Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 020902
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
502 AM EDT TUE SEP 2 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 500 AM EDT TUE SEP 2 2014

WV IMAGERY AND RUC ANALYSIS INDICATED A BROAD LOW AMPLITUDE
MID/UPPER LEVEL TROUGH THROUGH FROM THE NRN PLAINS INTO THE UPPER MS
VALLEY AND WRN GREAT LAKES WITH SEVERAL WEAK EMBEDDED SHORTWAVES.
ONE WAS LOCATED FROM SW MN INTO NW IA WHILE ANOTHER UPSTREAM SHRTWV
WAS MOVING THROUGH NORTH DAKOTA. AT THE SFC...WRLY FLOW PREVAILED
ACROSS UPPER MI BETWEEN A 987 MB LOW NEAR JAMES BAY AND A WEAK RIDGE
INTO THE CNTRL PLAINS.IR LOOP SHOWED MAINLY CLEAR SKIES ACROSS MOST
OF THE CWA BUT WITH INCREASING CLOUDS FROM MN INTO NW WI AND WRN
UPPER MI AHEAD OF THE SW MN SHRTWV.

TODAY...MOST OF THE FORCING ASSOCIATED WITH THE MN SHRTWV IS
EXPECTED TO REMAIN SOUTH OF UPPER MI. HOWEVER...THE COMBINATION OF
DAYTIME HEATING AND 850-600 MB LAPSE RATES TO NEAR 7.5C/KM AND LOW
LEVEL CONV ALONG LAKE BREEZE BOUNDARIES(ESPECIALLY OVER THE EAST)
WILL SUPPORT ISOLD/SCT SHRA BY THIS AFTERNOON. AS THE NORTH DAKOTA
SHRTWV NEAR BY MID TO LATE AFTERNOON SOME ADDITIONAL WEAK QVECTOR
CONV MAY ALSO CONTRIBUTE TO PCPN CHANCES. ALTHOUGH MLCAPE VALUES
INTO THE 400-800 J/KG RANGE WILL BE MARGINAL FOR TS...SOME ISOLD COULD
DEVELOP. WITH FREEZING HEIGHTS ONLY NEAR 9K-10K FT...SOME SMALL HAIL
MAY BE POSSIBLE.

TONIGHT...WITH THE LOSS OF DAYTIME HEATING AND THE SHRTWVS EXITING
TO THE EAST...ANY PCPN SHOULD QUICKLY DIMINISH. WITH THE FAST
MID/UPPER LEVEL FLOW ACROSS THE NRN CONUS...MODELS SUGGEST THAT
ANOTHER WEAK SHRTWV COULD MOVE THROUGH THE NRN LAKES AND PRODUCE
SOME LIGHT PCPN. HOWEVER...WITH VERY LIMITED MOISTURE AND LITTLE
INSTABILITY...CONFIDENCE IN ADDITIONAL PCPN DEVELOPING WAS LOW AND NO
ADDITIONAL RAIN WAS MENTIONED.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 401 AM EDT TUE SEP 2 2014

THOUGH ACTIVE WEDNESDAY NIGHT INTO THURSDAY EVENING...THE REST OF
LONG TERM WILL BE QUIET AS HIGH PRESSURE DOMINATES FROM FRIDAY INTO
EARLY NEXT WEEK.

STARTING ON WEDNESDAY...WEAKER SHORTWAVES WORK THEIR WAY ACROSS
NORTHERN PLAINS AND TO UPPER GREAT LAKES BY LATE IN THE DAY IN A
ZONAL FLOW PATTERN ALOFT. LARGE SCALE LIFT IS PRESENT BUT THERE IS
NOT MUCH FOR A STRONGER SHORTWAVE AND ALSO OVERALL MOISTURE IS
LIMITED. BULK OF SHRA/TSRA LATER ON WEDNESDAY SHOULD STAY WEST OF
UPR MICHIGAN...MAINLY OVER CENTRAL AND SOUTHERN MINNESOTA CLOSER TO
SFC WARM FRONT AND BUILDING INSTABILITY. COULD SEE ISOLD SHRA/TSRA
OVER WESTERN LK SUPERIOR OR EVEN FAR WEST UPR MICHIGAN DUE TO
GENERAL H85-H7 WARM AIR ADVECTION AND MID-LEVEL MOISTURE ADVECTION.
TEMPS ON WEDNESDAY SHOULD PUSH INTO THE UPPER 70S OR LOWER 80S EVEN
WITH SCT-BKN MID CLOUDS IN THE AFTN.

POTENTIAL FOR PERIOD OF ACTIVE WEATHER WEDNESDAY NIGHT INTO THURSDAY
MORNING AS THE APPROACH OF A SFC LOW OVER THE NORTHERN PLAINS INCREASES
LOW-LEVEL JET /40 KTS AT H85/ INTO THE UPPER GREAT LAKES. SINCE THERE
IS NOT REALLY A STRONG SHORTWAVE MOVING THROUGH AT THAT TIME THOUGH...THINK
THAT THE BULK OF SHRA/TSRA WILL BE VCNTY OF WHERE LOW- LEVEL JET
INTERSECTS THE SFC-H85 WARM FRONT. BASED ON SFC WINDS AND DWPNTS...BEST
GUESS AT LOCATION OF THAT BOUNDARY IS FM CNTRL MN INTO WESTERN WI
WEDNESDAY NIGHT. MAX INSTABILITY BOTH IN TERMS OF MLCAPE AND ELEVATED
MUCAPE WILL BE MAXIMIZED OVER MUCH OF MINNESOTA AND INTO WISCONSIN
WITH INSTABILITY TRAILING OFF CONSIDERABLY INTO UPR MICHIGAN AND LK
MICHIGAN/LOWER MICHIGAN. MAJORITY OF MODELS INDICATE WIDESPREAD QPF
OVER UPR MICHIGAN WEDNESDAY NIGHT...BUT HAVE MY DOUBTS ON THIS AS
MOST OF THE HEAVY SHRA/TSRA COULD END UP FARTHER SOUTH ALONG WARM
FRONT AND ALSO BASED ON H85-H3 THICKNESSES WHICH...ALONG WITH FORWARD
PROPAGATING CORFIDI VECTORS...CAN BE USED TO DETERMINE GENERAL MOTION
OF AN MCS. SIMILAR TO EARLIER IN THE NIGHT...THERE IS STILL MID-LEVEL
MOISTURE ADVECTION FARTHER NORTH OF THE BOUNDARY THOUGH SO CANNOT
COMPLETELY RULE OUT SHRA/TSRA MAKING IT ACROSS UPR MICHIGAN. ANOTHER
FACTOR THAT COULD BUMP SHRA/TSRA FARTHER NORTH INTO THE CWA IS
INCREASING CAPPING THAT DEVELOPS IN THE H8-H7 LAYER OUT AHEAD OF THE
SFC LOW. AT THIS POINT THOUGH IT APPEARS THAT MAIN EXTENT OF CAPPING
WILL REMAIN BACK OVER THE CENTRAL PLAINS ON WEDNESDAY NIGHT.

GIVEN THE CONCERNS ABOUT TSRA OVERAGE...BACKED DOWN A BIT ON THE
HIGHER POPS WE HAD GOING BUT DID KEEP POPS HIGH CHANCE TO LOW END
LIKELY WITH BETTER CHANCES OVER THE WEST INITIALLY SHIFTING TO THE
EAST FOLLOWING THE TREND OF H7-H5 Q-VECTOR CONVERGENCE TIED TO
INITIAL WEAK SHORTWAVE AND ALSO WHERE THIS FORCING SYNCS UP WITH
GREATER MID-LEVEL MOISTURE TRANSPORT. TSRA INTENSITY SHOULD DIMINISH
INTO THE EAST BY LATE WED NIGHT INTO THURSDAY MORNING AS SHRA/TSRA
OUTRUN GREATER POOL OF INSTABILITY OVER MINNESOTA AND WISCONSIN.

FOR THURSDAY...RETAINED MUCH OF THE PREVIOUS FORECAST SHOWING TREND
TOWARD LOWER POPS BY LATE THURSDAY MORNING IN WAKE OF THE INITIAL
SHRA/TSRA MOVING EAST THEN POPS RAMPING BACK UP IN THE AFTN WITH
POSSIBLE ADDITIONAL SHRA/TSRA AHEAD OF APPROACHING COLD FRONT.
CAPPING SHOULD INCREASE MARKEDLY BY LATE MORNING/EARLY AFTN BASED
ON FORECAST SOUNDINGS SO THIS WILL IMPACT ADDITIONAL DEVELOPMENT OF
SHRA/TSRA. COULD GET QUITE WARM WITH EVEN JUST A LITTLE CLEARING.
MIXING TO H9 WITH SHARPER INVERSION AROUND THAT LEVEL SHOWN ON
SOUNDINGS MAY BE CONSERVATIVE BUT STILL RESULTS IN HIGHS AROUND 80
OVER MUCH OF CWA. NUDGED TEMPS UP INTO THE LOWER 80S AS A STARTING
POINT...BUT A MUGGY DAY /SFC DWPNTS 65-70/ WITH MID 80S IS CERTAINLY
POSSIBLE IN SOME AREAS. PRIMARY SHORTWAVE DRIVING THE COLD FRONT WILL
BE JUST NORTH OF MINNESOTA BY LATE THURSDAY AFTN. GIVEN THE WARM AND
HUMID AIRMASS...MLCAPES AHEAD OF THE FRONT OVER WEST HALF OF CWA
COULD PUSH OVER 2500J/KG...BUT MAIN QUESTIONS ARE HOW MUCH DEEPER
MOISTURE WILL BE AROUND AHEAD OF THE FRONT AND WILL CAPPING IN THE
H8-H7 LAYER BE TOO STRONG TO PROHIBIT SHRA/TSRA FROM DEVELOPING?
BASED ON CONSENSUS OF MODELS AND LATEST TRENDS...SEEMS THAT THERE IS
A RISK OF STORMS FORMING MID-LATE THURSDAY AFTN OVER THE WEST AND
AFFECTING REST OF CWA INTO THE EARLY EVENING AS BETTER MOISTURE IS
RE-INTRODUCED INTO THE AREA FM THE WEST/SOUTHWEST AND LIFT INCREASES
AND CAPPING DECREASES AS SHORTWAVE AND H5 SPEED MAX DRAW CLOSER. GIVEN
THE DEGREE OF INSTABILITY...IF STORMS FORM...SEVERE WEATHER POTENTIAL
IS ELEVATED AS 0-6KM SHEAR IS OVER 45 KTS AND 0-3KM SHEAR IS OVER 30
KTS. THE FORECASTED INSTABILITY...IF IT IS INDEED REALIZED...AND
SUCH SHEAR WOULD SUPPORT ROTATING/SUPERCELL TYPE STORMS AND ALSO
POTENTIAL FOR STORMS CONSOLIDATING INTO SEVERE WIND GUST PRODUCING
MCS ALONG THE COLD FRONT. A CONDITIONAL RISK ATTM...BUT CERTAINTLY
WORTH MONITORING AS WE GET CLOSER TO THIS TIME FRAME. SPC DAY3
OUTLOOK HIGHLIGHTS WI INTO WEST HALF OF UPR MICHIGAN WITH A 15 PCT
RISK FOR SEVERE /SLIGHT CATEGORICAL RISK/.  WILL MENTION POTENTIAL
FOR SEVERE IN THE MORNING HAZARDOUS WEATHER OUTLOOK.

ONCE THE COLD FRONT SLIDES THROUGH ON THURSDAY NIGHT...ANY LINGERING
SHRA/TSRA WILL QUICKLY COME TO AN END BY THE OVERNIGHT SOUTH AND
EAST CWA. MAIN ISSUE LATE THURSDAY NIGHT INTO FRIDAY WILL BE GUSTY
NORTHWEST WINDS ON LK SUPERIOR AS IT BECOMES UNSTABLE IN THE 1000-900MB
LAYER. MIXED LAYER WINDS ARE OVER 30 KTS SO IT COULD BE GUSTY ALONG
THE LK SUPERIOR SHORE TO BEGIN THE DAY ON FRIDAY. DUE TO PRESSURE
RISES BTWN DEPARTING LOW AND APPROACHING HIGH...EVEN HIGHER WINDS
WOULD NOT BE OUT OF QUESTION. INCREASING WAVE ACTION WOULD ALSO LEAD
TO HIGH SWIM RISK ON BEACHES FROM MARQUETTE TO GRAND MARAIS.

QUIET WEATHER FOR THE WEEKEND AS IT LOOKS NOW. HIGH PRESSURE SETTLES
OVERHEAD AND STAYS IN PLACE INTO EARLY NEXT WEEK. TEMPS AT NIGHT MAY
DIP BLO 40 DEGREES IN THE INTERIOR. DAYTIME HIGHS WILL BE SEASONABLY
COOL IN THE 60S FOR MOST AREAS.
&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 122 AM EDT TUE SEP 2 2014

EXPECT VFR CONDITIONS TO PREDOMINATE THIS FCST PERIOD WITH
RELATIVELY DRY LLVL AIR SHOWN ON UPSTREAM RAOBS DOMINATING. AN
APRCHG UPR DISTURBANCE/DAYTIME HEATING AND DESTABILIZATION COULD
CAUSE SOME -SHRA AT SAW AND PERHAPS IWD THIS AFTN...BUT THE DRY LLVL
AIR SHOULD MAINTAIN PREDOMINANT VFR WX EVEN IF THE -SHRA OCCUR.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 500 AM EDT TUE SEP 2 2014

WINDS WILL BE 20 KNOTS OR LESS THROUGH MOST OF THIS FORECAST PERIOD
EXCEPT FOR THU NIGHT INTO FRI WHEN WEST TO NORTHWEST WINDS BEHIND A
STRONG COLD FRONT WILL APPROACH 30 KNOTS. THIS WILL BE THE WHEN THE
STRONGEST WINDS OCCUR.
&&

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

$$

SHORT TERM...JLB
LONG TERM...JLA
AVIATION...KC
MARINE...JLB





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