Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 200829
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
329 AM EST SAT DEC 20 2014

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

.SYNOPSIS...
ISSUED AT 329 AM EST SAT DEC 20 2014

QUIET AND MILD WEATHER IS EXPECTED FOR THE AREA THROUGH THE FIRST
PART OF THE DAY ON MONDAY. CLOUDS WILL GENERALLY BE ON THE INCREASE
WITH MAINLY DRY CONDITIONS EXPECTED INTO EARLY MONDAY. A WEATHER
SYSTEM WILL BEGIN TO IMPACT THE AREA MONDAY AFTERNOON BY BRINGING
RAIN INTO THE AREA.

THE WEATHER WILL BECOME MORE UNSETTLED LEADING UP TO THE CHRISTMAS
HOLIDAY ON THURSDAY. RAIN WILL AFFECT THE AREA OFF AND ON FROM
MONDAY NIGHT INTO CHRISTMAS EVE BEFORE RAIN CHANGES TO SNOW
CHRISTMAS DAY.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 329 AM EST SAT DEC 20 2014

THE MAIN CHALLENGES IN THE SHORT TERM PORTION OF THE FCST THROUGH
MON ARE CLOUD TRENDS INITIALLY...THEN PCPN TRENDS FOR THE LATER
PORTION OF THE PERIOD.

LOW CLOUDS HAVE GENERALLY REMAINED WEST AND SOUTH OF THE AREA THUS
FAR THIS MORNING...WHILE HIGH CLOUDS ARE MOVING OVERHEAD. THE HIGH
CLOUDS ARE STREAMING IN AHEAD OF THE WAVE THAT IS DIVING SOUTH OF
THE STATE. LOW CLOUDS CLEARED MOST OF THE AREA YESTERDAY...AND HAVE
NOT MOVED MUCH WITH THE WEAK FLOW IN PLACE. WE ARE EXPECTING THE LOW
CLOUDS TO SPREAD IN OVER ATLEAST A PORTION OF THE AREA LATER TODAY
AND TONIGHT AS THE FLOW BRINGS THEM BACK IN ACROSS THE AREA.

WE WILL SEE PERIODS OF CLOUDS AT DIFFERENT LAYERS THEN THROUGH MOST
OF SUN NIGHT. THE LOW CLOUDS WILL REMAIN AROUND THE AREA...AND SOME
MID/HIGH LEVEL CLOUD COVER WILL MOVE OVER AS WARMTH AND MOISTURE
ALOFT ADVECTS OVER THE AREA.

WE WILL NOT SEE MUCH OF A CHC OF PCPN THROUGH EARLY MON. THE ONLY
REAL CHC WILL COME LATE SUN AFTERNOON AND SUN EVENING ACROSS THE FAR
NW CORNER OF THE CWFA WHERE SOME LIGHT SNOW WILL BE POSSIBLE. WE
WILL SEE A WARM FRONT PUSH NORTH THROUGH THE AREA AT THAT TIME. THE
BEST MOISTURE TRANSPORT WILL OCCUR NW OF THE AREA AND THIS IS WHERE
THE DEEPEST MOISTURE WILL BE FOUND. ONCE THE FRONT PASSES BY 12Z
MON...WE COULD ACTUALLY SEE SOME TEMPORARY CLEARING.

THE THREAT OF RAIN WILL THEN INCREASE LATER ON MON FROM WEST TO EAST
AS THE INITIAL UPPER WAVE AND ASSOCIATED SFC LOW APPROACH THE AREA.
THE ATMOSPHERE WILL HAVE WARMED SUFFICIENTLY BY THE TIME PCPN MOVES
IN THAT ALL PCPN SHOULD BE RAIN. WE WILL SEE TEMPS INTO THE 40S ON
MON AHEAD OF THE INITIAL FRONT.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 329 AM EST SAT DEC 20 2014

ALTHOUGH AN IMPRESSIVE LOW WILL BE MOVING THROUGH OR CLOSE TO THE
FORECAST AREA NEXT WEEK...IMPACTS MAY NOT AMOUNT TO MUCH. FOR NOW IT
LOOKS LIKE SNOW TOTALS WILL NOT BE HEAVY AS THE COLD AIR IS LATE TO
WRAP IN AND LAKE EFFECT WILL NOT ADD MUCH. A FEW HOURS OF STRONG
WINDS FROM THIS SO CALLED SANTA BOMB COULD BE THE ONLY THREAT.

THE 00Z MODEL GUIDANCE IS NARROWING IN ON THE TIMING FOR THE CHANGE
FROM LIQUID TO FROZEN PRECIP. LOOKS LIKE COLD AIR MOVES IN FROM
SOUTHWEST TO NORTHEAST ON WEDNESDAY AFTERNOON WITH SNOW AMOUNTS
GENERALLY UNDER 4 INCHES. THEN SOME LAKE EFFECT FOLLOWS FOR THURSDAY
BUT SHOULD NOT BE HEAVY AS INVERSION HEIGHTS REMAIN AOB 5 KFT.

NEXT STORM END OF THE WEEK IS LOW CONFIDENCE WITH HIGH MODEL SPREAD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 944 PM EST FRI DEC 19 2014

THE LOW CLOUDS HAVE SCATTERED OUT ACROSS MUCH OF SOUTHWEST LOWER
MI...BUT HIGH LEVEL CLOUDS...OVER 15K FT...WERE MOVING IN. THERE
IS A RISK THAT FOG COULD FORM IN THE NEXT FEW HOURS...BUT THIS
RISK IS LIMITED BY THE HIGHER LEVEL CLOUDS MOVING IN. THUS I DID
NOT INCLUDE THE FOG IN THE FORECAST AT THIS TIME.

MVFR CLOUDS WILL GRADUALLY MOVE IN LATE TONIGHT FROM THE SOUTH AND
WEST. THIS WILL LIKELY PERSIST THROUGH SAT AM. FOR NOW I KEPT THE
RETURN TO VFR FOR MOST TAF SITES SAT AFTN...BUT THIS IS NOT
CERTAIN TO HAPPEN AS THE LOW LEVELS REMAIN FAIRLY MOIST.

AVIATORS MAY ENCOUNTER SOME ICING IN THESE LOWER CLOUDS.

&&

.MARINE...
ISSUED AT 339 PM EST FRI DEC 19 2014

HIGH PRESSURE WILL BRING FAIRLY LIGHT WINDS AND LOW WAVE ACTION
TONIGHT INTO SATURDAY. SOUTHERLY FLOW BEGINS TO PICK UP ON SUNDAY.
SMALL CRAFT ADVISORY CONDITIONS MAY DEVELOP AS EARLY AS SUNDAY
AFTERNOON IN THE NORTH. SUNDAY NIGHT IT APPEARS SCA CONDITIONS WILL
BE LIKELY...NORTH OF HOLLAND. WILL HOLD OFF AT THIS POINT ON A
FOURTH PERIOD SCA...BUT ONE WILL LIKELY BE NEEDED GOING FORWARD.
NEXT WEEK LOOKS ROUGH ON LAKE MICHIGAN GIVEN A DEEP LOW MOVING
THROUGH THE REGION.

&&

.HYDROLOGY...
ISSUED AT 339 PM EST FRI DEC 19 2014

RIVER LEVELS ACROSS THE AREA ARE NEAR NORMAL FOR THIS TIME OF YEAR
WITH NO SIGNIFICANT PRECIP EXPECTED THROUGH THE WEEKEND. SO...NO
HYDRO ISSUES THROUGH MONDAY. DEEP LOW PRESSURE WILL LIKELY BRING
SOAKING RAINS TO THE AREA MONDAY NIGHT INTO TUESDAY WITH RAINFALL
AMOUNTS OF A HALF TO ONE INCH. GIVEN THE LOW FLOWS CURRENTLY THIS
SHOULD BE ABLE TO BE ABSORBED WITHOUT MUCH ISSUE.

&&

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

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...OSTUNO
AVIATION...MJS
HYDROLOGY...DUKE
MARINE...DUKE




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