FXUS63 KDLH 220106 AAA
AFDDLH
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DULUTH MN
706 PM CST MON DEC 21 2009
.UPDATE...
INCREASED CLOUDINESS ACROSS OUR AREA BOTH TONIGHT AND TUESDAY. WE
ALSO CONTINUED ISOLATED FLURRIES UNTIL LATE THIS EVENING.
&&
.DISCUSSION...
THE MAP IS RATHER WARM ACROSS MOST AREAS...WARM AIR WILL REMAIN ABOVE
THE 900-850 MB LEVEL UNTIL THE CHRISTMAS STORM ARRIVES. HIGH PRESSURE
OVER SOUTHERN HUDSON BAY WILL CAUSE WINDS TO VEER ALONG THE COAST
AS IT BUILDS NORTH OF LAKE SUPERIOR TONIGHT AND TUESDAY. DRY AIR
WILL REMAIN JUST WARM ENOUGH TO KEEP FROM BREAKING THE INVERSION
ACROSS THE ARROWHEAD. SO...MOISTURE JUST BELOW THE INVERSION WILL
REMAIN TRAPPED...LEADING TO CLOUDS AND ISOLATED FLURRIES...SOME OF
THOSE CONTINUE TO FALL OVER THE UPLANDS OF THE ARROWHEAD. WITH THE
VEERING WIND BECOMING ONSHORE ALONG THE NORTH SHORE...WE LEFT A
SLIGHT CHANCE OF SNOW SHOWERS ALONG THE NORTH SHORE THROUGH
TUESDAY. THE LOW LEVEL OF THE INVERSION WILL PREVENT ACCUMULATING
SNOW...AND THE CLOUDS SEEM TOO SHALLOW FOR FREEZING DRIZZLE...SO
MOSTLY CLOUDY SKIES AND WEAK WINDS WILL CONTINUE.
LOOKING AT THE NEW GUIDANCE...IT SEEMS THAT THE CHRISTMAS STORM
WILL APPROACH OR BORDER OUR AREA MOST OF CHRISTMAS EVE...THEN
SPREAD RAPIDLY NORTHEASTWARD ACROSS OUR AREA LATE AFTERNOON OR
EARLY EVENING CHRISTMAS EVE. THERE IS LITTLE IF ANY CHANCE OF
ARCTIC AIR ENTERING THE SYSTEM BEFORE SUNDAY-AFTER-CHRISTMAS WHICH
WILL PREVENT IT FROM DEEPENING EXPLOSIVELY UP HERE...MITIGATING
SNOW AMOUNTS THROUGHOUT WESTERN PARTS OF OUR AREA. HOWEVER...A
PERSISTENT DEEP AND MOIST ONSHORE FLOW WOULD ACT TO ENHANCE SNOW
AMOUNTS ACROSS THE TWIN-PORTS AREA AND ALONG THE NORTH SHORE. WE
ARE WATCHING THIS SYSTEM CLOSELY FOR FURTHER CLARIFICATION.
&&
.PREV DISCUSSION... /ISSUED 557 PM CST MON DEC 21 2009/
AVIATION.../00Z TAF ISSUANCE/
WEAK FLOW CONTINUES TO RESULT IN BKN TO OVC STRATUS ACROSS MUCH OF
NE MN AND NW WI. SOME BREAKS IN THE LOW STRATUS SEEN AT KHYR.
MODELS HAVING A DIFFICULT TIME IN CIG HEIGHTS...BEING TOO
OPTIMISTIC THROUGH THE FIRST PART OF THE TAF PD. SOME QUESTION AS
TO WHETHER OR NOT CIGS WILL LIFT AND SCATTER ON TUE. WENT WITH A
MORE PESSIMISTIC APPROACH BASED ON PERSISTENCE...AND KEPT MOST
AREAS MVFR THROUGH THE PD. LOW LVL CONDENSATION PRES DEFICITS
INDICATING AN AREA OF SNOW AND LOWER CIGS MAY BREAK OUT IN THE
KDLH...AND NORTH SHORE AREA LATER TONIGHT/EARLY TUE...THOUGH
CONFIDENCE IS TOO LOW TO INCLUDE IN FCST ATTM.
PREV DISCUSSION... /ISSUED 344 PM CST MON DEC 21 2009/
DISCUSSION...
LATEST SAT IMAGERY SHOWS A WAVE CURRENTLY MAKING LANDFALL ON THE
PACIFIC NW COAST. MDLS CONTINUE TO SHOW GOOD CONTINUITY THAT THE
WAVE DEEPENS WHILE DIVING S OVER TEXAS THROUGH WED...FINALLY
BECOMING A CUT OFF LOW ROTATING OVER THE CEN PLAINS THURS/FRI.
CURRENT SFC ANALYSIS SHOWS A WEAK SFC LOW ASSOCIATED WITH A SHORT
WAVE OVER ERN LK SUP. THE LOW WILL PUSH E OVERNIGHT AS CANADIAN HIGH
PRESSURE BUILDS OVER ONTARIO/NRN MN. THE HIGH WILL STRENGTHEN TO
AROUND 1035 MB OVER ONTARIO/HUDSON BAY WITH STRONG MID LVL RIDGING
AHEAD OF THE APPROACHING LOW TUES/TUES NIGHT. THIS WILL ACT TO
ANCHOR A LARGE AREA OF VERY DRY AIR TO THE IMMEDIATE NE OF THE FA.
THE NAM/ECM/GFS ARE ALL SHOWING 850-700 MB RH FIELDS FALL INTO THE
20-30 PERCENT RANGE OVER THE ERN HALF OF THE FA BY 12Z WED WITH A
E/NE BDRY LAYER FLOW. THE DRY CANADIAN AIR WILL PLAY A SIGNIFICANT
ROLE IN TIMING THE ONSET OF THE PRECIPITATION...ESPECIALLY IN THE
MN ARROWHEAD AND FAR NE WISCONSIN ZONES.
MEANWHILE...AS THE CYCLONE APPROACHES FROM THE S A 30 KT E/SE LLJ
WILL BRING THETA-E/WAA TO THE SW ZONES. THIS WILL CREATE A STRONG
MOISTURE GRADIENT ACROSS THE CWA WED/WED NIGHT. PULLED BACK TIMING
OF STORM ARRIVAL BY 6-12 HOURS FOR NE HALF OF FA WHERE THE DRY AIR
WILL HOLD OFF PCPN UNTIL THURS AFTRN/EVENING. MODEL ARE COMING
INTO AGREEMENT THAT THE LEADING EDGE OF THE SN PUSHES NE INTO THE
SRN ZONES...KBRD TO KRZN...AROUND 12Z THURS. THE SN WILL CONTINUE
TO LIFT NE...REACHING THE KINL/KHIB/KDLH/KHYR AREAS AROUND THE
21-00Z FRI TIME FRAME. THE SN WILL ARRIVE THE LATEST IN THE MN
ARROWHEAD...GENERALLY LATE WED EVENING.
LONG TERM...CHRISTMAS EVE NIGHT THROUGH MONDAY...
MAIN FOCUS FOR THIS TIME PERIOD CONTINUES TO BE ON THE SIGNIFICANT
WINTER STORM TO AFFECT MUCH OF THE MIDDLE PART OF THE COUNTRY FOR
THE CHRISTMAS HOLIDAY PERIOD. AT THIS TIME CONFIDENCE CONTINUES TO
INCREASE FOR AT LEAST SEVERAL INCHES OF SNOW ACROSS A LARGE PART OF
THE DULUTH CWA.
WITH ONLY A FEW EXCEPTIONS FROM SOME OF THE INDIVIDUAL ENSEMBLE
MEMBERS..ALL GUIDANCE HAS MADE A SIGNIFICANT SHIFT WESTWARD IN THE
TRACK OF THIS STORM SINCE LATE LAST WEEK..WHICH WILL PLACE MOST OF
THE NORTHLAND IN ACCUMULATING SNOWS CHRISTMAS EVE/CHRISTMAS DAY.
WHILE THE TYPICAL DIFFERENCES IN DETAIL EXIST FROM MODEL TO MODEL
AND RUN TO RUN..MOST GUIDANCE DEVELOPES THE SURFACE LOW SOMEWHERE IN
THE OKLAHOMA/N TEXAS AREA THURSDAY NIGHT..AND THEN RAPIDLY
INTENSIFIES THE SFC LOW AND CLOSES THE DEEP LAYER CIRCULATION OFF
THRU 500 MB WHILE MOVING IT NORTH-NORTHEAST TO SOMEWHERE IN NRN
MISSOURI/SRN IOWA AREA BY CHRISTMAS MORNING. THEREAFTER..THE UPPER
LOW CENTER AND ASSOCIATED SFC REFLECTION IS FORECAST TO MOVE NEWD
INTO WISCONSIN WHILE SLOWLY FILLING LATER CHRISTMAS DAY AND
CHRISTMAS NIGHT.
ALTHOUGH THE MAIN SYSTEM INTENSIFICATION WILL TAKE PLACE WELL TO OUR
SOUTH..ALL GUIDANCE IS FAIRLY CONSISTENT IN BRINGING A PRIMARY LOBE
OF SYNOPTIC SCALE FORCING FOR UVM ACROSS NE MN/NW WI BEGINNING LATE
AFTERNOON ON THURSDAY THRU ABOUT MIDDAY ON CHRISTMAS..AND THIS IS
SEEMINGLY THE MOST LIKELY TIME PERIOD FOR SUSTAINED ACCUMULATING
SNOW. HOWEVER..IT SHUD BE NOTED THAT LONG EASTERLY FETCHES WED
NITE/THUR MAY RESULT IN AN EARLIER ONSET TIME..AND A LONGER DURATION
PERIOD OF LINGERING LIGHT SNOW MAY PERSIST WELL INTO CHRISTMAS NIGHT
ALONG WRN PERIPHERY OF BENT-BACK TROWAL FEATURE AND DEEP-LAYER
DEFORMATION ON THE WRN EDGE OF THE 500 MB CIRCULATION CENTER. WE
HAVE DECIDED TO HOLD OFF ON A WINTER STORM WATCH AT THIS TIME..BUT
UNLESS THERE ARE DRASTIC CHANGES TO THE OVERALL GUIDANCE..A WATCH
WILL LIKELY BE NEEDED FOR MOST OF THE CWA THIS EVENING OR TOMORROW
MORNING.
LAKE EFFECT SNOWS ARE AGAIN EXPECTED ON THE SOUTH SHORE IN THE WAKE
OF THE DEPARTING STORM INTO SUNDAY. A WEAK/FAST-MOVING WAVE IS
EXPECTED TO SHOOT ACROSS NRN MN SUNDAY NIGHT AND MONDAY WITH ANOTHER
CHANCE OF LIGHT SNOW..WITH MORE LAKE EFFECT SNOW SHOWERS WITH COLDER
ARCTIC AIR AT THE END OF THE 7 DAY FORECAST WINDOW.
PREV DISCUSSION... /ISSUED 1247 PM CST MON DEC 21 2009/
UPDATE...
CONTINUED POPS ACROSS WIS ZONES..MAINLY E OF KHYR THROUGH THE
AFTERNOON. A SNOWFALL SPOTTER NEAR HURLEY REPORTED 1.5" HAD FALLEN
SINCE 500 AM. ASOS AT KHYR/KASX/KPBH/KIWD ARE CURRENTLY REPORTING
SN WITH VSBYS 2SM OR LESS. HOWEVER..THE SHSN WILL TAPPER OFF
THROUGH THE AFTRN HOURS. THE RUC/NAM SHOW THE 850-700 RH FIELDS
TAKE A SHARP DIP DOWN BELOW 50 PERCENT AFT 21Z. LINGERING -SHSN
WITH LITTLE OR NO ADDITIONAL ACCUM WILL BE FOUND ALONG THE
GOGEBIC RANGE THOUGH THE EVENING AS WINDS VEER TO THE N.
&&
.POINT TEMPS/POPS...
DLH 8 26 18 27 / 10 10 10 10
INL 0 21 8 22 / 10 10 10 10
BRD 8 25 17 25 / 10 10 10 10
HYR 6 24 12 26 / 10 10 10 10
ASX 11 25 14 26 / 60 10 10 10
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...NONE.
&&
$$
EOM/LONKA
