FXUS63 KMQT 160241 AAA
AFDMQT
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MARQUETTE MI
940 PM EST TUE DEC 15 2009
.UPDATE...
FORECAST CONTINUES TO PROCEED AS ANTICIPATED THIS EVENING. POTENT
S/WV THAT MOVED ACROSS LAKE SUPERIOR THIS AFTERNOON CONTINUES TO
MOVE TO THE EAST INTO ONTARIO AND QUEBEC. AS SURFACE RIDGE AXIS
BUILDS EASTWARD OVERNIGHT WINDS WILL CONTINUE TO SUBSIDE. WILL
CANCEL GALE WARNING FOR THE WESTERN LAKE EARLY BUT KEEP GALE WARNING
OVER THE EASTERN LAKE TIL ITS 6Z EXPIRATION WITH RECENT SHIP OB OVER
THE EASTERN LAKE REPORTING WINDS TO 40 KTS. STDN4 HAS HOWEVER SHOWN
A SLOW BUT STEADY DECREASE IN WINDS THE LAST COUPLE OF HOURS.
WESTERLY WINDS OVER THE LAKE FROM EARLIER THIS EVENING HAVE BACKED
SOME OVER THE LAST HOUR OR TWO. WEST/EAST ORIENTED LAKE EFFECT BANDS
HAVE BEGUN TO PUSH SOUTHWARD AND NOW BEGINNING TO AFFECT AREAS EAST
OF MUNISING AS THE BAND REORIENT THEMSELVES MORE FROM THE NORTHWEST.
STILL SOME LIGHT SNOW FLURRIES OCCURRING OVER THE KEWEENAW PER
WEBCAMS BUT ENVIRONMENT IS BECOMING LESS CONDUCIVE FOR LAKE EFFECT
THERE WITH INVERSION CONTINUING TO LOWER. WILL LET LAKE EFFECT SNOW
ADVISORIES FOR HOUGHTON AND ONTONAGON COUNTIES EXPIRE AT 10 PM.
LOWER CLOUDS HAVE EXPANDED SOME DOWNWIND OF LAKE SUPERIOR AND THIS
MAY HAVE SOME IMPACT ON TEMPS OVERNIGHT. HOWEVER...WITH TEMPS
ALREADY AT OR BELOW ZERO ACROSS WESTERN AREAS WILL NOT MAKE TOO MANY
ADJUSTMENTS AT THIS TIME.
.SYNOPSIS (PREVIOUS DISCUSSION)...
12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW VIGOROUS SHRTWV
EMBEDDED IN PROGRESSIVE FLOW ALF MOVING THRU THE UPR GRT LKS. THIS
SHRTWV IS DRAWING A VERY COLD AIRMASS INTO THE AREA WITH 12Z H5/7/85
TEMP AT INL -38C/-25C/-21C. WITH THE ARRIVAL OF THIS VERY COLD AIR
OVER THE RELATIVELY WARM WATERS OF LK SUP...THERE IS MODERATE LES IN
AREAS DOWNWIND OF LK SUP FAVORED BY THE PREVAILING WNW FLOW BTWN
ARCTIC HI PRES IN THE PLAINS AND LO PRES OVER HUDSON BAY. SHARP
CNVGC BTWN SW WIND AT ONTONAGON AND NNW WIND AT P59 HAS ENHANCED AN
LES BAND OVER THE KEWEENAW THAT IS STREAMING INTO AREAS E OF P53.
ALTHOUGH THE AIRMASS AT INL IS SUFFICIENTLY COLD FOR LES...THE INVRN
BASE THERE HAS SUNK TO H925...VS H85/H825 SHOWN ON THE 12Z GRB/APX
RAOBS. SFC DWPTS UPSTREAM ARE AS LO AS -25C...WITH 12Z PWAT AT INL
ONLY 0.05 INCH. SKIES ARE CLR-PCLDY OVER THE SCNTRL...WHERE THIS DRY
AIR WLY FLOW IS NOT MODIFIED BY PASSAGE OVER LK SUP.
&&
.SHORT TERM DISCUSSION /TNGT AND WED/...
MAIN FCST CONCERNS THIS PACKAGE INCLUDE LES/GOING HEADLINES AND
TEMPS IN ARCTIC AIR/POTENTIAL NEED FOR WIND CHILL ADVY TNGT INTO
EARLY WED.
TNGT...THE PREVAILING WLY H925 FLOW IS PROGGED TO VEER A BIT MORE NW
AS HI PRES RDG AXIS NOW IN THE PLAINS MOVES TO FAR WRN LK SUP BY 12Z
UNDER RISING H5 HGTS IN THE WAKE OF DEPARTING SHRTWV. WITH INVRN
BASE OVER THE W PROGGED TO LOWER TO 3K FT AGL THIS EVNG...EXPECT LES
INTENSITY THERE TO DIMINISH THRU THE NGT...ESPECIALLY WITH ARRIVAL
OF MUCH DRIER LLVL AIR. OPTED TO KEEP 00Z EXPIRATION TIME OF LES
ADVY OVER THE W. ACRS THE E...LONGER FETCH AND POTENTIAL SHARPER
LLVL CNVGC BTWN VEERING FLOW AND STRENGTHENING WSW LAND BREEZE FLOW
INDICATES SHARPER LLVL CNVGC WL BE PSBL NEAR LK SUP E OF P53. SO
ALTHOUGH DIMINSHING LAND BREEZE HAS WEAKENED DOMINANT LES BAND OVER
THE E THIS AFTN...EXPECT THESE SHSN TO STRENGTHEN AGAIN OVERNGT. WL
MAINTAIN GOING ADVY THERE INTO WED MRNG. AWAY FM THE FAVORED SN
BELTS...EXPECT MOCLR SKIES WITH MIN TEMPS AOB THE LO END OF MOS
GUIDANCE. WINDS WL BE STRONGEST THIS EVNG...THEN DIMINISH OVERNGT
ESPECIALLY OVER THE COLDER INTERIOR WITH APRCH OF HI PRES/WEAKER
PRES GRADIENT. ALTHOUGH WIND CHILLS MAY FLIRT WITH ADVY CRITERIA AT
SOME PLACES ESPECIALLY OVER THE FAR W...THINK WINDS WL BE UNDER 10
MPH BY THE TIME TEMPS BOTTOM OUT LATE TNGT/EARLY WED. SO OPTED TO
NOT TO ISSUE ANY WIND CHILL ADVYS.
AS LLVL RDG AXIS SHIFTS OVHD ON WED...EXPECT LES OVER THE W TO
DIMINISH TO NOTHING MORE THAN SCT -SHSN. LES SHOULD BE MORE
PERSISTENT OVER THE ERN ZNS WITH LLVL NW FLOW...BUT TREND TOWARD
LOWER INVRN BASE/MORE ACYC LLVL FLOW THAT WL WEAKEN NEAR SFC CNVGC
ONCE NOCTURNAL LAND BREEZE FADES AS WELL AS IMPACT OF DRY AIR
UPSTREAM SUGGESTS ONLY LGT ACCUMS THERE. WL LET GOING ADVY RIDE THRU
MID MRNG AND UNTIL LAND BREEZE WOULD WEAKEN. THE INTERIOR WL BE
DRY...BUT SOME MID CLDS ASSOCIATED WITH A WEAK DISTURBANCE STREAKING
ESEWD FM SW CAN WL IMPACT THAT AREA. TENDED TOWARD THE LO END OF MOS
GUIDANCE FOR HI TEMPS GIVEN EXPECTED HI STABILITY.
&&
.LONG TERM...
A ZONAL FLOW PERSIST THROUGH WEDNESDAY NIGHT AND THURSDAY WHILE THE
SURFACE RIDGE REMAINS OVER THE UPPER GREAT LAKES. WINDS WILL BE
RATHER LIGHT. THE 850MB THERMAL TROUGH WILL CONTINUE TO PUSH EAST
LEAVING DELTA-T'S OVER THE FORECAST AREA AROUND 7C. WEAK SHORTWAVES
WILL SAIL ACROSS THE FORECAST AREA. CONDITIONS ARE NOT SUPPORTIVE OF
LAKE EFFECT SNOWS. HOWEVER...CONDITIONS SUGGEST ENOUGH INSTABILITY
ALOFT TO GENERATE A SHOWERS OR TWO. SINCE THE AIR MASS IS FAIR
DRY...PLAN TO STAY WITH LOW POPS.
THE SHORTWAVE TROUGH WILL RACE ACROSS THE FORECAST AREA THURSDAY
NIGHT AND FRIDAY. A SURFACE LOW WILL TRACK OUT OF THE CENTRAL PLAINS
AND INTO NORTHERN INDIANA. WITH IT...AN INVERTED TROUGH WILL SHIFT
ACROSS THE FORECAST AREA. LOW LEVEL MOISTURE WILL WORK ACROSS THE
AREA. 850MB TEMPERATURES WILL BE AROUND -10C. A NORTHERLY FLOW AT
THE SURFACE...AND WEAK SHORTWAVE ENERGY WILL SWEEP THROUGH THE AREA.
THE LOW LEVEL MOISTURE WILL CONTRIBUTE TO SNOW DEVELOPMENT MAINLY
OVER THE NORTHERN U.P. WITH THE NORTH WIND.
THE MID LEVEL LOW OVER NORTHERN ONTARIO WILL SLIDE SOUTH TO JUST
NORTH OF LAKE SUPERIOR FRIDAY AND SATURDAY. THE SURFACE RIDGE WILL
REMAIN OVER THE NORTHERN AND CENTRAL PLAINS CONTINUING TO KEEP A
NORTHERLY FLOW ACROSS THE REGION. AN 850MB THERMAL TROUGH WILL SHIFT
OUT OF WESTERN ONTARIO TO CENTRAL ONTARIO AND WESTERN LAKE SUPERIOR
PRODUCING A DELTA-T OF AROUND 14C. THE FLOW WITH THE DELTA-T'AND THE
SHORTWAVE ENERGY FROM THE LOW JUST NORTH OF LAKE SUPERIOR WILL
CONTRIBUTE TO KEEPING LES GOING ACROSS THE NORTHERN U.P. THROUGH
SATURDAY.
THE MID LEVEL LOW WILL SETTLE OVER NORTH CENTRAL LAKE SUPERIOR WITH
MORE SHORTWAVE ENERGY SWEEPING ACROSS THE AREA SATURDAY NIGHT AND
SUNDAY. A SURFACE RIDGE WILL PUSH INTO NORTHWEST ONTARIO ON SUNDAY.
THE LOW LEVEL FLOW WILL CONTINUE OUT OF THE NORTH AND WITH THE 850MB
THERMAL TROUGH REMAINING OVER WEST CENTRAL ONTARIO...THE DELTA-T'S
WILL REMAIN AROUND 14C. THESE FACTOR SHOULD CONTRIBUTE A
CONTINUATION OF SNOW ACROSS THE AREA.
THICKNESS AND 850MB TEMPERATURES POINT TO A POCKET OF COLD AIR
SLIDING DOWN OVER MINNESOTA AND THE UPPER MISSISSIPPI RIVER VALLEY
MONDAY AND TUESDAY. THE SURFACE FLOW WILL CONTINUE OUT OF THE NORTH
KEEPING LES AND LAKE ENHANCED SNOWS GOING THROUGH TUESDAY.
TEMPERATURES WILL BE COOLER OVER THE WEST ALSO.
&&
.AVIATION /FOR THE 00Z TAF ISSUANCE/...
EXPECT LIFR/IFR VSBY CONDITIONS TO CONTINUE AT CMX FOR THE NEXT
SEVERAL HOURS IN PRIMARILY BLSN. HI PRESSURE RIDGING WILL CONTINUE
TO BUILD INTO THE UPPER LAKES OVERNIGHT AND WINDS WILL BEGIN TO
DIMINISH. AS WINDS DECREASE VSBYS WILL ALSO IMPROVE TO VFR LATE
TNGT. A MVFR CIG SHOULD PERSIST THE ENTIRE PD WITH PERSISTENT WNW
FLOW OVER WRN LK SUP UPSLOPING INTO THE KEWEENAW.
PLAN ON VFR CONDITIONS AT SAW THIS FCST WITH WLY FLOW OF UNMODIFIED
DRY ARCTIC AIR DOMINATING.
&&
.MARINE /FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE/...
EXPECT GALES AND HEAVY FREEZING SPRAY THIS EVNG TO DIMINISH
OVERNIGHT WITH APRCH OF HI PRES RDG. WITH THE RIDGE MOVING OVER LAKE
SUPERIOR...THE WINDS WILL GENERALLY BE 25 KNOTS OR THROUGH THE REST
OF THE PERIOD.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
LAKE EFFECT SNOW ADVISORY UNTIL 10 PM EST THIS EVENING FOR
MIZ002-003.
LAKE EFFECT SNOW ADVISORY UNTIL 10 AM EST WEDNESDAY FOR MIZ006-
007.
LAKE SUPERIOR...
GALE WARNING UNTIL MIDNIGHT EST TONIGHT FOR LSZ263>267.
HEAVY FREEZING SPRAY WARNING UNTIL 1 AM EST /MIDNIGHT CST/
WEDNESDAY FOR LSZ162-263.
LAKE MICHIGAN...NONE.
&&
$$
UPDATE...MZ
SHORT TERM...KC
LONG TERM...DLG
AVIATION...MZ
MARINE...KC/DLG
