Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 290531
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
131 AM EDT FRI AUG 29 2014

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 359 PM EDT THU AUG 28 2014

DRY WEATHER WILL COME TO AN END LATE TONIGHT INTO FRIDAY AS A
MOISTURE-LADEN SYSTEM BRINGS MODERATE RAINFALL TO UPPER MICHIGAN.

TONIGHT...A MID-LEVEL RIDGE CURRENTLY ALIGNED SOUTH TO NORTH OVER
UPPER MI WILL SHIFT EASTWARD THROUGH THE NIGHT. MEANWHILE...A TROUGH
OVER ALBERTA THIS AFTERNOON WILL TRACK EAST AND BEGIN TO PICK UP A
SLOW-MOVING TROUGH OVER THE CENTRAL PLAINS. A SFC LOW OVER SE SD AND
AN ASSOCIATED WARM FRONT STRETCHING FROM WESTERN IA TO CENTRAL IL
WILL LIFT NORTHWARD THROUGH THE NIGHT. THIS WARM FRONT HAS BEEN
PRODUCING MODERATE RAINFALL ACROSS NORTHERN IA AND SOUTHERN MN
TODAY. MUCH OF THIS RAIN IS BEING FORCED BY ASCENT ON THE 300 TO
310K THETA SFCS. AMPLE MOISTURE WITH PWAT VALUES SURPASSING 1.5
INCHES AND INCREASING LOW-LEVEL FLOW WILL SUPPORT CONTINUED
WIDESPREAD PRECIP ALONG THE FRONT.

THE FIRST QUESTION WITH THIS SYSTEM IS THAT OF TIMING. A FAIRLY DRY
ANTECEDENT AIR MASS ABOVE 850 HPA AS NOTED BY THE 12Z GRB RAOB
SUPPORTS SOME INITIAL SUPPRESSION OF PRECIP. THIS BEHAVIOR HAS BEEN
APPARENT ON RADAR IMAGERY SW OF THE AREA. THEREFORE...HAVE
MAINTAINED A DRY FORECAST THROUGH THIS EVENING FOR ALL
LOCATIONS...WITH RAIN REACHING THE WI BORDER AFTER 04Z. WHILE THERE
IS PLENTY OF DRY AIR...THE AFOREMENTIONED MOISTURE ALONG WITH ADDED
SUPPORT UNDER THE RIGHT ENTRANCE OF A WEAK UPPER JET SHOULD PRODUCE
HIGHER-INTENSITY RAINFALL THAT WILL QUICKLY ERODE THE DRY LAYER.
ADDITIONALLY...MUCH OF THE INITIAL FORCING FROM ISENTROPIC
ASCENT/FGEN WILL OCCUR IN ABOVE-FREEZING AIR. THE WARM RAIN
PROCESSES IN THIS LAYER WOULD BE EFFICIENT AT PRODUCING MODERATE TO
SOMETIMES HEAVY RAINFALL INTO FRIDAY MORNING.

THE NEXT QUESTION REVOLVES AROUND LOCATION. FORCING ALONG THE WARM
FRONT WILL BE ENOUGH TO PRODUCE WIDESPREAD COVERAGE OF SHOWERS LATE
TONIGHT INTO FRIDAY MORNING. SOME OF THE 12Z GUIDANCE HAS MOVED THE
GREATEST PRECIP CHANCES FARTHER WEST. HAVE HAVE OPTED TO MAINTAIN
THE HIGHEST CHANCES ACROSS THE SW AS THE THOSE MODEL RUNS WERE
HAVING DIFFICULTY HANDLING ONGOING PRECIP. OVERALL...THE CENTRAL CWA
IS EXPECTED TO SEE 0.5 TO 1.0 INCH OF RAINFALL BY LATE FRIDAY
MORNING...WITH LOCALIZED GREATER THAN 1 INCH AMOUNTS POSSIBLE.

FRIDAY...AS THE WARM FRONT LIFTS ACROSS THE CWA IN THE
MORNING...EXPECT A DECREASE IN PRECIP COVERAGE ACROSS THE WEST AND
CENTRAL CWA. WITH ABUNDANT LOW-LEVEL MOISTURE AND A PERSISTENT JET
INFLUENCE AHEAD OF A TROUGH MOVING OUT OF THE NORTHERN
PLAINS...SCATTERED SHOWERS WILL REMAIN POSSIBLE FROM LATE MORNING
INTO THE AFTERNOON. AS THE TROUGH TO THE WEST NEARS THE CWA BY LATE
AFTERNOON...SHOWER COVERAGE WILL INCREASE ACROSS THE WESTERN CWA.

WITH LITTLE TO NO INSTABILITY...EVEN ELEVATED...AHEAD OF THE WARM
FRONT...HAVE OPTED TO REMOVE ALL THUNDER FROM THE FORECAST THROUGH
FRIDAY MORNING. HOWEVER...POST-FRONTAL TEMPS SHOULD BE WARM ENOUGH
TO ALLOW FOR SOME SFC BASED INSTABILITY ACROSS THE WEST AND CENTRAL
CWA. CAPE VALUES OVER 500 J/KG WILL BE POSSIBLE...BUT RESIDUAL CLOUD
COVER SHOULD PREVENT ANYTHING MORE.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 328 PM EDT THU AUG 28 2014

NAM SHOWS A SHORTWAVE TROUGH AFFECTING THE UPPER GREAT LAKES 00Z SAT
AND AFFECTS THE AREA FRI NIGHT. THE TROUGH AXIS PASSES THROUGH THE
AREA SAT AND IS FOLLOWED BY A SHORTWAVE RIDGE SAT NIGHT INTO SUN
WHILE ANOTHER TROUGH MOVES INTO THE NORTHERN PLAINS. NAM BRINGS IN
SOME DEEPER MOISTURE AND 850-500 MB Q-VECTOR CONVERGENCE FRI NIGHT
WHICH MOVE OUT ON SAT. WENT CATEGORICAL POPS FOR FRI NIGHT ACROSS
THE CENTRAL AND EASTERN CWA WITH LESSER POPS IN THE FAR NORTH AND
WEST. LIKELY POPS PULL OUT ON SAT WITH DIMINISHING POPS SAT NIGHT
AND DRY FOR SUN. DID NOT MAKE TOO MANY CHANGES TO THE GOING
FORECAST. DOES LOOK HUMID FOR SAT.

IN THE EXTENDED...ECMWF AND GFS SHOW A BROAD 500 MB TROUGH ACROSS
THE WESTERN HALF OF THE U.S. WITH RIDGING ACROSS THE EASTERN HALF AT
12Z MON. THERE IS A NEGATIVE TILTED SHORTWAVE AFFECTING THE UPPER
GREAT LAKES AT THAT TIME. THIS SHORTWAVE PASSES THROUGH...BUT THE
500 MB TROUGH REMAINS OVER THE AREA 12Z TUE. UPPER FLOW THEN BECOMES
MORE ZONAL ACROSS THE AREA 12Z WED INTO THU WITH A HINT OF THE 500
MB RIDGE ACROSS THE EASTERN U.S. TRYING TO BUILD BACK TOWARDS THE
AREA. WHAT THIS WILL MEAN IS A BRIEF COOL DOWN IN THE FIRST PART OF
THE PERIOD...THEN TEMPERATURES START TO WARM UP AGAIN AND WILL GET
TO NEAR NORMAL. SHOULD BE DRY FOR THE MOST PART AFTER MON NIGHT AS A
COLD FRONT EXITS THE AREA...BUT THERE COULD STILL BE INSTABILITY
SHOWERS ON TUE AND HAVE SLIGHT CHANCE POPS IN FOR THAT. WARM FRONT
APPROACHES THE AREA ON THU...SO POPS START TO RETURN THEN.
&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 127 AM EDT FRI AUG 29 2014

VFR CONDITIONS ARE EXPECTED INTO LATE TONIGHT. LOW PRESSURE
APPROACHING FROM THE SW WILL BRING RAIN AND QUICKLY LOWER CIGS LATE
TONIGHT FOR ALL SITES. IFR CIGS ARE EXPECTED FOR SAW AND CMX...WITH
NEAR IFR CONDITIONS FOR IWD...BY 15Z FRIDAY. GIVEN UPSLOPE ASSISTANCE
WITH SSE FLOW...CIGS AT SAW AND CMX MAY FALL BELOW ALTERNATE LANDING
MINS. ALTHOUGH CONFIDENCE IS LOW...SOME IMPROVEMENT TO MVFR LATE FRI
AFTERNOON AT SAW IS POSSIBLE. OTHERWISE...AN EXTENDED PERIOD OF SUB-
IFR CIGS IS THEN EXPECTED TO CONTINUE INTO SATURDAY.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 359 PM EDT THU AUG 28 2014

HIGH PRESSURE OVER LAKE HURON WILL SHIFT EAST OVERNIGHT AS A WARM
FRONT ASSOCIATED WITH A LOW OVER EASTERN SD MOVES NORTHWARD ACROSS
WI. INCLUDING THIS WARM FRONT...SEVERAL WEAK TROUGHS WILL MOVE
NORTHEAST ACROSS THE UPPER GREAT LAKES REGION THROUGH SATURDAY. THE
WEAK PRESSURE GRADIENT ASSOCIATED WITH THESE FEATURES WILL KEEP
WINDS BELOW 20KTS THROUGH THE WEEKEND. RAINFALL EXPECTED LATE
TONIGHT THROUGH SATURDAY WILL BRING THE POTENTIAL FOR FOG TO DEVELOP
OVER LAKE SUPERIOR...ESPECIALLY OVER THE NORTHEAST...AND CONTINUE
INTO SUNDAY MORNING. A STRONGER TROUGH LIFTING NORTHEAST ACROSS THE
AREA ON MONDAY WILL LIKELY LEAD TO SOUTHERLY WINDS TO 25KTS SUNDAY
NIGHT INTO MONDAY.
&&

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

$$

SHORT TERM...KLUBER
LONG TERM...07
AVIATION...JLB
MARINE...KLUBER






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