FXUS63 KMQT 050002 AAA
AFDMQT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MARQUETTE MI
700 PM EST THU DEC 4 2008

UPDATE INCLUDES UPDATED AVIATION DISCUSSION FOR 00Z TAF ISSUANCE

.UPDATE...

UPDATED FCST TO EXTEND LAKE EFFECT SNOW WARNING UNTIL 7 AM FRI FOR
ONTONAGON COUNTY. CURRENTLY...KMQT AND KDLH RADAR IMAGERY INDICATE
HEAVIER BANDS OF SNOW IMPACTING THE AREAS FROM THE PORCUPINE
MOUNTAINS TO BERGLAND AND ALSO N OF MASS CITY. WHILE WINDS WILL
BEGIN TO BACK TONIGHT...IT WON'T BE ENOUGH TO SHIFT HEAVIER SNOW N
OF THE COUNTY UNTIL EARLY FRI MORNING. ALSO...AS THE BACKING BEGINS
AND LAND BREEZES BECOME STRONGER DURING THE NIGHT...LOW-LEVEL
CONVERGENCE WILL STRENGTHEN AND BECOME FOCUSED ACROSS NRN ONTONAGON
COUNTY. SO...SNOW WILL LIKELY INCREASE INTENSITY DURING THE NIGHT
ACROSS THE NRN PORTION OF THE COUNTY.

&&

.SYNOPSIS... ISSUED AT 350 PM EST

UPPER AIR PATTERN CONSISTS OF A 500 MB RIDGE OFF THE WEST COAST AND
EAST COAST AND A BROAD 500 MB TROUGH ACROSS THE REST OF THE U.S.
WITH SOME SHORTWAVES EMBEDDED IN THIS TROUGH. ONE STRONG WAVE IN
THIS TROUGH IS ACROSS CENTRAL ONTARIO AND THIS IS DROPPING SOUTH
TODAY AND WILL AFFECT THE AREA TONIGHT.

&&

.SHORT TERM THROUGH 00Z SAT... ISSUED AT 350 PM EST

UPPER LEVEL TROUGH REMAINS ACROSS THE REGION. NAM SHOWING 850-500 MB
Q-VECTOR CONVERGENCE MOVING OUT BY THIS EVENING. A CLIPPER TYPE
SYSTEM WILL AFFECT THE AREA FRI NIGHT. NAM SHOWING WEAK ISENTROPIC
LIFT ON I270K-I285K AND SOME MOISTURE ACROSS THE CWA TONIGHT AND
THIS IS MOSTLY ACROSS THE NORTHERN AND EASTERN CWA. THIS LIFT AND
MOISTURE REMAIN ACROSS THE NORTH AND EAST IN THE LOW LEVELS ON FRI
AS WELL ON I270K-I275K SURFACES. DID NOT MAKE TOO MANY CHANGES TO
THE GOING FORECAST AS PREVIOUS FORECAST HAD THINGS WELL IN HAND.
LAKE EFFECT SNOW LOOKS TO CONTINUE AS THE WIND SLOWLY BACKS TO THE
WEST AND WSW LATE TONIGHT AND ALSO FOR FRI. 850 MB TEMPERATURES WARM
UP A BIT AND INVERSION HEIGHTS FALL BEFORE THE CLIPPER SYSTEM
ARRIVES FOR FRI NIGHT...SO COMBO OF WINDS AND LOWERING INVERSION
HEIGHTS SHOULD KEEP LAKE EFFECT SNOW IN CHECK LATE TONIGHT AND ALSO
FOR LATE FRI AFTERNOON. OVERALL...DID NOT CHANGE MUCH.

.LONG TERM...00Z SAT - 00Z MON

GUIDANCE REMAINS IN STRONG AGREEMENT THROUGH DAY 4. GFS STILL LOOKS
FAVORABLE THROUGH DAY 6. MODELS SHOWING CONSIDERABLE DIVERGENCE
THERE AFTER CONTRIBUTING TO LOWER CONFIDENCE IN THE MODELS.
THEREFORE, WILL FOLLOW HPC RECOMMENDATION OF GOING WITH GFS THROUGH
DAY 6 AND A BLEND OF THE ENSEMBLE MEANS DAY 7.

A WEAK SHORTWAVE TROUGH ROTATING THROUGH THE BASE OF THE MID LEVEL
LOW OVER HUDSON BAY WILL SWEEP THROUGH UPPER MICHIGAN FRIDAY NIGHT
AND SATURDAY. THE SURFACE LOW OVER SOUTHERN MANITOBA WILL ALSO SWEEP
ACROSS UPPER MICHIGAN AND REACH LAKE HURON BY SATURDAY EVENING. A
RIDGE DEVELOPING OVER CENTRAL CANADA WILL DIVE INTO SOUTH CENTRAL
CANADA AND THE NORTHERN PLAINS BY SATURDAY EVENING. Q-VECTOR
CONVERGENCE AND ISENTROPIC ASCENT ASSOCIATED WITH THIS SYSTEM WILL
PRODUCE SYSTEM SNOW OVER THE AREA.

THE SHORTWAVE WILL DEEPEN INTO A LONGWAVE TROUGH AND PUSH EAST INTO
SOUTHWEST QUEBEC. A WEAK RIDGE AND A PRONOUNCED SURFACE RIDGE WILL
PUSH INTO WISCONSIN AND WESTERN LAKE SUPERIOR BY SUNDAY EVENING. THE
SYSTEM SNOWS WILL WEAKEN AS THE NORTHERLY WINDS BRING AN 850MB
THERMAL TROUGH INTO THE AREA INCREASING THE DELTA-T'S TO AROUND 23C
AND INCREASING THE POTENTIAL FOR LES OVER THE AREA. THE AREAS MOST
LIKELY TO RECEIVE THE HEAVY LES WILL BE THOSE MOST AFFECTED BY
NORTHWEST WINDS FLOWS. STRONG WINDS COMING OFF OF LAKE SUPERIOR
ALONG WITH SNOWFALL POTENTIAL OF 4 TO 6 INCHES. THUS PLAN TO GO WITH
A WINTER STORM WATCH FOR THE KEWEENAW PENINSULA. LIMITING FACTORS
OF LES WILL BE THE STRONG WINDS AND THE DURATION BEFORE THE DRY AIR
MOVES INTO THE AREA.

AS THE LONGWAVE TROUGH LIFTS NORTHEAST INTO THE CANADIAN
MARITIME...ANOTHER LONGWAVE TROUGH WILL DEVELOP OVER THE CENTRAL
PLAINS ON SUNDAY NIGHT AND MONDAY INTO MONDAY NIGHT. THE SURFACE
RIDGE WILL SHIFT EAST AS COLD FRONT TRACKS INTO THE U.P. ON MONDAY
AND PROGRESS ON TO LOWER MICHIGAN MONDAY NIGHT. WINDS WILL VEER
NORTHWEST FOLLOWING THE FROPA. THIS WILL PRODUCE A LAKE-850MB
DELTA-T OF AROUND 18C. THIS WILL LEAD TO A LES PRODUCTION ACROSS
MUCH OF THE NORTHERN PART OF THE AREA. AS DRY AIR DESCEND ON THE
AREA AND WINDS BACK SOUTHWEST ENDING THE CHANCES OF LES.

A MID LEVEL LOW WILL SHIFT OUT OF NORTHERN MANITOBA INTO NORTHERN
ONTARIO...IN ASSOCIATION WITH A LONGWAVE TROUGH TRACKING THROUGH THE
UPPER MISSISSIPPI RIVER VALLEY. THE LONGWAVE TROUGH WILL SWEEP
THROUGH THE FORECAST AREA TUESDAY NIGHT AND WEDNESDAY WHILE
DEEPENING. MEANWHILE...ANOTHER RIDGE WILL SETTLE SOUTH OUT OF
CENTRAL CANADA COLD AIR ADVECTION AHEAD OF THE RIDGE WILL CONTINUE
TO PRODUCE DELTA-T'S OF 23C TO 27C OVER LAKE SUPERIOR. THIS IS
PLENTY UNSTABLE AT THE LOW LEVELS TO KEEP THE CHANCES OF LAKE EFFECT
SNOW SHOWERS GOING. THIS WILL ALSO PRODUCE VERY COLD TEMPERATURES
ACROSS THE AREA. TUESDAY NIGHT LOW TEMPERATURES WILL DIP TO NEAR
ZERO OVER THE WESTERN U.P.

&&

.AVIATION (FOR THE 00Z TAF ISSUANCE)...

WITH LAKE EFFECT -SHSN CONTINUING AT KCMX...EXPECT CONDITIONS TO
VARY BTWN IFR AND LIFR THRU FRI MORNING. THERE MAY BE SOME BRIEF
PERIODS OF MVFR AND PERHAPS VFR...BUT THOSE PERIODS WILL BE VERY
INFREQUENT. AS WINDS BACK MORE TO THE SW VERY LATE TONIGHT/FRI
MORNING...ENHANCING LOW-LEVEL CONVERGENCE...EXPECT A PREVAILING
PERIOD OF VLIFR CONDITIONS IN HEAVIER SHSN. AS WINDS CONTINUE TO
BACK...EXPECT CONDITIONS TO IMPROVE TO MVFR LATE MORNING AND VFR IN
THE AFTN.

AT KSAW...LOW-LEVEL WRLY WINDS ARE NOT FAVORABLE FOR LAKE EFFECT
-SHSN. EXPECT VFR CONDITIONS TO PREVAIL THRU THE PERIOD.

&&

.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...

GALES POSSIBLE ON SAT AND SATURDAY NIGHT...OTHERWISE WINDS LOOK TO
STAY BELOW 30 KNOTS THROUGH THE PERIOD WITH A COUPLE OTHER PERIODS
CLOSE TO GALES THOUGH. WINDS DIMINISH BY SUNDAY AS HIGH PRESSURE
MOVES ACROSS THE GREAT LAKES. SRLY GALES POSSIBLE ON MONDAY...MAINLY
ERN SECTIONS OF LK SUPERIOR...AHEAD OF LOW PRESSURE SYSTEM DROPPING
INTO THE REGION FM CNTRL CANADA.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...

UPPER MICHIGAN...
LAKE EFFECT SNOW WARNING UNTIL 7 AM EST FRI MIZ002.
LAKE EFFECT SNOW WARNING UNTIL 10 AM EST FRI MIZ006-007.
LAKE EFFECT SNOW WARNING UNTIL 7 PM EST FRI MIZ003.
LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST FRI MIZ001.
LAKE EFFECT SNOW ADVISORY UNTIL 1 AM EST FRI MIZ085.

WINTER STORM WATCH SAT MORNING THRU SUN MORNING MIZ001>003.
WINTER STORM WATCH SAT AFTN THRU SUN AFTN MIZ006-007-085.

LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.

&&

$$

UPDATE...ROLFSON
SYNOPSIS/SHORT TERM...GM
LONG TERM...DLG
AVIATION...ROLFSON
MARINE...GM


Back to Main Forecast Discussion Page