Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 210020
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
720 PM EST SAT DEC 20 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 257 PM EST SAT DEC 20 2014

THE THEME OF THIS SHORT TERM PERIOD WILL BE STEADY S WINDS...WITH
INCREASED MOISTURE PUSHING INTO THE UPPER GREAT LAKES REGION.

TAKING A LOOK AT THE LATEST WV IMAGERY...MOISTURE WAS SET UP FROM W
ONTARIO THROUGH MUCH OF THE UPPER GREAT LAKES...ASSOCIATED WITH THE
500MB TROUGH EXTENDING ACROSS THE AREA. MOISTURE STUCK UNDER THE
500MB RIDGE OVER MANITOBA THROUGH E ND/SD AND FAR W MN IS KEEPING
CEILINGS AROUND 1KFT OR LOWER WITH VIS DOWN AOB 5SM.

PW VALUES AT A LOW OF AROUND 0.3IN THIS MORNING WILL SLOWLY INCREASE
THROUGH THE DAY SUNDAY...TO AN AVERAGE OF AROUND 0.4IN. NOT
EXPECTING MUCH IMPROVEMENT TO THE MID TO OCCASIONAL CLOUDS CURRENTLY
PUSHING INTO THE CWA THROUGH THE PERIOD. ALTHOUGH...A FEW POCKETS
OF TEMPORARY CLEARING COULD DEVELOP OVER THE E HALF OF UPPER MI.

THE MAIN 500MB TROUGH EXTENDING ACROSS THE REGION WILL SHIFT
SLIGHTLY N THROUGH THE MORNING HOURS SUNDAY...IN ADVANCE OF THE NEXT
TROUGH NEARING FROM THE E DAKOTAS AND W MN. CAN/T RULE OUT PATCHY
FREEZING DRIZZLE OVER THE S CENTRAL CWA EARLY SUNDAY MORNING...SO
FEW CHANGES WERE MADE TO THE ONGOING PRECIP FCST. ALSO KEPT HIGH
CHANCE POPS GOING FOR THE S CENTRAL CWA BY LATE SUNDAY AFTERNOON AS
THIS NEXT TROUGH NEARS.

BREEZY S WINDS WILL BEGIN SUNDAY AFTERNOON. THIS WILL BE AS THE
PRESSURE GRADIENT INCREASES ACROSS THE REGION...IN BETWEEN EXITING
HIGH PRESSURE STRETCHING FROM EASTERN QUEBEC THROUGH THE MID
ATLANTIC STATES...AND THE SFC LOW NEARING FROM S
SASKATCHEWAN/ALBERTA/E MT.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 325 PM EST SAT DEC 20 2014

LONG TERM FORECAST IS COMPLICATED THROUGH THE ENTIRE PERIOD.

GENERAL SETUP...THE GOOD NEWS IS THAT THE MODELS AGREE WELL ON THE
BASIC PATTERN. WEAK/BROAD UPPER TROUGHING OVER THE WCENTRAL CONUS
WILL BE AMPLIFIED BY 3 PIECES OF SHORTWAVE ENERGY...THE FIRST OF
WHICH IS CURRENTLY OVER THE NE PACIFIC...LEADING TO A WEAKER LOW
PRESSURE SYSTEM OVER THE NRN PLAINS/UPPER MISSISSIPPI VALLEY ON MON
THAT WEAKENS BEFORE SHIFTING ACROSS/NEAR THE CWA TUE INTO TUE NIGHT.
FOCUS THEN TURN TO THE STRONGER OF THE SHORTWAVE IS IT LEADS TO MUCH
GREATER AMPLIFICATION OF THE UPPER TROUGH...POSSIBLY CLOSING OFF OR
AT LEAST RESULTING IN THE UPPER TROUGH BECOMING VERY NEGATIVELY
TILTED AND SHARP AS IT TRANSITIONS WED INTO CHRISTMAS DAY. MODELS
THEN SHOW ANOTHER SHORTWAVE ROUNDING A LARGE SCALE UPPER TROUGH AND
MOVING THROUGH/NEAR THE CWA FRI/FRI NIGHT. BY NEXT SAT...THE UPPER
TROUGH WILL BE OVERHEAD...BRINGING A COLDER AIRMASS TO THE CWA AS
MODELS SHIFT THE COLDEST AIRMASS IN THE NHEM INTO CENTRAL CANADA IN
THE 7-10 DAY PERIOD.

WHILE GENERAL AGREEMENT BETWEEN THE MODELS IS GENERALLY
HELPFUL...SPECIFICS WILL MAKE ALL THE DIFFERENCE IN THIS FORECAST
PERIOD AS TIGHT GRADIENT IN QPF ARE LIKELY GIVEN THE STRONG DYNAMICS
OF THE MID-LATE WEEK SYSTEM AND MIXED PRECIP WILL ALSO BE AN ISSUE.
ADDITIONALLY...FURTHER SHIFTS IN MODEL SOLUTIONS ARE TO BE EXPECTED
AS THE SHORTWAVES MOVE INTO BETTER OBSERVING NETWORKS. THE ENTIRE
LONG TERM IS BEING WATCHED VERY CLOSELY AND EXTENSIVE
REGIONAL/NATIONAL COLLABORATION IS OCCURRING TO ENSURE THE BEST
FORECAST FOR HOLIDAY TRAVELERS.

FOR 00Z-18Z MON...MODELS AGREE THAT A SWATH OF SNOW /SOME MIXED
PRECIP POSSIBLE MON MORNING/ WILL SHIFT S-N ACROSS THE CWA...WITH
SNOW ACTUALLY STARTING ON SUN /SEE SHORT TERM FORECAST SECTION FOR
ADDITIONAL DETAILS ON SUNDAY/. FORCING WILL COME FROM WAA/ISENTROPIC
ASCENT AHEAD OF THE PREVIOUSLY DISCUSSED LOW FORMING OVER THE NRN
PLAINS ALONG WITH UPPER DIFFLUENCE SHIFTING ACROSS THE CWA. AS SFC
AND LOW LEVEL TEMPS WARM MON MORNING...MAY SEE SOME MIXED PRECIP
OVER WRN UPPER MI. WILL LEAN MORE TOWARD SNOW AS WET BULB TEMPS WILL
BE CLOSE TO 0C. SNOWFALL AMOUNTS LOOK TO BE BELOW 3 INCHES...AND
MORE LIKELY 1-2 INCHES.

FOR MON AFTERNOON THROUGH LATE TUE...THE FORECAST STARTS BECOMING
MORE UNCERTAIN AS THIS POINT AS THE LOW SHOULD WEAKEN AND SHIFT
ACROSS THE AREA WITH ADDITIONAL SHORTWAVE ENERGY POSSIBLY
PROPAGATING AROUND THE UPPER TROUGH AND THROUGH THE AREA. THE COLDER
AIRMASS ASSOCIATED WITH THE LOW SHOULD TRANSITION PRECIP BACK TO
SNOW OVER THE WRN CWA WHILE STRENGTHENING WAA OVER THE ERN CWA
TRANSITIONS PRECIP MORE TO RAIN. REALLY DO NOT EXPECT ENOUGH SNOW
FOR HAZARDS...MAINLY NUISANCE AMOUNTS.

CHRISTMAS EVE AND CHRISTMAS DAY...THIS IS WHEN THE FORECAST GETS
QUITE CHALLENGING AND PROBLEMATIC AS THE THIRD SHORTWAVE REALLY
AMPLIFIES THE TROUGH. WILL FAVOR THE ECMWF AS ENSEMBLE SPREAD AND
RUN TO RUN DISCONTINUITY IS LESS THAN THE GFS. THE ECMWF BRINGS A
DEEPENING SFC LOW FROM IN AT 06Z WED TO THE FAR ERN U.P. AT 983MB AT
18Z WED TO JUST NE OF LAKE SUPERIOR AT 971MB AT 06Z THU BEFORE
MOVING OFF TO THE NNE. WHILE THE GFS IS NOT PREFERRED...IT IS STILL
WORTH DISCUSSING THE POSSIBLE IMPACTS OF THAT MODEL VERIFYING. THE
GFS DEEPENS THE SYSTEM INTO A CLOSED LOW OVER SRN LOWER MI BY 06Z
THU...THEN WEAKENS THE SYSTEM AND SHIFTS IT RAPIDLY NE BY 18Z THU.
OBVIOUSLY THERE ARE TIMING/STRENGTH/TRACK DIFFERENCES BETWEEN
MODELS...BUT THE HEAVIEST PRECIP /IN THE MQT CWA/ OF BOTH MODELS IS
OVER THE ERN CWA AND FEATURES A FAIRLY TIGHT GRADIENT AS IS EXPECTED
IN STRONG FGEN BANDS. ALSO...BOTH MODELS SUGGEST THAT PTYPE WOULD BE
MOSTLY RAIN UNDER THE ERN/SERN HALF OF THE FGEN BAND...AND MORE SNOW
UNDER THE WRN/NWRN PART OF THE BAND. COLDER AIR SURGING IN WED
NIGHT/THU WILL TRANSITION ALL PRECIP TO SNOW BY THU MORNING. 925MB
WINDS LOOK TO INCREASE UP TO 40-45KTS WED NIGHT/THU...WHICH WOULD
LEAD TO SIGNIFICANT BLOWING AND DRIFTING OF SNOW. OVERALL...IT DOES
LOOK LIKE A SIGNIFICANT WINTER STORM WILL MOVE ACROSS THE
REGION...BUT EXACTLY WHERE THAT WILL MOVE IS HIGHLY UNCERTAIN. AT
THIS TIME...THE WORST TRAVEL CONDITIONS ACROSS THE CWA LOOK TO BE
OVER THE E. ESPECIALLY THOSE WITH TRAVEL CONCERNS WILL NEED TO
MONITOR LATER FORECASTS.

SAT WILL EASILY BE THE COLDEST DAY OF THE WEEK AS AN UPPER TROUGH
MOVES INTO THE AREA...BRINGING 850MB TEMPS AS COLD AS -20C. OF
COURSE...THIS WILL ALSO LEAD TO W-NW WINDS LES. THE FORECAST SEEMED
TO BE HANDLED WELL BY CONSENSUS OF MODELS FOR FRI AND SAT SO JUST
USED THAT.
&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 715 PM EST SAT DEC 20 2014

MVFR CEILINGS SHOULD BE THE RULE THROUGH THE PERIOD. LIGHT S WINDS
WILL BE ON THE INCREASE DURING THE DAY SUNDAY BRINGING IN HIGHER DEW
POINTS IN THE AFTERNOON AND A SLIGHT LOWERING OF CEILINGS. THERE MAY
BE A CHANCE OF LIGHT SNOW IN THE AFTERNOON AT MAINLY KIWD AND KSAW
BUT EXPECTING MUCH IF ANY VSBY RESTRICTION WITH THE SNOW.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 257 PM EST SAT DEC 20 2014

THE LARGE HIGH OVER QUEBEC WITH A RIDGE EXTENDING THROUGH THE LOWER
GREAT LAKES WILL SLOWLY EXIT TO THE ATLANTIC THROUGH MONDAY. LOOK
FOR A LOW OVER THE N PAINS SUNDAY NIGHT WILL PUSH ACROSS MINNESOTA
MONDAY NIGHT...AND THE UPPER GREAT LAKES TUESDAY. IN THE
MEANTIME...A DEEPENING LOW OVER TEXAS MONDAY NIGHT WILL SWING ACROSS
KENTUCKY AND INDIANA TUESDAY NIGHT...BEFORE SHIFTING TO LOWER
MICHIGAN WEDNESDAY AND WEDNESDAY NIGHT...AND EXITING TO AROUND JAMES
BAY THURSDAY. EXPECT OUR STEADY S WINDS TO INCREASE UP TO 25KTS OVER
MAINLY E LAKE SUPERIOR SUNDAY INTO MONDAY AS A RESPONSE TO THE
TIGHTENING PRESSURE GRADIENT. N-NW GALES OF 35-45KTS WILL BE
POSSIBLE /STRONGEST OVER THE E HALF OF LAKE SUPERIOR/ LATE WEDNESDAY
NIGHT THROUGH THURSDAY EVENING. A GALE WATCH WILL LIKELY BE NEEDED
WHEN WE GET CLOSER TO OUR 60HR /2.5DAY/ ISSUANCE PERIOD.
&&

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

$$

SHORT TERM...KF
LONG TERM...TITUS
AVIATION...VOSS
MARINE...KF





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