Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 181747
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
147 PM EDT THU SEP 18 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 506 AM EDT THU SEP 18 2014

WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH FROM
NRN QUEBEC INTO THE ERN CONUS AND A RIDGE OVER THE ROCKIES RESULTING
IN NW FLOW THROUGH THE NRN GREAT LAKES. AT THE SFC...HIGH PRES WAS
CENTERED OVER NRN ONTARIO BRINGING LIGHT ENE ACROSS LAKE SUPERIOR
AND UPPER MI. THE SHALLOW INTRUSION OF COLD AIR BEHIND A COLD FRONT
INTO SRN WI HAS SHARPENED A 925 MB INVERSION AND TRAPPED ENOUGH LOW
LEVEL MOISTURE TO MAINTAIN EXTENSIVE CLOUD COVER ACROSS UPPER MI AND
NRN WI. IN ADDITION...MOISTENING FROM THE FLOW ACROSS LAKE
SUPERIOR... WITH SOME BANDING EVIDENT...HAS ALSO HELPED TO REINFORCE
THE CLOUDS. AS A RESULT...TEMPS ARE NOT EXPECTED TO DROP OFF ENOUGH
TO PRODUCE FROST OR FREEZING CONDITIONS.

TODAY...AS THE HIGH BUILDS TO THE SE AND WINDS VEER TO THE EAST
DAYTIME HEATING/MIXING WILL HELP ERODE THE LOW CLOUDS AND BRING
CLEARING BY THIS AFTERNOON. WITH 925 MB TEMPS REBOUNDING TO AROUND
6C...EXPECT MAX READINGS IN THE MID 50S EAST AND THE UPPER 50S SOUTH
AND WEST.

TONIGHT...SRLY FLOW WILL INCREASE FROM THE UPPER MS VALLEY TOWARD
THE WRN GREAT LAKES AS THE HIGH SHIFTS TO THE EAST AND LOW PRES
DEVELOPS FROM MANITOBA INTO THE PLAINS. ALTHOUGH THE STRONGER
MOISTURE INFLOW...ISENTROPIC LIFT AND RESULTING PCPN WILL REMAIN NW
OF THE CWA...MID/HIGH CLOUDS ARE EXPECTED TO INCREASE OVERNIGHT FROM
WEST TO EAST. TEMPERATURES WILL ALSO REMAIN STEADY OR SLOWLY RISE
LATE. HOWEVER...THERE STILL MAY BE SOME PATCHY FROST OVER THE EAST.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 459 AM EDT THU SEP 18 2014

MAIN FCST CONCERN FOCUSES ON CHCS FOR SHRA FRI THRU SUN AS A SERIES
OF SHRTWVS IN A W-NW FLOW MOVE ACROSS THE UPPER GREAT LAKES REGION.

MODELS COMING INTO BETTER AGREEMENT SHOWING THE FIRST IN A SERIES OF
SHORTWAVES MOVING INTO THE NRN PLAINS ON FRI. STRENGTHENING WAA AND
INCREASINGLY MOIST SW FLOW AHEAD OF THIS SHORTWAVE AND ITS ASSOC
TROUGH/FRONTAL BOUNDARY OVER THE NRN PLAINS WILL INCREASE PWAT
VALUES TO 1.5 INCHES OR HIGHER (MORE THAN 180 PCT OF NORMAL) OVER
THE FCST AREA BY FRI AFTERNOON. MODEL SNDGS INDICATE 500-1000 J/KG
OF MUCAPE AND SHOWALTER INDICES DROPPING AS LOW AS -2 TO -4C BY FRI
AFTERNOON/FRI NIGHT SO WOULD EXPECT AN INCREASING POTENTIAL FOR
ELEVATED TSRA AS THE WARM FRONT APPROACHES LATE IN THE DAY. MODEL
CONSENSUS SUGGESTS THE BEST CHC FOR SHOWERS WL BE OVER THE W HALF
OF THE CWA FRI AFTERNOON AND OVER THE E HALF FRI EVNG...WHEN
ISENTROPIC ASCENT/H925-7 MSTR TRANSPORT AND DEEP LAYER Q-VECT CONV
WL BE MAXIMIZED OVER THOSE AREAS. AS FOR TEMPS...INCREASING CLD COVER
WL HOLD DOWN SFC HI TEMPS INTO THE 60S ON FRI DESPITE INFLUX OF MUCH
WARMER AIR. EXPECT RELATIVELY SMALL TEMP FALL ON FRI NGT WITH STRONG
SW FLOW AND INFLUX OF HIGHER PWAT.

SAT...ANOTHER STRONGER SHRTWV APPROACHING FROM SCNTRL CANADA AND THE
NRN PLAINS WILL PROPEL THE SFC LOW PRES TROUGH AND ASSOC COLD FNT
THRU THE UPR LAKES. THERE MAY BE A BETTER CHANCE OF SHOWERS/TS
AGAIN SAT AFTERNOON MAINLY OVER CENTRAL AND ERN COUNTIES AS DYNAMICS
WITH SHORTWAVE LOOK TO BE IN SYNC WITH DAYTIME HEATING AND TIMING OF
COLD FRONTAL PASSAGE. MLCAPES FCST IN EXCESS OF 1000 J/KG WOULD
SUPPORT THUNDER AND WITH DEEP LAYER SHEAR VALUES OF 45-50 KTS A FEW
STRONG TO POSSIBLY SVR STORMS WOULD NOT BE OUT OF THE QUESTION IF
INSTABILITY IS REALIZED. WILL MENTION THIS POTENTIAL IN HWO.
DEPENDING ON HOW QUICKLY THE SFC COLD FNT PASSES ON SAT AND
POTENTIAL BREAKS IN CLOUD COVER...SOME PLACES MAINLY OVER THE CNTRL
CWA COULD SEE TEMPS RISE WELL INTO THE 70S AS H85 TEMPS ARE FCST TO
PEAK AS HI AS 16-17C.

SAT NGT INTO SUN...ALTHOUGH MODELS SHOW TIMING DIFFERENCES...THEY
SEEM TO BE IN AGREEMENT THAT ADDITIONAL SHRTWVS WILL BE DROPPING
INTO THE GREAT LKS THAT ARE FCST TO DEEPEN AN UPR TROF OVER THE
REGION. THE RESULTING NW CYCLONIC FLOW OVER THE AREA ALONG WITH THE
PASSAGE OF A SECONDARY COLD FRONT SHOULD YIELD A GOOD DEAL OF CLD
COVER...PERIODS OF SHOWERS AND COOLER WX AS H85 TEMPS DROP FM AS HI
AS 15C ON SAT AFTN TO AS LO AS 2-4C BY LATE SUN. IT APPEARS
UNLIKELY THAT H85 TEMPS WL FALL ENOUGH TO REALIZE MUCH OF A LK
ENHANCED COMPONENT TO THE CLDS/SHOWERS SUN AND SUN NGT WITH WSHFT TO
THE N GIVEN FAIRLY CHILLY LAKE SUPERIOR TEMPS OF 8-9C.

EXTENDED...WITH HI PRES AND MUCH DRIER AIR MOVING INTO THE GREAT LKS
EARLY NEXT WEEK...EXPECT DRY WX TO PREVAIL FROM MON THRU WED. MON IS
LIKELY TO BE RATHER COOL...BUT RETURN SW FLOW ON THE NW FLANK OF THE
HI SHIFTING TOWARD THE LOWER LKS WL BRING A WARMING TREND TUE THRU
WED.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 146 PM EDT THU SEP 18 2014

LOW-LEVEL MOISTURE WRAPPING AROUND THE BACKSIDE OF HIGH PRESSURE
OVER THE REGION WILL CONTINUE WITH MVFR CIGS AT IWD...AND BRING MVFR
CIGS TO CMX AND SAW OVERNIGHT THROUGH MUCH OF FRIDAY. AN INCREASING
PRESSURE GRADIENT ACROSS THE REGION WILL ALLOW FOR GUSTY S TO SSW
WINDS AT ALL SITES BEGINNING FRIDAY MORNING...ESPECIALLY AT SAW.
EXPECT GUSTS AS HIGH AS 30KTS DURING THE AFTERNOON HOURS. AN
APPROACHING LOW-LEVEL TROUGH IS EXPECTED TO BRING -SHRA TO WESTERN
UPPER MI DURING THE AFTERNOON...BUT ANY PRECIP SHOULD HOLD OFF AT
IWD OR CMX UNTIL AFTER 18Z.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 506 AM EDT THU SEP 18 2014

AS HIGH PRES OVER NRN ONTARIO SHIFTS TOWARD NEW ENGLAND TODAY INTO
TONIGHT...WINDS WILL VEER TO THE S AND THEN INCREASE THROUGH THE DAY
ON FRI AS THE PRES GRADIENT SHARPENS BETWEEN THE DEPARTING HIGH AND
A TROUGH MOVING THRU SCENTRAL CANADA/NORTHERN PLAINS. SSW WINDS
COULD REACH 30 KTS...BUT HIGHER STABILITY OVER THE COLD LAKE
WATERS WILL LIMIT THE POTENTIAL FOR ANY GALES DESPITE THE STRENGTH
OF THE EXPECTED WINDS NOT FAR ABOVE THE WATER. WINDS WILL THEN
DIMINISH TO AROUND 20 KTS AND GRADUALLY VEER TO THE W-NW FOLLOWING A
COLD FRONTAL PASSAGE SAT BEFORE VEERING FURTHER TO THE N AND
INCREASING UP TO 25 KTS ON SUN/MON FOLLOWING THE PASSAGE OF A
REINFORCING COLD FRONT.
&&

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

$$

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





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