Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 242336
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
736 PM EDT MON AUG 24 2015

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 440 PM EDT MON AUG 24 2015

WATER VAPOR IMAGERY AND RAP ANALYSIS SHOW AN UNSEASONABLY DEEP MID
LEVEL LOW OVER THE UPPER GREAT LAKES REGION WITH 500MB HEIGHT
ANOMALIES OF 2.5 STANDARD DEVIATIONS BELOW THE LONG TERM LATE AUG
AVG. SEVERAL SHORTWAVES ARE ROTATING AROUND THE CIRCULATION. ONE IS
JUST E OF LAKE SUPERIOR...ANOTHER IS NEAR LAKE NIPIGON AND A THIRD
IS MOVING ACROSS WRN UPPER MI. SHRA HAD NOT BEEN AS NMRS AS EXPECTED
OVER UPPER MI UNTIL RECENTLY WHEN SHORTWAVE REACHED WRN UPPER MI.
FOR MUCH OF THE DAY OVER LAKE SUPERIOR...THERE HAD BEEN A RATHER
SOLID BAND OF SHRA...EXTENDING FROM AROUND LAKE NIPIGON SE AND E TO
ERN LAKE SUPERIOR IN SHARP CYCLONIC FLOW/ZONE OF WAA/RATHER FOCUSED
THETA-E ADVECTION. 850MB THERMAL TROF WITH 850MB TEMPS AS LOW AS 1C
AT KINL PER 12Z RAOBS RUNS FROM NRN MN INTO NRN WI/SRN UPPER MI
AND TOWARD LWR MI.

ON LATEST WATER VAPOR IMAGERY...SHORTWAVE NEAR LAKE NIPIGON LOOKS
QUITE VIGOROUS...AND CANADIAN RADARS SHOW DECENT SHIELD OF SHRA
ADVANCING S WITH FEATURE. THUS...EXPECT ANOTHER INCREASE IN SHRA
COVERAGE OVER THE W IN THE NEXT FEW HRS. MEANWHILE...SHORTWAVE
CURRENTLY MOVING ACROSS WRN UPPER MI WILL SPREAD INCREASED SHRA
ACTIVITY EASTWARD INTO THE ERN FCST AREA. AT THE SAME TIME...
VEERING WINDS WILL HELP PUSH THE SHRA OVER THE ERN LAKE SE INTO THE
ERN FCST AREA AS WELL. LAKE NIPIGON SHORTWAVE WILL THEN CONTINUE TO
AID SHRA ACTIVITY OVER THE E THRU LATE EVENING INTO AT LEAST THE
EARLY OVERNIGHT. OTHERWISE...DEEP CYCLONIC FLOW AND WEAK WAA WILL
CONTINUE TO SUPPORT SCT/NMRS SHRA OVERNIGHT. 850MB TEMPS WILL BE LOW
ENOUGH...ESPECIALLY ALONG SRN PORTIONS OF LAKE SUPERIOR WHERE
WARMEST WATER RESIDES...TO ADD A LAKE COMPONENT TO PCPN AS WELL.
UPSLOPE COMPONENT TO PCPN WILL BE GREATEST OVER THE WRN FCST AREA.

ALTHOUGH MID LEVEL LOW DRIFTS FARTHER E ON TUE AND HEIGHT RISES
CONTINUE...LINGERING DEEP CYCLONIC FLOW/UPSLOPING AND SOME LAKE
COMPONENT WILL KEEP SHRA GOING...ESPECIALLY IN THE AREAS NORMALLY
FAVORED BY NW WINDS OFF LAKE SUPERIOR. HOWEVER...COVERAGE OF SHRA
SHOULD TEND TO SHOW SOME DIMINISHING TREND DURING THE DAY. IT WILL
BE ANOTHER UNSEASONABLY COOL DAY UNDER ABUNDANT CLOUD COVER. COOLEST
CONDITIONS (MID 50S FOR MAX TEMPS) WILL BE ACROSS THE HIGHER TERRAIN
AND WHERE PCPN IS MOST FREQUENT. NEW RECORD LOW MAX TEMPS MAY BE SET
AT SOME LOCATIONS.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 429 PM EDT MON AUG 24 2015

DAMP AND FALL-LIKE CONDITIONS WILL GIVE WAY TO MODERATION TOWARD
MORE SEASONAL WEATHER BY THU INTO THE WEEKEND. A DEEP CLOSED MID/UPPER
LEVEL LOW SOUTH OF JAMES BAY WILL GRADUALLY FILL AND MOVE INTO QUEBEC
WED. RIDGING WILL THEN PUSH BACK TOWARD THE WESTERN LAKES BY THU INTO
THE WEEKEND.

TUE NIGHT AND WED...AS THE MID LEVEL LOW SHIFTS TO THE EAST...MODELS
SUGGEST THAT MAINLY NNW FLOW WITH 330-340 WINDS WILL PREVAIL WITH
850 MB TEMPS REMAINING AROUND 6C INTO EARLY WED. WITH THE NNW FLOW
AND MOST FAVORABLE MOISTURE OVER THE CNTRL AND ERN LAKE...EXPECT THE
GREATEST -SHRA COVERAGE INTO N CNTRL UPPER MI EVEN AS THE AMOUNTS
DIMINISH. THE PCPN WILL DIMINISH AND END WED AS THE DEEP MOISTURE
SHIFTS TO THE EAST. MAX TEMPS ARE EXPECTED REBOUND BACK INTO THE MID
TO UPPER 60S.

WED NIGHT INTO THU...WITH FAVORABLE RADIATIONAL COOLING CONDITIONS
AS THE SFC RIDGE BUILDS INTO THE AREA AND PWAT VALUES BLO 0.5
INCH...EXPECT INLAND MIN TEMPS INTO THE MID 40S INLAND. ABUNDANT
SUNSHINE THU SHOULD PUSH TEMPS BACK TO SEASONAL AVERAGES IN THE
LOWER TO MID 70S.

FRI-MON...UNCERTAINTY INCREASES DUE TO MODEL DIFFERENCES IN HANDLING
THE POSITION OF THE SFC FRONT AND IMPACT OF A SHRTWV MOVING OUT OF
THE PLAINS. THE ECMWF HAS BEEN THE MOST CONSISTENT IN KEEPING MOST
OF THE PCPN WITH THIS FEATURE SOUTH AND WEST OF WI. THIS WOULD ALLOW
A WEAK SFC FRONT/TROUGH TO SLIDE TOWARD OR INTO UPPER MI. THE FRONT
COMBINED WITH THE POTENTIAL FOR WNW FLOW SHRTWVS SUPPORTS CONTINUED
CHANCE SHRA/TSRA POPS FRI INTO FRI NIGHT. THE MODELS HAVE TRENDED
AWAY FROM PCPN FOR SAT INTO MON AS THE MID LEVEL RIDGE BUILDS INTO
THE REGION.
&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 735 PM EDT MON AUG 24 2015

A GUSTY NW FLOW OF COOL...MOIST AIR AROUND LOW PRES TO THE NE OF
LAKE SUPERIOR WILL BRING PREVAILING MVFR CONDITIONS TO
KIWD/KCMX/KSAW THRU THE FCST PERIOD. IN GENERAL...KCMX WILL SEE THE
WORST CONDITIONS...WITH MORE FREQUENT...HEAVIER SHRA AND SOME
PERIODS OF IFR CONDITIONS AT TIMES DUE TO A MORE PRONOUNCED UPSLOPE
WIND COMPONENT. ALSO EXPECT THE STRONGEST WINDS AT THE MORE EXPOSED
KCMX TERMINAL. &&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE) ISSUED AT
455 AM EDT MON AUG 24 2015

AN UNSEASONABLY DEEP LO PRES JUST N OF THUNDER BAY EARLY THIS
MORNING WILL DRIFT SLOWLY TO THE ESE THRU TUE. UNDER THE SHARPER PRES
GRADIENT ON THE SW FLANK OF THIS LO WHERE THE SURGE OF COOLER AIR IS
MOST PRONOUNCED AND DESTABLIZATION IS GREATEST...WNW GALES UP TO 35
KTS WILL CONTINUE OVER THE SW HALF OF THE LAKE THRU THE AFTN.
CANCELLED THE GALE WARNING FOR THE NCENTRAL PORTION OF THE LAKE AS
THIS AREA HAS FALLEN UNDER A SLACKER GRADIENT CLOSER TO THE LO PRES.
ADDED A MENTION OF WATERSPOUTS OVER THE EASTERN PORTION OF THE LAKE
WHERE WATER TEMPERATURES ARE WARMEST AND WINDS MAY BE WEAKER FOR A
TIME TODAY AHEAD OF AN APPROACHING LO PRES TROUGH MOVING AROUND THE
LO JUST TO THE N. AS THE LO CONTINUES E OF LAKE SUPERIOR
TONIGHT/TUE...NW GALES TO 35 KTS WILL BE POSSIBLE OVER MAINLY THE
CENTRAL PORTION OF THE LAKE WHERE GUIDANCE HINTS THE PRES GRADIENT
WILL BE SHARPEST. AS THE LO MOVES FARTHER TO THE E AND HI PRES TO THE
W APPROACHES...THE PRES GRADIENT AND WINDS WILL DIMINISH W-E ON TUE
NIGHT/WED. WINDS WILL BE UNDER 20 KTS FOR WED NIGHT THRU FRI.
&&

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

$$

SHORT TERM...ROLFSON
LONG TERM...JLB
AVIATION...VOSS
MARINE...KC


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