Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 142002
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
402 PM EDT SUN SEP 14 2014

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 401 PM EDT SUN SEP 14 2014

WV IMAGERY AND RUC ANALYSIS INDICATED A BROAD MID/UPPER LEVEL TROUGH
FROM CENTRAL CANADA INTO THE NRN CONUS. A SHORTWAVE TROUGH WAS
MOVING THROUGH NRN ONTARIO JUST N OF LAKE SUPERIOR WHILE THE MOST
PROMINENT UPSTREAM SHRTWV WAS DIVING INTO ERN MONTANA. AT THE
SFC...LOW PRES NEAR CYQT HAD DRAGGED A COLD FRONT THROUGH WRN UPPER
MI. THE SHRTWV TAIL AHEAD OF THE COLD FRONT WITH MODERATE 700-300
QVECTOR CONV WAS ENOUGH TO SUPPORT SCT LIGHT SHOWERS OR SPRINKLES
FROM ERN LAKE SUPERIOR INTO CNTRL UPPER MI. RELATIVELY DRY LOW LEVEL
AND THE QUICK MOVEMENT OF THE SHOWERS HAS LIMITED POTENTIAL FOR MORE
THAN TRACE PCPN AMOUNTS. OTHERWISE...PARTIAL CLEARING WAS MOVING
INTO W UPPER MI WITH A PROMINENT CU FIELD IN THE SEASONABLY COOL
AIRMASS WHERE 850 MB TEMPS WERE NEAR 4C.

TONIGHT...AS THE SHRTWV TROUGH EXITS TO THE EAST...EXPECT THE
REMAINING SHOWERS OVER THE ERN CWA TO DIMINISH THROUGH THE LATE
AFTERNOON AND EARLY EVENING. PARTLY CLOUDY SKIES AND DIMINISHING
WINDS WILL RESULT IN FAVORABLE RADIATIONAL COOLING CONDITIONS LATE
THIS EVENING. HOWEVER...THERE IS UNCERTAINTY ON HOW MUCH CLOUD COVER
WILL HOLD TOGETHER OVERNIGHT AS ADDITIONAL MOISTURE WILL SLIDE IN
WITH 850 MB TEMPS DROPPING TO NEAR 1C. EXPECT MIN READINGS TO DROP
INTO THE UPPER 30S AND LOWER 40S INLAND.

MONDAY...MODELS WERE IN GOOD AGREEMENT THAT THE STRONGEST QVECTOR
CONV AND PCPN ASSOCIATED WITH THE MONTANA SHRTWV WILL REMAIN SOUTH
OF UPPER MI. HOWEVER...THERE MAY BE ENOUGH LOW LEVEL MOISTURE
COMBINED WITH 850 MB TEMPS NEAR 1C TO SUPPORT SOME SHALLOW
CONVECTION WITH SCATTERED LIGHT SHOWERS OR SPRINKLES AS DAYTIME
HEATING INCREASES.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 350 PM EDT SUN SEP 14 2014

MODEL AGREEMENT IS GOOD IN THE EVOLUTION OF OVERALL LARGE SCALE
PATTERN INTO NEXT WEEKEND. TROUGHS CENTERED OVER ALASKA AND NUNAVUT
IN NORTHERN CANADA ARE EXPECTED TO DEAMPLIFY WITH FLOW ALOFT OVER
THE NORTHERN CONUS BECOMING MORE ZONAL THROUGH THE PERIOD. UNTIL
MIDWEEK THE TROUGH OVER THE GREAT LAKES AND ACROSS EASTERN CANADA
WILL KEEP GETTING REINORCED AS UPPER JET ENERGY DIGGING SSE OVER
WESTERN CANADA SLIDES INTO BASE OF TROUGH. STRONGER SHORTWAVE
WITHIN THE TROUGH CROSSES NORTHERN ONTARIO MONDAY NIGHT AND MOVES
INTO QUEBEC ON TUESDAY. COLD FRONT TIED TO THAT WAVE ALONG WITH
ANOTHER SHEARED OUT SHORTWAVE AND RIBBON OF HIGHER H85-H7 RH MAY
RESULT IN LGT RAIN OR SHOWERS TURSDAY NIGHT INTO WEDNESDAY AND
POSSIBLY EVEN INTO WEDNESDAY NIGHT IF THE ECMWF AND GEM-NH ARE ON
THE RIGHT TRACK. MAIN IMPACT WILL BE A NOTICABLE COOLER DAY ON
WEDNESDAY COMPARED TO TUESDAY WHERE TEMPS WILL ACTUALLY BE AROUND OR
EVEN SLIGHTLY ABOVE NORMAL /NORMAL HIGHS AVERAGE THE MID 60S FOR
MID SEPT/.

SFC HIGH PRESSURE BUILDS ACROSS WEDNESDAY NIGHT THROUGH THURSDAY
NIGHT IN CONFLUENT FLOW IN UPPER LEVELS BTWN RIDGING EXPANDING OVER
THE WESTERN CONUS AND DEPARTING TROUGH OVER EASTERN CANADA. MAINLY
DRY WEATHER ALONG WITH PARTLY CLOUDY OR MOSTLY CLEAR SKIES SHOULD
RESULT. STILL COULD BE CHILLY OVER THE INLAND AREAS ON WEDNESDAY
NIGHT WITH FROST. HOWEVER...BASED ON THAT SIGNAL OF MID-LEVEL
MOISTURE RIBBON FM ECMWF/GEM-NH...LOWEST TEMPS AND GREATEST RISK OF
FROST MIGHT END UP OVER THE INTERIOR EAST CWA.

BY LATE THIS WEEK...RIDGING OVER THE WESTERN CONUS IS REPLACED BY
TROUGHING AS SHORTWAVE AND UPPER JET STREAKS CURRENTLY OVER PACIFIC
WELL OFFSHORE OF WESTERN CONUS COAST SLIDES ACROSS THE NORTHERN AND
CENTRAL PLAINS WITH A SFC TROUGH ALSO PUSHING WEST TO EAST. MAIN
QUESTION IS HOW QUICKLY THIS OCCURS. NO REAL TREND IN THE MODEL
GUIDANCE...AS THE ECMWF AND GFS HAVE JUMPED AROUND IN HOW QUICKLY TO
BRING THE TROUGH AND INITIAL SURGE OF H85 THETA-E ADVECTION ACROSS
THE NORTHERN PLAINS AND DOWNSTREAM INTO THE UPPER GREAT LAKES. ONCE
THE FRONT...AND MORE SO THE THETA-E ADVECTION AHEAD OF THE FRONT...
ARRIVES COULD BE MULTIPLE ROUNDS OF SHRA/TSRA LATER FRIDAY THROUGH
SATURDAY WITH MAINLY JUST SHRA ON SUNDAY. HEAVY RAINS POSSIBLE SINCE
THE SFC FRONT WOULD BE PARALLEL TO THE UPPER LEVEL FLOW AND PWATS
ARE FORECAST 200-250 PCT OF NORMAL. AT FIRST GLANCE AND IT IS JUST
THAT...LOOKS LIKE ONLY A SMALLER RISK OF SEVERE WX AS INITIAL
ELEVATED INSTABILITY...MAYBE UP TO 500 J/KG...ON FRIDAY/FRIDAY NIGHT
DOES NOT LINK UP WITH MUCH EFFECTIVE SHEAR. THEN AS PRIMARY FRONT
COMES THROUGH EITHER SATURDAY AS IT LOOKS NOW...APPEARS BETTER
MLCAPE REMAINS SOUTH OF THE AREA CLOSER TO AREA OF 65F SFC DWPNTS.
ALL THAT SAID...GIVEN THE STRONG WINDS ALOFT THAT WILL BE
PRESENT...IF INSTABILITY ENDS UP GREATER THAN FORECAST...WOULD BE AT
LEAST SOME RISK OF STRONGER STORMS FRIDAY THROUGH SUNDAY. MAX TEMPS
BOTH FRI AND SAT MAY TRY TO REACH 70 DEGREES IF THERE IS ENOUGH
BREAKS IN THE CLOUD COVER AS H85 TEMPS ARE WELL ABOVE +12C. A BIT
LOWER TEMPS NEXT SUNDAY...THOUGH COOLDOWN WILL NOT BE AS MUCH AS
THAT EXPECTED ON WEDNESDAY.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 132 PM EDT SUN SEP 14 2014

EXCEPT FOR SOME MVFR CIGS AT CMX EARLY THIS AFTERNOON...UNDER
RELATIVELY DRY LOW LEVELS...MAINLY VFR CONDITIONS WILL PREVAIL AT
THE TAF SITES THROUGH THE FCST PERIOD. ROACHING COLD FRONT WILL
BRING SCT -SHRA OR SPRINKLES AT SAW EARLY THIS AFTERNOON WHERE VCSH
WAS MENTIONED. SW WINDS GUSTING TO 20 KT WILL SHIFT W BEHIND THE
FRONT THIS AFTERNOON AND MAY GUST AS HIGH AS 25 KTS AT KCMX BEFORE
TAPERING OFF TOWARD EVENING.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 350 PM EDT SUN SEP 14 2014

SW WINDS GUST TO 25 KTS THROUGH EARLY THIS EVENING...THEN WEST
WINDS DIMINISH TO LESS THAN 20 KTS LATER TONIGHT INTO MONDAY. WEST
WINDS MAY INCREASE TO 25 KTS MONDAY NIGHT INTO TUESDAY AHEAD OF A
COLD FRONT. WINDS THEN SHIFT TO NORTHEAST UP TO 25 KTS IN WAKE OF
THE COLD FRONT TUESDAY NIGHT. WINDS DIMINISH TO LESS THAN 20 KTS
LATER WED INTO THU AS HIGH PRESSURE RIDGE CROSSES REGION. NEXT
CHANCE OF STRONG WINDS ARRIVES FRIDAY WITH SOUTH WINDS INCREASING
TO 20 TO 30 KTS AHEAD OF DEVELOPING LOW PRESSURE SYSTEM IN THE
PLAINS.
&&

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

$$

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





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