Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 221152
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
652 AM EST SAT NOV 22 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 330 AM EST SAT NOV 22 2014

A LOW PRESSURE SYSTEM WILL EMERGE FROM THE PLAINS STATES THIS
WEEKEND AND BRING WARMER AND WET CONDITIONS TO THE AREA. SOME
FREEZING RAIN WILL OCCUR ACROSS THE AREA THIS MORNING AS THE LEADING
EDGE OF THE PRECIPITATION MOVES IN. THE FREEZING RAIN WILL CHANGE
OVER TO RAIN MID MORNING. RAIN WILL CONTINUE THROUGH THE WEEKEND AND
TEMPERATURES WILL WARM WELL INTO THE 40S AND EVEN SOME 50S WILL BE
POSSIBLE.

COLDER AIR WILL MOVE BACK IN ACROSS THE AREA LATER ON MONDAY AND
INTO TUESDAY. PRECIPITATION WILL CHANGE OVER FROM RAIN TO SNOW.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 330 AM EST SAT NOV 22 2014

THE BIGGEST IMPACT WEATHER EXPECTED IN THE SHORT TERM WILL BE THE
FREEZING RAIN THAT IS EXPECTED THIS MORNING. SHOWERS HAVE BEEN
EXPANDING IN COVERAGE ACROSS WI...IL...AND IN THIS MORNING...AND
THEY ARE NOW STARTING TO MAKE THEIR WAY INTO SW LOWER.

P-TYPES WITH THIS PCPN HAVE RANGED FROM RAIN TO FREEZING RAIN
DEPENDING ON THE TEMP. TEMPS ARE COMING UP ACROSS THE CWFA THIS
MORNING...HOWEVER EVERYWHERE AWAY FROM THE LAKESHORE IS STILL BELOW
FREEZING AND DEW POINTS ARE IN THE TEENS. WE WILL SEE SOME EVAP
COOLING TAKE PLACE INITIALLY AS PCPN BEGINS...HELPING THE CAUSE FOR
SOME FREEZING RAIN. SOME SLEET AND SNOW WILL BE POSSIBLE ALSO. THE
ADVECTION OF WARM AIR REMAINS STEADY THIS MORNING...AND ALL SITES
LOOK TO BE ABOVE FREEZING BY NOON TODAY. THE SLICK ROADS MAY LAST A
LITTLE LONGER THAN TEMPS RISING ABOVE FREEZING DUE TO ROAD TEMPS IN
THE MID TO UPPER 20S.

WE WILL SEE THE PCPN DIMINISH SOME THIS AFTERNOON AFTER THE INITIAL
WAVE PASSES BY THE AREA TO THE E/NE. WE WILL SEE ONGOING WARM AND
MOISTURE ADVECTION WHICH WILL HELP TO FORM AREAS OF DRIZZLE TO GO
ALONG WITH RESIDUAL SHOWERS FLOATING THROUGH THE AREA. THIS WILL
ESSENTIALLY CONTINUE THROUGH TONIGHT AND INTO THE FIRST HALF OF SUN.
FOG IS ALSO EXPECTED TO BE PRESENT DUE TO THE SNOW PACK IN PLACE AND
WITH THE COLD GROUND THAT IS PRESENT.

WE WILL SEE THE RAIN PICK UP IN INTENSITY DURING THE AFTERNOON HOURS
ON SUN AND ESPECIALLY ON SUN NIGHT. THIS OCCURS AS THE MAIN UPPER
WAVE FOR OUR AREA WITH THIS SYSTEM THAT IS CURRENTLY ACROSS NRN
MEXICO WILL LIFT UP TOWARD OUR AREA. IT WILL TAP MOISTURE DIRECTLY
FROM THE GULF OF MEXICO AND BRING IT ALL OF THE WAY UP INTO THE
AREA. THE CHCS OF THUNDER ARE NOT ZERO WITH THIS SYSTEM...HOWEVER
THEY DO LOOK QUITE LOW WITH ELEVATED LI/S NOT QUITE GOING BELOW ZERO.

WE WILL SEE THE COLDER AIR SWEEP BACK IN DURING THE DAY ON MON
ACROSS THE AREA. THE SFC LOW WILL MOVE NORTH INTO CANADA...AND WE
WILL SEE THE COLDER AIR ASSOCIATED WITH THE LONG WAVE TROUGH MOVE IN
DURING THE DAY. IT DOES LOOK LIKE IT WILL TAKE UNTIL THE AFTERNOON
ON MON FOR RAIN TO CHANGE OVER TO SNOW FOR THE AREA.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 330 AM EST SAT NOV 22 2014

SLIPPERY TRAVEL IS EXPECTED TO DEVELOP MONDAY NIGHT AND CONTINUE
INTO TUESDAY AS COLD AIR AND LAKE ENHANCED SNOW SHOWERS IMPACT THE
AREA ON THE BACK SIDE OF THE DEPARTING LOW. DEEP MOISTURE AND
CYCLONIC FLOW DURING THIS TIME SHOULD LEAD SOME SNOW
ACCUMULATIONS... WITH THE PROGGED WESTERLY LOW LEVEL FLOW FAVORING
OTTAWA...KENT...ALLEGAN AND BARRY COUNTIES.

SURFACE RIDGING AND WARM ADVECTION SHOULD BRING A DIMINISHING TREND
TO SNOW SHOWERS ON TUESDAY NIGHT. WEDNESDAY THE BIG TRAVEL DAY
CURRENTLY LOOKS RELATIVELY TRANQUIL WITH A SOUTHERLY LOW LEVEL FLOW
PROGGED AHEAD OF A SFC LOW DEVELOPING TO OUR WEST ALONG A SHARPENING
BAROCLINIC ZONE.

MODEL CONSENSUS IS FOR MORE COLD AIR AND LAKE EFFECT SNOW SHOWERS TO
RETURN FOR THANKSGIVING DAY INTO FRIDAY. HOWEVER CONFIDENCE IS LOW
WITH RESPECT TO THE TIMING OF THE PASSAGE OF THE COLD FRONT... THE
STRENGTH OF THE COLD ADVECTION BEHIND IT... AND THE LOW LEVEL FLOW
PATTERN THAT SETS UP. THIS LEADS TO UNCERTAINTIES REGARDING ANY
POTENTIAL SNOW ACCUMULATIONS OVER THE HOLIDAY PERIOD.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 649 AM EST SAT NOV 22 2014

ONGOING MODERATE ICING WILL CHANGE TO RAIN FROM WEST TO EAST THIS
MORNING WITH THE ICING THREAT ENDING AT ALL TERMINALS BY 1430Z.
NO THREAT AT MKG DUE TO WARMER SFC TEMPS OFF LK MI.

MVFR CIGS/VSBYS AT 12Z WILL TREND INTO IFR CATEGORY BY 18Z AND
CONTINUE INTO TONIGHT WITH OCCASIONAL LIGHT RAIN/DRIZZLE
PERSISTING. SOUTH WINDS WILL AVERAGE AROUND 12 KTS TODAY AND
TONIGHT.

&&

.MARINE...
ISSUED AT 330 AM EST SAT NOV 22 2014

WE WILL BE MAINTAINING THE MARINE HEADLINES AS IS WITH THIS FCST
PACKAGE. WE ARE LIKELY SEEING THE PEAK WINDS OCCURRING RIGHT
NOW...OR THEY WILL PEAK VERY SOON. IT APPEARED EARLIER THAT THE NRN
HALF OF THE NEARSHORE WOULD LIKELY HIT GALES...HOWEVER GALE REPORTS
HAVE BEEN VERY ISOLATED THUS FAR WITH THE STABLE CONDITIONS OVER THE
LAKE. WE WILL CONTINUE TO MONITOR THE SITUATION.

IT DOES LOOK LIKE WE WILL HOLD IN SMALL CRAFT ADVISORY CONDITIONS
ALL WEEKEND AND INTO EARLY NEXT WEEK. IT WILL BE POSSIBLE WE SEE
GALES ON MON IN THE WAKE OF THE FRONT.


&&

.HYDROLOGY...
ISSUED AT 330 PM EST FRI NOV 21 2014

COMPLICATED FORECAST FROM A HYDROLOGY FORECAST.  AT THIS TIME IT
APPEARS THAT HYDRO LOGIC IMPACTS WILL BE MINIMAL...BUT WE WILL NEED
TO MONITOR TRENDS CLOSELY.

SNOW WATER EQUIVALENT VALUES RANGE FROM LESS THAN A HALF INCH INLAND
AROUND LANSING AND JACKSON TO AN INCH AROUND GRAND RAPIDS TO JUST
UNDER AN INCH FOR MUCH OF THE LAKESHORE.  BASED ON RAIN FORECASTS
AND WARMER TEMPERATURES...WE SHOULD LOSE A CONSIDERABLE AMOUNT OF
THIS SNOW PACK.  AFTER PUTTING IN ROUGHLY AND INCH TO AN INCH AND A
HALF OF RAIN...FACTORING IN MELTING MOST OF THE SNOW PACK...ALL THE
RIVERS SHOW A CONSIDERABLE RISE.  HOWEVER VERY LITTLE IF ANY
FLOODING SHOWED UP IN THE HYDROGRAPHS.  THIS IS SUPPORTED BY THE
RIVER ENSEMBLE FORECASTS.  THE PORTAGE RIVER NEAR VICKSBURG WAS ON
OF THE SITES THAT WAS SHOWN TO APPROACH FLOOD STAGE ON MONDAY.

ANOTHER POTENTIAL FLOODING FACTOR IS THAT SOME OF THE RIVERS HAVE
ICE IN THEM.  THIS INCLUDES THE GRAND AND MUSKEGON RIVERS.  HOWEVER
THE ICE DOES NOT APPEAR TO BE THICK...GENERALLY LESS THAN 4 INCHES.
HOWEVER WE ARE TRYING TO GAIN A BETTER HANDLE ON HOW THICK THE ICE
IS.  IF THE ICE IS THICKER THAN 4 INCHES...THAT COULD POTENTIALLY
LEAD TO PROBLEMS.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR
     MIZ037>040-043>046-050>052-056>059-064>067-071>074.

LM...SMALL CRAFT ADVISORY UNTIL 4 AM EST SUNDAY FOR LMZ847>849.

     GALE WARNING UNTIL 7 AM EST THIS MORNING FOR LMZ847>849.

     SMALL CRAFT ADVISORY UNTIL 4 AM EST SUNDAY FOR LMZ844>846.

&&

$$

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





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