Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 201816
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
216 PM EDT SAT SEP 20 2014

.SYNOPSIS...
ISSUED AT 247 AM EDT SAT SEP 20 2014

OCCASIONAL WET WEATHER IS EXPECTED THIS WEEKEND...AS A COLD FRONT
AND LOW PRESSURE SYSTEM MOVES ACROSS THE GREAT LAKES REGION. HIGH
PRESSURE WILL PASS TO OUR SOUTH EARLY IN THE WORK WEEK...DRYING US
OUT AND STARTING TO WARM US UP. AN EXTENDED PERIOD OF DRY AND WARM
WEATHER IS EXPECTED FOR THE REST OF THE WORK WEEK.

&&

.UPDATE...
ISSUED AT 216 PM EDT SAT SEP 20 2014

ANOTHER SMALL SWIRL IN THE PROCESS OF SLIPPING THROUGH THE SRN
TIER OF COUNTIES AND HAS FIRED OFF ANOTHER SMALL CLUSTER OF
SHOWERS AND STORMS. CERTAINLY LOOKING LIKE THIS NEXT BATCH OF
CONVECTION WILL SLIP EAST/NE THROUGH NRN LOWER MICHIGAN OVER THE
NEXT FEW HOURS. MEANWHILE...ANOTHER THIN LINE OF SHOWERS/STORMS
DEVELOPING ALONG THE COLD FRONT PRESSING INTO EASTERN UPPER
MICHIGAN. MAY CONTINUE TO SEE THAT LINE DEVELOP UPSCALE AND
EVENTUALLY DROP DOWN INTO NRN LOWER MICHIGAN LATER ON. NAM12
FORECASTS WOULD CERTAINLY SUGGEST THAT TO BE TRUE. WILL TWEAK
FORECASTS ACCORDINGLY.

UPDATE ISSUED AT 928 AM EDT SAT SEP 20 2014

INTERESTING CONVECTIVE EVOLUTION THIS MORNING. LOW LEVEL THETA-E
AXIS CONTINUES TO LEAN INTO NORTHERN AND CENTRAL LOWER MICHIGAN. A
COUPLE OF MCS WANNABES HAVE DEVELOPED ALONG THAT AXIS...
ESSENTIALLY WHERE BETTER/DEEPER MOISTURE AND QG ASCENT PRESSING
IN FROM THE NORTH HAS CAUGHT THE NRN EDGE OF AN AXIS OF STEEP MID
LEVEL LAPSE RATES DOWN ACROSS NRN AND CENTRAL LOWER MICHIGAN. ONE
MCV IS NOW ROLLING NE ACROSS NRN LAKE HURON. A SECOND MCV IS
EVIDENT IN THE RADAR REFLECTIVITY DATA ROLLING NORTHEASTWARD
AROUND THE LEELANAU PENINSULA...AND IS HELPING TO ENHANCE
CONVECTIVE LINE THAT EXTENDS FROM NRN LAKE MICHIGAN INTO EASTERN
UPPER MICHIGAN.

HAVE TWEAKED POPS FOR THE NEXT FEW HOURS TO FOCUS HIGH POPS
ACROSS THE TIP OF THE MITT INTO EASTERN UPPER...AS THIS SECOND MCV
ROLLS THROUGH.

REST OF THE DAY...PER RADAR TRENDS...MAY CATCH A BIT OF A LULL IN PRECIP
LATE MORNING INTO THE AFTERNOON ONCE THIS SECOND MCV MOVES OUT OF
THE REGION. MEANWHILE...THETA-E AXIS/STEEP MID LEVEL LAPSE
RATES/DEEPER MOISTURE AND AXIS OF QG-ASCENT SETTLES SOUTHWARD
INTO CENTRAL AND SOUTHERN LOWER MICHIGAN. STILL APPEARS THAT WE
SEE ANOTHER ROUND OF SHOWERS AND STORMS DEVELOP DOWN ACROSS THAT
AREA LATER IN THE AFTERNOON INTO THIS EVENING THAT SKIRTS OUR S/SE
CWA. BUT THERE COULD ALSO BE ADDITIONAL SHOWERS/STORMS THAT
DEVELOP ALONG THE UPSTREAM COLD FRONT THAT WILL BE SWINGING DOWN
THROUGH NRN MICHIGAN LATER THIS AFTERNOON AND EVENING. NOT GONNA
RAIN ALL DAY...BUT THERE WILL BE VARYING CHANCES FOR PRECIP
THROUGH THE DAY INTO THE EVENING.

SEVERE WEATHER THREAT WILL BE MAINLY ACROSS CENTRAL AND SOUTHERN
LOWER MICHIGAN. BUT WITH IN EXCESS OF 50 KNOTS MID LEVEL
FLOW...RESULTING GOOD EFFECTIVE BULK SHEAR FOR ORGANIZED
UPDRAFTS...WILL NEED TO KEEP AN EYE ON ANY AND ALL CONVECTION
TODAY.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 247 AM EDT SAT SEP 20 2014

...SHOWER AND THUNDERSTORMS EXPECTED TODAY AND TONIGHT...

HIGH IMPACT WEATHER POTENTIAL: TYPICAL THUNDERSTORM CONCERNS
(LIGHTNING/BRIEF HEAVY RAIN/GUSTY WINDS) RIGHT THROUGH TONIGHT.
ISOLATED SEVERE STORM POSSIBILITIES THIS AFTERNOON?

PATTERN SYNOPSIS/ANTICIPATED EVOLUTION: BRIEF INTERLUDE TO A MUCH
MORE DEAMPLIFIED PATTERN CONTINUES...WITH A NEARLY ZONAL APPEARANCE
TO MID AND UPPER LEVEL FLOW ACROSS THE NORTHERN CONUS/SOUTHERN
CANADA. PLENTY OF ACTIVITY WITHIN THIS FLOW REGIME...WITH LEAD WAVE
CUTTING ACROSS THE UPPER MISSISSIPPI VALLEY...WITH SECONDARY STRONGER
WAVE DIVING SOUTHEAST INTO SASKATCHEWAN. BOTH OF THESE FEATURES WILL
HAVE SIGNIFICANT IMPACT ON OUR WEATHER THROUGH THIS WEEKEND...WITH
THE FORMER BRINGING SHOWERS AND EMBEDDED STORMS TODAY INTO THIS
EVENING...WITH THE LATTER KEEPING CONDITIONS UNSETTLED LATER TONIGHT
AND SUNDAY. ALREADY PLENTY OF SHOWERS ONGOING OVER PARTS OF THE
NORTHERN LAKES WITH SHARP MOISTURE ADVECTION INTERACTING WITH
APPROACHING MID LEVEL SUPPORT AND ATTENDANT COLD FRONT. SOME OF THIS
ACTIVITY IS WETTING THE GROUND ACROSS THE NORTHWEST HALF OF OUR
AREA...WITH SOUTHEAST AREAS REMAIN DRY (SO FAR AT LEAST). A MUCH
MILDER NIGHT...WITH CURRENT READINGS MOSTLY IN THE 50S AND LOWER 60S.

PRIMARY FORECAST CHALLENGES/CONCERNS: SHOWER AND STORM EVOLUTION
TODAY AND TONIGHT. ADDRESSING THUNDERSTORM INTENSITY (ISOLATED
SEVERE?) FOR THIS AFTERNOON.

DETAILS: UNFORTUNATELY...JUST NOT AN OVERLY CONFIDENT FORECAST
TODAY. FORCING REMAINS DISJOINTED...WITH SHARP MOISTURE
ADVECTION/THETA-E GRADIENT OVERHEAD THIS MORNING...WELL AHEAD OF
UPSTREAM COLD FRONT EXPECTED TO PASS LATE THIS AFTERNOON AND
EVENING. SURFACE BASED INSTABILITY AHEAD OF THIS FRONT NEARLY
COMPLETELY TIED TO BEING ABLE TO GENERATE SOME SUNSHINE...AND THAT
IS ANYTHING BUT CERTAIN. AND IF THAT IS NOT ENOUGH TO GENERATE
UNCERTAINTY...BEST MID LEVEL SUPPORT ARRIVES POST-FRONTAL...EXPECTED
TO CROSS THE AREA LATE TONIGHT INTO THE START OF SUNDAY. HAVE SEEN
THIS BEFORE...AND REALLY STARTING TO WONDER IF MOST SHOWERS/ELEVATED
THUNDERSTORMS OCCUR THIS MORNING ALONG RAMPED-UP MOISTURE AXIS/LOW
LEVEL JET SUPPORT...WITH WEAK FORCING ALONG FRONT LATER TODAY
IGNITING JUST SOME SCATTERED ACTIVITY. WILL WAIT FOR FULL PERUSAL OF
LATEST AND GREATEST GUIDANCE TRENDS...BUT STRONGLY LEANING TOWARD
THIS LESS AGGRESSIVE AFTERNOON APPROACH. OF COURSE...THIS DOES NOT
BODE WELL FOR SEVERE WEATHER POTENTIAL...WITH LIMITED DEEP LAYER
FORCING AND PLENTY OF INSTABILITY CONCERNS. BEST FOCUS FOR SEVERE
WEATHER REMAINS OFF TO OUR SOUTH...AND IN FULL SUPPORT OF SUCH GIVEN
ABOVE DETAILS. IF SOME CLEARING/DESTABILIZATION IS REALIZED...
OVERHEAD MID LEVEL SPEED MAX AND ASSOCIATED DEEP LAYER SHEAR VALUES
DOES SUPPORT AN ISOLATED SEVERE WIND THREAT. BEST BET FOR THIS WILL
BE ALONG/SOUTH OF M-55...BUT EVEN THIS SEEMS LIKE A LOW PROB
SCENARIO AT THIS TIME.

COLD FRONT EXITS THIS EVENING...LIKELY LEAVING BEHIND A QUIET
STRETCH OF WEATHER THROUGH THE EARLY MORNING HOURS. STRONG VORT MAX
APPROACHES QUICKLY TOWARD SUNRISE...WITH DEEP LAYER RESPONSE
SUPPORTED BY LER UPPER JET DYNAMICS. SUSPECT SHOWERS WILL INCREASE
IN COVERAGE ONCE AGAIN...TARGETING THE SOUTHERN THIRD OF THE AREA
PER BEST UPPER JET SUPPORT. ELEVATED CAPE AND DECENT MID LEVEL LAPSE
RATES IN LOCKSTEP WITH DEEPENING FORCING...SUPPORTING AT LEAST A
CHANCE WORDING FOR ELEVATED THUNDER.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 247 AM EDT SAT SEP 20 2014

...RAIN CHANCES SUNDAY FOLLOWED BY AN EXTENDED DRY PERIOD...

VIGOROUS DIGGING SHORTWAVE WILL BE BARELY CLOSED OFF AS IT CROSSES
LOWER MI ON SUNDAY. A WEAK SURFACE WAVE WILL BE JUST AHEAD OF THIS
FEATURE...OVER CENTRAL LOWER MI SUNDAY MORNING BEFORE MOVING TOWARD
THE THUMB AND EVENTUALLY LAKE ONTARIO. THIS TROF WILL OPEN UP AS IT
DEPARTS SUNDAY NIGHT AND BEYOND...WITH STEADY HEIGHT RISES ALOFT. AT
THE SURFACE...HIGH PRESSURE WILL BUILD FROM THE NORTHERN PLAINS TO
THE OHIO VALLEY. SO...AFTER UNSETTLED WX SUNDAY...DRIER AND WARMER
CONDITIONS WILL BE SEEN FOR MUCH OF THE WORK WEEK.

SUNDAY...LOW LEVEL COLD ADVECTION WILL ALREADY BE UNDERWAY IN
EASTERN UPPER MI ON NE FLOW TO START THE DAY. NORTHERLY FLOW WILL
EXPAND ACROSS NORTHERN MI BY MID-AFTERNOON AS THE SURFACE LOW PULLS
OUT. THERE IS STILL A WINDOW FOR WARM-SECTOR DEEP CONVECTION IN SE
SECTIONS IN THE MORNING...ALONG WITH A QUICK SPIKE IN TEMPS INTO THE
MID/UPPER 60S. OTHERWISE...THE ORGANIZING COLD CONVEYOR BELT WILL BE
THE MAIN SOURCE FOR PRECIP. THIS FEATURE WILL SIT OVER FAR NORTHERN
LOWER MI IN THE MORNING...ROTATE INTO NW LOWER BY MIDDAY...THEN PUSH
SE-WARD DURING THE AFTERNOON. THE NAM IS FASTER TO ORGANIZE THE COLD
CONVEYOR BELT THAN THE OTHER MODELS...AND IT/S POPS LOOK TOO HIGH.
HOWEVER...WILL STILL INCREASE POPS TO LIKELY IN THE SE THIRD OF THE
FORECAST AREA. MINIMAL POPS NEEDED IN CENTRAL/NORTHERN CHIPPEWA
CO...WHERE THE SUN SHOULD APPEAR BY MID/LATE AFTERNOON. (REST OF
EASTERN UPPER INTO NW LOWER SHOULD BREAK OUT OF CLOUDS TOWARD EARLY
EVENING.)

MAX TEMPS WILL RANGE FROM THE UPPER 50S TO NEAR 70F...MOSTLY IN THE
MORNING. PM HOURS WILL BE SOMEWHAT BLUSTERY WITH STEADY TO FALLING
TEMPS.

SUN NIGHT/MONDAY...CLEARING WILL PROCEED APACE INTO N CENTRAL AND NE
LOWER MI SUNDAY EVENING. MAINLY CLEAR OVERNIGHT. PRESSURE GRADIENT
WILL RELAX SOMEWHAT...SUCH THAT PROTECTED INTERIOR LOCALES WILL NO
DIFFICULTY DECOUPLING...WHILE COASTAL SITES MAINTAIN A NORTH BREEZE.
MIN TEMPS WILL THUS VARY CONSIDERABLY...FROM LOW/MID 40S IN SOME
COASTAL LOCALES...TO AROUND 30F IN THE COLDEST INTERIOR LOCALES (PLN
A PRIME CANDIDATE). FROST REMAINS A THREAT IN THE LATTER PLACES...
AND WILL CONTINUE TO BE HIGHLIGHTED IN THE HWO. MONDAY COULD SEE
SOME MID/HIGH CLOUDS IN NORTHERN SECTIONS...AS THE PRESSURE
GRADIENT/WARM ADVECTION INCREASES BETWEEN HIGH PRESSURE IN THE OHIO
VALLEY AND A COLD FRONT SAGGING ACROSS FAR NORTHERN ONTARIO. THAT
WON/T BE ENOUGH TO PREVENT A PARTLY TO MOSTLY SUNNY DAY. AFTER A
COOL START...MAX TEMPS WILL REBOUND INTO THE UPPER 50S TO MID 60S.

REST OF THE FORECAST...VERY QUIET TUE/WED AS A SHORTWAVE RIDGE
BUILDS INTO THE CENTRAL LAKES. WITH LOW LEVEL WARM ADVECTION
UNDERWAY AS HIGH PRESSURE SLIPS TO THE EAST COAST...MAX TEMPS WILL
TAKE A RUN AT 70F IN PARTS OF NORTHERN LOWER. SUBSTANTIAL
DISAGREEMENT AS TO HOW PROGRESSIVE THE UPPER FLOW WILL BE AFTER
THIS. GFS/GEM ARE BOTH INCLINED TO CUT OFF THE NEXT PIECE OF
ENERGY...LEAVING IT BACK IN THE CENTRAL PLAINS. THE ECMWF DOES BRING
A DEAMPLIFYING TROF OVERHEAD THU AFTERNOON. EVEN IN THIS LATTER
SCENARIO...WE ARE RATHER STARVED FOR MOISTURE...AND AM COMFORTABLE
WITH A DRY FORECAST. REGARDLESS...ALL MODELS ARE INCLINED TO CLOSE
OFF A 500MB HIGH OVER THE CENTRAL/EASTERN LAKES LATE IN THE
WEEK...RESULTING IN DRY AND EVEN WARMER WX BY FRIDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 216 PM EDT SAT SEP 20 2014

CONVECTION APPEARS TO BE TAKING OFF ONCE AGAIN ACROSS NRN LOWER
MICHIGAN AND WILL IMPACT THE TERMINAL SITES AT VARIOUS TIMES
HEADING INTO THE EVENING. MEANWHILE...LOWER MVFR CLOUD COVER WILL
OVERSPREAD NRN LOWER MICHIGAN OVER THE NEXT FEW HOURS. COLD FRONT
SWINGS DOWN THROUGH NRN LOWER MICHIGAN THIS EVENING AND WILL TURN
WINDS INTO THE NORTH OVERNIGHT. BEHIND THE FRONT...CIGS WILL
REMAIN MVFR THROUGH THE NIGHT INTO SATURDAY MORNING.

&&

.MARINE...
ISSUED AT 247 AM EDT SAT SEP 20 2014

GUSTY SOUTHWEST WINDS VIA STRONG LOW LEVEL JET
SUPPORT/APPROACHING COLD FRONT EXPECTED TO SLOWLY SUBSIDE HEADING
THROUGH LATER THIS MORNING AND AFTERNOON...ESPECIALLY ACROSS CURRENT
GALE AREAS OF NORTHERN LAKE MICHIGAN. INHERITED GALES END AT
12Z...AND WILL SIMPLY LET THEM RUN THEIR COURSE. PLETHORA OF SCA/S
ELSEWHERE THROUGH TODAY. WINDS REALLY SUBSIDE TONIGHT AS THEY VEER
WEST TO NORTHWEST...ENDING ALL HEADLINES. BREAK LIKELY TO BE
SHORT-LIVED...WITH GUSTY NORTHWEST WINDS DEVELOPING ONCE AGAIN
SUNDAY...LIKELY NECESSITATING THE NEED FOR ADDITIONAL SCA/S FOR AT
LEAST SOME OF THE BIG WATERS.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LHZ345-348-
     349.
     SMALL CRAFT ADVISORY FROM 8 AM SUNDAY TO 2 AM EDT MONDAY FOR
     LHZ347>349.
LM...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LMZ323-341-
     342-344>346.
     SMALL CRAFT ADVISORY FROM 8 AM SUNDAY TO 2 AM EDT MONDAY FOR
     LMZ323-342-344>346.
LS...SMALL CRAFT ADVISORY FROM 8 AM SUNDAY TO 2 AM EDT MONDAY FOR
     LSZ321.

&&

$$

UPDATE...ADAM
SYNOPSIS...JZ
SHORT TERM...MSB
LONG TERM...JZ
AVIATION...ADAM
MARINE...MSB







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