FXUS63 KDLH 111819
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
1219 PM CST FRI DEC 11 2009
.AVIATION.../18Z TAF ISSUANCE/
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD...EXCEPT FOR
LAKE EFFECT CLOUDS AND SNOW SHOWERS WITH MVFR/IFR CIGS/VSBYS OVER
LAKE SUPERIOR. A WEAK SHORTWAVE WILL TRACK EWD ACROSS THE
NORTHLAND TONIGHT. HOWEVER ONLY AREAS OF 4-8KFT CIGS ARE EXPECTED
WITH THE SYSTEM.
&&
.PREV DISCUSSION... /ISSUED 855 AM CST FRI DEC 11 2009/
DISCUSSION...
WE HAVE TWO HEADLINES THAT ARE SET TO EXPIRE AT 9 AM...A WIND
CHILL ADVISORY FOR A GOOD PORTION OF NORTHERN MINNESOTA...AND A
LAKE EFFECT SNOW ADVISORY FOR BAYFIELD COUNTY.
OBSERVATIONS INDICATE WIND CHILL ADVISORY THRESHOLDS ARE ONLY
BEING MET IN A COUPLE LOCATIONS AS OF 14Z...AND TEMPERATURES WILL
BE INCREASING. WE WILL LET THAT EXPIRE.
THE LAKE SNOW ADVISORY IS A BIT MORE OF A CHALLENGE. CALLS TO
SPOTTERS REVEAL ONLY A HALF INCH HAS FALLEN OVERNIGHT AT BARK
ISLAND AND JUST INLAND OF HERBSTER. THE BAND LOOKS TO HAVE STRENGTHENED
SOME THIS MORNING...BUT THE HIGHER RETURNS ON RADAR ARE OVER THE
LAKE. THE BAND HAS MOVED NORTH OVER THE PAST FEW RUNS AS WELL. WE
ARE GOING TO LET THIS EXPIRE...AS FEW RETURNS ARE EVEN OVER THE
SHORE AT THIS TIME...AND THE RUC13 SHOWS CONDITIONS CHANGING
LITTLE OVER THE NEXT FEW HOURS. WE WILL KEEP HIGHER POPS GOING FOR
FLURRIES AND THE PERIODIC SNOW SHOWER...WITH ADDITIONAL
ACCUMULATIONS OF AN INCH OR SO.
REST OF FORECAST UNCHANGED AT THIS TIME.
PREV DISCUSSION... /ISSUED 539 AM CST FRI DEC 11 2009/
AVIATION...12/11/12Z ISSUANCE...
VFR CONDS UNDER CLEAR SKIES...WITH MVLIFR IN SNOW SHOWERS WELL
OFFSHORE OVER LAKE SUPERIOR TODAY AND TONIGHT. MVFR IN SCATTERED
SNOW SHOWERS WILL DEVELOP ALONG THE CANADIAN BORDER LATE TONIGHT
OR EARLY SATURDAY AND SLOWLY WORK THEIR WAY SOUTH. EOM
DISCUSSION...COLD MORNING ACROSS THE NORTHLAND WITH MOST
LOCATIONS BELOW ZERO EXCEPT THE APOSTLE ISLANDS AND ALONG THE
IMMEDIATE SOUTH SHORE. HAVE TRIMMED SRN PART OF CWA FROM WIND
CHILL ADV AS TEMPS NOT LOW ENOUGH AND WINDS HAVE SUBSIDED. EVEN
MARGINAL ACROSS NRN CWA AS WELL AND MAY NEED TO TRIM FURTHER
BEFORE ACTUAL EXPIRATION TIME. MAIN STORY TODAY IS MODIFICATION OF
COLD AIR AS MID LVL TROF RELAXES AND LIFTS NORTHEAST. AS THIS
OCCURS...A SHIFTING OF AMBIENT WIND IN BDRY LAYER WILL ALLOW MORE
FAVORABLE ALIGNMENT OF SFC/85H WIND ALONG SOUTH SHORE. THIS SHOULD
ALLOW EXISTING LES PLUME TO REORIENT ALONG NRN BAYFIELD COUNTY
FROM PORT WING EAST TOWARDS NRN APOSTLE ISLANDS. ANIMATION OF 88D
SUGGESTS THIS PROCESS IS UNDERWAY. INHERITED ADVISORY STILL LOOKS
ACCEPTABLE AS NAM12 85/70H MOISTURE DECREASES QUICKLY AFTER 15Z SO
THEORETICALLY WE SHOULD SEE SOME DECREASE IN BANDING AFTER THAT
TIME. SNSH MAY LINGER INTO AFTERNOON SO LEFT POPS IN FCST THROUGH
AFTERNOON...WITH IDEA THAT MAIN LES BAND SHOULD MIGRATE MORE
OFFSHORE AS AFTERNOON UNFOLDS. THIS IS INDICATED IN WRF ARW COMP
REFLECTIVITY PRODUCTS.
OTHERWISE...WARMING TREND WILL CONTINUE INTO WEEKEND AS INITIAL
ARCTIC AIR IS MODIFIED BY RETURN FLOW AND SYNOPTIC SCALE WAA
REGIME. TEMPS MAY LOWER INITIALLY THIS EVENING HOWEVER NOT AS LOW
AS PREVIOUS NITE AS SOME MIXING EXPECTED IN BDRY LYR WITH RETURN
FLOW AND LOWERING SFC PRESSURES. HI RES MDLS INDICATE ENOUGH SW
BDRY LAYER FLOW AND LOWERING OF COND PRESSURE DEFICITS OCCUR ALONG
NORTH SHORE AFTER MIDNIGHT FRIDAY NIGHT TO KEEP SOME CHANCE OF
SNOW DEVELOPING BEFORE WINDS PUSH OFFSHORE IN BDRY LYR EARLY FRIDAY..
ZONAL MID LVL FLOW AND INCREASING INVERTED SFC TROUGHING WILL PUSH
ACROSS CWA SATURDAY. GRADUAL MOISTENING OF LOW LAYERS MAY ALLOW
SOME LIGHT SNOW TO OCCUR IN NORTH BY EARLY AFTERNOON...AND
POSSIBLY ALONG ST LOUIS RIVER VALLEY BY END OF THE DAY. NEW ARCTIC
HIGH PUSHES INTO REGION BY EARLY SUNDAY WITH SOME CHANCE OF
SQUEEZING OUT SOME LIGHT SNOW FROM RESIDUAL MOISTURE BEFORE
SUBSIDENCE WINS OUT AND ONLY FLURRIES OCCUR.
EXTENDED...SUNDAY THROUGH THE COMING WEEK...
AFTER A BRIEF RETREAT OF ARCTIC AIR...A WEAK FRONT WILL DROP SOUTH
THROUGH THE AREA...WITH A SHALLOW LAYER OF MODIFIED ARCTIC AIR LATE
SATURDAY NIGHT OR EARLY SUNDAY. A WAVE FORMS AND DEEPENS ON THIS
FRONT...OVER THE WY/CO BORDER LATE SUNDAY...REACHING WESTERN IOWA
EARLY MONDAY. HERE THE MODELS DIFFER...WITH THE EUROPEAN AND NEW
NAM TAKING THE LOW ON A SOUTHERLY TRACK...NEAR OR JUST SOUTH OF
CHICAGO ON ITS WAY TO LAKE HURON LATE MONDAY. ALL MODELS AGREE ON
RAPID MOVEMENT...WHICH WOULD ACT TO NARROW AND INTENSIFY THE SNOW
TRACK NORTH OF ITS PATH. THE GFS BRINGS THE LOW JUST NORTH OF GRB
THEN TOWARD YAM DURING MONDAY NIGHT...A TRACK THAT WOULD PUT THE
HEAVY PRECIP OVER DLH AND ALSO ENHANCE THAT PRECIP WITH LAKE
EFFECT. WE WILL GO WITH THE OTHER MODELS AND KEEP THINGS IN THE
CHANCE CATEGORY. BEHIND THE LOW...TRUE ARCTIC AIR SPREADS ACROSS
THE AREA ON ALL THE MODELS MONDAY NIGHT...TEMPERATURES ARE APT TO
REMAIN BELOW GUIDANCE THROUGH THURSDAY. ALSO...THE ARCTIC AIR WILL
LIKELY LINGER A FEW HOURS LONGER THAN GUIDANCE SUGGESTS...DUE TO THE
DIFFICULTY MODELS HAVE WITH THE LOWEST LAYERS MORE THAN A DAY OUT.
SO...THURSDAY MORNING IS APT TO BE ALSO QUITE COLD ACROSS OUR
AREA...ESPECIALLY ACROSS NW WISCONSIN. MODELS INDICATE A RETREAT OF
ARCTIC AIR TO THE NORTH AND EAST AFTER THURSDAY.
&&
.POINT TEMPS/POPS...
DLH 7 3 20 15 / 10 10 20 20
INL 0 -2 14 -1 / 10 20 20 20
BRD 10 3 19 10 / 10 10 10 10
HYR 9 -2 19 13 / 10 10 20 20
ASX 7 1 21 16 / 10 10 20 20
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...SMALL CRAFT ADVISORY UNTIL 4 PM CST SATURDAY FOR LSZ121-140>148.
&&
$$
BERDES
