000
FXUS63 KMQT 200501
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
100 AM EDT SAT MAR 20 2010
UPDATED AVIATION DISCUSSION FOR 06Z TAFS
.SYNOPSIS... ISSUED AT 414 PM EDT
12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW UPR TROFFING OVER
SCNTRL CAN AND THE NRN PLAINS SUPPRESSING THE PERSISTENT UPR RDG
THAT HAS DOMINATED THE UPR GRT LKS FOR A COUPLE OF WEEKS S INTO THE
TN RIVER VALLEY. THE PASSAGE OF A COLD FNT ATTENDANT TO SHRTWV/SFC
LO PASSAGE THRU SRN ONTARIO HAS BROUGHT A RETURN OF MORE SEASONABLE
TEMPS TO THE CWA THIS AFTN WITH TEMPS MAINLY IN THE 30S IN THE
CHILLY NW FLOW BEHIND THE FNT. 12Z H85 TEMPS UPSTREAM ARE AS LO AS
-12C AT INL AND -16C AT YPL. THE INL/YPL RAOBS ALSO SHOW A MOIST
ATMOSPHERE...WITH EXTENSIVE LO CLD OBSVD UPSTREAM FM NW ONTARIO INTO
MN. THIS LO CLD HAS INVADED THE NW HALF OF UPR MI EARLY THIS AFTN.
DESPITE THE RATHER DEEP MSTR SHOWN ON THE INL/YPL RAOBS...MAINLY
JUST FLURRIES AND LIGHTER -SHSN ARE FALLING UNDER THE SC IN MN/
ADJOINING SRN ONTARIO/THE CWA DUE TO LARGER SCALE UPR CNVGC/DNVA/
CAD/H85-5 QVECTOR DVGC IN THE WAKE OF THE SHRTWV DEPARTING TO THE E.
THE PRESENCE OF DRIER LLVL AIR SHOWN ON THE 12Z YQD RAOB AND THE
APRCH OF HI PRES IN SCNTRL CAN HAS CAUSED THE SC TO BREAK UP IN ERN
NDAKOTA AND ARND LK WINNIPEG. THIS CLRG IS EDGING INTO NW MN CLOSER
TO FCST ISSUANCE TIME.
&&
.SHORT TERM DISCUSSION /TNGT AND SAT/... ISSUED AT 414 PM EDT
MAIN FCST CONCERNS DURING THIS TIME ARE CLD TRENDS/IMPACT ON TEMPS.
TNGT...CONFLUENT UPR FLOW OVER THE UPR GRT LKS WL ALLOW SFC HI PRES
NOW MOVING THRU SCNTRL CAN TO BUILD E INTO THE UPR GRT LKS...WITH
SFC RDG AXIS FCST TO EXTEND FM THE NRN PLAINS ENEWD ACRS THE CWA TO
NEAR JAMES BAY. THE SLOW ARRIVAL OF COLDER AIR IN THE NNW FLOW AHEAD
OF THIS RDG AS WELL AS THE RATHER EXTENSIVE MSTR OBSVD UPSTREAM
SHOULD SUPPORT SOME LGT LES TNGT WITH THE ARRIVAL OF H85 TEMPS AS LO
AS -15C...ESPECIALLY AFT THIS EVNG WITH THE LOSS OF DAYTIME HEATING
THAT OFTEN DISRUPTS THE LES PROCESS THIS LATE IN THE SEASON. ANY SN
FALL SHOULD BE ON THE LGT SIDE THOUGH WITH ARRIVAL OF LLVL DRIER AIR
FM THE NW/GENERAL ACYC FLOW LIMITING LLVL CNVGC AND CAUSING INVRN
HGTS TO FALL TO ARND 4K FT MSL. THE APRCH OF THE RDG AXIS/SHARPER
ACYC FLOW LATER TNGT SHOULD ALSO CAUSE A DIMINISHING TREND TO THE
SHSN...ESPECIALLY OVER THE W. ALTHOUGH THE EXTENSIVE LO CLD UPSTREAM
WOULD SUG TRENDING TOWARD THE HI END OF MOS GUIDANCE...COMPROMISED A
LITTLE LOWER TO ACCOUNT FOR FALLING DWPTS UPSTREAM OF THE LK. STILL
TENDED TO KEEP QUITE A BIT OF SC IN THE FCST TNGT DESPITE ARRIVAL OF
THE DRIER AIR AND RDG AXIS/ACYC FLOW AFT 06Z. THE LOWEST TEMPS ARE
MOST LIKELY OVER THE FAR W WHERE THE APRCH OF THE SFC RDG AXIS IS
MOST LIKELY TO BRING SOME CLRG.
SAT...THE SFC RDG AXIS IS FCST TO DRIFT SLOWLY S ACRS THE FA. WITH
ARRIVAL OF DRIER AIR/SHARP ACYC FLOW/DAYTIME HEATING...EXPECT ANY
LINGERING LES IN THE MRNG TO END AND THE SC TO MIX OUT THRU THE DAY
TO YIELD MORE SUNSHINE. MIXING TO H8 ON GFS FCST SDNGS YIELDS HI
TEMPS IN THE 35 TO 40 RANGE...SO TENDED TOWARD A BLEND OF THE COOLER
NAM/WARMER GFS MOS GUIDANCE.
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
MUCH OF THIS PERIOD WILL BE MARKED BY A BROAD TROUGH...SET UP FROM
MANITOBA THROUGH MICHIGAN TO THE NEW ENGLAND STATES...AS MUCH OF THE
ENERGY REMAINS WELL TO OUR SOUTH. ONE FEATURE OF INTEREST IS A 500MB
TROUGH STRETCHING FROM COLORADO THROUGH MINNESOTA...TO THE MAIN LOW
OVER NORTHERN HUDSON BAY. LOOK FOR THIS FEATURE TO CUT OFF SATURDAY
OVER NORTHERN TEXAS...AND SLOWLY INCHING TO THE CAROLINAS BY MONDAY
NIGHT. CLOSER TO HOME...AS THIS LOW EXITS THE CONTINENTAL STATES...A
WEAK 500MB RIDGE WILL FORM MONDAY NIGHT THROUGH TUESDAY NIGHT. THE
ECMWF IS STRONGER WITH THIS RIDGE...WHILE THE GFS AND CANADIAN WOULD
KEEP MORE ZONAL FLOW...TO A TROUGH OVER THE UPPER GREAT LAKES. BY
DAYBREAK TUESDAY THE SURFACE LOW WILL BE OVER FAR WESTERN LAKE
SUPERIOR...STRETCHING BACK THROUGH THE FOUR CORNERS REGION. THIS
WILL ALLOW THE WEAK COLD FRONT TO SWING OVER THE CWA DURING THE DAY
TUESDAY...BEFORE HIGH PRESSURE SETTLES BACK IN WEDNESDAY MORNING.
FOR MIDWEEK...THE 500MB LOW TO OUR NORTH WILL CONTINUE TO SLOWLY DIP
AND SWING INTO NORTHERN QUEBEC
OVERALL...DECIDED TO STAY AWAY FROM THE STRONGER WINDS OF THE 06Z
GFS...AND FOCUS ON A BLEND BETWEEN THE ONGOING FORECAST AND THE
LATEST ECMWF AND HPC GUIDANCE FOR MONDAY AND BEYOND. SINCE THEN THE
12Z RUN OF THE GFS HAS COME BACK INTO BETTER AGREEMENT WITH THE
MAJORITY OF AVAILABLE MODELS.
&&
.AVIATION /FOR THE 06Z TAFS/...
COLDER AIR FLOWING OVER LAKE SUPERIOR IS COLD ENOUGH TO GENERATE
LAKE EFFECT CLOUDS. HOWEVER...A WELL MIXED LAYER DEVELOPED NW OF THE
LAKE DURING THE DAY...AND THIS DRIER BOUNDARY LAYER AIR IS NOW
WORKING TO INHIBIT WIDESPREAD CLOUD DEVELOPMENT DESPITE FAVORABLE
OVERWATER INSTABILITY. WITH THE MIN OF THE DIURNAL CYCLE YET TO
ARRIVE...BKN MVFR CLOUDS (2500-3000FT) MAY STILL DEVELOP/EXPAND AND
AFFECT KCMX/KSAW OVERNIGHT/EARLY MORNING. OTHERWISE...VFR CONDITIONS
WILL PREVAIL WITH A TREND TO CLR SKIES AT KCMX/KSAW TODAY AS DEEP
DRY AIRMASS BECOMES MORE FIRMLY ESTABLISHED IN ASSOCIATION WITH HIGH
PRES RIDGE.
&&
.MARINE /FOR THE 4 PM LAKE SUPERIOR FORECAST/...
EXPECT NNW WINDS TO 30 KTS THIS EVENING TO DIMINISH WITH THE ARRIVAL
OF A HI PRES RIDGE TONIGHT. ONCE THIS RIDGE SHIFTS TO THE SE LATE
SAT...SW WINDS ON THE NW FLANK OF THIS FEATURE WL INCREASE TO 25 TO
30 KTS...HIGHEST IN THE CORRIDOR BETWEEN THE KEWEENAW AND ISLE
ROYALE WHERE TERRAIN FUNNELING ACCENTUATES THIS FLOW. LOOK FOR THESE
WINDS TO DIMINISH SUN NIGHT INTO MON WITH THE ARRIVAL OF A HI PRES
RDG IN ONTARIO. PLAN ON WINDS NO HIER THAN 20 KTS ON TUE/WED.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.
&&
$$
SYNOPSIS...KC
SHORT TERM...KC
LONG TERM...KF
AVIATION...ROLFSON
MARINE...KC
