AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
748 PM EDT WED JUN 19 2013
.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 429 PM EDT WED JUN 19 2013
WV IMAGERY AND RUC ANALYSIS INDICATED WNW MID/UPPER LEVEL FLOW
THROUGH THEN NRN GREAT LAKES BETWEEN A TROUGH OVER ERN CANADA AND A
RIDGE OVER THE PLAINS. SCT SHRA AND ISOLD TSRA HAD DEVELOPED NEAR
CYRL ON THE TAIL OF A SHORTWAVE TROUGH THROUGH NW ONTARIO. AN
UPSTREAM SHRTWV WAS ALSO LOCATED OVER ERN SD. AT THE SFC...SRLY
WINDS HAD INCREASED BETWEEN HIGH PRES OVER THE ERN GREAT LAKES AND A
TROUGH EXTENDING INTO ND FROM LOW PRES W OF JAMES BAY. LOW LEVEL
MOISTURE WAS ONLY SLOWLY INCREASING WITH DEWPOINTS CLIMBING TO NEAR
50F OVER THE WEST.
TONIGHT...EVEN THOUGH THE FORCING WITH THE NW ONTARIO SHRTWV WILL
REMAIN NORTH OF THE CWA...MODELS SUGGEST THAT THE SHRA AND POSSIBLY
SOME TSRA WILL DEVELOP LATER THIS EVENING NW OF LAKE SUPERIOR AND
SLIDE INTO THE WRN CWA OVERNIGHT. MOISTURE TRANSPORT AND THE
POSITION OF THE 850-700 MB FRONTAL ZONE FAVORS GREATER PCPN
CHANCES/COVERAGE OVER NW LAKE SUPERIOR INTO MAINLY THE NW CWA.
MUCAPE VALUES ARE EXPECTED TO BE HIGH ENOUGH FOR ELEVATED TSRA
DEVELOPMENT.
THURSDAY...THE COMBINATION OF INCREASING MOISTURE
TRANSPORT...DAYTIME HEATING AND THE SD SHRTWV SHOULD BRING
INCREASING SHRA/TSRA COVERAGE ACROSS THE CWA. ALTHOUGH INSTABILITY
WILL BE MARGINAL FOR STRONGER STORMS WITH MLCAPE VALUES INTO THE
500-1000 J/KG RANGE...AND A RELATIVELY NARROW CAPE PROFILE....SOME
STORMS WITH SMALL HAIL AND GUSTY WINDS TO 35 MPH MAY BE POSSIBLE.
.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 429 PM EDT WED JUN 19 2013
CONVECTION WILL MAKE FOR A VERY TRICKY AND UNCERTAIN FORECAST THU
NIGHT THROUGH AT LEAST THE WEEKEND.
AN UPPER RIDGE WILL MOVE E INTO THE AREA THU NIGHT THROUGH THE
MIDDLE OF NEXT WEEK. AT THE SFC...A WEAK LOW WILL REMAIN FAIRLY
STATIONARY OVER THE CENTRAL AND NRN PLAINS...LEAVING A WARM FRONT
ACROSS OR NEAR THE CWA THROUGH THIS WEEKEND. CONFIDENCE IS VERY LOW
/AS WITH MOST CONVECTIVE SITUATIONS/ WITH THE EXACT TRACK/TIMING OF
ANY CONVECTIVE COMPLEXES MOVING ALONG OR NEAR THE WARM FRONT. MODELS
SHOW MULTIPLE SCENARIOS FOR CONVECTIVE DEVELOPMENT AND
MOVEMENT...INCLUDING MOVING THE WARM FRONT N OF THE CWA KEEPING THE
BULK OF CONVECTION N OF THE CWA...TO HAVING THE WARM FRONT STALL S
OF THE CWA WHICH WOULD KEEP MOST OF THE CONVECTION S. OVERALL...THE
BULK OF THE MODELS SHOW CONVECTIVE COMPLEXES MOVING OVER THE
CWA...SO WILL CONTINUE TO PUT THAT INTO THE FORECAST AS HAS BEEN
DONE BY PREVIOUS SHIFTS.
SOME OF THE THUNDERSTORMS COULD VERY WELL BE STRONG WITH LARGE HAIL
AND DAMAGING WINDS THE PRIMARY THREATS...BUT CONFIDENCE IS STILL TOO
LOW TO INCORPORATE THAT INTO THE FORECAST BUT WILL CONTINUE SOME
MENTION OF STRONGER STORMS IN THE HWO. SPC HAS AREAS ALONG THE
BORDER UNDER A SLIGHT RIGHT...AND GENERALLY AGREE WITH THAT GIVEN
THE LOCATION OF THE GREATEST INSTABILITY. MODELS SHOW UP TO 4500J/KG
/GFS/ OF SBCAPE NOSING INTO WRN UPPER MI FRI AFTERNOON...BUT THAT IS
THE HIGHEST AMOUNT AND LOOKS LIKE LOW LEVELS ARE OVERLY MOIST IN THE
MODEL. THE NAM IS ANOTHER MODEL THAT SEEMS TOO HIGH ON LOW LEVEL
MOISTURE AND SBCAPE AT UP TO 3500J/KG ON FRI. ECMWF AND GEM SEEM
MORE REASONABLE AT 1000-1500J/KG ALONG THE WI BORDER SO WILL FAVOR
THAT SOLUTION. COULD HAVE DAYTIME CONVECTION BREAK OUT OVER WRN AND
CENTRAL UPPER MI...BUT MOST LIKELY SCENARIO AT THIS POINT CONTINUES
TO BE CONVECTION FORMING UPSTREAM AND MOVING TO THE ESE ALONG THE
FORWARD PROPAGATING CORFIDI VECTORS AND INSTABILITY GRADIENT FRI.
ANOTHER RISK FACTOR WILL BE HEAVY RAIN WITH ANY THUNDERSTORMS AS
PWATS WILL BE 150-200 PERCENT OF NORMAL.
SAT AND SUN LOOK SIMILAR TO FRI...WITH SIMILAR UNCERTAINTY DUE TO
CONVECTIVE UNCERTAINTY. IN FACT...SIMILAR CONDITIONS SHOULD BE
OBSERVED INTO THE MIDDLE OF NEXT WEEK...BUT CONFIDENCE INCREASES TOO
MUCH MON-WED TO TALK TOO MUCH ABOUT THIS TIME FRAME.
LOOKING AT TEMPS...SHOULD SEE SFC TEMPS INCREASE SLIGHTLY FROM DAY
TO DAY THROUGH THE FORECAST PEROID WITH HIGHS IN THE 80S ACROSS A
LARGE PART OF UPPER MI BY SUN.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 748 PM EDT WED JUN 19 2013
VFR CONDITIONS WILL CONTINUE AT KIWD/KCMX/KSAW THRU THE EVENING.
OVERNIGHT...ATTENTION TURNS TO SFC TROF DROPPING S TOWARD THE UPPER
LAKES IN ASSOCIATION WITH SHORTWAVE CURRENTLY PASSING THRU NRN
ONTARIO. SCT SHRA/TSRA ARE CURRENTLY OCCURRING ALONG/AHEAD OF
TROF...AND SOME OF THOSE SHRA MAY HOLD TOGETHER AND AFFECT ALL 3
TERMINALS LATE TONIGHT/THU MORNING. WITH COVERAGE LIMITED...
CONFIDENCE IN SHRA OCCURRING AT EACH TERMINAL IS LOW...SO VCSH WAS
UTILIZED EXCEPT AT KCMX WHICH MAY HAVE A SLIGHTLY BETTER POTENTIAL
OF SHRA. IF SHRA DO OCCUR AT KCMX AND ACROSS LAKE SUPERIOR...
STRATUS/MVFR CIGS AND FOG/MVFR VIS MAY DEVELOP AT KCMX...ESPECIALLY
IF AN E WIND DEVELOPS EARLY IN THE DAY. DURING THE AFTN...DAYTIME
HEATING SHOULD GENERATE SCT SHRA/TSRA ACROSS UPPER MI WITH BETTER
POTENTIAL AT KIWD/KSAW. AGAIN...THERE IS LIMITED CONFIDENCE IN PCPN
ACTUALLY OCCURRING AT A TERMINAL...SO ONLY VCTS WAS INCLUDED IN
FCST. IF SHRA/TSRA OCCUR AT ANY TERMINAL THU...MVFR CONDITIONS WOULD
LIKELY ACCOMPANY PCPN.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 429 PM EDT WED JUN 19 2013
WINDS SHOULD REMAIN BELOW 25KTS THROUGH THE PERIOD...WITH RELATIVELY
LOW WAVES. THE MAIN HAZARD WILL BE STRONGER WINDS/HAIL/LIGHTNING
WITH ANY THUNDERSTORMS MOVING ACROSS LAKE SUPERIOR FROM LATE TONIGHT
THROUGH INTO EARLY NEXT WEEK. AREAS OF FOG THAT DEVELOP AS A RESULT
OF INCREASED MOISTURE AND SHOWER ACTIVITY MAY ALSO BECOME LOCALLY DENSE.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...JLB
LONG TERM...TITUS
AVIATION...ROLFSON
MARINE...JLB
