FXUS63 KMQT 251135 AAA
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
635 AM EST FRI DEC 25 2009
.UPDATED FOR AVIATION...
&&
.SYNOPSIS...
00Z RAOBS/LATEST WV IMAGERY SHOW INTENSE AND INCRSGLY NEGATIVELY
TILTED UPR TROF IN THE CNTRL CONUS WITH PAIR OF PHASING SHRTWVS. THE
FIRST AND MOST INTENSE OF THESE IS OVER ARKANSAS EARLY THIS MRNG AND
LIFTING DUE N AS 2ND SYS NEAR THE BLACK HILLS SINKS S. AT 03Z
12/25...ASSOCIATED SFC LO WAS 998MB OVER SCNTRL MISSOURI. STRONG
LLVL SSE FLOW...WITH H85 AND H7 WINDS AS HI AS 70KTS TO THE E OF THE
TROF ARE PUMPING COPIOUS GLFMEX MSTR TO THE N...WITH 00Z PWAT OF
0.70 INCH AT GRB OVER 250 PCT OF NORMAL. DESPITE THIS ABUNDANCE OF
ABSOLUTE MSTR OVERALL...PRESENCE OF DRIER AIR ARND H85 OVER LWR MI
ASSOCIATED WITH DRY AIR FEED WITHIN ELY FLOW OUT OF HI PRES IN
QUEBEC AND SHOWN ON 00Z APX RAOB HAS CUT INTO PCPN INTENSITY ACRS
UPR MI SO FAR THIS MRNG. MAINLY -SN HAS BEEN REPORTED TNGT...BUT
SOME -FZDZ HAS BEEN OBSVD DURING LULLS IN THE PCPN WITH TEMPS ABV
-10C WITHIN MOIST LYR BLO THE DRY AIR AT H85. IN FACT...SFC TEMPS
HAVE SURGED AOA 32 NEAR THE LK SHORES. THE SFC WBLB TEMP FM THE 00Z
LOCAL WRF-ARW APPEARS TO HAVE BEST HANDLE ON TEMP/TD FIELD ACRS THE
UPR GRT LKS. AT 00Z...THE 0C H85 ISOTHERM RAN SW-NE ACRS NRN LK
MI...NOT MUCH FARTHER N THAN OBSVD AT 12Z 12/24.
.DISCUSSION...
FCST CONCERNS THIS PACKAGE ARE MANY AND INCLUDE SN AMTS/PTYPE WITH
ICING CONCERNS/GOING HEADLINES ASSOCIATED WITH DEEP LO PRES TO THE S.
TDAY...AS UPR TROF DEEPENS INTO CLOSED H5 LO CENTER OVER MISSOURI/
IOWA BY 00Z WITH CONTINUED PHASING OF SHRTWVS NOTED ABV...INCRSGLY
VERTICAL SFC LO TO SHIFT OVER SW IOWA BY 00Z SAT. WITH THIS LO
TRACK...THE SFC-H85 FLOW WL REMAIN PRIMARILY ESE...MAINTAINING LLVL
DRY ADVECTION INTO THIS MRNG THAT HAS SO FAR KEPT PCPN INTENSITY ON
THE LGT SIDE. WL TEND PTYPE TOWARD -DZ/-FZDZ THIS MRNG DEPENDING ON
TEMPS FCST BY LOCAL WRF-ARW. BEST CHC FOR SN WL BE OVER THE FAR W
AND AWAY FM THE VIGOROUS DRYING ARND H85. BUT TOWARD THE AFTN...WARM
CONVEYOR BELT MSTR LIFTED TO THE N BY THE STRONG H85-7 WINDS WL
BEGIN TO IMPACT THE UPR LKS. THIS MOISTENING IN CONCERT WITH INCRSG
UPR DVGC PROGGED BY NAM/GFS TO ARRIVE IN THE AFTN WITH H3 JET CORE
SHOULD RESULT IN EXPANDING PCPN COVG. PTYPE WL BE A MAJOR CONCERN
WHEN THIS MSTR SLUG ARRIVES S-N. GUIDANCE SHOWS ELEVATED WARM LYR
ARRIVING WITH THE DRYING THIS MRNG WITH TEMPS WITHIN THE WARM NOSE
RISING ABV 0C. BUT WITH ARRIVAL OF HIER UVV IN THE AFTN...THE
ELEVATED WARM LYR IS PROGGED TO COOL WITH ADIABATIC/EVAP COOLING.
PREFER THE GFS HANDLING OF THIS COOLING ALF...WHICH WOULD SUG A MUCH
FASTER TRANSITION TO SN THAN THE NAM. HELD ON TO A CHANCE OF ZR AS
WELL WITH POCKETS OF LLVL COLD AIR PSBL GIVEN STABLE LOOK OF FCST
SDNGS/ELY FLOW OF DRY NEAR SFC AIR OUT OF HI TO THE E. TEMPTED TO GO
WITH WINTER WX ADVY FOR THE ERN ZNS FOR SOME LGT FZDZ/FZRA WITH
CONCERN ABOUT LLVL TRAJECTORIES...BUT AIR ARRIVING FM THE E IS SO
DRY THAT ANJ LOST ALL BUT MID CLD OVC AT 07Z. AS FOR GOING
HEADLINES...OPTED TO DOWNGRADE WRNG FOR IRON/GOGEBIC/ONTONAGON TO A
WINTER WX ADVY WITH PREVAILING DOWNSLOPE E WIND RESULTING IN LLVL
DRYING AND LIMIT ON SN ACCUMS. ALTHOUGH DRY SLOTTING WL LIKELY
IMPACT THE KEWEENAW AS WELL...HEAVIER SN CONTINUES THERE EARLY THIS
MRNG WITH FAVORABLE ELY WIND. SO OPTED TO MAINTAIN THE WARNING THERE
AS IS. MAINTAINED ALL OTHER GOING ADVYS EXCEPT TO EXTEND THEM A BIT
IN TIME INTO THE EVNG TO ACCOUNT FOR LINGERING UPR DVGC.
TNGT...OCCLUDED LO IS PROGGED TO DRIFT SLOWLY ENEWD TNGT TO NE IOWA
BY 12Z SAT...WITH COLDER/DRIER AIR WRAPPING ARND ITS ERN FLANK AND
INTO THE FA FM THE S FOLLOWING PASSAGE OF OCCLUDED FNT. EXPECT THE
MOST WDSPRD PCPN IN THE EVNG WITH LINGERING UPR DVGC/CYC FLOW...BUT
EXIT OF UPR DVGC AFT MIDNGT AND DRYING ALF WL TEND TO DIMINISH THE
PCPN INTENSITY. BETTER CHC FOR HIER POPS MAY ACTUALLY BE ACRS THE S
LATE AT NGT WITH ARRIVAL OF OCCLUDED COLD FNT/LOWER H85 TEMPS THAT
MAY ACTUALLY BRING IN SOME SHSN OFF LK MI. UNTIL THIS COLDER AIR
ARRIVES...MODELS SUG THE LLVLS WL REMAIN WARM ENUF FOR A MIX WITH RA
NEAR THE SHORES.
OCCLUDED LO IS PROGGED TO DRIFT INTO WI ON SAT. MSTR WRAPPING ARND
THE WEAKENING OCCLUDED LO WL MAINTAIN AT LEAST CHC POPS THRU THE DAY
ON SAT. BUT LACK OF DYNAMIC FORCING WL LIMIT PCPN INTENSITY/SN
AMNTS. ACTUALLY THE BEST CHC FOR SN WL AGAIN BE OVER THE S WITH SE
FLOW AND H85 TEMPS ARND -12C OVER THE RELATIVELY WARM LK MI WATERS.
MAINTAINED LIKELY POPS IN THOSE AREAS INFLUENCED BY THE SSE FLOW OFF
THESE WATERS. TENDED TO DIMINISH POPS SLOWLY ON SAT NGT WITH
WEAKENING OCCLUSION/CYC FLOW IN ABSENCE OF SGNFT DYNAMIC FORCING.
COORDINATED WITH APX/GRB.
&&
.AVIATION.../FOR THE 12Z TAF ISSUANCE/...
CEILINGS WILL GENERALLY BE IN THE LIFR RANGE AT CMX AND IN THE IFR
RANGE AT SAW THROUGH THE PERIOD. ONLY EXCEPTION WILL BE AS DRIER AIR
CONTINUES TO FEED INTO THE U.P. ON EASTERLY WINDS CEILINGS AT SAW
MAY OCCASIONALLY INCREASE INTO THE MVFR RANGE. A MIX PRECIPITATION
WILL BE THE RULE FOR TODAY...CHANGING OVER TO MAINLY SNOW TONIGHT
FOLLOWING THE FROPA. VISIBIILTIES AT KSAW DURING THE HEAVIEST
PRECIPITATION WILL LIKELY FALL INTO THE 1-3SM RANGE. ON THE OTHER
HAND...UPSLOPE CONDITIONS AT KCMX WILL REDUCE VISIBILITIES TO AROUND
1/2 MILE TONIGHT.
&&
.MARINE.../FOR THE 4 AM LAKE SUPERIOR ISSUANCE/...
EAST GALES WILL CONTINUE OVER LAKE SUPERIOR AS THE LOW PRESSURE
SYSTEM OVER THE MID MISSISSIPPI RIVER VALLEY REMAINS STATIONARY
THROUGH TONIGHT. GRADIENTS WILL ALSO GRADUALLY WEAKEN TONIGHT AS A
SECONDAY LOW ROTATING AROUND THE MAIN LOW SWEEPS THROUGH THE
FORECAST AREA. HOWEVER...TIGHTER GRADIENTS WILL REMAIN OVER THE
EASTERN LAKE SUPERIOR INTO MID SATURDAY MORNING. THE INITIAL LOW
WILL FINALLY REACHES UPPER GREAT LAKES EARLY SUNDAY MORNING WHILE
WEAKENING SUBSTANTIALLY...SO WINDS SHOULD REMAIN 25 KNOTS OR LESS
THROUGH TUESDAY WHILE BACK GRADUALLY TO THE NORTH.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
WINTER WEATHER ADVISORY UNTIL 10 PM EST /9 PM CST/ THIS EVENING
FOR MIZ002-004-005-009>012-084.
WINTER STORM WARNING UNTIL 10 PM EST THIS EVENING FOR MIZ001-003.
LAKE SUPERIOR...
GALE WARNING FROM 10 PM THIS EVENING TO 5 AM EST SATURDAY FOR
LSZ264>267.
GALE WARNING FROM 5 AM TO 11 PM EST FRIDAY FOR LSZ244-245-250-
251.
GALE WARNING UNTIL 5 AM EST /4 AM CST/ SATURDAY FOR LSZ162-263.
LAKE MICHIGAN...
GALE WARNING UNTIL 11 PM EST FRIDAY FOR LMZ221-248-250.
&&
$$
SYNOPSIS/DISCUSSION...KC
AVIATION...MZ
MARINE...DLG
