Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 192030
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
430 PM EDT SUN APR 19 2015

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 258 PM EDT SUN APR 19 2015

TWO UPPER LEVEL WAVES WILL BE AFFECTING THE REGION TONIGHT BEFORE
MERGING TOGETHER INTO A LARGE UPPER TROUGH THAT WILL PERSIST OVER
EASTERN CANADA AND THE GREAT LAKES REGION FOR MUCH OF THE UPCOMING
WORK WEEK. THIS WILL LEAD TO A TRANSITION FROM THE ABOVE NORMAL
TEMPERATURES AND DRY CONDITIONS TO A PERIOD OF BELOW NORMAL
TEMPERATURES AND PERIODS OF RAIN/SNOW SHOWERS.

THE FIRST WAVE OF PRECIPITATION JUST BRUSHED THE WESTERN U.P.
EARLIER TODAY...ASSOCIATED WITH A SHORTWAVE AND MID LEVEL WARM AIR
ADVECTION. MUCH OF THAT PRECIPITATION HAS SHIFTED OFF TO THE NORTH
OF THE MINNESOTA ARROWHEAD...BUT LINGERING MID LEVEL MOISTURE AND
BROAD BUT WEAK WARM AIR ADVECTION HAS PRODUCED A FEW RAIN SHOWERS
OVER WESTERN/CENTRAL UPPER MICHIGAN LATE THIS MORNING AND THROUGH
THE EARLY AFTERNOON. WHILE THE 12Z KGRB SOUNDING STILL SHOWS SOME
DRY AIR BELOW THE CLOUD BASES...IT HAS ERODED SIGNIFICANTLY SINCE
THE 00Z KGRB SOUNDING AND ALLOWED SOME OF THAT RAIN TO REACH THE
GROUND. THAT DISTURBANCE PRODUCING THE SHOWERS WILL SHIFT TO THE
NORTH OVER THE NEXT COUPLE OF HOURS AND SHIFT THE FOCUS TO THE RAIN
CURRENTLY TO THE WEST AND SOUTH OF THE CWA.

WITH THE LATEST TRENDS IN THE MODELS DELAYING THE ARRIVAL OF THE
PRECIPITATION FROM THE SOUTH (ASSOCIATED WITH THE SOUTHERN WAVE AND
SURFACE LOW QUICKLY LIFTING NORTH ACROSS THE SOO MONDAY MORNING)
UNTIL LATE IN THE EVENING AND MORE DURING THE OVERNIGHT HOURS...HAVE
CONTINUED TO SHOW THAT SLOWING TREND IN THE POPS FOR THIS EVENING.
IN FACT...OTHER THAN SOME CHANCES OVER THE FAR WEST THIS
EVENING...HAVE REMOVED THE POPS OVER THE CENTRAL EAST BETWEEN THE
23Z-03Z PERIOD AND THEN RAMPED THEM UP AS THAT WAVE AND LOW ARRIVES
FROM THE SOUTH. THAT PRECIPITATION WILL THEN QUICKLY SHIFT NORTH
ACROSS THE AREA AND EXPECT MUCH OF THE CENTRAL/EASTERN U.P. TO SEE
AT LEAST 0.3 INCH OF RAIN. THERE WILL BE SOME HIGHER
AMOUNTS...LIKELY 0.5-0.6IN WHERE THE DEFORMATION ZONE OCCURS ON THE
NORTHWEST SIDE OF THE SURFACE LOW (SOMEWHERE AROUND THE CENTRAL OR
WEST-CENTRAL U.P.). FARTHER TO THE WEST...EXPECT THE ONGOING RAIN
SHOWERS STRETCHING FROM THE ARROWHEAD OF MINNESOTA THROUGH WESTERN
WISCONSIN AND INTO NORTHEAST IOWA TO SLOWLY SHIFT EAST INTO FAR
WESTERN UPPER MICHIGAN THIS EVENING...AS THE 850-700MB TROUGH SLOWLY
WORKS ITS WAY TO THE EAST. THIS PRECIPITATION WILL MERGE WITH THE
WAVE COMING UP FROM THE SOUTH AND FILL IN THE EXPECTED GAP OVER THE
KEWEENAW OVERNIGHT.

WITH THE SHORTWAVE AND SURFACE LOW QUICKLY MOVING TO THE NORTH ON
MONDAY...EXPECT THE PRECIPITATION TO DIMINISH FROM SOUTHWEST TO
NORTHEAST THROUGH THE DAY (AIDED BY THE MID LEVEL DRY SLOT THAT
SLOWLY MOVES INTO THE AREA). WHILE MUCH OF THIS PRECIP WILL OCCUR AS
RAIN...THE COLD AIR GRADUALLY MOVING INTO THE WESTERN CWA LATE
TONIGHT AND MONDAY COULD CAUSE IT TO MIXING WITH OR EVEN CHANGING
OVER TO SNOW OVER THE WEST AND POSSIBLY EVEN NORTH CENTRAL. THOUGHT
THAT THE WETBULB ZERO HAD A GOOD HANDLE ON THE WEST TO EAST
TRANSITION OF THAT MIX WITH SNOW...BUT DO HAVE A CONCERN ON THE
AMOUNT OF ICE CRYSTALS THAT WILL BE PRESENT ON MONDAY. MODELS
SHOWING THAT THE DEEPER MOISTURE REALLY BEGINS TO PULL OUT THROUGH
THE DAY AS THE MID LEVEL DRY SLOT MOVES BEHIND THE 850/700MB TROUGH.
THAT CONCERN WARRANTS KEEPING RAIN POTENTIAL IN THE FORECAST EVEN
THOUGH SOME AREAS THE WETBULB ZERO VALUES WOULD SUPPORT ALL SNOW.
ONE FINAL NOTE...THE HIGHER RESOLUTION 12Z MODELS ARE SHOWING A
SLOWER DEPARTURE TO THE PRECIP ON MONDAY...SO DID TREND SLIGHTLY
SLOWER WITH THIS FORECAST AND IT MAY NEED TO BE DELAYED FURTHER WITH
THE UPCOMING SHIFT. THAT SLOWER DEPARTURE AND INDICATIONS OF COLDER
AIR...COULD LEAD TO SOME MINOR SNOW ACCUMULATIONS ON GRASSY SURFACES
OVER THE WEST AROUND MID MORNING.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 423 PM EDT SUN APR 19 2015

THE PATTERN WILL BE DOMINATED BY A MID/UPPER LEVEL LOW MOVING SLOWLY
THROUGH THE GREAT LAKES BRINGING UNSETTLED WEATHER ALONG WITH BELOW
NORMAL TEMPERATURES. THE LOW SHOULD FINALLY SHIFT TOWARD ERN CANADA
AND NEW ENGLAND BY THE WEEKEND LEAVING NW FLOW IN PLACE WITH
CONTINUED BELOW NORMAL TEMPERATURES.

MON NIGHT THROUGH TUE NIGHT...MODELS SUGGEST THAT THE MID LEVEL LOW
WILL SLOWLY WOBBLE INTO THE NRN GREAT LAKES. WITH THE COMBINATION OF
DEEP MOISTURE AND WEAK SHORTWAVES NEAR THE LOW...EXPECT INCREASING
PCPN CHANCES AS MAINLY SNOW...PER FCST SOUNDINGS. THERE MAY BE SOME
ADDITIONAL LAKE ENHANCED (850 MB TEMPS DROP TO AROUND -8C) INTO THE
HIGHER TERRAIN OVER THE WEST WITH UPSLOPE WNW FLOW. SNOW
ACCUMULATIONS OF A FEW INCHES ARE POSSIBLE...MAINLY ON GRASSY
SURFACES. HOWEVER...WITH THE ARRIVAL OF THE SNOW OVERNIGHT SOME
ACCUMULATION ON ROADS MAY ALSO CREATE HAZARDOUS TRAVEL TUE MORNING.
DAYTIME HEATING TUE MAY ENHANCE THE PCPN OVER INLAND AREAS WITH STEEP
SFC-700MB LAPSE RATES DEVELOPING. WITH TEMPS CLIMBING TO AROUND
40F...THE PCPN MAY MIX WITH RAIN OVER THE SE HALF OF THE CWA. 12Z NAM
FCST WET-BULB ZERO HEIGHTS WERE USED TO DELINEATE PCPN TYPE. ANOTHER
INCH OR TWO OF SNOW WILL BE POSSIBLE MAINLY OVER THE NW WIND
SNOWBELTS IN THE WEST TUE NIGHT AS 850 MB TEMPS DROP TO AROUND -12C
WHILE THE DEEP MOISTURE AND LOW LEVEL CYCLONIC FLOW REMAIN IN PLACE.

WED-THU...THE LARGE COLD MID-LEVEL LOW WILL ONLY SLOWLY SHIFT TO THE
ESE TO THE ERN LAKES BY LATE THU. COLD AIR ALOFT/SPRING DAYTIME
HEATING AND POTENTIAL OF SHORTWAVES ROTATING THROUGH THE AREA WITHIN
THE LARGE MID-LEVEL LOW CIRCULATION FAVORS AT LEAST SCT SHOWERY
PCPN... MOSTLY AS SNOW BUT POSSIBLY MIXING WITH RAIN SOUTH DURING
PEAK HEATING. ALTHOUGH THERE WILL BE SOME LAKE CONTRIBUTION AS 850
MB TEMPS RANGE FROM -10C TO -13C...THE BEST COVERAGE DURING THE
DAYTIME SHOULD BE IN THE AFTERNOON INLAND FROM LAKE SUPERIOR WHERE
HEATING WILL BE STRONGEST. HIGH TEMPS BOTH DAYS SHOULD BE WELL BELOW
NORMAL...IN THE MID 30S TO LOWER 40S...WARMEST S CNTRL.

FRI-SUN...FCST UNCERTAINTY IS GREATER AS THE GFS/GEFS/GEM MAINTAIN
TROUGHING INTO NRN ONTARIO AND THE NRN LAKES THROUGH THE WEEKEND
WHILE THE ECMWF BRINGS A RIDGE TOWARD THE WRN LAKES WITH DRIER AND
WARMER CONDITIONS. WITH EITHER SCENARIO...TEMPS ARE EXPECTED TO
REMAIN BELOW NORMAL WITH ONLY MINIMAL PCPN CHANCES.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 133 PM EDT SUN APR 19 2015

VFR CONDITIONS WILL CONTINUE INTO THE EVENING HOURS...BEFORE TWO
SEPARATE FEATURES BRING WIDESPREAD RAIN AND RAPIDLY LOWERING
CEILINGS TO THE AREA LATE THIS EVENING INTO MONDAY. LINGERING LOW
LEVEL DRY AIR WILL CONTINUE TO LEAD TO MID CLOUDS AND MAYBE AN
ISOLATED SHOWERS THIS AFTERNOON. THE MAIN QUESTION MARK FOR THE
FORECAST IS THE TIMING OF THE RAIN AND IN TURN LOWER
CEILINGS/VISIBILITIES.

AT KIWD...MODELS HAVE BEEN TRENDING TOWARDS KEEPING THE HEAVIEST
PRECIPITATION OFF TO THE WEST OF THE SITE THROUGH THE EVENING.
CONFIDENCE IS LOW ON THE EASTERN EDGE OF THE PRECIPITATION...BUT
HAVE KEPT THE IDEA OF THE SHOWERS BRUSHING THE SITE BY MID EVENING
AND THEN SPREADING EAST THROUGH THE SITE TONIGHT. EXPECT THE LOW
LEVEL WINDS TO TURN OFF LAKE SUPERIOR AND WITH RAIN OVER THE COLD
WATER WOULD EXPECT LOW CLOUDS AND FOG TO AFFECT THE SITE OVERNIGHT.
THE RAIN COULD MIX WITH OR CHANGE TO SNOW TOMORROW MORNING BEFORE
ENDING TOWARDS THE END OF THE TAF PERIOD.

AT KCMX/KSAW...BOTH SITES STAY IN THE DRIER AIR LONGER BEFORE THE
PRECIPITATION QUICKLY DETERIORATES BOTH CEILINGS AND VISIBILITIES
(AFTER MIDNIGHT AND TOWARDS 09Z). WITH BOTH SITES EXPERIENCING
FAVORABLE WINDS OFF LAKE SUPERIOR LATE TONIGHT INTO MONDAY...EXPECT
LIFR CEILINGS AND SOME FOG TO OCCUR. THOSE IFR/LIFR CEILINGS WILL
REMAIN THROUGH MUCH OF MONDAY MORNING.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 258 PM EDT SUN APR 19 2015

SOUTHEASTERLY WINDS UP TO 25-30KTS ARE OCCURRING OVER NORTHEAST
LAKE SUPERIOR...WITH A FEW GUSTS NEARING GALE FORCE VALUES AT THE
HIGHER PLATFORMS (SHIP OBS AND PILM4). AS A LOW IN SOUTHERN ILLINOIS
LIFTS NORTH TONIGHT AND THROUGH THE SOO ON MONDAY MORNING...WINDS
WILL WEAKEN THIS EVENING AND THEN BACK TO THE WEST-NORTHWEST ON
MONDAY. WITH THE LOW BECOMING STATIONARY JUST TO THE SOUTHWEST OF
JAMES BAY MONDAY NIGHT 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.
&&

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

$$

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


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