Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 200909
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
509 AM EDT MON APR 20 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 316 AM EDT MON APR 20 2015

UPPER AIR PATTERN CONSISTS OF A ELONGATED 500 MB TROUGH WITH SEVERAL
SHORTWAVES EMBEDDED IN IT. THE SHORTWAVE OVER LOWER MICHIGAN WILL BE
SPREADING PCPN UP INTO THE CWA THIS MORNING WHILE ANOTHER SHORTWAVE
OVER THE RED RIVER VALLEY OF THE NORTH WILL PUT PCPN IN OVER THE FAR
WEST THIS MORNING. BOTH THESE SHORTWAVES WILL COMBINE OVER THE AREA
AND CAUSE SOME WIDESPREAD PCPN THIS MORNING OVER THE CWA. UPPER
TROUGH SLOWLY MOVES EAST WITH A 500 MB LOW MOVING OVER THE U.P. LATE
TONIGHT. NAM SHOWS DEEPER MOISTURE AND 850-500 MB Q-VECTOR
CONVERGENCE OVER THE CWA THIS MORNING. THE DEEPER MOISTURE REMAIN
OVER THE AREA THROUGH TONIGHT WHILE THE Q-VECTOR CONVERGENCE WEAKENS
AND MOVES OUT BY THIS EVENING BEFORE MOVING BACK IN LATE TONIGHT
WITH THE 500 MB LOW. GFS AND ECMWF SHOW ABOUT THE SAME THING AS
WELL.

HAD TO HANG ONTO THE DRIER AIR ACROSS THE CENTRAL CWA A BIT LONGER
THIS MORNING AND CUT THE QPF AMOUNTS BECAUSE OF THIS. DID GO WITH A
COMBO OF WET BULB HEIGHTS AND WARM TEMPERATURES ALOFT TO DETERMINE
SNOW FOR THIS FORECAST AND LOOKS LIKE THE ACCUMULATING SNOW WILL BE
TONIGHT WHERE UP TO 2 INCHES COULD FALL ACROSS THE WESTERN
HIGHLANDS. OTHERWISE...DID NOT MAKE TOO MANY CHANGES TO THE GOING
TEMPERATURE FORECAST AND WENT WITH CATEGORICAL POPS FOR TODAY FOR
THE CWA AND THEN LIKELY POPS IN NORTHWEST LAKE EFFECT BELTS TONIGHT
AND KEPT SOME SLIGHT CHANCE POPS IN THE FAR SOUTH DUE TO THE UPPER
LOW MOVING INTO THE AREA AND WRAPAROUND PCPN IN THE AREA.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 507 AM EDT MON APR 20 2015

COLDER...WITH LITTLE BREAK IN IN THE NEAR FUTURE. THE BEST CHANCE OF
LIGHT PRECIP WILL BE ALONG THE LAKE SUPERIOR SHORELINE.

AT 12Z TUESDAY THE SFC LOW WILL HAVE SHIFTED TO JUST W OF JAMES
BAY...WITH A TROUGH/SECONDARY COLD FRONT EXTENDING OVER CENTRAL LAKE
SUPERIOR AND CENTRAL UPPER MI. 850MB TEMPS AHEAD OF THE TROUGH WILL
AVERAGE AROUND -4C...AND FALL TO AROUND -7C BY THE END OF THE DAY
BEHIND THE TROUGH. THIS WILL COINCIDE WITH THE PASSAGE OF THE LARGE
500MB LOW...CENTERED OVER THE CWA TUESDAY. THE SIZABLE TROUGH WILL
ENCOMPASS E MT THROUGH THE GULF STATES...AND BACK UP THROUGH THE NEW
ENGLAND STATES.

THE 500MB LOW WILL NOT MOVE MUCH...ONLY TO E ONTARIO BY THURSDAY
MORNING. THIS WILL BE SIMILAR TO THE SFC LOW WHICH WILL ONLY SHIFT
TO FAR W ONTARIO DURING THE SAME TIME. LOOK FOR PERSISTENT NW WINDS
AND 850MB TEMPS OF -8 TO -12C.

THE 500MB LOW WILL CONTINUE ITS E PROGRESSION THURSDAY NIGHT THROUGH
FRIDAY...MOVING ACROSS S QUEBEC. WHILE A WEAK RIDGE WILL ATTEMPT TO
BUILD OVER FAR W LAKE SUPERIOR/UPPER MI...THE TROUGH WILL STILL
REMAIN OVER THE E. WHILE THE SFC LOW INITIALLY SHIFTS TO SE QUEBEC
EARLY THURSDAY EVENING...IT LOOKS TO SHIFT BACK W DURING THE DAY
FRIDAY /PARTICULARLY OFF THE GFS SOLUTION/.

THERE LOOKS TO BE SOME DISCREPANCIES IN THE HANDLING OF THE 500MB
LOW FOR THE LATTER HALF OF THE WEEKEND BY THE 00Z MODEL RUNS. WHILE
THE ECMWF PUSHES A RIDGE OVER THE UPPER GREAT LAKES SATURDAY AND
SUNDAY...THE GFS KEEPS THE TROUGH IN PLACE. AS A RESULT...FEW
CHANGES WERE MADE TO THE ONGOING FCST FOR THE WEEKEND. TEMPS MAY
RISE AROUND 5F SUNDAY COMPARED TO SATURDAY...BUT WAS LACKING
CONFIDENCE TO DO MUCH MORE THAN THAT. THE ECMWF SOLUTION WOULD BRING
850MB TEMPS BACK TO -2C BY SATURDAY AFTERNOON WITH THAT RIDGE
BUILDING IN. HOWEVER...THE GFS IS STILL AROUND -8C.
&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 106 AM EDT MON APR 20 2015

LOW PRES OVER SW MI WILL LIFT N TODAY WHILE A LOW PRES TROF MOVES E
AND MERGES WITH THE LOW. THESE 2 FEATURES WILL SPREAD SHRA ACROSS
THE AREA OVERNIGHT...BRINGING DETERIORATING CONDITIONS.

SFC TROF HAS ALREADY PASSED KIWD. WITH RAIN OVER THE COLD LAKE
WATERS AND AN UPSLOPE NW WIND...LIFR CONDITIONS WILL LIKELY PREVAIL
THRU THE MORNING HRS. THE -SHRA WILL MIX WITH OR CHANGE TO -SHSN
AROUND MID MORNING. PCPN WILL THEN DIMINISH IN THE AFTN WITH
CONDITIONS IMPROVING TO MVFR UNDER GUSTY WNW WINDS. MIGHT EVEN SEE A
PERIOD OF VFR CONDITIONS. ANOTHER DISTURBANCE MAY BRING
DETERIORATING CONDITIONS AGAIN LATE THIS EVENING.

AT KCMX...WITH MAIN AREA OF PCPN AND SFC TROF NOT ARRIVING UNTIL
AROUND DAYBREAK...VFR CONDITIONS SHOULD PREVAIL UNTIL AROUND 10Z.
EXPECT A QUICK DROP TO LIFR DURING THE MORNING UNDER INCREASING
UPSLOPE NW WINDS...THEN ONLY GRADUAL IMPROVEMENT TO IFR IN THE AFTN
AS -SHRA CONTINUE. NW WIND WILL LIKELY GUST TO AROUND 30KT DURING
THE AFTN.

AT KSAW...UNTIL ARRIVAL OF SHRA FROM THE S...VFR CONDITIONS WILL
PREVAIL FOR THE NEXT FEW HRS. ARRIVAL OF SHRA AND WINDS BACKING
AROUND TO AN UPSLOPE NE TO N DIRECTION OFF LAKE SUPERIOR WILL RESULT
IN CONDITIONS QUICKLY FALLING TO LIFR BEFORE 12Z. AS WINDS BACK TO
THE NW AND THEN W IN THE AFTN AND PCPN DIMINISHES...EXPECT
IMPROVEMENT TO MVFR. MIGHT EVEN SEE A PERIOD OF VFR LATE AFTN/EARLY
EVENING.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 316 AM EDT MON APR 20 2015

AS A LOW LIFTS THROUGH THE SOO THIS AFTERNOON...WINDS WILL BACK TO
THE WEST-NORTHWEST THIS AFTERNOON. WITH THE LOW BECOMING STATIONARY
JUST TO THE SOUTHWEST OF JAMES BAY TONIGHT THROUGH
WEDNESDAY...PERSISTENT NORTHWESTERLY WINDS OF 20-30KTS ARE EXPECTED.
ALTHOUGH THE LOW WILL WEAKEN AND MOVE EAST ACROSS QUEBEC WEDNESDAY
NIGHT INTO THURSDAY...THE NORTHWEST WINDS UP TO 25KTS WILL PERSIST
AS A RIDGE MOVES INTO THE NORTHERN PLAINS. THE WINDS DIMINISH THEN
BELOW 20 KNOTS BY THURSDAY NIGHT.
&&

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

$$

SHORT TERM...07
LONG TERM...KF
AVIATION...ROLFSON
MARINE...07



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