000
FXUS63 KMQT 200849
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
449 AM EDT MON MAY 20 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 449 AM EDT MON MAY 20 2013

UPPER AIR PATTERN CONSISTS OF A CLOSED 500 MB LOW OVER SD WITH A
DEEP TROUGH ACROSS THE PLAINS STATES AND A 500 MB RIDGE IN THE UPPER
GREAT LAKES. THE RIDGE GETS PUSHED FURTHER TO THE EAST OVER THE
LOWER GREAT LAKES THIS FORECAST PERIOD WHILE THE TROUGH HEADS SLOWLY
EAST WITH THE 500 MB LOW NOT MOVING VERY MUCH AT ALL.

850-500 MB Q-VECTOR CONVERGENCE AND DEEP MOISTURE REMAIN FOR THIS
FORECAST PERIOD AND THE NAM...ECMWF AND GFS SHOW THIS. TRICKY
FORECAST COMING UP WITH AMOUNT OF CLOUD COVER DUE TO CONVECTION
BEING HARD TO DETERMINE AND THIS OF COURSE WILL HAVE AN EFFECT ON
TEMPERATURES. THE MORE SUN THAT WE SEE...THE WARMER THE TEMPERATURES
WILL BE AND THE GREATER THE INSTABILITY FOR THE THUNDERSTORMS TO
WORK WITH. TEMPERATURES HAVE A BIG BUST POTENTIAL FOR TODAY WITH
CLOUD COVER BEING THE BIG QUESTION. THOUGHT THERE WOULD BE SOME
LIMITED SUNSHINE AND ENDED UP WARMING HIGH TEMPERATURES A FEW
DEGREES...ESPECIALLY OVER THE EAST WHERE THAT AREA IS FURTHER FROM
THE STRONG FORCING AND HAS SOME DRIER AIR AWAY FROM THE SFC WARM
FRONT. DID GRADUALLY BRING HIGH POPS OVER THE CWA TODAY AS SYSTEM
DRAWS CLOSER AND KEPT LIKELY POPS IN FOR TONIGHT AS THERE WILL
PROBABLY BE AN MCS/MCC IN THE AREA BRINGING WIDESPREAD RAINFALL TO
THE AREA. DID NOT HAVE ANY TIME TO LOOK AT SEVERE WEATHER
POTENTIAL...BUT THINKING IS THERE COULD BE A FEW STORMS WITH STRONG
WINDS AND LARGE HAIL AND THE SLIGHT RISK ACROSS THE SOUTHERN CWA
LOOKED REASONABLE. ALL DEPENDS ON AMOUNT OF SUNSHINE SEEN TO THE
SOUTH OF THE AREA AND THAT IS THE QUESTION THAT CANNOT BE ANSWERED
AT THIS TIME.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 353 PM EDT SUN MAY 19 2013

MONDAY NIGHT INTO TUE...THE MID/UPPER LEVEL LOW IS EXPECTED TO
REMAIN NEARLY STATIONARY OVER THE ERN DAKOTAS WHILE THE MAIN SFC
FRONTAL BOUNDARY EXTENDS FROM THE LOW OVER NE SD THROUGH SRN MN INTO
CNTRL WI. SHRA AND POSSIBLE TSRA ARE STILL EXPECTED WITH SFC
TROUGH/FRONT JUST TO THE SOUTH...CONTINUED MODERATE 700-300 MB
QVECTOR CONV AHEAD OF THE MID LEVEL LOW. ALTHOUGH LIKELY POPS
CONTINUE...THERE IS MORE UNCERTAINTY WITH THE TIMING/POSITION OF
PCPN AREAS THAT WILL BE SUPPORTED BY THE WEAKER SHORTWAVES. MUCAPE
VALUES GENERALLY IN THE 500-1000 J/KG RANGE MAY SUPPORT SCT/ISOLD
TSRA. HOWEVER...WITH THE MARGINAL INSTABILITY...THE RISK FOR STONGER
STORMS WILL BE MINIMAL.

TUE NIGHT AND WED...MODELS WERE IN GOOD AGREEMENT THAT THE MID LEVEL
LOW WILL FINALLY BEGINS TO SHEAR AND WEAKEN RESULTING IN SLOWLY
DIMINISHING PCPN CHANCES AND INTENSITY.

THU...MODELS HAVE CONTINUED WITH THE TREND TOWARD DRY WEATHER AS NW
FLOW NRN STREAM FLOW TAKES OVER AND A SFC RIDGE BUILDS INTO THE
REGION FROM NRN ONTARIO. BREEZY NORTH TO NE WINDS WILL KEEP TEMPS
MAINLY IN THE MID AND UPPER 50S WITH EVEN SOME UPPER 40S ALONG LAKE
SUPERIOR.

FRI-SAT...WITH CONFLUENT NW MID/UPPER LEVEL FLOW THROUGH THE WRN
GREAT LAKES BTWN THE TROUGH OVER ERN CANADA AND A RIDGE OVER THE
PLAINS...HIGH PRES AND COOL DRY CONDITIONS WILL PREVAIL. 850 MB
TEMPS FROM -2C TO 2C EARLY FRIDAY...PER GFS/ECMWF...SLOWLY MODIFY TO
AROUND 6C SATURDAY AS THE SFC RIDGE MOVES EAST OF THE AREA. WELL
BELOW NORMAL TEMPERATURES FROM AROUND 50 NORTH TO 60 SOUTH ARE
EXPECTED TO CLIMB BACK INTO THE 60S SATURDAY.

SUN...THE 00Z ECMWF WAS FASTER WITH THE TRANSITION TOWARD A MORE
ZONAL PATTERN COMPARED TO THE GFS/GEFS. THE ECMWF SCENARIO WOULD
RESULT IN PCPN CHANCES BY SAT NIGHT INTO SUN AS WAA AND MOISTURE
INFLOW RETURNS INTO THE AREA. GIVEN LARGE DIFFERENCES AND LARGE
ECMWF CHANGE COMPARED TO PREVIOUS RUNS...CONFIDENCE IN OVERALL
PATTERN DETAILS AND PCPN CHANCES IS LOW.
&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 122 AM EDT MON MAY 20 2013

CHALLENGING FCST WILL CONTINUE OVER THE NEXT DAY OR SO. WITH RADAR
SHOWING PLENTY OF PCPN UPSTREAM...EXPECT SHRA/OCNL TSRA AT KIWD
OVERNIGHT WITH CONDITIONS VARYING BTWN VFR/MVFR. AFTER MID
MORNING...PCPN FCST IS MUCH MORE UNCERTAIN. WHILE THERE MAY BE
SHRA/TSRA AT TIMES...DIFFICULT TO PIN DOWN BEST TIME FRAME.
GENERALLY FAVORED VFR CONDITIONS UNDER A DOWNSLOPING ESE/SE WIND. AT
KCMX...UPSLOPE E FLOW THRU THE FCST PERIOD SUGGESTS PREVAILING LIFR
CONDITIONS...BUT AS OBS HAVE SHOWN...THERE MAY BE SOME VARIABILITY
AT TIMES. EXPECT OCNL SHRA. AT KSAW...MVFR CONDITIONS WILL LIKELY
PREVAIL THRU MUCH OF THE FCST PERIOD ALONG WITH OCNL -SHRA. MAY
BREAK OUT TO VFR THIS AFTN...BUT CONFIDENCE IS LOW.
&&

.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 449 AM EDT MON MAY 20 2013

THE MAIN THREATS FOR THIS PERIOD WILL BE A FEW HIGHER GUSTS AT THE
HIGHEST OBSERVING PLATFORMS...AND THE POTENTIAL FOR FOG. A FEW GUSTS
OF 30-35KTS POSSIBLE THROUGH MONDAY...WITH MOST SITES ABOUT 10KTS
LOWER THANKS TO THE MARINE LAYER. HAVE ALREADY HAD REPORTS OF AROUND
2-5SM VIS OVER W LAKE SUPERIOR...WHICH WILL LIKELY CONTINUE AND
SLOWLY SPREAD E WITH THE BETTER CHANCE OF SHOWERS TODAY. EXPECT FOG
TO LINGER THROUGH TUESDAY /FOR MAINLY S LAKE SUPERIOR/.

EXPECT A RIDGE OVER N MANITOBA TO SLIDE ACROSS JAMES BAY
TONIGHT...AND EXIT E ACROSS QUEBEC TUESDAY NIGHT. IN THE
MEANTIME...A LOW OVER THE EASTERN DAKOTAS AND WESTERN MINNESOTA
TODAY AND TONIGHT SHOULD FILL SLIGHTLY ACROSS SOUTHERN MINNESOTA AND
CENTRAL WISCONSIN ON TUESDAY...AND SLOWLY OVER STRETCHING FROM
SOUTHERN WISCONSIN TO LOWER MICHIGAN DURING THE DAY WEDNESDAY. THE
LOW WILL FINALLY EXIT E ACROSS THE LOWER GREAT LAKES WEDNESDAY
NIGHT. BEHIND THE LOW...STRONG AND COOL HIGH PRESSURE ACROSS N
CENTRAL CANADA WILL EXTEND A RIDGE ACROSS LAKE SUPERIOR LATE
THURSDAY AFTERNOON THROUGH AT LEAST FRIDAY...AND MOST LIKELY THROUGH
THE WEEKEND.
&&

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

$$

SHORT TERM...07
LONG TERM...JLB
AVIATION...ROLFSON
MARINE...KF