Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 181017
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
517 AM EST THU DEC 18 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 403 AM EST THU DEC 18 2014

AN UPPER RIDGE STRETCHING FROM MINNESOTA THROUGH NORTHWEST ONTARIO
WILL BE THE MAIN FEATURE CONTROLLING THE WEATHER OVER THE UPPER
GREAT LAKES REGION OVER THE NEXT 24 HOURS. BENEATH THIS UPPER
RIDGE...A 1029MB SURFACE HIGH SITS JUST TO THE NORTH OF THE
MINNESOTA WHILE THE SURFACE TROUGH THAT LED TO THE SNOW YESTERDAY
IS OVER NORTHERN LAKE MICHIGAN AND NORTHERN LOWER MICHIGAN AND
WEAKENING. NORTH-NORTHEASTERLY FLOW AROUND THIS HIGH HAS PULLED
DRIER AIR INTO THE UPPER GREAT LAKES REGION...LEADING TO CLEARING
SKIES THIS PAST EVENING OVER MUCH OF LAKE SUPERIOR. BUT MOISTURE
TRAPPED BELOW THE SUBSIDENCE INVERSION...AND COMBINED WITH UPSLOPE
FLOW...HAS LED TO LOW CLOUDS PERSISTING OVER A GOOD PORTION OF
UPPER MICHIGAN EARLY THIS MORNING. THERE ARE A COUPLE SPOTS WHERE
THE CLOUDS DID CLEAR OUT...GENERALLY OVER THE KEWEENAW PENINSULA
AND ALSO IT/S STARTING TO OVER THE EAST. WHERE SKIES CLEARED
OUT...3AM TEMPERATURES ARE IN THE SINGLE DIGITS ABOVE ZERO (6
DEGREES AT KCMX)...WHILE THE CLOUDS HAVE KEPT THE TEMPERATURES IN
THE UPPER TEENS AND LOWER 20S ELSEWHERE. STILL SEEING LIGHT
FLURRIES HERE AT OUR OFFICE AT 330AM...SO WILL CONTINUE TO MENTION
ISOLATED FLURRIES IN THE FORECAST FOR THE UPSLOPE LOCATIONS THROUGH
DAYBREAK.

WITH THE UPPER RIDGE AND SURFACE HIGH MOVING OVER THE AREA
TODAY...EXPECT CONTINUED QUIET CONDITIONS FOR THE SHORT TERM
PERIOD. THERE ARE TWO AREAS OF FOCUS IN THE SHORT TERM
PERIOD...FIRST THE LOW CLOUDS AND THEIR DIMINISHMENT AND THEN THE
POTENTIAL FOR SOME FREEZING FOG OVERNIGHT TONIGHT. FOR THE LOW
CLOUDS...KMQT VWP INDICATES CLOUD TOPS AROUND 2.5KFT...WHICH
MATCHES UP WELL WITH THE INVERSION INDICATED ON THE MODELS AT
900MB. THE BIG QUESTION IS WHEN WILL THEY DISSIPATE TODAY. AT
THIS TIME OF THE YEAR WITH THE LOW SUN ANGLE AND LIMITED
MIXING...THERE IS LITTLE DAY TIME HELP AND WILL NEED TO RELY ON THE
ADVECTION OF DRIER AIR INTO THE AREA. UNFORTUNATELY...THIS IS WHERE
THE MODELS TEND TO DIFFER. THE 00Z NAM HOLDS ONTO THE CLOUDS FOR
MUCH OF THE DAY AND EVEN THROUGH THE NIGHT TONIGHT...BUT THINK THAT
IS LARGELY TIED TO IT TRADITIONALLY OVER DOING LOW LEVEL MOISTURE.
THAT APPEARS TO THE CASE EARLY THIS MORNING...WHERE IT HAS THE LOW
CLOUDS JUST TO THE WEST OF JAMES BAY BEING MUCH FARTHER TO THE
SOUTH AND SUPPOSEDLY ENTERING NORTHERN LAKE SUPERIOR AT THIS TIME.
THE RECENT RAP (ALONG WITH THE HRRR) RUNS ALSO HOLD ONTO THE CLOUDS
FOR MUCH OF THE DAY BEFORE CLEARING THEM OUT THIS AFTERNOON...BUT IT
APPEARS TO HAVE THE LOW LEVEL MOISTURE FARTHER NORTH OVER LAKE
SUPERIOR THAN WHAT IS ACTUALLY OCCURRING. THE MORE OPTIMISTIC
RUNS...WHICH SEEM TO HAVE A BETTER HANDLE ON THE LOCATION OF THE
LOW CLOUDS ARE THE 00Z GFS/ECMWF. THEY HOLD ONTO THE LOW CLOUDS
OVER THE NORTH CENTRAL AND WEST FOR THE FIRST PART OF THE MORNING
AND THEN SCATTER THEM OUT THROUGH THE LATER PART OF THE MORNING AND
EARLY AFTERNOON. WILL FOLLOW THAT IDEA AT THIS POINT FOR THE CLOUD
COVER FORECAST FOR TODAY. MEANWHILE OVER THE EAST...THE ADVECTION
OF THE DRIER AIR AND LITTLE UPSLOPE HELP SHOULD ALLOW THE LOW
CLOUDS TO DISSIPATE DURING THE FIRST PART OF THE MORNING. THAT DRY
AIR HAS ALREADY SCATTERED THE CLOUDS OUT OVER LUCE COUNTY AND
STARTING TO SEE IT WORK INTO ALGER/SCHOOLCRAFT COUNTIES. AS FOR
HIGHS TODAY...EXPECT THEM TO BE IN THE MID-UPPER 20S OVER MUCH OF
THE AREA.

FOLLOWING THE IDEA OF THE CLOUDS DIMINISHING TODAY...WOULD EXPECT A
VERY GOOD RADIATIONAL COOLING NIGHT TONIGHT UNDER THE CENTER OF THE
HIGH. THUS...WILL CONTINUE THE IDEA OF GOING AT OR BELOW THE
COLDEST GUIDANCE. THE GEM MODELS USUALLY PERFORM WELL IN
RADIATIONAL COOLING NIGHTS AND THEY HAVE LOWS IN THE LOWER SINGLE
DIGITS WHERE THEY ARE NOT INDICATING CLOUDS (ALTHOUGH THE REGIONAL
GEM REDEVELOPS LOW CLOUDS OVER THE HIGHER TERRAIN OF THE NORTH
CENTRAL TONIGHT). THUS...HAVE LOWS IN THE SINGLE DIGITS ABOVE ZERO
TO AROUND ZERO OVER THE INTERIOR LOCATIONS. WITH KCMX DROPPING TO 6
DEGREES AT 3AM THIS MORNING...THAT SUPPORTS TO EXPECTATIONS FOR
TONIGHT. THIS EXPECTED DROP IN TEMPS WILL LEAD TO THE POTENTIAL FOR
PATCHY FREEZING FOG OR AT LEAST SOME SOLID FROST. WITH DEWPOINTS IN
THE MID-UPPER TEENS TODAY...TEMPS SHOULD EASILY DROP THROUGH THOSE
VALUES THIS EVENING. DEWPOINTS THIS PAST EVENING AT KCMX WERE
SIMILAR TO WHAT IS EXPECTED ACROSS THE REST OF THE AREA THIS
AFTERNOON. WITH THEIR QUICK TEMP DROP AND LIGHT WINDS...THEY HAVEN/T
EXPERIENCED ANY FOG AT THIS POINT...BUT THE ICE ACCRETION ALGORITHM
DID INDICATE SOME ICE ACCUMULATION. THIS IS LIKELY DUE TO THAT QUICK
DROP AND IN TURN SOME QUICK/HARD FROST ON THE SENSOR. IT WILL BE
INTERESTING TO SEE IF ANY VERY SHALLOW FOG DEVELOPS AT KCMX OVER
THE NEXT COUPLE HOURS...AS IT WILL FORESHADOW WHAT WILL OCCUR
TONIGHT.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 514 AM EST THU DEC 18 2014

FRIDAY...A DRY AIRMASS ASSOCIATED WITH THE DEPARTING AREA OF
HIGH PRESSURE WILL LEAVE PARTLY TO MOSTLY SUNNY SKIES ACROSS UPPER
MICHIGAN. HOWEVER...THERE IS SOME UNCERTAINTY WHETHER MOISTURE
BENEATH THE PROMINENT 925 MB INVERSION WILL LINGER ENOUGH FOR MOSTLY
CLOUDY SKIES...ESPECIALLY OVER THE WEST. EVEN WITH SOME
CLOUDS...TEMPS ARE EXPECTED TO CLIMB INTO THE UPPER 20S.

FRI NIGHT...TEMPS SHOULD DROP OFF QUICKLY IN THE EVENING BUT MAY
REBOUND LATE AS CLOUDS INCREASE WITH STRENGTHENING 850 MB WAA AND
ASSOCIATED 280K ISENTROPIC ASCENT. WITH THE MID LEVEL REMAINING
DRY...NO PCPN IS EXPECTED.

SAT...AS THE SFC HIGH SLOWLY BUILDS INTO THE ERN LAKES...SRLY WINDS
WILL BRING WARMER AIR INTO THE REGION WITH TEMPS CLIMBING SLIGHTLY
ABOVE NORMAL WITH MAX READINGS CLIMB TO AROUND 30 DESPITE THE
THICKENING CLOUDS.

SUN...AS A MID LEVEL TROUGH DEVELOPS ACROSS THE CENTRAL CONUS...THE
MODELS SUGGEST POTENTIAL FOR A WEAK SHORTWAVE AND AREA OF MORE
SUBSTANTIAL 290K ISENTROPIC LIFT THAT COULD PRODUCE SOME LIGHT SNOW.
THE DYNAMICS REMAIN WEAK ENOUGH TO SUPPORT ONLY SLIGHT CHANCE POPS.
CONTINUED WAA WILL NUDGE MAX TEMPS INTO THE LOWER 30S.

MON-WED...ALTHOUGH THERE IS GENERAL MODEL AGREEMENT THAT A MID LEVEL
TROUGH WILL DEEPEN OVER THE NORTHERN GREAT LAKES...THERE ARE
CONSIDERABLE DIFFERENCES IN THE DETAILS OF HOW THE SHORTWAVES DIVING
INTO THE TROUGH WILL INTERACT AND HOW THAT WILL INFLUENCE
THE POSITION/STRENGTH OF THE SFC FEATURES. SNOW CHANCES INCREASE
FROM MON INTO MON NIGHT AS THE INITIAL LOW MOVES THROUGH THE UPPER MS
VALLEY. ENOUGH WARM AIR MAY BE DRAWN NORTHWARD TO BRING POTENTIAL FOR
SOME RAIN INTO THE EAST HALF. THE PREFERRED/MORE CONSISTENT 00Z/12Z
ECMWF KEEP THE LOW AND WARMER AIR SLIGHTLY FARTHER TO THE
SOUTH...MINIMIZING CHANCES FOR RAIN. THE LARGER DISPARITIES DEVELOP
BY WED WITH THE HANDLING OF A STRONGER SHRTWV THAT WOULD SUPPORT
RAPID DEEPENING OF THE SFC LOW. THE 18Z/00Z GFS AND 00Z ECMWF HAVE
BACKED OFF FROM THE VERY STRONG LOW MOVING INTO THE CNTRL LAKE AND
THEN NORTHWARD TOWARD JAMES BAY AND HAVE SHIFTED THE STRONGER LOW
THROUGH THE NORTHEAST CONUS. HOWEVER...IT WOULD NOT BE SURPRISING TO
SEE THE MODELS REVERT BACK TO THE STRONGER LOW THROUGH LOWER MI. WITH
SO MUCH UNCERTAINTY AND HIGH ENSEMBLE/MODEL SPREAD...THE FCST
MAINTAINS HIGHER END SNOW CHANCES BUT WITH LESS EMPHASIS FOR NOW ON
THE POTENTIAL FOR HEAVY SNOW AND HIGH WINDS UNTIL FCST CONFIDENCE IS
HIGHER.
&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1224 AM EST THU DEC 18 2014

SKIES HAVE ALREADY CLEARED OUT AT KCMX AS DRY AIR ARRIVES FROM THE
NORTH. LINGERING FLURRIES WILL END EARLY THIS MORNING AT KIWD AND
KSAW...BUT LOW MVFR CIGS SHOULD REMAIN AS MOISTURE IS TRAPPED BELOW
STRENGTHENING INVERSION. EXPECT SKIES TO GRADUALLY CLEAR AT BOTH
SITES BY THIS AFTERNOON DUE TO MIXING OUT OF THE SHALLOW MOIST
LAYER. RISK OF FREEZING FOG TONIGHT AT MAINLY KSAW AND POSSIBLY
KCMX. DID LEAVE OUT OF TAFS ATTM THOUGH AS GREATEST CHANCE OF VSBY
REDUCTION AND ICE DEPOSITION SHOULD NOT OCCUR UNTIL AFTER END OF TAF
PERIOD LATER ON THURSDAY NIGHT.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 403 AM EST THU DEC 18 2014

HIGH PRESSURE BUILDING INTO THE UPPER GREAT LAKES REGION TODAY AND
TONIGHT WILL DIMINISH THE NORTHERLY WINDS BELOW 15KTS. THE HIGH
WILL BEGIN TO SHIFT TO THE EAST OF THE REGION ON FRIDAY AND ALLOW
WINDS TO GRADUALLY TURN TO THE SOUTH THROUGH FRIDAY NIGHT. A NEARLY
STATIONARY TROUGH IN THE LEE OF THE NORTHERN ROCKIES THIS WEEKEND
WILL KEEP THE SOUTH TO SOUTHWESTERLY WINDS IN PLACE AND GENERALLY
UNDER 20KTS. THIS TROUGH WILL GIVE WAY TO A DEVELOPING LOW THAT
WILL MOVE INTO THE NORTHERN PLAINS SUNDAY NIGHT AND THE UPPER
MISSISSIPPI VALLEY ON MONDAY.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&

$$

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





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