Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 181312
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
912 AM EDT THU SEP 18 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 246 AM EDT THU SEP 18 2014

A WEAK COLD FRONT WILL SLIP SOUTHWARD THROUGH LOWER MICHIGAN THIS
MORNING. HIGH PRESSURE WILL BUILD IN FROM THE NORTH BEHIND THIS
SYSTEM DRAWING DOWN A COOLER AIRMASS. THIS HIGH WILL THEN TRACK
EASTWARD TO NEW ENGLAND ON FRIDAY. SOUTHWEST WINDS AROUND THIS
SYSTEM WILL DRAW UP A MILDER AIRMASS FROM THE CENTRAL PLAINS FOR
FRIDAY AND SATURDAY. UNSETTLED WEATHER WILL ARRIVE OVER THE
WEEKEND AS A COLD FRONT TRACKS IN FROM THE WEST.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 246 AM EDT THU SEP 18 2014

THE MAIN CHALLENGES IN THE SHORT TERM DEAL WITH THE POTENTIAL FOR
SHOWERS WITH THE COLD FRONT SLIPPING DOWN FROM THE NORTH
TODAY...AND ALSO THE SEVERE WEATHER POTENTIAL FOR SATURDAY.

STILL LOOKS LIKE THE COLD FRONT SLIPPING SOUTHWARD THROUGH LOWER
MICHIGAN WILL END UP AS A DRY FRONTAL PASSAGE. THE MOISTURE WILL
MOSTLY BE CONFINED TO THE LOW LEVELS...AND LIFT WILL BE
WEAK...THUS THE LOW RISK FOR RAIN. CLOUDS WILL THICKEN UP ACROSS
MY NORTHERN COUNTIES AS THIS FRONT MOVES IN...BUT AS THE FRONT
WEAKENS OVER THE AREA TODAY...THE CLOUDS WILL ALSO DIMINISH. AS A
RESULT SOUTHERN COUNTIES ALONG INTERSTATE 94 COULD STAY MOSTLY TO
PARTLY SUNNY THROUGH THE DAY.

WILL NEED TO MONITOR THE SEVERE POTENTIAL FOR SATURDAY. LATEST
TRENDS FROM THE HIGH RES EURO SHOW STRENGTHENING DEEP LAYER SHEAR
VALUES OF 40 TO 60 KNOTS AND DECENT INSTABILITY WITH LIFTED INDEX
VALUES DOWN TO -6 DEG C. NOT ALL MODELS ARE IN AGREEMENT ON THIS
SCENARIO SO CONFIDENCE IS NOT THAT HIGH ON THE OCCURRENCE OF
SEVERE STORMS. WILL KEEP THE HIGH POPS GOING AND MENTION THE RISK
IN THE HAZARDOUS WEATHER OUTLOOK.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 246 AM EDT THU SEP 18 2014

THE COLD FRONT WILL BRING POTENTIAL FOR A FEW THUNDERSTORMS SATURDAY
EVENING AND LINGERING SHOWERS OVERNIGHT INTO SUNDAY. A COOLER
AIRMASS WILL MOVE IN BEHIND THE FRONT SUNDAY INTO EARLY NEXT WEEK.
HOWEVER IT IS NOTED THAT OVERALL MEDIUM RANGE GUIDANCE TRENDS ARE
MILDER FOR EARLY NEXT WEEK.

TEMPS MONDAY WILL AVERAGE AROUND 5 TO 10 DEGREES BELOW NORMAL BUT
TEMPS SHOULD RECOVER QUICKLY TO NEAR NORMAL FOR TUE/WED. DRY WEATHER
IS ANTICIPATED DURING THE EARLY TO MIDDLE PORTION OF NEXT WEEK AS A
LARGE SURFACE HIGH PRESSURE RIDGE BUILDS IN.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 912 AM EDT THU SEP 18 2014

EXTENDED THE TEMPO GROUP FOR IFR AT LAN TO 15Z AS LATEST SATELLITE
IMAGES SHOW AREA OF FOG APPROACHING. MEANWHILE...JXN HAS GONE VFR
AS THE FOG THERE HAS SHIFTED EAST AND MAY AFFECT BTL AND RMY. THE
LIFR AT GRR SHOULD GRADUALLY IMPROVE AS THE COLD FRONT COMES IN BY
16Z.

&&

.MARINE...
ISSUED AT 848 AM EDT THU SEP 18 2014

WINDS WILL INCREASE BEHIND A COLD FRONT THIS MORNING ACROSS BIG
AND LITTLE SABLE POINTS BUT SHOULD REMAIN BELOW 25 KNOTS.
THEREFORE THE SMALL CRAFT ADVISORY HAS BEEN CANCELLED. WINDS AND
WAVES ARE EXPECTED TO INCREASE AGAIN LATE TOMORROW AND INTO
SATURDAY.


&&

.HYDROLOGY...
ISSUED AT 246 AM EDT THU SEP 18 2014

RIVER LEVELS WILL REMAIN NEARLY STEADY INTO SATURDAY. THE ARRIVAL
OF A COLD FRONT AND ASSOCIATED SHOWERS AND THUNDERSTORMS WILL LEAD
TO LOCALIZED HEAVY RUNOFF...ESPECIALLY WHERE THE STORMS PERSIST
FOR AN HOUR OR TWO. THIS COULD LEAD TO SOME URBAN AND POOR
DRAINAGE ISSUES...BUT CONSIDERABLE RISES ON AREA RIVERS IS NOT
EXPECTED FROM THIS NEXT FRONTAL PASSAGE.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
&&

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...LAURENS
AVIATION...OSTUNO
HYDROLOGY...MJS
MARINE...OSTUNO






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