WEDNESDAY NIGHT.
MAINLY RAIN COULD VERY WELL OCCUR IF BOUNDARY LAYER TEMPS REMAIN A
BIT WARMER THAN CURRENTLY FORECAST...AND THOSE DETAILS WILL BE
WORKED OUT AS THE SYSTEM NEARS. AT THIS TIME...THIS SYSTEM DOES NOT
LOOK LIKE A HEAVY PRECIP MAKER.
AVIATION...18Z TAFS
HIGH PRESSURE WILL CONTINUE TO DOMINATE THE WEATHER THROUGH THE
PERIOD. FOG AND SOME STRATUS WILL BE POSSIBLE AGAIN
OVERNIGHT...BUT INCREASING WINDS JUST ABOVE THE SURFACE MAY KEEP
THE FOG FROM BECOMING TOO WIDESPREAD AND DENSE TONIGHT. WE DID
INCLUDE FOG AND STRATUS IN ALL THE TAF SITES...EITHER AS A
PREDOMINATE ELEMENT...OR AS A TEMPORARY CONDITION. A STRONGER
PRESSURE GRADIENT WILL EXIST ON SATURDAY...SO THE FOG WILL BURN
OFF QUICKER THAN IT DID TODAY.
POINT TEMPS/POPS
DLH 26 49 36 48 / 0 0 20 40
INL 17 48 33 45 / 0 0 20 20
BRD 24 52 36 47 / 0 0 20 30
HYR 23 51 40 48 / 0 0 20 30
ASX 25 52 39 49 / 0 0 20 30
DLH WATCHES/WARNINGS/ADVISORIES
MN...NONE.
WI...DENSE FOG ADVISORY UNTIL 9 AM CST SATURDAY FOR WIZ009.
LS...NONE.
GSF
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