Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KGRR 241050
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
550 AM EST WED DEC 24 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 330 AM EST WED DEC 24 2014

LOW PRESSURE TRACKING NORTH FROM THE GULF COAST REGION WILL BRING
RAIN TODAY AND POSSIBLE EVEN A FEW THUNDERSTORMS OVER EAST CENTRAL
LOWER MICHIGAN. THE RAIN WILL BECOME MIXED WITH THEN CHANGE OVER
TO WET SNOW LATE THIS AFTERNOON AND EVENING AS COLDER AIR MOVES IN.
SNOW COULD BE HEAVY AT TIMES AND IMPACT TRAVEL THIS EVENING
ESPECIALLY NEAR TO WEST OF A LINE FROM SOUTH HAVEN TO MT.
PLEASANT. FAIR WEATHER WILL RETURN LATE THIS WEEK. AN ARCTIC
AIRMASS AND POTENTIAL FOR SNOW WILL LIKELY ARRIVE AROUND NEW YEARS
NEXT WEEK.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 330 AM EST WED DEC 24 2014

OUR PRIMARY SHORT TERM FCST CHALLENGE IS TO DETERMINE POTENTIAL
FOR HEAVY WET SNOW LATE THIS AFTERNOON THROUGH CHRISTMAS EVE. RAIN
IS ANTICIPATED FOR MOST OF THE DAY BUT PCPN WILL BECOME MIXED WITH
WET SNOW MID TO LATE THIS AFTERNOON DUE TO WET BULB AND DYNAMICAL
COOLING EFFECTS AND AS COLDER AIR BEGINS TO ADVECT IN ON THE BACK
SIDE OF THE LOW THAT WILL TRACK TO NEAR DTW BY EARLY THIS EVENING.

WE HAVE DECIDED TO HOIST A WINTER WX ADVISORY FOR PORTIONS OF OUR
FCST AREA FROM VAN BUREN COUNTY TO THE NNE INCLUDING KENT COUNTY
AND FURTHER NNE TO OSCEOLA AND MECOSTA COUNTY AND ALL COUNTIES
WEST OF THAT LINE. STRONG MID LEVEL FRONTOGENETICAL FORCING WILL
DEVELOP LATE THIS AFTERNOON AND EVENING FOLLOWED BY LINGERING
DEFORMATION ZONE SNOWFALL LATE THIS EVENING BEFORE PCPN BEGINS TO
TAPER OFF.

A PERIOD OF MODERATE TO HEAVY SNOW IS LIKELY FROM LATE THIS
AFTERNOON AND EARLY EVENING THROUGH AROUND MIDNIGHT. SNOWFALL
ACCUMULATIONS ACROSS THE ADVISORY AREA WILL VARY WIDELY FROM AROUND
TWO TO FIVE INCHES. POTENTIAL FOR HIGHER ACCUMULATIONS IS MITIGATED
BY FAST MOVEMENT OF THIS SYSTEM TO THE NNE.

ISOLATED LOCALLY HIGHER AMOUNTS ARE POSSIBLE WHERE THE PCPN CHANGES
OVER TO SNOW THE FASTEST IN CONJUNCTION WITH NARROW BANDS OF STRONG
MID LEVEL FGEN FORCING AND ASSOCIATED STRONG OMEGAS. THIS COULD
RESULT IN SNOWFALL RATES IN EXCESS OF AN INCH PER HOUR AT TIMES THIS
EVENING. THIS NOTION IS SUPPORTED BY SREF PROBABILISTIC GUIDANCE FOR
SNOWFALL RATES EXCEEDING 1 INCH/HR. THE SNOW WILL RESULT IN
POTENTIAL FOR HAZARDOUS TRAVEL CONDITIONS ACROSS THE ADVISORY AREA
AS DEFORMATION ZONE SNOWFALL LINGERS THROUGH THE LATE NIGHT HOURS.

A FEW THUNDERSTORMS ARE POSSIBLE LATER TODAY MAINLY OVER OUR EASTERN
FCST AREA... BUT A RELATIVELY BETTER CHANCE FOR SCATTERED CONVECTION
WILL BE A LITTLE FURTHER EAST AND CLOSER TO THE SFC LOW TRACK.

TRANQUIL WX WILL RETURN FOR CHRISTMAS DAY THROUGH FRIDAY AS A WEAK
SFC RIDGE TAKES HOLD OF THE WX PATTERN. TEMPERATURES THROUGH THE
SHORT TERM FCST PERIOD WILL CONTINUE TO AVERAGE AROUND TEN DEGREES
ABOVE NORMAL FOR THIS TIME OF YEAR.

IT IS NOTED THAT 00Z ECMWF GUIDANCE HAS NOW SHIFTED SLIGHTLY FURTHER
EAST WITH THE LOW TRACK AND ASSOCIATED SWATH OF HEAVIER PCPN. IT IS
NOT CLEAR THOUGH IF THIS IS A CLEAR TREND OR JUST A SHIFT IN ONE
MODEL RUN AS GUIDANCE HAS BEEN VERY INCONSISTENT WITH HANDLING OF
THIS SYSTEM. AS SUCH FUTURE SHIFTS WILL NEED TO MONITOR GUIDANCE
TRENDS VERY CLOSELY FOR A POTENTIAL SHIFT IN WHERE HEAVIER SNOW WILL
FALL THIS EVENING.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 330 AM EST WED DEC 24 2014

LOW TRACKS NORTH OF THE FORECAST AREA FRIDAY NIGHT AND SATURDAY WITH
LIGHT MIXED PRECIP ENDING AS SNOW ON SATURDAY NIGHT. THE TREND IS
FOR A WEAKER LOW...ESPECIALLY IN RECENT RUNS OF THE EURO. LITTLE OR
NO IMPACTS EXPECTED. COLDER AIR MOVES IN OVER THE WEEKEND AND SOME
LIGHT LAKE EFFECT SNOW SHOWERS ARE POSSIBLE...ESPECIALLY BY MONDAY
AND TUESDAY.

WE WILL ALSO HAVE TO WATCH SFC WAVES MOVING ALONG THE BAROCLINIC
ZONE SET UP OVER THE OHIO VALLEY SUNDAY THROUGH TUESDAY. THERE ARE
SOME INDICATIONS THAT THE NORTHERN EDGE OF OF THE SNOW COULD MAKE IT
INTO LOWER MICHIGAN ON MONDAY OR TUESDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 550 AM EST WED DEC 24 2014

IFR CONDITIONS ARE EXPECTED TODAY AND TONIGHT AS RAIN CHANGES TO
SNOW AROUND 20Z. NORTH WINDS TODAY AROUND 10 KNOTS WILL GO WEST
TONIGHT AND INCREASE TO 20 KNOTS WITH SOME GUSTS OVER 30 KNOTS.

&&

.MARINE...
ISSUED AT 330 AM EST WED DEC 24 2014

WAVE HEIGHTS WILL RAMP UP SIGNIFICANTLY BEGINNING LATE THIS
AFTERNOON. WILL HOIST A SMALL CRAFT ADVISORY TO COVER THIS FROM
LATE THIS AFTERNOON THROUGH CHRISTMAS DAY.


&&

.HYDROLOGY...
ISSUED AT 330 AM EST WED DEC 24 2014

THREE RIVER FLOOD ADVISORIES ARE IN EFFECT WITH MINOR FLOODING
POSSIBLE ON THE GRAND RIVER AT IONIA... SYCAMORE CREEK AT HOLT AND
MAPLE RIVER AT MAPLE RAPIDS. HOWEVER NO SIGNIFICANT HYDRO ISSUES
ARE EXPECTED WITH DRY WEATHER ANTICIPATED LATE THIS WEEK AFTER THE
PRECIPITATION TODAY AND MOST RIVERS WELL WITHIN BANK.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 7 AM EST
     THURSDAY FOR MIZ037>039-043>045-050-051-056-057-064-071.

LM...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 7 AM EST FRIDAY
     FOR LMZ844>849.

&&

$$

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




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.