FXUS63 KDLH 291803
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
1203 PM CST SUN NOV 29 2009
.AVIATION.../18Z TAF ISSUANCE/
A LOW CLOUD DECK WITH IFR/MVFR CIGS WILL LINGER OVER THE
NORTHLAND THROUGH EARLY THIS EVENING. HOWEVER THERE WILL BE AREAS
WHERE THE LOW CLOUDS SCATTER OUT...ESPECIALLY ACROSS NWRN WI AND
DOWNSLOPE OF THE SAWTOOTH RANGE. THE LOW COULD DECK SHOULD SCATTER
OUT EVERYWHERE AROUND 03Z MONDAY...EXCEPT ACROSS NWRN WI WHERE THE
LOW CLOUDS COULD PERSIST UNTIL 06Z TO 10Z. BECAUSE THE CLOUDS ARE
EXPECTED TO SCATTER OUT...THERE MAY BE ENOUGH RADIATIONAL COOLING
TO RESULT IN PATCHY FOG WITH MVFR/IFR VSBYS LATE TONIGHT AND EARLY
MONDAY MORNING. A QUICK MOVING CLIPPER SYSTEM FROM CANADA WILL
BRING INCREASING MID-LEVEL CLOUDS TO OUR FCST AREA LATE
TONIGHT...WITH LOW CLOUDS EXPECTED TO INCREASE ACROSS THE AREA ON
MONDAY. SNOW SHOWERS WITH REDUCED VSBYS ARE POSSIBLE ACROSS OUR
NWRN ZONES MONDAY MORNING AS WELL...WHICH WILL SPREAD SOUTHEAST IN
THE AFTERNOON.
&&
.PREV DISCUSSION... /ISSUED 1143 AM CST SUN NOV 29 2009/
UPDATE...
INCREASED CLOUDINESS FOR THE NEXT SEVERAL PERIODS AND TAPERED
SCATTERED SNOW SHOWERS TO FLURRIES THIS EVENING. LIFTED
TEMPERATURES BY VERY SMALL AMOUNTS. MODERATED WINDS.
DISCUSSION...
PACIFIC AIR IS WITH US...ADVECTION OF NOT VERY COLD AIR BEHIND
WEAK LOW PRESSURE OVER LOWER MICHIGAN AND CLOUDS OVER AND EAST OF
THE RED RIVER WILL KEEP TEMPERATURES CLOSE TO FREEZING THIS
AFTERNOON. RIDGING SHOULD END ANY SNOW SHOWERS...BUT WILL DO
LITTLE TO REMOVE CLOUDS TONIGHT. WARM AIR WILL RETURN...FIRST WITH
A SHOT OF VERY LIGHT WET SNOW OR A MIX...THEN RISING TEMPERATURES
MONDAY. CONTINUED WARMING WILL OCCUR AT LOWER LEVELS...WITH THE
PRECIPITATION TO OUR EAST AND TEMPERATURES KEPT FROM FALLING VERY
FAR MONDAY NIGHT. THERE SHOULD BE SOME PRETTY GOOD WARMING AHEAD
OF A RAPIDLY DEEPENING STORM TUESDAY. RAIN AND SNOW SHOWERS WILL
LIKELY BE CONFINED TO THE CANADIAN BORDER...WITH A PRETTY DECENT
SNOWSTORM TO THE NORTH. THE COLD FRONT WITH THIS LOW SHOULD ONCE
AND FOR ALL REMOVE PACIFIC AIR FROM OUR AREA AS IT SCOOTS THROUGH
TUESDAY EVENING. ALL THE RECENT MODEL RUNS AGREE VERY CLOSELY ON
THIS WHOLE SCENARIO. BEHIND THE FRONT...THERE IS A RISK OF QUITE A
WINDSTORM LATE TUESDAY NIGHT AND WEDNESDAY. EVEN AS THE VERY TIGHT
GRADIENT AND ISALLOBARIC VECTORS SUBSIDE...A DEEP AND STEEP LAPSE
RATE WILL KEEP THE WINDS QUITE STRONG AS MOMENTUM TRANSFER WITH
HIGHER AND HIGHER LEVELS CONTINUES LATE WEDNESDAY AND WEDNESDAY
EVENING. AGAIN...ALL THIS WILL RESULT IN VERY LITTLE PRECIPITATION
ACROSS OUR AREA. THE COOLING ALOFT WILL BE MORE DRAMATIC THAN AT
THE SURFACE LATE TUESDAY NIGHT AND WEDNESDAY...AND WITH THE
PACIFIC AIR REMOVED...A LONG IMPORTANT COOLING TREND WILL BEGIN.
PREV DISCUSSION... /ISSUED 636 AM CST SUN NOV 29 2009/
AVIATION...
HIGHLY VARIABLE CEILINGS AND ISOLD -SHSN FOR THE FA THROUGH
16Z. TAF SITES WILL GENERALLY HAVE PREVAILING VFR CIGS
TODAY...WITH PERIODS OF MVFR/IFR CEILINGS AS A SHORT WAVE TRACKS
SE OVER THE FA. LOWEST CEILINGS THIS MORNING WILL BE FOUND OVER
NW AND NC MN...WITH A PERIOD OF IFR POSSIBLE AT KBRD AND KINL.
CEILINGS WILL GRADUALLY LIFT THROUGH THE EVENING BEFORE ANOTHER
FAST MOVING WAVE SPREADS LOW CLOUDS BACK OVER THE REGION DURING
THE DAY MONDAY.
PREV DISCUSSION... /ISSUED 312 AM CST SUN NOV 29 2009/
DISCUSSION...
THRU MON...
BROAD UPR LVL TROF PASSING OVR CWA TDA PRODUCING SOME -SN OR
FLURRIES ACRS SRN ZONES N OF FNTL BNDRY ACRS ERN IA/SRN WI. AMS IS
VRY DRY WITH NO SIG MSTR SOURCE...SO ANY ACCUMS WILL BE VERY LIGHT.
BRIEF WINDOW OF OPPORTUNITY ABOUT MIDDAY FOR SOME LES ALG S SHORE
WITH DELTA-T ARND 16...BUT WINDS DO NOT REMAIN FAVORABLE FOR VERY
LONG AND AMS IS QUITE DRY...SO ANY ACCUMS SHUD BE LIMITED TO AN INCH
OR TWO. SFC AND UPR LVL RIDGING INCREASES TNGT...BUT STRONG VORT MAX
SLIDES DOWN ACRS THE WRN GRT LKS IN NW FLOW ON MON. STRONG LIFT MAY
OVERCOME THE LACK OF MSTR TO THE POINT WHERE AN INCH OR SO OF
SNOWFALL MAY BE REALIZED...ESPECIALLY ACRS NERN HALF OF CWA...AND
THIS WILL BE REFLECTED IN THE NEW FCST.
TUE THRU FRI...
MAIN FOCUS IN LONG TERM IS ON A STRONG SHORT WAVE THAT DIGS SOUTH
OUT OF MANITOBA AND INTO THE UPR MIDWEST TUES/WED. THE WAVE AND SFC
LOW WILL BRING A CHC FOR SNOW AND A COOL DOWN TO MORE SEASONABLE
TEMPERATURES THROUGH MID WEEK AND INTO THE WEEKEND. FCST DIFFICULTY
IN TIMING THE FAST MOVING WAVE WITH A 70-80KT MID LVL JET AND 40-50
KT TRAILING LLJ. THE MDL RUNS ARE DEEPENING THE TROUGH FURTHER THAN
PREVIOUS RUNS...WITH THE GFS/NAM80 DEPICTING A CLOSED LOW THAT CLIPS
THE INTERNATIONAL BORDER THROUGH 12Z WED. PREVIOUS FCST ON TRACK
WITH ONLY MINOR ADJUSTMENTS TO INCREASE POPS IN NRN WIS ZONES FOR
INCREASING CONFIDENCE OF LK EFFECT/ENHANCED SNOW AS THE LOW DEPARTS.
LAPSE RATES INCREASE AS 850 MB TEMPS FALL INTO THE TEENS WED/THURS.
THE FAVORABLE DELTA-T VALUES COMBINED WITH A 15-20KT W/NW BDRY LYR
FETCH AND LINGERING MOISTURE AREA EXPECTED TO PRODUCE A FEW INCHES
OF ACCUMULATING LK EFFECT/ENHANCED SNOW ALONG THE SNOW BELT REGION
OF NRN WIS. ALTHOUGH SPECIFIC WIND TRAJECTORY DETAILS TO STILL BE
WORKED OUT...THE BEST THREAT FOR SN OCCURS IN THE WED NIGHT THROUGH
THURS NIGHT PERIOD WHEN GFS BUFR SOUNDING AT KIWD SUGGESTS A
SATURATED PROFILE WITH STEEP LAPSE RATES TO 700-750 MB AND 40-50
J/KG OF CAPE.
AVIATION...06Z TAFS...
RADAR INDICATES SOME LIGHT SNOW HAD OCCURRED AT BRD AND SOME MAY
FALL AT HYR. ALSO MVFR TO IFR CIGS ARE MOVING SOUTHEAST THROUGH
FORECAST AREA. THIS TREND WILL CONTINUE THROUGH THE EARLY MORNING
HOURS. THE MVFR TO IFR CIGS WILL CONTINUE INTO THE DAYLIGHT HOURS
AND WILL IMPROVE TO VFR ACROSS ALL SITES EXCEPT WHERE MVFR CIGS
MAY LINGER UNTIL SUNSET. VSBYS AMY DROP DOWN INTO MVFR OVERNIGHT
IN THE AREAS OF LIGHT SNOW.
&&
.POINT TEMPS/POPS...
DLH 36 26 37 27 / 20 10 20 10
INL 33 19 34 22 / 30 10 30 10
BRD 35 23 39 26 / 10 10 20 10
HYR 37 21 39 21 / 10 10 20 10
ASX 35 25 37 24 / 50 10 40 10
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...NONE.
&&
$$
BERDES
