Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 171742
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
142 PM EDT WED SEP 17 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 217 AM EDT WED SEP 17 2014

A WEAKENING AREA OF HIGH PRESSURE OVER THE OHIO VALLEY WILL KEEP
THE WEATHER HERE IN SOUTHERN MICHIGAN DRY THROUGH TODAY.  A WEAK
COLD FRONT WILL SLIP SOUTHWARD THROUGH THE REGION TONIGHT. A HIGH
PRESSURE SYSTEM WILL STRENGTHEN AS IT DROPS SOUTHWARD FROM ONTARIO
ON THURSDAY. THIS FAIR WEATHER SYSTEM WILL KEEP CONDITIONS DRY AND
COOL INTO FRIDAY. SOME FROST WILL BE POSSIBLE FOR EARLY FRIDAY MORNING.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 217 AM EDT WED SEP 17 2014

THE MAIN CHALLENGES IN THE SHORT TERM DEAL WITH THE PRECIPITATION
POTENTIAL TONIGHT WITH THE COLD FRONTAL PASSAGE AND ALSO THE FROST
RISK THU NIGHT.

OVERALL THE RISK FOR PRECIPITATION LOOKS LOW TONIGHT. THE MOISTURE
REMAINS BELOW THE DGZ AND VERY LITTLE IN THE WAY OF LIFT IS SEEN.
WE WILL SEE A WIND SHIFT ALONG THE THE ARRIVAL OF SOME CLOUDS
MAINLY BELOW 5000 FT. THOSE CLOUDS WILL LINGER INTO THU. IF ANY
PRECIPITATION DOES FALL OUT OF THESE CLOUDS...IT WILL BE DRIZZLE.

A STRONGER HIGH PRESSURE SYSTEM MOVES IN FROM THE NORTH THU INTO
THU NIGHT. AFTER A COOL DAY WITH SOME CLOUDS THE SKIES WILL CLEAR
OUT SUPPORTING BETTER RADIATIONAL COOLING ESPECIALLY AS THE
PRESSURE GRADIENT WEAKENS. TEMPERATURES UNDER THIS HIGH IN MANITOBA ARE
IN THE 20S RIGHT NOW. GUIDANCE FOR THU NIGHT HERE IN MI ARE
GENERALLY IN THE LOW 40S. IT APPEARS THAT THE MODELS ARE TOO WARM
WITH THE TEMPERATURES THU NIGHT. THIS FORECAST REFLECTS MUCH LOWER
VALUES AND THE POSSIBILITY OF FROST HAS BEEN EXPANDED. WE MAY NEED
HEADLINES FOR PARTS OF SOUTHWEST LOWER MI THU NIGHT FOR FROST.

AFTER A COOL START FRIDAY...TEMPERATURES WILL START TO REBOUND AS
A SOUTH TO SOUTHWEST FLOW DEVELOPS.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 217 AM EDT WED SEP 17 2014

UNSEASONABLY WARM WEATHER IS ANTICIPATED FRIDAY NIGHT AND SATURDAY
IN STRONG SW FLOW WAA IN ADVANCE OF APPROACHING LOW PRESSURE AND THE
COLD FRONT. SCATTERED SHOWERS AND THUNDERSTORMS ARE ANTICIPATED IN
THE WAA PATTERN FRIDAY NIGHT AND FORCING FROM THE APPROACHING COLD
FRONT WILL BRING POTENTIAL FOR SOME TSTORMS SATURDAY THROUGH
SATURDAY NIGHT. TEMPS WILL AVERAGE AROUND TEN DEGREES ABOVE NORMAL
FOR THIS TIME OF YEAR FRIDAY NIGHT THROUGH SATURDAY.

A SIGNIFICANTLY COOLER AIRMASS WILL MOVE IN BEHIND THE FRONT
BEGINNING SUNDAY AND ESPECIALLY FOR MONDAY AND TUESDAY WHEN TEMPS
WILL LIKELY AVERAGE AROUND 5 TO 10 DEGREES BELOW NORMAL. MAX TEMPS
BY NEXT MON/TUE WILL STRUGGLE TO REACH THE UPPER 50S TO LOWER 60S
WITH MIN TEMPS GENERALLY RANGING FROM THE MIDDLE TO UPPER 30S UP
NORTH TO THE MIDDLE 40S SOUTH.

WE WILL MAINTAIN A DRY FCST FOR NOW FOR EARLY NEXT WEEK. HOWEVER IF
MORE AMPLIFIED MEDIUM RANGE GUIDANCE SOLUTIONS VERIFY THAT FEATURE
CYCLONIC FLOW... UPPER LEVEL TROUGHING AND H8 TEMPS DOWN AROUND 0 C
THEN THERE WOULD BE POTENTIAL FOR LAKE EFFECT SHOWERS NEXT MON/TUE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 143 PM EDT WED SEP 17 2014

VFR CONDITIONS ARE EXPECTED TO CONTINUE THIS AFTERNOON INTO
TONIGHT. HOWEVER THE PASSAGE OF A SFC COLD FRONT FROM NORTH TO
SOUTH VERY LATE TONIGHT AND EARLY THURSDAY MORNING WILL BRING A
FEW HOURS OF MVFR AND POSSIBLY IFR CIGS FROM ROUGHLY 10Z TO 16Z
THURSDAY.

THE HIGHEST CONFIDENCE FOR LOWER IFR/MVFR CIGS EXISTS AT LAN AND
JXN... WITH LESSER POTENTIAL/CONFIDENCE FARTHER WEST AND SOUTH AT
THE GRR/MKG/AZO/BTL TERMINALS. CIGS SHOULD IMPROVE AGAIN TO VFR BY
18Z THURSDAY AS THE BAND OF STRATUS BEHIND THE COLD FRONT LIFTS
AND BEGINS TO SCATTER OUT.

WEST SFC WINDS OF 10 KTS OR LESS WILL BECOME NORTHEASTERLY BEHIND
THE SFC COLD FRONT AFTER 09Z THURSDAY AND REMAIN 10KTS OR LESS.

&&

.MARINE...
ISSUED AT 217 AM EDT WED SEP 17 2014

WINDS AND WAVES COULD BECOME HAZARDOUS TO SMALL CRAFT LATE TONIGHT
MAINLY FOR THE LITTLE AND BIG SABLE POINT REGION. INCREASING
NORTHEAST FLOW BEHIND A SOUTHWARD SINKING FRONT MAY LEAD TO THESE
CONDITIONS. NOT CONFIDENT ENOUGH TO GO WITH A HEADLINE YET AS THE
SETUP IS MARGINAL AT THIS POINT.


&&

.HYDROLOGY...
ISSUED AT 217 AM EDT WED SEP 17 2014

NO MAJOR CHANGES TO THE RIVER LEVELS ARE EXPECTED THROUGH THE END
OF THE WEEK. WE WILL NEED TO MONITOR THE WEEKEND SYSTEM CLOSELY
WITH THE POSSIBILITY OF SOME HEAVIER RAIN IN PLACES.

&&

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

$$

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






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