Area Forecast Discussion
Issued by NWS Marquette, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KMQT 271752
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
1252 PM EST SAT DEC 27 2014

.UPDATE...
ISSUED AT 939 AM EST SAT DEC 27 2014

DIFFICULT HEADLINE DECISION THIS MORNING AS THERE WILL LIKELY BE A
SWATH OF SNOWFALL AMOUNTS RIGHT AROUND OUR 6IN/12HR CRITERIA OVER
CENTRAL UPPER MICHIGAN. BELIEVE THE SNOWFALL AMOUNTS THAT WE HAVE
IN THE FORECAST ARE IN LINE FOR WHAT IS EXPECTED WITH THIS LAST
AREA OF SNOW THAT WILL MOVE THROUGH THIS MORNING. THAT AREA WITH
THE FORECASTED HIGHEST AMOUNTS IS IN LINE WITH THE AREA OF RAPIDLY
COOLING CLOUD TOPS OVER CENTRAL UPPER MICHIGAN AND NORTHEAST
WISCONSIN AND MATCHES THE LATEST QPF AMOUNTS FROM THE RAP/HRRR. ON
THE WESTERN EDGE OF THIS SWATH (IRON/DICKINSON COUNTIES)...THEY HAVE
RECEIVED 2.5-3.5 INCHES OF SNOW THUS FAR OVER 9-10 HOURS AND WILL
RECEIVE ANOTHER 2-3 INCHES OVER THE NEXT 3-4HRS WHICH PUTS THEM ON
THE EDGE OF THE CRITERIA. FARTHER EAST...AMOUNTS HAVE BEEN LOWER AND
IN THE 1-2.5 INCH RANGE...BUT THEY WILL LIKELY SEE THE GREATEST
AMOUNTS OF 3.5-5 INCHES. THIS ALSO PUTS THOSE AREAS RIGHT AROUND THE
6 INCH CRITERIA. FEEL THE MOST CONFIDENT ON AMOUNTS JUST OVER
WARNING CRITERIA FROM NORTHERN DICKINSON THROUGH THE SOUTHEAST HALF
OF MARQUETTE AND WESTERN ALGER COUNTY...BUT NOT SURE IF THE UPGRADE
WITH ANOTHER 3-4HRS OF SNOW LEFT IS WORTH THE HEADLINE CHANGE. IN
ADDITION...THE OVERALL WORDING WILL STAY THE SAME. THUS...WILL
UPDATE THE WSW TO HIGHLIGHT THE HEAVIER SNOW OVER THE NEXT FEW HOURS
AND KEEP THE ADVISORIES AS IS...ESPECIALLY SINCE WEBCAMS SHOW MANY
LOCATIONS EAST OF A MARQUETTE TO IRON MOUNTAIN LINE STILL HAVING
MAINLY WET ROADS.
&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 535 AM EST SAT DEC 27 2014

LATEST WATER VAPOR LOOP AND RUC ANALYSIS SHOWS A VIGOROUS AND
WELL-DEFINED SHORTWAVE LIFTING NE INTO SRN MN AND NW WI WITH
DEVELOPING BAROCLINIC LEAF STRUCTURE/DEFORMATION ZONE. MID-LVL FGEN
ASSOC WITH SHORTWAVE STRETCHING FROM SRN MN AND NW WI INTO THE UPPER
MI HELPING SUPPORT LIGHT TO MODERATE SNOW.

TODAY...MID-LVL FGEN STRETCHING ACROSS THE UPPER MIDWEST TO THE
UPPER GREAT LAKES WILL CONTINUE TO SUPPORT MODERATE SNOW INTO EARLY
AFTERNOON. BROAD SCALE SYNOPTIC ASCENT WILL BE AIDED BY UPPER
DIVERGENCE IN THE LEFT EXIT REGION OF THE 300 MB JET. NEGATIVE EPV
NOTED ON CROSS-SECTIONS WITHIN A REGION OF MID-LVL FRONTOGENESIS
COULD LEAD TO SOME LOCALLY HEAVIER SNOW BANDS AS SFC LOW TRACKS JUST
SE OF AREA THIS MORNING AND THEN ACROSS THE STRAITS EARLY THIS AFTERNOON.
MODEL CONSENSUS QPF ARGUES FOR AREA OF HEAVIER SNOW JUST NW OF LOW
TRACK ALONG AND EAST OF A LINE FROM IRON RIVER THROUGH ISHPEMING
WHERE MODELS SHOW STRONG 285-290K ISENTROPIC ASCENT OVER A SIX-HR
PERIOD WITH 4 G/KG MIXR ADVECTING ACROSS AREA. THIS SWATH OF HEAVIER
SNOW WILL TAPER OFF BY MID AFTERNOON AS MID-LVL FGEN WEAKENS AND
BEGINS TO MOVE NE WITH DEPARTING SFC LOW. MODEL AVG QPF FM .25 INCH
WEST TO NEAR .5 INCH OVER PORTIONS OF THE CENTRAL CWA WITH EXPECTED
SNOW/WATER RATIOS FM 15/1 WEST TO NEAR 12/1 EAST HALF SHOULD YIELD
TOTAL SNOW ACCUMULATION FM 2-5 INCHES WEST TO 3-6 INCHES CENTRAL.
SINCE 6 INCH AMOUNTS SHOULD BE FAIRLY LOCALIZED WILL CONTINUE WITH
WINTER WX ADVISORY HEADLINES AT THIS POINT AND NOT UPGRADE TO
WARNINGS...BUT SITUATION WILL DEFINITELY WARRANT MONITORING THIS
MORNING. ALSO HAVE DECIDED TO INCLUDE ONTONAGON AND SRN HOUGHTON IN
ADVISORIES AS THEY SHOULD BE ON WRN EDGE OF HEAVIER QPF THIS MORNING.

TONIGHT...WITH SYSTEM SNOW OVER BY LATE AFTERNOON FOR EAST...EXPECT
TRANSITION TO PURE LAKE EFFECT SNOW TONIGHT AS 850MB TEMPS FALL FROM
-10 TO -12C IN THE EVENING TO -12 TO -16C BY 12Z SUN UNDER LOW-LEVEL
W TO WNW FLOW. LARGE SCALE DEEP LAYER Q-VECTOR DIVERGENCE WILL
DOMINATE THIS EVENING AND NAM/GFS FCST SOUNDINGS SHOWING INVERSIONS
BASED NEAR 4KFT...ANY DEVELOPING LES WILL BE ON THE LIGHT SIDE OVER
THE KEWEENAW. HOWEVER...LATER TONIGHT THERE IS A POTENTIAL FOR SOME
WEAK ENHANCEMENT AS A SHORTWAVE PASSES ACROSS NRN ONTARIO AND SENDS
A SFC TROF S ACROSS THE UPPER LAKES. GFS/NAM FCST SOUNDINGS SHOW AN
INCREASE IN MOISTURE DEPTH AND LIFTING OF THE INVERSION. THIS
ENHANCEMENT COMBINED WITH FAVORABLE PLACEMENT OF DGZ WITHIN
CONVECTIVE BOUNDARY LAYER AND SHARPENING OF THE WIND
SHIFT/CONVERGENCE AS TROF MOVES THROUGH AREA COULD YIELD MODERATE
SNOW LATE TONIGHT WITH A QUICK 1 TO LOCALLY 3 INCHES OF SNOW IN NRN
ONTONAGON/HOUGHTON COUNTIES WHERE SHARPEST CONVERGENCE IS INDICATED
AND WHERE UPSLOPING WILL FURTHER AID SNOW ACCUMULATIONS.

WENT ON COLDER SIDE OF GUIDANCE FOR MIN TEMPS ESPECIALLY OVER THE
WRN INTERIOR AS PCPN WATER FALL TO LESS THAN .25 INCH UNDER LIGHT
WINDS...A PERIOD OF CLEARING SKIES AND FRESH SNOW COVER. COULD SEE
THE TYPICAL COLD SPOTS NEAR THE WI BORDER FALL NEAR ZERO.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 458 AM EST SAT DEC 27 2014

WILL START OUT 12Z SUNDAY WITH A COLD FRONT DRAPED ACROSS THE FAR W
CWA. THIS WILL BE THE FOCUS FOR LIGHT TO POTENTIALLY MODERATE SNOW
SHOWERS FROM AROUND ONTONAGON UP THROUGH THE KEWEENAW PENINSULA. AS
NOTED IN THE PREVIOUS DISCUSSION...A LES ADVISORY BY BE NEEDED FOR
ONTONAGON AND HOUGHTON COUNTIES. CURRENTLY FORECASTING 3-5IN OF NEW
SNOW IN THIS AREA OVERNIGHT THROUGH SUNDAY EVENING. WILL HOLD OFF ON
ISSUING ANYTHING AS ONTONAGON AND S HOUGHTON HAVE BEEN INCLUDED IN
THE INITIAL WINTER WX ADVISORY FOR TODAY.

WITH COOLER AIR SLIDING IN...LOOK FOR SNOW RATIOS TO BE ON THE
INCREASE...RANGING FROM AROUND 20-23:1 THROUGH MUCH OF THIS PERIOD.
THE SFC TROUGH WILL SLOWLY EXIT AS STRONG AND COLD HIGH PRESSURE
PUSHES FROM FAR NW CANADA SUNDAY TO BRITISH COLUMBIA/ALBERTA ON
MONDAY...WITH A SIZABLE RIDGE EXTENDING INTO THE UPPER GREAT LAKES.

THE LOWERING INVERSION HEIGHTS /AROUND 850MB AT IWD/ WILL START TO
BECOME A CONCERN FOR MODERATE/HEAVY SNOWFALL DEVELOPMENT FROM 00Z
MONDAY ON ACROSS THE CWA. STILL EXPECTING 12HR SNOW TOTALS OF 1-3IN
WHERE THE BEST CONVERGENCE DEVELOPS WITH PLENTY OF MOISTURE STILL
STUCK IN OUR STEADY NW FLOW INTO TUESDAY.

THE COLDEST AIR LOOKS TO SWING IN TUESDAY NIGHT...ON THE ORDER OF
-21 TO -24C. IF WINDS BECOME MORE WESTERLY AND THE INTERIOR W HALF
CLEARS OUT...THIS COULD BE A VERY CHILLY NIGHT. CURRENTLY CALLING
FOR -5 TO -10F LOWS BY DAYBREAK WEDNESDAY UNDER A PARTLY CLOUDY SKY.

THERE MAY BE A BRIEF REPRISE FROM THE STEADY NW TO WNW WINDS
WEDNESDAY INTO WEDNESDAY NIGHT. POPS/WX MAY NEED TO BE DIMINISHED
FROM THE CURRENT FCST FOR WEDNESDAY NIGHT IF THIS TREND HOLDS UP.
THERE IS PLENTY OF DISCREPANCIES BETWEEN THE AVAILABLE GUIDANCE AT
THIS POINT...VARYING FROM -20C 850MB AIR OVERHEAD ON GUSTY NW WINDS
/UP TO 40KTS AT 850MB/ FROM THE 27/00Z GFS...AND MORE W-WSW WINDS
WITH -12C 850MB TEMPERATURES OFF THE 26/12Z ECMWF. WILL KEEP GOING
WITH A GENERAL BLEND BETWEEN THE CONSENSUS AND OUR PREVIOUS FORECAST
BEYOND THIS POINT GIVEN THE MODERATE TO LOWER CONFIDENCE.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1250 PM EST SAT DEC 27 2014

THE SYSTEM LEADING TO THE MODERATE SNOW ACROSS MUCH OF UPPER
MICHIGAN WILL BE QUICKLY LIFTING NORTHEAST AND OUT OF THE AREA OVER
THE NEXT COUPLE OF HOURS. HAVE ALREADY SEEN VISIBILITIES COMING UP
AT KIWD AS THE BACK EDGE OF THE SNOW IS DEPARTING. THAT WEST TO
EAST DIMINISHING TREND WILL CONTINUE AT ALL THREE SITES AND EXPECT
WINDS TO BACK TO THE WEST-NORTHWEST INTO THE EVENING. THIS SHOULD
LEAD TO A TREND TOWARDS VFR AT KIWD/KSAW...BUT KCMX MAY TRY TO HOLD
ONTO HIGH END MVFR THIS EVENING WITH SOME LAKE ENHANCED CLOUDS.

FOCUS THEN TURNS TO A SECOND TROUGH THAT WILL DROP ACROSS WESTERN
LAKE SUPERIOR LATE TONIGHT AND UPPER MICHIGAN ON SUNDAY. JUST AHEAD
OF THIS TROUGH...EXPECT LAKE EFFECT SNOW TO DEVELOP IN THE WESTERLY
WINDS AND AFFECT KCMX SHORTLY AFTER MIDNIGHT. THIS WILL LEAD TO A
PERIOD OF MODERATE SNOWFALL AND HAVE BROUGHT VSBYS BELOW ALTERNATE
LANDING MINS. ONCE THE TROUGH MOVES THROUGH...CONDITIONS WILL
BECOME LESS FAVORABLE AT KCMX AS WINDS TURN TO THE NORTHWEST BUT
BRING A BETTER OPPORTUNITY FOR SNOW AT KIWD. AT KSAW...EXPECT THE
VFR CONDITIONS TO REMAIN THROUGH MUCH OF THE MORNING...BUT BLOWOFF
FROM THE UPSTREAM LAKE EFFECT WILL LIKELY BRING SOME LIGHT SNOW
SHOWERS AND BORDERLINE MVFR/VFR CEILINGS AROUND NOON ON SUNDAY.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 535 AM EST SAT DEC 27 2014

EXPECT GENERALLY LIGHT WINDS INTO THIS MORNING AS A WEAK PRESSURE
GRADIENT IS IN PLACE DUE TO A SURFACE TROUGH STALLED OVER THE
MACKINAC STRAITS. BUT AS A LOW LIFTS NORTHEAST OF THE STRAITS THIS
AFTERNOON INTO QUEBEC TONIGHT...NORTHWEST WINDS WILL BE ON THE
INCREASE THIS AFTERNOON AND EVENING WITH GUSTS UP TO 30KTS OVER EAST
HALF. BEHIND THE LOW...A WEAK SURFACE TROUGH WILL REMAIN IN PLACE ON
SUNDAY AND KEEP WEST-NORTHWEST WINDS UP TO 25KTS IN PLACE. A HIGH
PRESSURE RIDGE BUILDING INTO THE AREA ON MONDAY FROM A STRONG HIGH
IN THE NORTHERN/CENTRAL PLAINS WILL LEAD TO NORTHWEST TO NORTHERLY
WINDS UP TO 25-30KTS THROUGH TUESDAY. AN APPROACHING TROUGH FROM A
LOW OVER HUDSON BAY ON TUESDAY NIGHT WILL LEAD TO A TIGHTER PRESSURE
GRADIENT AND WESTERLY GALES TO 35-40KTS LATE TUESDAY NIGHT INTO
WEDNESDAY.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
  WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR MIZ006-
     007-014-085.

  WINTER WEATHER ADVISORY UNTIL 4 PM EST /3 PM CST/ THIS AFTERNOON
     FOR MIZ004-005-010>013.

  WINTER WEATHER ADVISORY UNTIL 1 PM EST /NOON CST/ THIS AFTERNOON
     FOR MIZ002-009-084.

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

$$

UPDATE...SRF
SHORT TERM...VOSS
LONG TERM...KF
AVIATION...SRF
MARINE...VOSS






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.