Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 201939
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
339 PM 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 NIGHT THROUGH MONDAY)
ISSUED AT 338 PM EDT MON APR 20 2015

A LARGE UPPER LOW CENTERED OVER NORTHERN ONTARIO WILL BE
INFLUENCING THE GREAT LAKES REGION THROUGH THE FIRST HALF OF THE
LONG TERM PERIOD. THIS WILL LEAD TO BELOW NORMAL TEMPERATURES AND
PERIODS OF SNOW BEFORE GRADUALLY SHIFTING EAST INTO THE ATLANTIC BY
THE WEEKEND.

AS THAT UPPER LOW SPINS BETWEEN LAKE SUPERIOR AND JAMES BAY...IT
WILL ROTATE SEVERAL SHORTWAVES ACROSS THE UPPER GREAT LAKES REGION
TUESDAY NIGHT THROUGH THURSDAY. THESE WAVES WILL BRING PERIODS OF
SHOWERS TO THE AREA...WITH HELP FROM BOTH LAKE SUPERIOR (850MB
TEMPS FALLING TO -10C TO -12C ON WEDNESDAY MORNING) AND TERRAIN
ENHANCEMENT (PERSISTENT LOW LEVEL NORTHWESTERLY FLOW). WILL CONTINUE
TO FOCUS THE HIGHEST POPS (LIKELY VALUES) IN THOSE AREAS FAVORED BY
ALL THREE FEATURES (HIGHER TERRAIN OF THE WEST/NORTHWEST) AND ALSO
EAST DOWNWIND OF LAKE SUPERIOR...AND INCLUDE CHANCE/SLIGHTS FOR THE
REST OF THE CWA. WITH THE AMOUNT OF COLD AIR IN PLACE...EXPECT THE
PRECIPITATION TO FALL MAINLY AS SNOW. WITH LOW LEVEL TEMPERATURES
WARMING AWAY OVER THE SOUTHERN THIRD OF THE CWA...COULD SEE SOME
RAIN MIXING IN THERE...BUT OTHERWISE SNOW WILL BE THE NORM. COULD
SEE A COUPLE INCHES OF ACCUMULATION IN THE FAVORED LOCATIONS
TUESDAY NIGHT AND UP TO AN INCH WEDNESDAY AND AGAIN WEDNESDAY
NIGHT. WITH DRIER AIR STARTING TO MOVE INTO THE AREA ON
THURSDAY (ASSOCIATED WITH A SURFACE RIDGE MOVING INTO THE
NORTHERN PLAINS...SHOULD SEE THE COVERAGE OF THE SHOWERS
DIMINISHING THROUGH THE DAY THURSDAY AND CONTINUING TO WEAKENING
INTO FRIDAY. ALSO...DON/T EXPECT HIGHS TO RISE MUCH OUT OF THE
LOW-MID 30S ON WED/THURS OVER THE NORTH HALF OF THE CWA...WITH SOME
HIGHS AROUND 40 OVER THE SOUTH CENTRAL. WILL LIKELY BREAK THE
RECORD LOW HIGH TEMPERATURE HERE AT OUR OFFICE ON WEDNESDAY (36 SET
IN 1972).

EXTENDED RANGE MODELS DIFFER ON HOW QUICKLY THE UPPER LOW DEPARTS
THIS WEEKEND...BUT SHOULD STILL SEE ENOUGH INFLUENCE FROM THE
SURFACE RIDGE MOVING INTO THE NORTHERN PLAINS TO KEEP MOST OF THE
AREA DRY. WITH THE NORTHERLY FLOW OFF LAKE SUPERIOR...EXPECT
TEMPERATURES TO REMAIN BELOW NORMAL BUT IN THE 40S TO AROUND 50. AS
THE UPPER LOW RETROGRADES BACK OVER QUEBEC EARLY NEXT WEEK...COULD
SEE THE UPPER GREAT LAKES REGION BEING AFFECTED BY THE WESTERN EDGE
OF THE ENERGY ROTATING AROUND THE UPPER LOW AND LIKELY KEEPING
BELOW NORMAL TEMPERATURES IN PLACE THROUGH THE END OF APRIL.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 131 PM EDT MON APR 20 2015

AREA OF DEEPER MSTR ASSOCIATED WITH BAND OF SHARPER FORCING WL BRING
A PERIOD OF STEADY SN TO CMX THRU THIS AFTN ALONG WITH LIFR
CONDITIONS. GUSTY W WINDS TO NEAR 30 KTS WL ALSO IMPACT THIS MORE
EXPOSED LOCATION. THE AREA OF PCPN WL EXIT IWD SOON AFTER TAF
ISSUANCE...SO EXPECT AN IMPROVEMENT THERE FM IFR TO MVFR WITH THE
ARRIVAL OF SOME DRIER AIR/SUBSIDENCE. SINCE THE BAND OF HEAVIER PCPN
IS LIKELY TO REMAIN TO THE W OF SAW...THERE SHOULD BE MVFR CIGS WITH
ONLY SOME OCNL -SHRA IN THE PRESENCE OF A DOWNSLOPE WIND COMPONENT.
FOR THIS EVNG...MVFR CONDITIONS SHOULD BE THE RULE WITH MVFR CIGS
AND ONLY SOME SCT LIGHT -SHSN OR -SHSNRA. BUT THE APRCH OF ANOTHER
DISTURBANCE/LO PRES TROF LATE TNGT SHOULD RESULT IN DETERIORATING
CONDITIONS AGAIN WITH IFR CONDITIONS DVLPG AT IWD AND CMX. DOWNSLOPE
WINDS AT SAW WL RESTRICT THE IMPACT THERE...SO MVFR CIGS SHOULD
PREVAIL. AFTER THIS DISTURBANCE EXITS TO THE E...EXPECT MVFR
CONDITIONS TO RETURN TO IWD AND CMX BY LATE MRNG ON TUE.
&&

.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...SRF
AVIATION...KC
MARINE...07


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