FXUS63 KDLH 221705 AAA
AFDDLH
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DULUTH MN
1105 AM CST TUE DEC 22 2009
.UPDATE...
RATHER COLD SURFACE HIGH PRESSURE IS IN PLACE THIS MORNING TO THE
NORTH OF LAKE SUPERIOR..WITH THE SURFACE PRESSURE GRADIENT SLOWLY
REORIENTING TO SUPPORT E/NE WINDS ACROSS LK SUPERIOR AND THE REST
OF THE DLH CWA AS LOW PRESSURE SLOWLY DEVELOPS IN ERN COLORADO.
THROUGH THIS EVENING..FAIRLY TRANQUIL WEATHER WILL PERSIST AREA-
WIDE. EASTERLY LOW LEVEL FLOW WILL CONTINUE TO BRING ONSHORE
WINDS AND A CHANCE OF LAKE EFFECT SNOW SHOWERS TO THE NORTH SHORE
OF LAKE SUPERIOR TODAY AND TONIGHT PER THE LATEST GUIDANCE FROM
THE RUC/NAM AND LOCAL MODELS. WE DO NOT ANTICIPATE THE LAKE EFFECT
TO BE A MAJOR ISSUE HOWEVER..AS SLOWLY WARMING 850 TEMPS AND THE
PRESENCE OF VERY LOW RELATIVE HUMIDITY IMMEDIATELY ABOVE THE
INVERSION ARE EXPECTED TO BE LIMITING FACTORS. STILL..THE FACT
THAT LAKE EFFECT PROCESSES ARE CURRENTLY CLEARLY ACTIVATED PER
CURRENT SAT IMAGERY AND PERSISTENT EAST FLOW WITH 8-15 KFT OF
TERRAIN INDUCED LIFT WARRANTS AN EXPLICIT MENTION OF POPS AND SOME
LOCAL ACCUMS UP TO 2 INCHES IN THE FAVORED AREAS.
ALSO MADE SOME RATHER DRASTIC ADJUSTMENTS TO SHORT TERM TEMP
GRIDS TO BRING AREAS THAT CLEARED IN LINE WITH OBSERVED TEMPS AT
OR BELOW ZERO..AND REDUCING FORECASTED HIGH TEMPS THIS AFTERNOON
IN SOME AREAS THAT ARE STARTING OUT SO COLD.
CONCERNING MAJOR STORM CENTERED AROUND THE CHRISTMAS TIME
FRAME..WE WILL LIKELY BE EXPANDING THE WINTER STORM WATCH
NORTHWARD TO THE CANADIAN BORDER EARLY THIS AFTERNOON. 12Z
GUIDANCE CONTINUES THE TREND OF EVER-SO-SLIGHT WESTWARD
DISPLACEMENT..BUT QPF AMOUNTS GREATER THAN AN INCH OVER ALMOST OUR
ENTIRE CWA. THERE IS SOME CONCERN THAT SOME PRECIP MAY MIX WITH
SLEET/FZRA OVER NW WI AND CUT DOWN ON SNOW ACCUMS. BUT OVERALL
MESSAGE OF POTENTIAL FOR 8+ INCHES IN MOST AREAS WEST OF A LINE
FROM ROUGHLY SIREN TO THE BAYFIELD PENINSULA HAS NOT CHANGED AT
THIS TIME.
UPDATES TO GRIDS AND ASSOCIATED TEXT PRODUCTS ARE ALREADY AVAILABLE.
MILLER
&&
.PREV DISCUSSION... /ISSUED 601 AM CST TUE DEC 22 2009/
AVIATION...12Z TAFS
MVFR CEILINGS WERE AFFECTING PORTIONS OF THE NORTHLAND FROM THE
SOUTH SHORE OF LAKE SUPERIOR...PARTS OF THE ARROWHEAD...AND FROM
THE TWIN PORTS NORTHWEST THROUGH KGPZ TO KINL. VFR CONDITIONS WERE
OCCURRING FROM THE KBRD AREA...EAST TO KHYR AND KPBH. THERE WAS
ALSO A HOLE OF VFR CONDITIONS OVER KELO...KCDD...KCQM AS OF 12Z.
OVERALL...THIS CLOUD IS MOVING WITH THE LOW LEVEL MEAN FLOW TO
THE NORTHWEST AND CURRENT TRENDS HAS IT MOVING OUT OF KDLH AND
KINL IN A COUPLE HOURS. THE CLOUD MAY ALSO CLEAR OUT OF KHIB LATER
THIS MORNING. HOWEVER...MORE MVFR CEILINGS WERE WORKING WEST FROM
ONTARIO AND THE ARROWHEAD REGION. MORE MAY REFORM OVER LAKE
SUPERIOR THROUGH THE DAY...AND WITH SOUTHEAST 1000-850MB
FLOW...WOULD KEEP THEM IN KHIB AT TIMES. OVERNIGHT...EXPECT THE
MVFR CEILINGS TO REFORM AND SPREAD TO MOST AREAS.
PREV DISCUSSION... /ISSUED 344 AM CST TUE DEC 22 2009/
DISCUSSION...LARGE SFC HIGH OVER ONTARIO REMAINS THE DOMINANT
WEATHER FEATURE THIS MORNING. EASTERLY BDRY LYR FLOW ACROSS LAKE
SUPERIOR HAS ALLOWED AREAS OF LOW CLOUDS TO FORM. CLOUDS ARE
MOVING WEST AND NORTHWEST AROUND THE PERIPHERY OF THE HIGH.
OCCASIONALLY A FLAKE WILL SHAKE OUT OF THE CLOUDS BUT OVERALL
MAINLY CLOUDS AT THIS POINT. AREAS OF CLOUDS HAVE PRODUCED A LARGE
VARIATION IN TEMPS ACROSS REGION THIS MORNING...RANGING FROM 23 AT
KDYT WITH CLOUDS/ONSHORE FLOW... TO -6 AT KHYR AND KPBH UNDER
CLEAR/CALM CONDITIONS.
TODAY/TONIGHT/WEDNESDAY....MID LVL RIDGING...WITH LACK OF SYNOPTIC
SCALE ASCENT...COMBINED WITH LOW LEVEL ANTICYCLONIC FLOW WILL KEEP
REGIONAL WEATHER PATTERN QUIET. EXCEPTION IS WHERE PERSISTENT
ONSHORE FLOW MAY YIELD EXTENSIVE CLOUD COVER AND SOME LT
SNOW/FLURRIES. MAJORITY OF MESOSCALE MDLS AND PERTINENT
FIELDS...OMEGA/RH/SIM REFLECTIVITY/BDRY LYR WIND...SUGGEST AN AREA
OF PRECIP WILL TRY TO FORM ALONG NSHORE AND ADVECT NORTH WITH TIME.
DIFFERENCES EXIST ON PLACEMENT OF BEST LOW LEVEL MSTR FLUX. NAM12
KEEPS MAIN AXIS FOCUSED NEAR A KTWM VICINITY...WHILE REG GEM PUSHES
BEST AXIS NORTH INTO COOK COUNTY NEXT 24HRS. LATEST WRFARW KEEPS
AN AREA IN BETWEEN THE TWO. MINOR ACCUMULATION AT THIS POINT WITH
MARGINAL LAPSE RATES AND LOW INVERSION HEIGHT. HOWEVER WILL NEED
TO MONITOR FOR POTENTIAL OF INVERSION LIFTING ENOUGH TO ALLOW MORE
ACCUMULATION. MID LVL RIDGE AXIS WILL SHIFT FAR ENOUGH EAST
WEDNESDAY AFTERNOON TO ALLOW AN INCREASE IN MID/HIGH LVL CLOUDS.
EXTENDED...WEDNESDAY NIGHT THROUGH MONDAY
EMPHASIS IN THE EXTENDED IS ON A STORM THAT WILL AFFECT...IN SOME
WAY...MUCH OF THE NORTHLAND THURSDAY THROUGH FRIDAY NIGHT OR
SATURDAY.
MOST OF THE MODELS HAVE MADE A NORTH AND WEST SHIFT IN THE TRACK OF
THE LOW...WHICH WOULD SUGGEST OUR WESTERN ZONES HAVE A BETTER CHANCE
AT RECEIVING SIGNIFICANT SNOWFALL THAN WHAT LAST NIGHTS MODELS
SUGGESTED.
THE MODELS TAKE THE UPPER WAVE COMING INTO THE NORTHWEST CONUS
ATTM...INTO THE 4 CORNERS REGION BY 12Z WED...THEN UP ANYWHERE
FROM THE SOUTHERN PLAINS TO THE CENTRAL PLAINS BY 12Z THU...AND INTO
THE MO/IA AREA BY 12Z FRI. THE MODELS DIVERGE FURTHER ON SATURDAY AS
THE GFS IS MORE PROGRESSIVE LIFTING THE UPPER LOW THROUGH
WISCONSIN...VERSUS THE ECMWF THAT STALLS THE LOW IN WISCONSIN.
AT THE SURFACE...MOST OF THE MODELS DEEPEN THE SURFACE LOW ON
THURSDAY...THEN WEAKEN THE LOW BY FRIDAY AS IT MOVES INTO WISCONSIN.
THIS NORTH AND WEST SHIFT IN THE LOW TRACK CREATES A NEW SET OF
ISSUES ACROSS OUR CWA. FIRST OFF...IT ALLOWS WARMER AIR TO MOVE
CLOSER TO OUR CWA...AND MAY BRING A CHANCE FOR MIXED SNOW OR SLEET
AND FREEZING RAIN TO PARTS OF NORTHWEST WISCONSIN. THIS IS GOING TO
BE A PROLONGED EVENT...AND DURING A TIME OF LIGHTER PRECIP...AREAS
OF FREEZING DRIZZLE MAY OCCUR. THIS WOULD BE MOST LIKELY IN
NORTHWEST WISCONSIN. THE SHIFT IN TRACK ALSO GIVES THE WESTERN CWA A
BETTER CHANCE FOR HEAVY SNOW.
WE HAVE ISSUED A WINTER STORM WATCH FOR MUCH OF OUR CWA FROM 12Z
THURSDAY THROUGH 06Z SATURDAY. WE EXCLUDED OUR FAR NORTHERN ZONES
AND A PART OF THE ARROWHEAD...WHERE WE HAVE THE LEAST CONFIDENCE
THAT A WARNING MAY EVENTUALLY BE NEEDED. CONFIDENCE IN THE WATCH IS
ALSO LOWER OVER OUR SOUTHEAST ZONES...FROM PHILLIPS/PARK FALLS...TO
HAYWARD...AND UP TO ASHLAND...AND OVER TO HURLEY. THIS AREA COULD
EXPERIENCE MIXED PRECIP WHICH WOULD CUT DOWN ON SNOW AMOUNTS.
ALSO...THE NORTH AND WEST TREND OF THE LOW COULD CONTINUE PUTTING
THE HIGHER PRECIP AMOUNTS FURTHER WEST. THIS STORM IS STILL A LONG
WAY OUT...AND WE'VE SEEN RUN TO RUN DIFFERENCES IN ALL THE MODELS.
TIMING OF ANY EVENTUAL WARNINGS AND ADVISORIES WILL VARY FROM WHAT'S
IN THE CURRENT WATCH...NAMELY STARTING LATER ON THURSDAY OR EVEN
THURSDAY EVENING IN NORTHERN AREAS.
AVIATION.../06Z 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 AND
KBRD. SOME QUESTION AS TO WHETHER OR NOT CIGS WILL FILL IN AGAIN
ON TUE ACROSS THE SRN PART OF THE CWA. CONFIDENCE IS HIGHER FOR
PERSISTENT MVFR CIGS ACROSS NORTHERN TERMINALS THROUGH THE TAF
PD...AS INDICATED BY LOW LVL CONDENSATION PRES DEFICITS.
&&
.POINT TEMPS/POPS...
DLH 25 18 26 19 / 20 20 10 20
INL 12 9 22 14 / 10 10 10 10
BRD 19 19 25 19 / 10 10 10 60
HYR 19 14 26 19 / 10 10 10 40
ASX 19 16 26 20 / 20 20 10 20
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...WINTER STORM WATCH FROM THURSDAY MORNING THROUGH FRIDAY EVENING
FOR MNZ018>020-025-026-033>038.
WI...WINTER STORM WATCH FROM THURSDAY MORNING THROUGH FRIDAY EVENING
FOR WIZ001>004-006>009.
LS...NONE.
&&
$$
