Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 161207
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
707 AM EST TUE DEC 16 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 536 AM EST TUE DEC 16 2014

WV IMAGERY AND RUC ANALYSIS INDICATED A SRN STREAM SHRTWV/LOW OVER
NRN IL AND A NRN STREAM SHRTWV ACROSS NW ONTARIO INTO NW MN. AT THE
SFC...LOW PRES WAS LOCATED OVER NRN IL WITH A TROUGH TO THE NORTH
INTO ERN UPPER MI. 295K-300K ISENTROPIC LIFT AHEAD OF THE NRN IL LOW
HAS BROUGHT AN INCREASE IN PCPN COVERAGE/INTENSITY ACROSS CNTRL
UPPER MI WHILE 850-700 FGEN HAS SUPPORTED THE SNOW INTO WRN UPPER
MI. NRLY LOW LEVEL FLOW WITH THE TIGHTENING PRES GRADIENT BEHIND THE
TROUGH HAS BROUGHT COLDER AIR INTO WRN UPPER MI CHANGING THE RAIN TO
SNOW AT CMX/IWD/LNL. EVEN THROUGH TEMPS HAVE ALSO FALLEN BELOW 32F
AT KMQT...THE CIRCULATION AROUND THE SRN STREAM LOW HAS MAINTAINED
AN ELEVATED WARM LAYER (AROUND 850 MB FROM 1C TO 3C) OVER CENTRAL
UPPER MI. EVEN WITH AIR TEMPS FALLING BELOW FREEZING...THE RECENT
WARM CONDITIONS HAVE LIMITED GLAZE POTENTIAL AS MOST SURFACES HAVE
NOT COOLED OFF AS FAST.

TODAY...AS THE SRN STREAM SHRTWV LIFTS TO THE NW THE NRN STREAM
SHRTWV WILL BECOME THE DOMINANT FEATURE LATE TODAY INTO TONIGHT.
EXPECT THAT THE LINGERING WARM LAYER WILL SUPPORT A BRIEF PERIOD OF
LIGHT FREEZING RAIN OR SLEET THROUGH AROUND 14Z. THE BEST
CHANCE FOR ANY ICING WOULD BE OVER THE HIGHER TERRAIN WHERE TEMPS
HAVE ALREADY FALLEN OFF BELOW FREEZING. OTHERWISE...THE RAIN SNOW
CHANGE OVER IS EXPECTED TO MOVE INTO THE ERN CWA BY AFTERNOON WITH
ALL SNOW AT ERY AFTER 21Z. THE NRN STREAM SHRTWV WITH INCREASING
700-500 MB QVECTOR CONV WILL SUPPORT LIGHT TO MODERATE SNOW ACROSS
UPPER MI TODAY. 1 TO 4 INCH AMOUNTS ARE EXPECTED TODAY WITH HIGHEST
AMOUNTS OVER THE WEST HALF WHERE NRLY WINDS BRING ADDITIONAL LAKE
ENHANCEMENT AND UPSLOPE FLOW AS 850 MB TEMPS FALL INTO THE -6C TO
-10C RANGE.

TONIGHT...AS THE MID LEVEL LOW PIVOTS THROUGH NRN WI...LARGE SCALE
LIFT WILL PREVAIL ACROSS UPPER MI WITH CONTINUED LIGHT SNOWFALL
AMOUNTS. THE HEAVIER SNOWFAL WILL CONTINUE INTO THE NORTH NEAR LAKE
SUPERIOR WITH ADDITIONAL SNOWFALL TOTALS IN THE 3 TO 5 INCH RANGE.

HEADLINES...A WINTER WEATHER ADVISORY WAS ISSUED FOR THE NORTHERN
COUNTIES FOR THE MIXED PRECIPITATION THIS MORNING AND LONG DURATION
LIGHT TO MODERATE SNOW EVENT.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 330 AM EST TUE DEC 16 2014

THE UPPER LOW WILL BE OVER THE GREAT LAKES REGION AT 12Z
WEDNESDAY...WHILE THE 1006MB SURFACE LOW IS LOCATED OVER FAR
SOUTHEAST ONTARIO. A MID LEVEL TROUGH WILL BE STRETCHING WEST
ACROSS UPPER MICHIGAN AND WILL BE THE PRIMARY FOCUS FOR THE LIGHT
TO OCCASIONALLY MODERATE SNOW OVER MUCH OF UPPER MICHIGAN. THE
STRONGEST SNOW SHOWERS WILL BE OCCURRING OVER THE WESTERN AND NORTH
CENTRAL U.P. WHERE NORTH-NORTHWEST WINDS AND 850MB TEMPS AROUND
-14C WILL LEAD TO LAKE AND TERRAIN ENHANCEMENT. THESE FAVORABLE
CONDITIONS WILL REMAIN FOR THE MORNING HOURS...BUT THEN THE MID
LEVEL TROUGH WILL DROP SOUTH THROUGH UPPER MICHIGAN WEDNESDAY
AFTERNOON...LEADING TO WINDS SHIFTING TO THE NORTH-NORTHEAST AND
BRINGING WARMER 850MB AIR OVER THE AREA. THUS...SHOULD SEE THE
INTENSITY OF THE LAKE ENHANCEMENT DIMINISHING THROUGH THE AFTERNOON
AND INTO THE EVENING HOURS. IT WILL LIKELY LINGER THE LONGEST OVER
THE NORTH CENTRAL DUE TO THE FAVORABLE WIND DIRECTION. WITH MUCH OF
THE FORCING BELOW THE DGZ...WOULD EXPECT THE SNOW RATIOS FOR MUCH OF
THE AREA TO BE IN THE 12-15 TO 1 RANGE. THE ONE AREA WHERE VALUES
COULD BE A LITTLE HIGHER WOULD BE OVER THE WEST...WHERE THE LOW
LEVEL TEMPERATURES ARE A LITTLE COLDER AND PUTTING MORE OF THE CLOUD
IN THE DGZ. BUT EVEN THEN...A LOT OF THE LAKE ENHANCED FORCING IS AT
OR BELOW THE DGZ...WHICH WOULD SUPPORT RIMING OF ANY DENDRITES AND
IN TURN RATIOS IN THE 15-17 TO ONE RANGE. ALL IN ALL...ADDITIONAL
SNOWFALL AMOUNTS ON WEDNESDAY WILL BE IN THE 1-3 INCH
RANGE...HIGHEST IN THE TERRAIN/LAKE ENHANCED AREA OF NORTH CENTRAL
UPPER MICHIGAN.

WITH THE DRIER/WARMER AIR QUICKLY DIVE INTO THE REGION WEDNESDAY
NIGHT...WILL BRING AN END TO THE SNOW SHOWERS FROM NORTH TO SOUTH
THROUGH THE NIGHT. THIS TRANSITION IS SEVERAL HOURS FASTER THAN
SHOWN 24HRS AGO IN THE MODELS AND HAVE SHOWN THAT FASTER END IN THE
POPS. THAT WARMER/DRIER AIR IS ASSOCIATED WITH AN UPPER RIDGE AND
SURFACE HIGH SHIFTING OVER THE UPPER GREAT LAKES REGION. THESE
FEATURES WILL REMAIN IN PLACE THROUGH AT LEAST FRIDAY. THERE ARE
SOME HINTS OF MOISTURE AROUND 925MB BEING TRAPPED BELOW THE
SUBSIDENCE INVERSION ON THURSDAY. WILL HOLD ONTO MOSTLY CLOUDY SKIES
IN THE MORNING IN THE NORTH-NORTHEAST WIND FAVORED AREAS AND THEN
TRANSITION TO PARTLY CLOUDY IN THE AFTERNOON AS THE SFC-925MB
DELTA-T VALUES BECOME MORE MARGINAL.

MODELS CONTINUE TO DIFFER WITH THE EVOLUTION OF BOTH
UPSTREAM/DOWNSTREAM FEATURES WHICH LEADS TO A LITTLE LOWER
CONFIDENCE IN THE WEEKEND FORECAST. THE FIRST FEATURE THAT THEY
DIFFER ON IS A SHORTWAVE PULLING OUT OF THE SOUTHERN PLAINS AND OFF
THE MID ATLANTIC COAST. THE 12Z GEM/ECMWF DEVELOP A STRONGER LOW
WITH A MUCH MORE AMPLIFIED TROUGH...WHILE THE 00Z GFS IS MUCH WEAKER
WITH THE LOW AND FLATTER WITH THE WAVE. LOOKING AT THE ENSEMBLE
MEANS/MEMBERS...THE 12Z ECMWF MEMBERS ARE REMARKABLY CONSISTENT IN
THE EVOLUTION OF THE LOW OFF THE MID ATLANTIC STATES. BUT WHERE
THINGS DIFFER IS WITH THE HANDLING OF THE NEXT WEAK SHORTWAVE MOVING
THROUGH THE NORTHERN STREAM FLOW SATURDAY INTO SUNDAY. WHILE THE 12Z
GEM/ECMWF OPERATIONAL RUNS HOLD ONTO AN UPPER RIDGE OVER THE UPPER
MISSISSIPPI VALLEY DURING THIS TIME...THE ENSEMBLE MEANS MORE
CLOSELY RESEMBLE THE GFS IN THE IDEA OF A WEAK UPPER TROUGH MOVING
THROUGH THE UPPER MISSISSIPPI VALLEY AND THEN THE UPPER GREAT LAKES
THIS WEEKEND. BASED OFF THE 12Z ENSEMBLE MEANS AND THE 00Z
GEM/ECMWF OPERATIONAL RUNS COMING IN MORE IN LINE WITH THAT
IDEA...WILL FOLLOW THAT FOR THIS FORECAST. BUT EVEN WITH THAT WEAK
UPPER TROUGH MOVING THROUGH...THE SURFACE HIGH WILL BE PERSISTENT
AND SHOULD LEAD TO DRY CONDITIONS. 850MB TEMPS LOOK TO BE AROUND
-6C...WHICH IS EVEN MARGINAL FOR LAKE EFFECT CLOUDS IF THERE WAS
ENOUGH MOISTURE PRESENT...SO WILL GO WITH A DRY FORECAST AND PARTLY
CLOUDY SKIES ON SATURDAY AND MOSTLY CLOUDY ON SUNDAY. HIGHS THURSDAY
WILL START OUT NEAR NORMAL THEN SLOWLY WARM TO SLIGHTLY ABOVE NORMAL
VALUES (UPPER 20S AND LOWER 30S) FOR THE WEEKEND.

HEADING INTO NEXT WEEK...ECMWF/GEM/GFS ENSEMBLE MEANS HAVE BEEN
CONSISTENT FOR THE LAST SEVERAL DAYS TO A WEEK ON AN UPPER TROUGH
DROPPING SOUTHEAST FROM THE GULF OF ALASKA AND INTO THE NORTHERN
CONUS. THIS WILL LEAD TO A COOLER PERIOD AROUND CHRISTMAS AND
LIKELY REMAINING FOR THE END OF DECEMBER. ALTHOUGH IT IS STILL 8-9
DAYS OUT...THE CONSISTENCY IN THE ENSEMBLE MODELS ON THIS IDEA
IS WORTH MENTIONING. THEY CONTINUE TO SHOW A CANADIAN LOW TO DROP
THROUGH ONTARIO OR THE UPPER GREAT LAKES REGION ON THE 24TH OR
25TH. WHILE SNOW AMOUNTS ARE UNFORECASTABLE AT THIS TIME...AT
LEAST LIGHT SNOW IS EXPECTED DURING THAT BUSY HOLIDAY TRAVEL PERIOD.
&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 705 AM EST TUE DEC 16 2014

A WARM LAYER ALOFT MAY BRING A PERIOD OF SLEET TO SAW THROUGH AROUND
14Z. OTHERWISE...COLD CYCLONIC NRLY FLOW SUPPORTED BY AN UPPER LEVEL
LOW PRESSURE SYSTEM WILL BRING SNOW TO THE TAF SITES THROUGH THE
FCST PERIOD WITH IFR CONDITIONS EXPECTED. THERE MAY ALSO BE SOME
PERIODS OF LIFR VSBY BUT CONFIDENCE IN TIMING ANY EXTENDED PERIOD OF
VSBY BLO 1SM IS LOW.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 552 AM EST TUE DEC 16 2014

A TIGHTENING PRES GRADIENT BETWEEN LOW PRES OVER NRN IL LIFTING TO
THE NE AND HIGH PRES OVER MANITOBA INTO THE NRN PLAINS WILL RESULT
IN NORTH WINDS OF 20 TO 30 KNOTS WITH A FEW GALE FORCE GUSTS TO 35
KNOTS TODAY INTO THIS EVENING. AS HIGH PRES BUILDS INTO THE NRN
LAKES FROM WED INTO THU...WINDS WILL DIMINISH TO 20 KNOTS OR LESS.
HIGH PRESSURE WILL THEN DOMINATE INTO THE WEEKEND WITH WINDS
REMAINING BELOW 20 KNOTS.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
  WINTER WEATHER ADVISORY UNTIL 7 PM EST WEDNESDAY FOR MIZ006-085.

  WINTER WEATHER ADVISORY UNTIL 7 PM EST /6 PM CST/ WEDNESDAY FOR
     MIZ001>005-009-084.

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

$$

SHORT TERM...JLB
LONG TERM...SRF
AVIATION...JLB
MARINE...JLB






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