Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 250731
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
331 AM EDT MON AUG 25 2014

.SYNOPSIS...
ISSUED AT 329 AM EDT MON AUG 25 2014

A COLD FRONT WILL MARCH ACROSS NORTHERN MICHIGAN TONIGHT INTO
TUESDAY MORNING. WE WILL SEE THE WARMEST DAY OF THE WEEK JUST AHEAD
OF THE FRONT TODAY. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE UNTIL
THE FRONT HAS GONE THROUGH. COOLER AND LESS HUMID AIR WILL SETTLE IN
FOR THE REST OF WORK WEEK...THOUGH RAIN CHANCES WILL RETURN BY
FRIDAY.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 329 AM EDT MON AUG 25 2014

HIGH IMPACT WEATHER POTENTIAL: MARGINAL THUNDERSTORMS

PRIMARY FORECAST CHALLENGES: DO THE THUNDERSTORMS HOLD TOGETHER TO
PRODUCE DECENT RAIN?

CURRENTLY, A SFC TROUGH ALONG THE LEADING EDGE OF 50 KNOT 500 MB
SPEEDMAX HAS KICKED OFF A LINE OF THUNDERSTORMS IN E UPPER AND NW
WISCONSIN. THE SFC TROUGH EXTENDS SW TO KANSAS WITH MORE
THUNDERSTORMS ALONG THE BOUNDARY IN IOWA. THE NORTH END OF THE SFC
TROUGH IS ANCHORED TO THE SFC LOW THAT IS ALONG THE MANITOBA/NORTH
DAKOTA BORDER WHICH IS NOW BEGINNING TO FILL A BIT AS THE 500 MB LOW
BEGINS TO LIFT OVER TOP OF THE SFC LOW.

TODAY...AS WAS POINTED OUT IN THE FORECAST CONCERN, WILL THESE
THUNDERSTORMS HOLD TOGETHER ENOUGH FOR A SUSTAINED RAIN? IT LOOKS
LIKE THAT THE MODELS AGREE THAT E UPPER COULD GET THIS AS THE 500 MB
SPEEDMAX AND DIFLUENT AXIS ENDS UP OVER E UPPER BY THE AFTERNOON. SO
HAVE THE POPS INCREASING THERE ESPECIALLY. THE PROBLEM HOWEVER, WITH
THE 500 MB LOW HOLDING NEAR LAKE WINNIPEG AND THE SFC LOW MOVING TO
JAMES BAY AND THE OTHER SFC LOW IN W KANSAS WE HAVE A TENDENCY TO
GET INTO A ZONE WHERE THE FORCING BETWEEN THE TWO IS WEAK, AND THE
BETTER THUNDER/RAIN TENDS TO BE NORTH AND SOUTH OF THE UPPER GREAT
LAKES. THE MODELS, ESPECIALLY THE ECMWF SUGGEST THIS. SO THE PROBLEM
THAT COULD CREEP IN, IS THAT THE MAIN FORCING WILL GO NORTH, AND THE
RAIN WITH IT, LEAVING ONLY SCATTERED SHOWERS AND MAYBE A
THUNDERSTORM.

ONE THING TO POINT OUT IS THAT IF THE THUNDERSTORMS CAN HOLD
TOGETHER THIS AFTERNOON, THERE IS A SMALL CHANCE THAT THEY COULD
APPROACH SEVERE LIMITS AS SPC HAS POINTED OUT WITH THE WIND PROFILES
MORE FAVORABLE WITH THE 0-6KM BULK SHEAR VALUES BETWEEN 30 AND 40
KNOTS, ESPECIALLY IN E UPPER.

TONIGHT...THE TREND OF THE DIVIDED ENERGY CONTINUES THROUGH THE
NIGHT, AND WITH THE LACK OF INSTABILITY COULD CAUSE THE RAIN TO
STOP, SO HAVE THE POPS SETTLING DOWN OVERNIGHT. THE ONLY THING THAT
COULD CREATE SOME RAIN IS THE COLD FRONT. THE MODELS HAVE A PRETTY
WELL DEFINED TEMPERATURE GRADIENT THAT STARTS IN E UPPER AROUND 00Z
AND IS INTO N LOWER BY 12Z. THE GFS AND NAM SUGGEST THAT THIS COULD
KICK OF MORE SHOWERS AS A 500 MB SHORTWAVE TROUGH MOVES THROUGH LAKE
SUPERIOR. MAYBE. THERE IS A PRETTY DECENT RIBBON OF DRY AIR JUST
BEHIND THE FRONT AT 850 MB, THAT EXTENDS INTO THE 700-500 MB LAYER.
SO AM FAVORING THE ECMWF EVOLUTION OF THINGS, RATHER THAN THE WET
GFS.

&&

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 329 AM EDT MON AUG 25 2014

...WARM AND STICKY MONDAY BEFORE COOLING OFF SOME...

MUCH BETTER AGREEMENT SEEN IN THE MODELS TODAY. IN THE WAKE OF THE
UPPER LOW EJECTING ACROSS FAR NORTHERN ONTARIO TODAY AND TONIGHT...A
NORTHERN STREAM SHORTWAVE WILL DIG INTO THE NORTHERN LAKES WEDNESDAY
MORNING. THIS WILL GIVE EXTRA IMPETUS TO THE TRAILING SURFACE COLD
FRONT...WHICH WILL EXIT NORTHERN MI TUESDAY AND EVENTUALLY REACH THE
OHIO VALLEY. HIGH PRESSURE BUILDS INTO THE UPPER MS VALLEY/WESTERN
LAKES BEHIND IT. THE NEXT UPPER TROF WILL STILL BE SOUTH IN THE
CENTRAL ROCKIES BY THURSDAY MORNING. OUTSIDE OF PRECIP CHANCES
TUESDAY ASSOCIATED WITH FROPA...THE MID-WEEK PERIOD IS LOOKING
DRYER.

TUESDAY...IMPRESSIVE THERMAL GRADIENT ACROSS THE STATE...WITH 850MB
TEMPS AROUND 19C OVER SAGINAW BAY AT 12Z...BUT DROPPING TO AROUND 4C
NEAR COPPER HARBOR. THE COLD FRONT WILL REACH SAGINAW BAY BY OR JUST
AFTER 18Z. OBVIOUSLY...THAT DOESN/T ALLOW MUCH TIME TO DESTABILIZE.
THERE/S PROBABLY A BETTER CHANCE OF NOCTURNAL CONVECTION LINGERING
INTO MORNING IN NORTHERN LOWER...THAN THERE IS OF REFIRING
CONVECTION HERE BEFORE THE FRONT EXITS. BUT WHICHEVER WAY IT
GOES...WILL HAVE A MORNING CHANCE FOR SHRA/PERHAPS A TSRA OVER THE
SE 1/2 OF THE FORECAST AREA. WILL GO DRY AFTER 18Z. MID-LEVEL DRY
SLOT WILL OVERSPREAD EASTERN UPPER TOWARD MIDDAY...AND NORTHERN
LOWER DURING THE AFTERNOON...OPENING THE DOOR FOR MORE SUNSHINE AS
THE DAY. MAX TEMPS WILL RANGE WIDELY...FROM AROUND 70F IN EASTERN
UPPER TO THE MID 80S IN THE SE.

TUE NIGHT/WED...COLD FRONT SETTLES TO OUR SOUTH...WHILE HIGH
PRESSURE SLOWLY BUILDS IN FROM THE WEST. THE 850MB THERMAL GRADIENT
DOES REMAIN QUITE TIGHT ACROSS MI...AND WE MIGHT BE PRONE TO E-W
ORIENTED FGEN BANDING WHEN RETURN FLOW GETS GOING TO OUR SW. THE
CHANCE FOR GENERATING PRECIP THIS FAR NORTH LATE TUE NIGHT/WED
MORNING (BETWEEN MID-LEVEL DRY PUNCHES) SEEMS TOO SMALL TO INCLUDE
IN THE FORECAST IN THIS POINT...BUT IT ISN/T QUITE ZERO EITHER. WE
CERTAINLY WILL SEE INCREASING MID/HIGH CLOUDS TUE NIGHT INTO THE
VERY START OF WED...BUT WITH CONSIDERABLE CLEARING TO FOLLOW DURING
THE DAY. MIN TEMPS WILL BE MAINLY WITHIN A FEW DEGREES OF 50F...WITH
MAX TEMPS IN THE MID 60S TO LOWER 70S.

REST OF THE FORECAST...OUR NEXT CHANCE FOR PRECIP WILL WAIT UNTIL
RETURN FLOW GETS GOING AHEAD OF AN UPPER TROF EMERGING FROM THE
CENTRAL ROCKIES. THE DISPOSITION OF THIS TROF GETS A LITTLE DICEY BY
THE END OF THE WORK WEEK AND ESPECIALLY THE WEEKEND. BOTH MODELS
TEND TO SPLIT THIS TROF INTO NORTHERN AND SOUTHERN SEGMENTS...WITH
THE GFS EMPHASIZING THE SOUTHERN PORTION AS IT HEADS TOWARD THE
LOWER MS VALLEY...AND THE ECMWF THE NORTHERN PORTION AS IT HEADS
TOWARD US. NO NEED TO GET FANCY AT THIS POINT...THE FORECAST WILL
PORTRAY INCREASING CHANCES FOR PRECIP FROM SOUTH TO NORTH FROM THU
INTO SAT. TEMPS WILL REMAIN SOMEWHAT COOLER THAN NORMAL...THOUGH
GETTING A LITTLE CLOSER TO CLIMO AS WE MOVE INTO THE WEEKEND.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1144 PM EDT SUN AUG 24 2014

LOW STRATUS...AREAS OF FOG AND MVFR/IFR CONDITIONS WILL CONTINUE
TO DEVELOP OVERNIGHT...ESPECIALLY AROUND PLN AND APN THANKS TO
ESE FLOW OFF OF LAKE HURON. WINDS WILL SWITCH TO THE SOUTH ON
DURING THE DAY AND LOW CIGS/FOG WILL MIX OUT WITH DIURNAL HEATING
AND STRENGTHENING SOUTHERLY FLOW. SMALL CHANCES OF SHOWERS AND
STORMS WILL BEGIN TO ENTER THE FORECAST PICTURE FROM WEST TO EAST
THROUGHOUT THE DAY...BUT THE CHANCES ARE TOO SMALL TO INCLUDE IN
THE TAF FOR NOW.


&&

.MARINE...
ISSUED AT 329 AM EDT MON AUG 25 2014

TODAY AND TONIGHT WILL FEATURE INCREASING WINDS VEERING
MORE TO THE WEST OVER THE NEXT 24 HOURS. AS THEY DO THE WAVES WILL
BUILD A BIT, BUT AT THIS TIME IT DOESN`T LOOK LIKE WE`LL NEED SMALL
CRAFT ADVISORIES. TUESDAY AND TUESDAY NIGHT THE WINDS VEER TO THE NW
AND HOLD FOR A WHILE. WHILE THERE`S NO INCREASE IN STRENGTH, IT DOES
LOOK LIKE THAT THE WINDS WILL BE HIGH ENOUGH THAT OUR NW FLOW
REGIONS COULD HAVE WAVES THAT ARE 2 TO 4 FEET, JUST BELOW SMALL
CRAFT CONDITIONS. THE OUTLOOK FOR WEDNESDAY IS THAT WINDS AND WAVES
INCREASE ENOUGH TO POSSIBLY WARRANT SMALL CRAFT HEADLINES.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.

&&

$$

SYNOPSIS...JZ
SHORT TERM...JL
LONG TERM...JZ
AVIATION...MR
MARINE...JL






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