Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 292002
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
402 PM EDT TUE JUL 29 2014

.SYNOPSIS...
ISSUED AT 402 PM EDT TUE JUL 29 2014

SEVERAL WEAK UPPER LEVEL DISTURBANCES ROTATING ACROSS THE REGION
THIS WEEK WILL BRING PERIODIC CHANCES FOR SHOWERS AND A FEW
THUNDERSTORMS...ESPECIALLY DURING THE AFTERNOON HOURS. DESPITE A
SLOW MODERATION...TEMPERATURES WILL REMAIN BELOW NORMAL INTO THE
START OF THE WEEKEND.

&&

.SHORT TERM...(THIS EVENING THROUGH TONIGHT)
ISSUED AT 402 PM EDT TUE JUL 29 2014

...SCATTERED THUNDERSTORMS DIMINISHING BY SUNSET...

CURRENTLY, RADAR IS BEGINNING TO BECOME A BIT MORE ACTIVE AS
SHOWERS, AND SOME ISOLATED THUNDERSTORMS ARE SHOWING UP ON KAPX
RADAR. THIS IS DUE TO THE INSTABILITY AXIS AND A 500 MB JET STREAK
THAT IS BEGINNING TO NOSE INTO THE UPPER GREAT LAKES. THE JET STREAK
IS ROTATING ABOUT THE 500 MB LOW THAT HAS BEEN RETROGRADING TO A
POINT OVER JAMES BAY THIS AFTERNOON.

TONIGHT...AS THIS JET STREAK ROTATES ABOUT THE LOW, AND WITH THE
LOSS OF DIURNAL HEATING, WILL EXPECT THE POPCORN TYPE CONVECTION TO
END AROUND 23Z. AT THIS POINT IT LOOKS LIKE THE MAIN AREAS OF
CONCERN ARE IN NE LOWER AND SOME LOCATIONS IN NW LOWER ALONG AND
SOUTH OF M-72 AND EAST I-75. LOOKING AT THE VISIBLE SATELLITE IMAGE,
IT LOOKS LIKE THE MARINE LAYER HAS PUSHED INTO MOST OF NW LOWER BY
10-15 MILES. THIS SHOULD KEEP THE MAJORITY OF THE RAIN SHOWERS OUT
OF COASTAL LOCATIONS LIKE TVC, FKS, AND MBL. ONCE THE HEATING IS
GONE, THE SHOWERS WILL DIMINISH LEAVING ONLY AN ISOLATED THREAT
FROM THE 500 MB JET STREAK. THE CHANCES ARE ONLY ISOLATE, ONLY
BECAUSE THE 700-500 MB RH FALLS TO LESS THAN 30% BY 06Z, AND THERE
IS SOME SUGGESTION THAT THE 850 MB RH FALLS A BIT AS WELL. THIS
SEEMS TO GO ALONG WITH SFC TROUGH THAT SHARPENS UP SOUTH OF THE
FORECAST AREA IN S LOWER. SO OVERNIGHT IS EXPECTED TO BE DRY.

&&

.LONG TERM...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 402 PM EDT TUE JUL 29 2014

...VARYING SHOWER CHANCES WITHIN COOL AIR MASS THROUGH MIDWEEK...

HIGH IMPACT WEATHER POTENTIAL: MINIMAL.

PATTERN SYNOPSIS/FORECAST: ANOMALOUSLY AMPLIFIED PATTERN FOR LATE
JULY PATTERN...DEEP TROUGHS OVER EASTERN NORTH AMERICA (3+ STANDARD
DEVIATIONS BELOW THE MEAN) AND THE NORTHEAST PACIFIC.  RIDGING IN
BETWEEN ACROSS WESTERN NORTH AMERICA WHERE THE HEAT HAS RETURNED TO
THE PACIFIC NORTHWEST.  BUT WATER VAPOR IMAGERY DOES SHOW A WELL
DEFINED CIRCULATION CAUGHT WITHIN THE UPPER RIDGE OVER THE GREAT
BASIN.  DEEP LAYER CYCLONIC FLOW EXISTS ACROSS THE UPPER GREAT
LAKES...WITH SEVERAL VORTICITY CENTERS SPINNING ACROSS NORTHERN
ONTARIO.  SURFACE LOW PRESSURE OVER ATLANTIC CANADA WITH SEVERAL
TROUGHS ROTATING AROUND THE BACK SIDE OF THIS LOW OVER NORTHWEST
ONTARIO AND GREAT LAKES.  SURFACE HIGH PRESSURE RIDGE STRETCHED FROM
THE PRAIRIE PROVINCES SOUTHEAST INTO THE CENTRAL PLAINS/MIDWEST.

LARGE SCALE PATTERN WILL BE SOMEWHAT INTRANSIGENT THROUGH THE
REMAINDER OF THIS WEEK AS EASTERN NORTH AMERICAN TROUGH/CANADIAN
UPPER LOW HANGS TOUGH...THOUGH MAGNITUDE OF TROUGHING EXPECTED TO
SLOWLY MODERATE BY THE WEEKEND.  VORTICITY CENTER ROTATING BACK TO
THE WEST ACROSS HUDSON BAY THIS AFTERNOON WILL EVENTUALLY CIRCULATE
AROUND AND ACROSS NORTHERN MICHIGAN WEDNESDAY.  THERMAL TROUGHING
BEGINS TO RELAX HEADING INTO THE WEEKEND...WITH NO REAL SIGNIFICANT
FEATURES OUT THERE UNTIL A SHORT WAVE PASSAGE ON SATURDAY.

PRIMARY FORECAST CONCERNS (NEAR TERM): VARYING PRECIPITATION CHANCES
WITH PERSISTENT CYCLONIC FLOW ACROSS MICHIGAN.

NEAR TERM (WEDNESDAY/THURSDAY):  INTERESTING FORECAST FOR WEDNESDAY
WITH A STRONG PIECE OF ENERGY DROPPING SOUTH OUT OF NORTHERN ONTARIO
AND INTO NORTHERN MICHIGAN BY EVENING...ALONG WITH ATTENDANT MID
LEVEL COOLING.  BUT THE BIG QUESTION IS GIVEN COOLING ALOFT...WILL
THERE BE ENOUGH LOW LEVEL MOISTURE TO SUPPORT SHOWER DEVELOPMENT?
FORECAST SOUNDINGS ARE PRETTY MARGINAL ON THIS IDEA...WITH
INDICATIONS THAT DEW POINTS WILL MIX DOWN INTO THE 40S (SUPPORTED BY
UPSTREAM DEW POINTS THIS AFTERNOON).  A LITTLE NERVOUS ABOUT GOING
TOTALLY DRY IN THIS SYNOPTIC SETUP...BUT CAN MOSTLY JUSTIFY IT
PROVIDED DEW POINTS DO MIX OUT.  IF SURFACE DEW POINTS REMAIN IN THE
LOWER 50S THEN ALL BETS ARE OFF.  HOWEVER...WILL STILL HAVE SOME
MENTION FOR SHOWER POTENTIAL FOCUSED ALONG THE EASTERN UPPER AND
NORTHEAST LOWER LAKE BREEZE BOUNDARIES DURING THE AFTERNOON WHERE
LOW LEVEL MOISTURE POOLING WILL BE POSSIBLE.  ANOTHER POSSIBILITY IS
THAT AS SHORT WAVE DROPS INTO UPPER MICHIGAN DURING THE EVENING...IT
MAY DRAG UPSTREAM SHOWER REMNANTS INTO THE FORECAST AREA AS WELL
THOUGH THIS WILL LIKELY BE MORE OF A WEDNESDAY EVENING ISSUE.
GUIDANCE QPF FIELDS NOT THRILLED WITH THIS IDEA BUT THE MASS FIELDS
DO SUPPORT THE POTENTIAL.

DEEP LAYER CYCLONIC FLOW CONTINUES THURSDAY...AND WHILE MID LEVEL
TEMPERATURES MAY WARM A LITTLE COOL AIR STILL LINGERS IN LOWER
LAYERS.  THERE IS ALSO BETTER MOISTURE MID/UPPER LEVEL MOISTURE
WRAPPING AROUND THE MAIN CIRCULATION AND INTO MICHIGAN FROM THE
NORTHWEST...BUT LOW LEVEL MOISTURE (IN AN ABSOLUTE SENSE) NOT
EXPECTED TO IMPROVE MUCH FROM WEDNESDAY (DEW POINTS PROBABLY IN THE
40S-AROUND 50).  THIS COMBINED WITH WARMING MID LEVEL TEMPERATURES
(E.G., 500MB TEMPERATURES AROUND 6C WARMER) WILL MAKE GENERATING
INSTABILITY DIFFICULT (PROBABLY MORE DIFFICULT THAN WEDNESDAY
AFTERNOON).  THERE IS A SECONDARY PIECE OF ENERGY THAT WILL MOSTLY
SIDESWIPE THE FORECAST AREA TO THE EAST...AND SOME INDICATIONS OF A
WEAK BOUNDARY ASSOCIATED WITH THIS THAT SLIPS INTO NORTHERN MICHIGAN
DURING THE DAY.  THINKING THAT THIS SHORT WAVE TROUGH MAY BE THE
BEST CHANCE FOR PRECIPITATION THURSDAY AS IT BRINGS SOME SHOWERS TO
EASTERN UPPER/NORTHEAST LOWER STARTING THURSDAY MORNING...THEN WILL
TRY TO DRY THINGS OUT FOR THURSDAY NIGHT.

MEDIUM RANGE (FRIDAY/SATURDAY/SUNDAY): COOL UPPER LEVEL CYCLONIC
FLOW CONTINUES FRIDAY...SO WILL STILL BE CONTINUING WITH THE
POSSIBILITY OF MOSTLY DIURNALLY DRIVEN SHOWERS THOUGH LIKE THE NEAR
TERM PERIODS LOW LEVEL MOISTURE WILL REMAIN A QUESTION.  LOOKING AT
ANOTHER SHORT WAVE TROUGH PASSAGE IN THE SATURDAY TIME FRAME...AND
ATTENDANT SHOWER CHANCES.  WEAK HIGH PRESSURE SHOULD BE IN PLACE FOR
SUNDAY SO LOOKING DRIER TO END THE WEEKEND.

OUTLOOK (MONDAY/TUESDAY): POSSIBLE RAIN CHANCES MONDAY WITH SHORT
WAVE/COLD FRONT PASSAGE.  WILL START TUESDAY DRY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 116 PM EDT TUE JUL 29 2014

MAIN CONCERN FOR THE AFTERNOON, IS THE CHANCE FOR THUNDERSTORMS.
AT THIS POINT AS AN UPPER LEVEL DISTURBANCE DROPS INTO THE UPPER
GREAT LAKES, IT LOOKS LIKE THE STRATUS/STRATOCU HAS BEEN KEEPING A
LID ON THE TEMPERATURES, AND THE INSTABILITY. THUNDERSTORMS IN W
UPPER HAVE BEEN FALLING APART BY THE TIME THEY GET TO LAKE
MICHIGAN AND THEN QUICKLY DIMINISH. SO WILL LEAVE THE VICINITY
SHOWERS IN TVC AND MBL. THE AIR UPSTREAM OF PLN LOOKS RATHER
STABLE AT THIS POINT, SO WILL LEAVE THE PRECIPITATION OUT. THAT
LEAVES APN, WHERE THERE HAVE BEEN SOME BREAKS IN THE CLOUDS AND IT
IS BEGINNING TO LOOK LIKE SOME CLOUDS UPSTREAM ARE ORGANIZING INTO
SOME SHOWERS. SO HAVE PULLED THE VCTS BACK TO VCSH FOR NOW AND SEE
HOW THE AFTERNOON EVOLVES.

&&

.MARINE...
ISSUED AT 402 PM EDT TUE JUL 29 2014

OVERALL PRESSURE GRADIENT WILL BE PRETTY LAX THROUGH THURSDAY...AND
LARGE SCALE PATTERN NOT SUPPORTIVE OF MANY MARINE ISSUES IN THE NEAR
TERM.  LAKE BREEZE/ONSHORE WIND COMPONENTS EXPECTED TO SET UP WITHIN
MOST NEARSHORE ZONES WEDNESDAY.

&&

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

&&

$$

SYNOPSIS...KB
SHORT TERM...JSL
LONG TERM...JPB
AVIATION...JSL
MARINE...JPB





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