Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 161731
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1231 PM EST TUE DEC 16 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 321 AM EST TUE DEC 16 2014

LOW PRESSURE WILL MOVE ACROSS LOWER MICHIGAN TODAY SPREADING RAIN
SHOWERS AS IT GOES. COLDER AIR WILL WRAP INTO THE SYSTEM LATER THIS
EVENING AND THE RAIN WILL MIX WITH AND THEN CHANGE TO LIGHT SNOW.
THIS WILL BEGIN A PERIOD OF NEAR NORMAL TEMPERATURES...ALTHOUGH MUCH
COLDER THAN WHAT WE`VE SEEN LATELY...THAT WILL LAST THROUGH THE
WEEKEND. LIGHT LAKE EFFECT SNOW SHOWERS ARE POSSIBLE WEDNESDAY INTO
THURSDAY WITH LIGHT ACCUMULATIONS POSSIBLE MAINLY WEST OF US-131.

&&

.UPDATE...
ISSUED AT 839 AM EST TUE DEC 16 2014

FOG HAS BECOME DENSE OVER A GOOD PART OF SOUTHWEST LOWER MICHIGAN.
LOOKING AT THE LATEST RAP MODEL DATA...THE LOWEST VISIBILITIES ARE
WHERE THE WINDS ARE CALM...WHICH IS UNDER THE SURFACE LOW. THIS
AREA OF CALM WINDS SHIFTS TO THE EAST NORTHEAST OVER TIME AND BY
16Z IS OVER OUR NORTHEAST CWA....REED CITY TO CLAIR TO NEAR ALMA.
AFTER THAT IT IS GONE. SO I BELIEVE THE FOG AREA WILL PERSIST A
GOOD PART OF THE MORNING BUT ANY ONE LOCATION SHOULD HAVE ONLY 2
TO 3 HOURS OF LOW VISIBILITIES. GIVEN THE SHORT TIME WINDOW FOR
THIS FOG I AS THINKING NOT TO ISSUE A FOG ADVISORY AT THIS POINT.
WE HAVE ALREADY ISSUED A SPECIAL WEATHER STATEMENT ON THE FOG AND
WE WILL CALL THAT GOOD FOR NOW.

OTHERWISE THE ON GOING FORECAST IS GOOD...SHOWERS WILL CONTINUE
THROUGH THE DAY AND CHANGE TO SNOW SHOWERS OVERNIGHT.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 321 AM EST TUE DEC 16 2014

FORECAST CONCERNS DEAL WITH THE EVOLUTION OF THE LOW CURRENTLY
MOVING THROUGH NORTHWEST ILLINOIS.

REGIONAL RADAR AND IR LOOP SHOWS A WELL DEFINED LOW JUST CROSSING
THE MISSISSIPPI. LIGHT RAIN SHOWERS CONTINUE TO PIVOT NORTHWARD FROM
INDIANA AND WE/LL BE LOOKING AT SHOWERS THROUGHOUT THE DAY AS THE
LOW MOVES ACROSS LOWER MICHIGAN. HEAVY RAIN ISN/T ANTICIPATED.
HOWEVER...THERE HAS BEEN SOME LIGHTNING OVER SOUTHERN INDIANA.
MODELS SHOW SOME ELEVATED INSTABILITY DEVELOPING OVER FAR WESTERN
LAKE ERIE THIS MORNING BUT IT PROBABLY TOO FAR AWAY TO RESULT IN
THUNDER IN OUR CWA.

COLDER AIR WILL WRAP INTO THE SYSTEM TONIGHT AND TURN THE LINGERING
PCPN TO LIGHT SNOW SHOWERS. H8 TEMPS FALL TO -12C WEDNESDAY AND THIS
NORMALLY CREATES SUFFICIENT OVER-LAKE INSTABILITY TO GENERATE SNOW
SHOWERS. THE ISSUE THIS TIME THOUGH IS THE SHALLOW MOISTURE. THE
DGZ IS VERY SMALL AND RESIDES AT THE TOP OF THE SHALLOW MOISTURE
AROUND 4K FT. IT/S PROBABLY ENOUGH TO SEE SOME SNOW SHOWERS...AND
LIGHT ACCUMS WEST OF US-131 BUT NOT MUCH MORE THAN THAT. THE SHSN
WILL GRADUALLY DIMINISH WEDNESDAY NIGHT.

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 321 AM EST TUE DEC 16 2014

MORE QUIET WEATHER IS IN STORE IN THE LONG TERM PERIOD AS THE SPLIT
FLOW ALOFT CONTINUES AND SURFACE HIGH PRESSURE DOMINATES. THE POLAR
JET STAYS WELL TO OUR NORTH AND THE SRN STREAM BRANCH REMAINS
SOUTH... SO STILL NO MAJOR WINTER SYSTEMS OR ARCTIC AIR IN OUR
FUTURE.

THE MAIN CONCERN WILL BE CLOUD COVER AS STRATUS/FOG/DRIZZLE COULD BE
AN ISSUE AGAIN UNDER THE SFC HIGH. FOR NOW WILL BE OPTIMISTIC WITH
PARTLY SUNNY WORDING BUT THIS COULD CHANGE IN LATER FORECASTS.
TEMPERATURES ARE FORECAST TO BE NEAR NORMAL WITH HIGHS IN THE LOWER
TO MID 30S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1231 PM EST TUE DEC 16 2014

THE ENTIRE AREA REMAINED UNDER IFR OR LIFR CONDITIONS AS OF 17Z.
EXPECT ONLY A SLOW IMPROVE IN THIS. COLDER AIR AND STRONGER WINDS
WILL ARRIVE EARLY THIS EVENING...AND ALONG WITH THESE FACTORS...
THE IFR SHOULD ALSO IMPROVE INTO THE EVENING. EXPECT THAT MOST OF
THE IFR WILL LIFT TO MVFR AROUND 06Z.

AS THE COLDER AIR CONTINUES TO POUR IN...LAKE EFFECT SNOW SHOWERS
SHOULD DEVELOP LATE TONIGHT/EARLY WEDNESDAY MORNING. THE MEAN LOW
LEVEL FLOW WILL BE 290-300 WHICH FAVORS AZO SEEING THE BEST CHANCE
OF SNOW SHOWERS WITH SOME IFR REDEVELOPING. MKG...GRR...AND BTL
MAY ALSO SEE SOME SNOW SHOWERS INTO WED MORNING.

&&

.MARINE...
ISSUED AT 321 AM EST TUE DEC 16 2014

WINDS WILL INCREASE AS THE LOW MOVES BY THIS AFTERNOON. ISSUED A SCA
TO COVER INCREASED WINDS AND WAVES FROM THIS AFTERNOON THROUGH
THURSDAY MORNING.


&&

.HYDROLOGY...
ISSUED AT 321 AM EST TUE DEC 16 2014

NO HYDRO ISSUES.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL NOON EST THURSDAY FOR LMZ844>849.

&&

$$

UPDATE...WDM
SYNOPSIS...93
SHORT TERM...93
LONG TERM...MEADE
AVIATION...JK
HYDROLOGY...93
MARINE...93






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