Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 220812
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
315 AM EST MON DEC 22 2014

LATEST UPDATE...
SYNOPSIS/SHORT TERM/LONG TERM/HYDRO/MARINE

.SYNOPSIS...
ISSUED AT 315 AM EST MON DEC 22 2014

TEMPERATURES WILL CONTINUE TO AVERAGE ABOVE NORMAL THIS WEEK. A
LOW PRESSURE SYSTEM WILL BRING RAIN SHOWERS THIS AFTERNOON AND MAINLY
FOR TONIGHT THROUGH TUESDAY. SOME LIGHT FREEZING RAIN IS POSSIBLE
TONIGHT NEAR TO NORTH OF A LINE FROM PENTWATER TO MOUNT PLEASANT.
RAIN SHOWERS WILL LINGER TUESDAY NIGHT AND WEDNESDAY.
PRECIPITATION WILL LIKELY BECOME MIXED WITH THEN CHANGE OVER TO
SNOW LATE WEDNESDAY THROUGH WEDNESDAY NIGHT. ACCUMULATING SNOW IS
LIKELY WEDNESDAY NIGHT.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 315 AM EST MON DEC 22 2014

DRY WEATHER WILL CONTINUE THROUGH THE MORNING INTO THE EARLY
AFTERNOON BEFORE A WARM FRONT AND CONTINUED SOUTHERLY FLOW RESULT
IN DEVELOPMENT OF LIGHT RAIN SHOWERS FROM SW TO NE THIS AFTERNOON.
SHOWERS WILL BECOME MORE PREVALENT ACROSS OUR AREA THIS EVENING.

WE HAVE ADDED MENTION OF A CHANCE OF LIGHT FREEZING RAIN ACROSS
OUR FAR NORTHERN FCST AREA NEAR TO NORTH OF A LINE FROM AROUND
PENTWATER TO MT. PLEASANT. A POLLING OF 00Z NAM/GFS FCST SOUNDINGS
ACROSS THIS AREA SHOWS WARM AIR ALOFT COMING IN BUT THAT BOUNDARY
LAYER TEMPS WILL LIKELY GET STUCK RIGHT AROUND THE FREEZING MARK
TONIGHT.

RAIN SHOWERS WILL CONTINUE TUESDAY AND SOME LINGERING LIGHT
SHOWERS ARE ANTICIPATED TUESDAY NIGHT. LOW PRESSURE TRACKING NORTH
FROM THE GULF COAST REGION WILL BRING STEADIER RAIN SHOWERS BACK
INTO OUR AREA WEDNESDAY.

PCPN MAY BECOME MIXED WITH WET SNOW LATE WEDNESDAY AND BE AIDED BY
POTENTIALLY STRONG MID LEVEL FRONTOGENETICAL FORCING AND EVENTUALLY
DEFORMATION ZONE PROCESSES AND DYNAMICS. HOWEVER THE POTENTIAL FOR
ACCUMULATING SNOW SHOULD HOLD OFF UNTIL WEDNESDAY EVENING/WEDNESDAY
NIGHT WHEN COLDER AIR WILL MOVE IN.

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 315 AM EST MON DEC 22 2014

ALTHOUGH MODELS HAVE STRUGGLED MIGHTILY WITH THE DETAILS...WE STILL
EXPECT SOME IMPACTS FROM THE STORM EARLY IN THE PERIOD. THE 00Z
MODEL GUIDANCE HAS GONE TOWARDS THE GFS IDEA FROM YESTERDAY OF MORE
SEPARATION IN THE NORTHERN AND SOUTHERN STREAMS RESULTING IN A SFC
LOW TRACKING ACROSS OHIO LATE WEDNESDAY. THIS BRINGS F-GEN BANDS OF
SNOW INTO THE FORECAST AREA.

TEMPERATURES ARE MARGINAL FOR SNOW EARLY IN THE EVENING BUT THE
PROFILES SUGGEST ANY MIX WILL TRANSITION TO SNOW AFTER 00Z THURSDAY
AS COLDER AIR WRAPS IN. THE CURRENT SCENARIO WOULD ALLOW FOR A
COUPLE INCHES OF SNOW ACROSS MOST OF THE FORECAST AREA WITH THE
POTENTIAL FOR HIGHER AMOUNTS WHERE BANDS PIVOT OVERNIGHT. SOME LIGHT
LAKE EFFECT SNOW SHOWERS ARE EXPECTED CHRISTMAS MORNING BUT SHOULD
NOT AMOUNT TO MUCH AS INVERSION HEIGHTS DROP BLO 5 KFT.

WARM AIR ADVECTION IS ALREADY UNDER WAY BY THURSDAY NIGHT AND SOME
LIGHT SNOW OR MIXED PRECIP COULD FOLLOW BY FRIDAY AS A WEAK
SHORTWAVE TROUGH MOVES THROUGH. A NEW WRINKLE WITH THE 00Z ECMWF IS
ANOTHER LOW MOVING THROUGH THE OHIO VALLEY ON SUNDAY BUT THIS IS LOW
CONFIDENCE AS THE ECMWF AND GFS ARE COMPLETELY OUT OF PHASE WITH THE
UPPER TROUGHS BY THIS TIME. WENT WITH SNOW SHOWERS OVER THE WEEKEND
AS COLD AIR AND CYCLONIC FLOW APPEARS TO DOMINATE TO SOME EXTENT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1104 PM EST SUN DEC 21 2014

MVFR FOG WILL CONTINUE TO EXPAND OVERNIGHT...WHILE THE SOUTHEAST
FLOW SHOULD LIMIT THE POTENTIAL FOR IFR.

VFR SHOULD RETURN ON MONDAY...BUT CONDITIONS WILL LOWER AS WE GO
THROUGH THE LATE AFTERNOON INTO THE EVENING HOURS. RAIN WILL BE
OVERSPREADING THE REGION AND SOME FOG. WE WILL NEED TO MONITOR THE
FREEZING RAIN POTENTIAL...BUT AT THIS TIME THE RISK IS LOW FOR THE
TAF SITES. FURTHER NORTH OF KGRR AND KLAN...IT APPEARS THAT
FREEZING RAIN MAY OCCUR...CLOSER TO KMOP.


&&

.MARINE...
ISSUED AT 315 AM EST MON DEC 22 2014

THE SMALL CRAFT ADVISORY REMAINS IN EFFECT FROM HOLLAND NORTH TO
MANISTEE THROUGH MONDAY EVENING. SOUTHERLY WINDS WILL RESULT IN
WAVE HEIGHTS OF 3 TO 6 FEET NORTH OF HOLLAND THROUGH MONDAY
AFTERNOON.

&&

.HYDROLOGY...
ISSUED AT 315 AM EST MON DEC 22 2014

NO HYDRO ISSUES ANTICIPATED WITH RELATIVELY LIGHT RAINFALL AMOUNTS
ON THE ORDER OF A QUARTER TO THREE QUARTERS OF AN INCH THIS
AFTERNOON THROUGH MIDWEEK. PRECIPITATION WILL NOT BE SIGNIFICANT
ENOUGH TO CAUSE ANY ISSUES WITH AREA RIVER LEVELS NORMAL AND WELL
WITHIN BANK.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR LMZ846>849.

&&

$$

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







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