Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 212350
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
750 PM EDT TUE APR 21 2015

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 352 PM EDT TUE APR 21 2015

12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW CLOSED UPR LO OVER
THE UPR LKS DOWNSTREAM OF HI AMPLITUDE UPR RDG OVER WRN NAMERICA.
COMBINATION OF DEEP CYC FLOW W TO NW FLOW AND INSTABILITY ENHANCED
BY DAYTIME HEATING UNDER ACCOMAPANYING THERMAL TROF /12Z H5 TEMP AT
GRB WAS -31C/ AND DEEP MSTR SHOWN ON THE 12Z RAOBS IS RESULTING IN
SCT-NMRS SN SHOWERS THAT ARE MIXED WITH RA IN THE WARMER LOCATIONS.
BUT COLDER CLD TOP TEMPS/MORE WIDESRPEAD SN SHOWERS ARE CONFINED
MAINLY TO NW ONTARIO/FAR NRN MN IN AREA WHERE MODELS INDICATE DEEP
QVECTOR CNVGC.

MAIN FCST CONCERNS IN THE SHORT TERM FOCUS ON POPS AND POTENTIAL SN
ACCUMS ASSOCIATED WITH DEEP CYC...MOIST NW FLOW ARND SLOW MOVING
CLOSED LO TO THE NE OF UPR MI.

CLOSED LO CENTERED OVER ERN LK SUP THIS AFTN IS FCST TO DRIFT SLOWLY
TO THE NE AND TO JUST S OF JAMES BAY ON WED. ALTHOUGH ACCOMPANYING
DEEP LYR QVECTOR CNVGC THAT IS SUPPORTING COLDER CLD TOPS TO THE NW
IS FCST TO REMAIN TO THE N OF UPR MI...PERSISTENT MOIST...CYC NW
FLOW ARND THIS FEATURE WL MAINTAIN AT LEAST CHC POPS OVER THE CWA
THRU WED...WITH THE LOWER POPS GENERALLY OVER THE SCENTRAL AND THE
HIER POPS OVER THE HIER TERRAIN OF THE NW WITH UPSLOPE WIND
COMPONENT. BUT LOSS OF DAYTIME HEATING TNGT WL CAUSE THE
CHARACTER OF THE SHOWER PATTERN TO TRANSITIONS FM ONE THAT SUPPORTS
THE HIER POPS OVER THE INTERIOR THIS AFTN TO A MORE WINTRY LES
LOOK TNGT. IN FACT...THE NW FLOW IS PROGGED TO ADVECT H85 TEMPS AS
LO AS -13 TO -14C OVER THE KEWEENAW BY 12Z WED...TEMPS LO ENUF TO
SUPPORT LES AND INCRS SN/WATER RATIOS ONCE THE EFFECT OF DAYTIME
INSOLATION HAS FADED. OVER THE HIER TERRAIN OF THE W...THERE WL
LIKELY BE SEVERAL INCHES OF WET SN ACCUM TNGT INTO WED MRNG EVEN IN
THE ABSENCE OF SGNFT LARGER SCALE FORCING. OPTED TO ISSUE AN SPS
TO ALERT THE PUBLIC TO THE POTENTIAL OF SOME SLUSHY SN ACCUMS ON
ROADS LATER THIS EVNG INTO WED MRNG. DAYTIME HEATING ON WED WL
BRING ABOUT A RETURN TO A MORE LAND BASED INSTABILITY SHOWER
PATTERN. BUT SOMEWHAT HIER HGTS/SHARPENING MID LVL INVRN FARTHER FM
THE SLOWLY DEPARTING CLOSED LO THAT RESTRICTS DESTABILIZATION WL
TEND TO LIMIT COVERAGE/INTENSITY OF THE SHOWERS AS COMPARED TO TODAY.
ALTHOUGH H85 TEMPS ARE FCST TO MODERATE TO -10C TO -12C...MAX TEMPS
ON WED WL HOLD IN THE 30S EXPECT WHERE SOME DOWNSLOPE WARMING AIDS
DIURNAL TEMP RECOVERY INTO THE LO 40S OVER THE SCENTRAL. THERE COULD
BE SOME RECORD LO MAX TEMPS ON WED.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 305 PM EDT TUE APR 21 2015

THE UPPER LOW THAT IS CURRENTLY AFFECTING THE AREA WILL SHIFT EAST
INTO THE CANADIAN MARITIMES SHORTLY AFTER THE START OF THE LONG TERM
PERIOD. THIS WILL LEAVE THE AREA BETWEEN THAT UPPER LOW AND AN UPPER
RIDGE IN THE CENTRAL/SOUTHERN PLAINS. THUS...THE AREA WILL BE UNDER
NORTHWESTERLY FLOW ALOFT FOR MOST DAYS THROUGH THE UPCOMING WEEKEND.
WITH A SURFACE RIDGE STRETCHING SOUTH FROM A HIGH IN NORTHERN CANADA
MOVING INTO THE AREA BY FRIDAY AND FRIDAY NIGHT...EXPECT DRIER AIR
TO GRADUALLY MOVE INTO THE REGION AND DIMINISH THE PRECIPITATION
POTENTIAL AND LEAD TO A DRY WEEKEND (ALTHOUGH THERE ARE HINTS OF A
WEAK DISTURBANCE BRINGING AN ISOLATED SHOWER TO THE FAR WESTERN U.P.
LATE FRIDAY NIGHT INTO SATURDAY MORNING). WITH THE MAIN UPPER LOW
SHIFTING EAST...TEMPERATURES WILL SLOWLY WARM BUT STILL STAY BELOW
NORMAL FOR LATE APRIL (AIDED BY THE LIGHT NORTHERLY FLOW OFF LAKE
SUPERIOR).

HEADING INTO NEXT WEEK...THE UPPER LOW CURRENTLY OVER THE GULF OF
ALASKA WILL MOVE INTO THE PACIFIC NORTHWEST OVER THE NEXT 24-48HRS
AND THEN INTO THE CENTRAL CONUS ON MONDAY. AS THE WAVE CONTINUES
EAST...IT WILL INTERACT WITH THE UPPER LOW NEAR THE CANADIAN
MARITIMES AND RE-ESTABLISH THE UPPER TROUGH OVER THE EASTERN CONUS.
THIS WILL KEEP BELOW NORMAL TEMPERATURES IN PLACE INTO NEXT WEEK AND
POSSIBLY LEAD TO SOME SHOWERS AROUND THE GREAT LAKES REGION.
OVERALL...FAIRLY COOL AND QUIET END TO APRIL WITH NO HAZARDOUS
WEATHER EXPECTED.
&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 750 PM EDT TUE APR 21 2015

AS DEEP MOISTURE LINGERS AND COLDER AIR ARRIVES TONIGHT...SHSN WILL
TEND TO INCREASE IN FREQUENCY AT KIWD/KCMX WITH USPLOPE NW WIND
COMPONENT OFF LAKE SUPERIOR. EXPECT A TREND TO PREVAILING IFR BY
LATE EVENING...THEN CONTINUING THRU MID MORNING WED. TYPICAL FOR
SHSN...THERE WILL LIKELY BE FLUCTUATION WITH SOME BRIEF PERIODS OF
LIFR AND MVFR. INTO WED AFTN...EXPECT IMPROVEMENT TO MVFR AS SHSN
INTENSITY DIMINISHES. DOWNSLOPE NATURE OF THE NW FLOW WILL LIMIT THE
POTENTIAL FOR LOWER VIS/CIG AT KSAW...BUT MVFR CIGS SHOULD BECOME
PREVAILING MID TO LATE EVENING WITH RATHER MOIST LOW-LEVELS.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 305 PM EDT TUE APR 21 2015

NORTHWESTERLY WINDS UP TO 30 KNOTS WILL CONTINUE OVER LAKE SUPERIOR
THROUGH THURSDAY MORNING. THERE COULD BE A FEW PERIODS OF GALE
FORCE GUSTS TO 35KTS LATE TONIGHT INTO WEDNESDAY...BUT THEY
SHOULDN/T BE WIDESPREAD. HIGH PRESSURE WILL BEGIN TO BUILD INTO
WESTERN LAKE SUPERIOR THURSDAY AFTERNOON/NIGHT AND LEAD TO
GRADUALLY DIMINISHING WINDS INTO FRIDAY. LIGHT NORTHERLY WINDS UP
TO 15KTS ARE EXPECTED THIS WEEKEND.
&&

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

$$

SHORT TERM...KC
LONG TERM...SRF
AVIATION...ROLFSON
MARINE...SRF


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