Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 151757
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
157 PM EDT TUE APR 15 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 507 AM EDT TUE APR 15 2014

WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH FROM
HUDSON BAY THROUGH THE WRN GREAT LAKES AND THE MID MS VALLEY INTO
ERN TX. A WEAK SHRTWV INTO WRN LAKE SUPERIOR SUPPORTED SOME ISOLD
-SHSN TO NEAR IWD WHILE ANOTHER WEAK SHRTWV OVER CNTRL MANTIOBA
INTO NW ONTARIO WAS SLIDING TO THE SE TOWARD WRN LAKE SUPERIOR. AT
THE SFC...NRLY FLOW PREVAILED BTWN A RIDGE EXTENDINGD FROM MANTIOBA
THROUGH THE ERN DAKOTAS AND A TROUGH FROM THE ERN LAKES INTO SRN
QUEBEC. THE NORTH WINDS AND 850 MB TEMPS TO AROUND -17C SUPPORTED
SOME LIGHT LES TO NEAR P53 DESPITE THE EXTENSIVE ICE COVER OVER THE
ERN LAKE.

TODAY...THE UPSTREAM SFC RIDGE WILL BUILD INTO THE WRN LAKES
TODAY BRINGING DIMINISHING WINDS. THIS SHOULD LIMIT OR END THE LES
THIS MORNING OVER THE EAST. SOME ISOLD -SHSN ASSOCIATED WITH THE WRN
LAKE SHRTWV ARE EXPECTED SPREAD INTO THE WRN CWA THIS MORNING. WITH
DAYTIME HEATING...LOW LEVEL LAPSE RATES TO 8-9C/KM WITH 850/700 MB
TEMPS OF -17C/-27C WILL SUPPORT SCT DIURNAL SNOW SHOWERS OVER MAINLY
WEST AND CNTRL UPPER MI. SOME INLAND LOCATIONS COULD SEE A DUSTING
TO AROUND A HALF INCH. OTHERWISE...UNSEASONABLY COLD CONDITIONS WILL
PREVAIL WITH MAX TEMPS IN THE MID 20S TO LOWER 30S WHICH WILL BE
NEAR OR BELOW THE RECORD LOW HIGH TEMP OF 27 FOR THE NWS OFFICE.

TONIGHT...ANY LEFTOVER DIURNAL SHSN OVER S CNTRL UPPER MI
DIMINISH...PARTLY CLOUDY SKIES AND LIGHT WINDS WILL ALLOW TEMPS TO
FALL INTO THE 8F TO 15F RANGE OVERNIGHT. TEMPS MAY CLIMB LATE AS
CLOUDS INCREASE AHEAD OF THE APPROACHING LOW PRESSURE SYSTEM. WAA
LIGHT SNOW WITH INCREASING 280K-290K ISENTROPIC LIFT IS EXPECTED TO
REMAIN MAINLY WEST OF UPPER MI BUT MAY SLIDE INTO THE FAR WEST LATE.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 459 AM EDT TUE APR 15 2014

...POTENTIAL WINTER STORM STILL ON TRACK FOR WEDNESDAY INTO
THURSDAY...

SHORTWAVE CURRENTLY CROSSING SOUTHERN BRITISH COLUMBIA IS FEATURE OF
INTEREST THAT HELPS TO FOCUS SFC LOW ACROSS THE NORTHERN PLAINS BY
TONIGHT. WARM AIR ADVECTION AND ISENTROPIC ASCENT ALONG AND AHEAD OF
THE LOW AND INVERTED SFC TROUGH SHOULD SUPPORT EXPANDING SHIELD OF
SNOW VCNTY OF CNTRL MINNESOTA INTO NORTHWEST WI LATE TONIGHT THROUGH
DAYBREAK ON WEDNESDAY. IF THERE IS ANY TREND IN MODELS IT IS FOR A
SLOWER ARRIVAL OF QPF/SNOW INTO WESTERN UPR MICHIGAN BTWN 12Z-18Z ON
WEDNESDAY. TREND IS NOTHING TOO DRASTIC THOUGH...SO CHANGES TO THIS
PART OF THE FORECAST WERE RELATIVELY MINOR. SFC TROUGH EDGES CLOSER
TO UPR MICHIGAN ON WEDNESDAY AFTN. ISENTROPIC ASCENT MAXIMIZED ON
290K SFC /H775-H650/ AND 285K SFC /H8-H7/ SURGES SOUTH TO NORTH
ACROSS UPR MICHIGAN ROUGHLY 15Z-03Z...THOUGH GFS/NAM REMAIN QUICKER
WITH THIS INITIAL PUSH OF WHAT WILL ESSENTIALLY BE MAINLY SNOW FOR
CWA. H7 MIXING RATIOS IN 2.5-2.75G/KG RANGE SUGGESTS 12 HOUR SNOW
AMOUNTS NEARING 6 INCHES. SUPPOSE ACTUAL SNOW AMOUNTS COULD BE
HELD DOWN SOME AS SNOW ARRIVES DURING THE DAYTIME WHEN SOME INSOLATION
COULD LIMIT ACCUMS ESPECIALLY ON HIGHER TRAFFIC/TRAVELLED ROADS.
THUS OVERALL POSSIBLE IMPACT FROM THE SNOW COULD BE MITIGATED SOME
COMPARED TO IF THE SNOW ARRIVED DURING THE NIGHTTIME HOURS.
ULTIMATELY IT ALL DEPENDS ON SNOWFALL RATES...WITH HIGHER RATES
ALLOWING FOR SLUSHY ACCUMS EVEN ON THE PRIMARY ROADS.

NAM QPF STILL APPEARS OVERDONE ESPECIALLY WHEN COMPARED TO ITS OWN
MIXING RATIOS. DO NOT DOUBT THAT AREAS OVER MAINLY WESTERN TIER OF
CWA WILL SEE HIGHER QPF/SNOW DUE TO INCREASING AND FAIRLY ROBUST
H8-H7 FGEN AND STRONG FN VECTOR CONVERGENCE. FAR WEST TOWARD KEWEENAW
SEEMS IN LINE FOR THE HIGHEST PROBABILITY OF THIS ADDITIONAL FORCING
WHICH COULD BE SUPPLEMENTED WITH INSTABILITY AS SOME NEGATIVE EPV IS
PRESENT ATOP THE FGEN. NET RESULT IS POTENTIAL FOR BANDED SNOWFALL
SOMEWHERE IN THE WESTERN CWA.

EVEN TRENDING AWAY FM THE NAM 1 INCH PLUS QPF AMOUNTS...BLEND OF GFS
AND ECMWF WOULD SUGGEST SOME AREAS WILL SEE 0.8 INCH OF TOTAL QPF.
THIS LINES UP WELL WITH SREF PROBS SHOWING OVER 70 PCT CHANCE OF
EXCEEDING 0.50 INCH BUT NOT EVEN REACHING 10 PCT PROBS OF SEEING 1
INCH OF LIQUID. SOUNDINGS OVERALL SHOW BULK OF LIFT OCCURRING IN THE
DGZ UP OVER 10KFT AGL. LIFT BLO THIS LAYER IN TEMPS WARMER THAN -10C
WILL LOWER SLR/S SLIGHTLY. EXPECTING MOST AREAS CENTERED IN THE 12:1
RANGE...A BIT HIGHER IN THE FGEN AREA AND POSSIBLY A BIT LOWER
FARTHER SOUTH AND EAST IN THE CWA WITH WARMER TEMPS BLO 5KFT. WHAT
ALL THIS MEANS FOR SNOW AMOUNTS IS DECENT LIKLIHOOD OF SEEING TOTALS
OVER 10 INCHES OVER WEST VCNTY OF PERSISTENT FGEN FORCING...BUT
PROBABLY MORE IN THE 7 TO 10 RANGE FARTHER EAST INTO CNTRL CWA.
SINCE THE SNOW DOES NOT ARRIVE UNTIL ON WEDNESDAY AND GIVEN
UNCERTAINTY IN THE SNOW AMOUNTS OVR THE CNTRL CWA...COORD WITH GRB
AND DLH AND WILL BE LEAVING WINTER STORM WATCH AS IS ATTM.

FARTHER SOUTH AND EAST IN THE CWA...SOUNDINGS AND 1000-850MB AND
850-700MB THICKNESSES INDICATE INITIAL SURGE OF PRECIPITATION
WEDNESDAY AFTN WILL BE GENERALLY SNOW. ENOUGH WARMING OCCURS SOUTH
OF LINE FM KIMT TO KERY WEDNESDAY NIGHT INTO THURSDAY TO RESULT IN
RAIN/SNOW MIX OR POSSIBLE CHANGEOVER TO RAIN. BEST CHANCE FOR ONLY
RAIN REMAINS AT KMNM AS WBZERO HEIGHT INCREASE OVER 2000FT AGL. MAY
SEE MORE AREAS CHANGE TO RAIN BY THURSDAY AFTN AS TEMPS RISE INTO
THE UPPER 30S...BUT HEAVIER PRECIP IS EXPECTED TO BE EAST AND NORTH
OF CWA BY THAT TIME. SOUNDINGS INDICATE EXITING DEEP MOISTURE MAY
RESULT IN SITUATION WHERE DRIZZLE OR FLURRIES ARE MAIN PCPN THAT IS
OCCURRING BY THURSDAY AFTN. SNOW AMOUNTS IN THE EAST SHOULD BE HELD
DOWN OVERALL WITH THIS SYSTEM DUE TO THE WARMER AIR BLO H85 WORKING
IN LATER WEDNESDAY NIGHT INTO THURSDAY. ATTM THINKING AREAS EAST OF
THE WATCH WILL NEED AN ADVY. MODELS DO SHOW SOME DISAGREEMENT ON
THIS ASPECT OF THE SYSTEM THOUGH. GFS/NAM/ECMWF GENERALLY IN LINE
WITH DIMINISHING PRECIP TREND ON THURSDAY...WHILE THE GEM-NH AND
UKMET ARE SLOWER AND FARTHER SOUTH WITH PRIMARY AREA OF HEAVIER
SNOW. SHIFTS TODAY AND TONIGHT WILL NEED TO PIN THIS DOWN FURTHER.
RIGHT NOW THE FORECAST LEANED TOWARD GFS/ECMWF BLEND WHICH WAS ALSO
PREFERRED BY HPC.

NOT A WHOLE LOT OF DETAIL FOR THE EXTENDED PERIOD AS MAIN FOCUS WAS
ON THE HIGHER IMPACT WEDNESDAY/THURSDAY WEATHER. PROBABLY JUST AS
WELL TO AS MODELS ARE STRUGGLING MIGHTILY ON SPECIFICS FOR THE
WEEKEND.

ONE TREND THAT WAS ACTED UPON WAS TO GO WITH DRIER FORECAST FOR
FRIDAY AND FRIDAY NIGHT AS GFS WHICH WAS SHOWING WRAPPED UP SYSTEM
ACROSS THE UPR LAKES A COUPLE DAYS AGO IS NOW SHUNTING PRECIP WELL
TO THE SOUTH AND EAST OVER THE CNTRL GREAT LAKES ALONG PRIMARY H85
MOISTURE AXIS. THIS AGREES WELL WITH GEM-NH AND ECMWF. HIGH PRESSURE
AND DRY WEATHER DOMINATES SOUTH CNTRL CANADA INTO UPPER GREAT LAKES.
THUS DROPPED POPS ON FRIDAY AND FRIDAY NIGHT. SHOULD STAY SEASONABLY
CHILLY THOUGH WITH MID 30S NORTH AND LOWER 40S SOUTH AS NE WINDS
FLOW OFF THE ICY WATERS OF LK SUPERIOR AND THERE COULD BE MID CLOUDS
ON THE NORTHWEST SIDE OF THE FRONTAL BOUNDARY OVR THE CNTRL GREAT
LAKES.

MODEL CONSENSUS WAS USED FOR SATURDAY/EASTER SUNDAY/MONDAY. ECMWF
AND GEM-NH TRENDING WETTER FOR SATURDAY NIGHT INTO SUNDAY. PTYPE
WOULD MOSTLY BE RAIN...WITH MIX OF RAIN/SNOW POSSIBLE ON SATURDAY
NIGHT AS COOLER LOW-LEVEL AIR GRADUALLY RETREATS. GFS NOT AS EXCITED
ON THE OVERALL PCPN CHANCES. FORECAST CAME OUT WITH SLIGHT CHANCES
WITH MOSTLY CLOUDY SKIES. THIS WORKS FOR NOW AS THE CONSISTENCY IN
THE MODELS IS LESS THAN DESIRED FOR SURE. TEMPS INDICATE GRADUAL
WARMING TREND...BUT COULD SEE WARMER TEMPS THAN FORECAST IF ANY OF
THESE DAYS ENDS UP DRY WITH SOME SUNSHINE.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 138 PM EDT TUE APR 15 2014

DIURNAL HEATING AND THE PRESENCE OF AN UPPER LEVEL TROUGH WILL SUPPORT
-SHSN WITH POTENTIAL FOR CONDITIONS INTO THE MVFR CATEGORY THROUGH 21Z.
AFTER THE DAYTIME HEATING SUBSIDES THIS EVENING...EXPECT CLEARING
WITH VFR CONDITIONS. LOOK FOR CONDITIONS TO LOWER TO IFR AT KIWD BY
LATE WED MORNING AND TO MVFR AT KCMX AND KSAW BTWN 16-18Z WITH THE
ONSET OF SNOW AHEAD OF APPROACHING SYSTEM OVER THE NRN PLAINS.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 459 AM EDT TUE APR 15 2014

WINDS LESS THAN 20 KTS THROUGH TONIGHT. APPROACHING LOW PRESSURE
SYSTEM RESULTS IN INCREASING EAST TO NORTHEAST WINDS ON WEDNESDAY.
30 KTS WITH GALE GUSTS SEEMS LIKELY OVER FAR WESTERN LK SUPERIOR
WEDNESDAY AFTN INTO WEDNESDAY EVENING AS WINDS ARE ENHANCED DUE TO
CHANNELING AND TERRAIN EFFECTS. WINDS SHIFT TO THE NORTH-NORTHWEST
TO 25 KTS ON THURSDAY AS THE LOW WEAKENS WHILE MOVING TO THE EAST OF
LK SUPERIOR. WINDS STAY BLO 20 KTS FOR THE REST OF THE FORECAST
PERIOD.
&&

.HYDROLOGY...
ISSUED AT 459 AM EDT TUE APR 15 2014

GIVEN COLDER TEMPERATURES OVER THE NEXT COUPLE OF DAYS...EXPECT
SLOWER RUNOFF OF MELTING SNOW TO REDUCE THE POTENTIAL FOR ADDITIONAL
ICE JAMS. WIDESPREAD PRECIPITATION IS IN THE FORECAST FOR WEDNESDAY
THROUGH THURSDAY WITH THE POTENTIAL FOR AN ADDITIONAL INCH OF LIQUID
EQUIVALENT PRECIPITATION OVER WESTERN UPPER MICHIGAN. THIS PRECIP
ADDED TO EXISTING SNOWPACK WITH WATER EQUIVALENT OF 4-9 INCHES WILL
RESULT IN ANOTHER PERIOD OF SNOWMELT/RUNOFF AND POSSIBLE ICE JAMS ONCE
WARMER TEMPERATURES MOVE BACK INTO THE REGION NEXT WEEK.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
  WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY
     MORNING FOR MIZ001>005-009>011-084.

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

$$

SHORT TERM...JLB
LONG TERM...JLA
AVIATION...VOSS
MARINE...JLA
HYDROLOGY...JLA






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