Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 250652
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
252 AM EDT TUE AUG 25 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...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 251 AM EDT TUE AUG 25 2015

COULD SEE SOME ISOLATES SHOWERS OVER THE ERN CWA WED MORNING AS NW
WINDS AND 850MB TEMPS OF 5-6C ALLOW FOR LAKE ENHANCED RAIN...BUT
OVERALL FORCING WILL BE WEAK. HIGH PRESSURE MOVING IN WILL BRING AN
END TO RAIN POTENTIAL BY WED AFTERNOON. HIGHS WED IN THE 60S WILL
COMBINE WITH GOOD RADIATIONAL COOLING...DRY CONDITIONS AND LIGHT
WINDS WED NIGHT TO BRING LOWS IN THE 40S INLAND...WITH A FEW SPOTS
IN THE UPPER 30S.

SW FLOW AS THE HIGH MOVES OUT WILL BRING 850MB TEMPS UP TO 14C BY
THE END OF THE DAY THU...RESULTING IN NEAR NORMAL HIGHS IN THE LOW
TO MID 70S. DRY WEATHER PERSISTS THROUGH THU.

MODELS CONTINUE TO INDICATE A COLD FRONT MOVING S FROM CANADA AND
INTO THE CWA THU NIGHT AND FRI WHILE A SHORTWAVE RIDES DOWN NW FLOW
AND PASSES OVER OR NEAR THE CWA. MODELS HAVE BEEN VARIABLE WITH
SOLUTIONS FOR THIS TIME PERIOD...BUT THE ECMWF HAS BEEN THE MOST
STEADY. OVERALL...CHANCES FOR SHOWERS AND THUNDERSTORMS SEEM
REASONABLE.

PRECIP IS QUESTIONABLE FOR SAT...BUT COULD SEE SOME SHOWERS IF
SHORTWAVE ENERGY MOVES THROUGH. LEFT SLIGHT CHANCE POPS FOR NOW.
TEMPS LOOK SIMILAR TO FRI.

TEMPS LOOK TO BE ABOVE NORMAL SUN AND MON WITH DRY WEATHER AS
RIDGING BUILDS OVER THE AREA. HIGHS SHOULD RANGE FROM THE MID/UPPER
70S TO LOW 80S.
&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 124 AM EDT TUE AUG 25 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 MUCH OF THE FCST PERIOD. IN GENERAL...KCMX WILL
SEE THE WORST CONDITIONS...WITH OCCASIONAL HEAVIER SHRA AND SOME
PERIODS OF IFR CONDITIONS AT TIMES MAINLY THIS MORNING 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...TITUS
AVIATION...VOSS
MARINE...KC


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