Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 201739
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1239 PM EST THU NOV 20 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 310 AM EST THU NOV 20 2014

LAKE EFFECT SNOW SHOWERS WILL CONTINUE TODAY THROUGH TONIGHT BEFORE
TAPERING OFF TO A FEW FLURRIES FRIDAY. UNSEASONABLY COLD WEATHER
WILL CONTINUE THROUGH FRIDAY BEFORE TEMPERATURES FINALLY UNDERGO A
GRADUAL MODERATING TREND THIS WEEKEND. A STRONG LOW PRESSURE SYSTEM
WILL BRING RAIN AND VERY WINDY CONDITIONS SUNDAY INTO MONDAY BEFORE
COLDER AIR MOVES BACK IN FOR THE MIDDLE PORTION OF NEXT WEEK.

&&

.UPDATE...
ISSUED AT 1110 AM EST THU NOV 20 2014

I PLAN NO CHANGES IN OUR HEADLINES FOR THIS AFTERNOON. I DID
INCREASE SNOW AMOUNTS SINCE OUR 88D IS SHOWING 1 TO 2 INCH PER
HOUR SNOWFALL RATES IN THE SNOW BAND THE EXTENDS FROM NEAR
MUSKEGON TO GRAND RAPIDS TO IONIA AT 11 AM. THAT BAND IS MID LEVEL
FRONTOGENESIS AREA ON THE NORTH SIDE OF THE POLAR JET AND IT DOES
NOT MOVE MUCH DURING THE DAY TODAY. SO THE AREA FROM NEAR MUSKEGON
TO CENTRAL KENT COUNTY INTO IONIA COUNTIES COULD SEE 3 TO 4 INCHES
OF SNOWFALL TODAY. THIS IS THE SAME SNOW BAND THAT HEADS EAST INTO
SHIWASSEE AND GENESSE COUNTY. HELPING THE CAUSE IS 35 KNOT WINDS
AT 850 MB FROM THE WEST WITH COLD ADVECTION CONTINUING INTO THIS
EVENING.

TONIGHT AS THE UPPER LEVEL JET AXIS MOVES CLOSER TO OUR AREA THE
LAKE CLOUD LEVEL WIND TURN MORE NORTHWEST AND THAT REFORMS THE
AXIS OF THE SNOW BAND TO MORE NORTH/SOUTH ALONG US-131. SNOWFALL
THEN SHOULD NOT BE AS HEAVY AS IT IS TODAY.

UPDATE ISSUED AT 730 AM EST THU NOV 20 2014

HAVE EXPANDED THE WINTER WEATHER ADVISORY EASTWARD ALONG THE I-96
AND I-94 CORRIDORS AS SHORT TERM GUIDANCE FAVORS HEAVIER SNOW
BANDS PENETRATING WELL INLAND TODAY DUE TO BRISK 20-30KT LOW LEVEL
WESTERLY FLOW. LATEST RADAR TRENDS SUPPORT THIS IDEA WITH BETTER
BANDS NOW STREAMING ACROSS IONIA COUNTY AND EDGING INTO CLINTON.
WILL HAVE THIS NEW HEADLINE EXPIRING AT 7 PM THIS EVENING WHEN THE
WINDS RELAX. NO CHANGE TO THE EXISTING HEADLINE WHICH GOES THROUGH
7 AM FRIDAY.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 310 AM EST THU NOV 20 2014

WEST TO WNW FLOW LAKE EFFECT SNOW SHOWERS WILL CONTINUE TO DEVELOP
TODAY THROUGH THIS EVENING WITH H8 TEMPS STILL DOWN AROUND -16 TO
-18 C YIELDING HIGH DELTA T/S AND MODERATE TO HIGH LAKE INDUCED
INSTABILITY. THE BRISK WINDS WILL CONTINUE TO CARRY THE SNOW
SHOWERS INLAND.

HOWEVER THE SNOW SHOWERS HAVE DECREASED IN INTENSITY AND ARE
MAINLY JUST LIGHT. THIS TREND SHOULD CONTINUE AS INVERSION HEIGHTS
CONTINUE TO LOWER SLOWLY FROM AROUND 7-8 KFT AGL TO ONLY AROUND
4-5 KFT AGL BY LATE THIS EVENING.

ADDITIONAL ACCUMULATIONS TODAY WILL RANGE FROM AROUND 1 TO 2 AND
LOCALLY UP TO 3 INCHES ACROSS OUR WESTERN TWO TIERS OF COUNTIES
WHERE SOME MODERATE 1000-850 MB CONVERGENCE LINGERS TODAY... TO ONLY
AROUND AN INCH OR LESS ACROSS OUR EASTERN TWO TIERS OF COUNTIES. THE
ADVISORY HEADLINE FOR OUR WESTERN TWO TIERS OF COUNTIES LOOKS
GOOD AND WILL REMAIN UNCHANGED.

THE LAKE EFFECT SNOW SHOWERS WILL LINGER TONIGHT WITH ADDITIONAL
ACCUMULATIONS OF ONLY AROUND AN INCH OR LESS ACROSS OUR WESTERN TWO
TIERS OF COUNTIES WITH VERY LITTLE TO NO ADDITIONAL ACCUMULATION
WELL INLAND.

ANY LIGHT LINGERING SNOW SHOWERS OR FLURRIES EARLY FRIDAY WILL COME
TO AN END AS H8 TEMPS MODERATE CONSIDERABLY AND HIGH PRESSURE BUILDS
IN. HOWEVER IT WILL REMAIN COLD WITH MAX TEMPS STILL ONLY REACHING
THE 20S.

A CONSENSUS OF 00Z SHORT RANGE GUIDANCE AND THERMAL PROFILES
CONTINUE TO SUGGEST THAT A BRIEF PERIOD OF LIGHT FREEZING RAIN IS
POSSIBLE ACROSS MOST OF OUR AREA VERY LATE FRIDAY NIGHT (AFTER
MIDNIGHT) THROUGH SATURDAY MORNING.

THIS IN A SW FLOW WAA REGIME AS WARMER AIR ALOFT OVERRUNS THE
COLDER AIR NEAR THE SFC. -FZRA ACCUMULATIONS OF FIVE HUNDREDTHS OF
AN INCH OR LESS ARE ANTICIPATED BEFORE P-TYPE TRANSITIONS TO PLAIN
LIGHT RAIN/DRIZZLE SATURDAY AFTERNOON AS TEMP PROFILES MODERATE.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 310 AM EST THU NOV 20 2014

A WARM UP WITH RAIN OVER THE WEEKEND WILL BRING A BRIEF THAW BEFORE
ANOTHER COOL DOWN WITH WINDY CONDITIONS AND SNOW SHOWERS RETURN
EARLY NEXT WEEK.

OVER AN INCH OF RAIN MAY FALL WITH THIS SYSTEM ON TOP OF A SNOW PACK
CONTAINING UP TO AN INCH OF WATER EQUIVALENT AROUND GRR. SOME MINOR
FLOODING ISSUES ARE POSSIBLE BUT SINCE THE DEEPER SNOW PACK DOES NOT
COVER THE ENTIRE AREA SUSPECT THIS WILL NOT BE TOO BIG OF A DEAL AS
FAR AS THE MAINSTEM RIVERS ARE CONCERNED.

THE UPCOMING ROLLER COASTER PATTERN IS COURTESY OF A DEEPENING SFC
LOW LIFTING NORTH FROM THE GULF COAST. THE BULK OF THE RAINFALL IS
EXPECTED TO OCCUR SUNDAY AFTERNOON AND EVENING WHEN THE NEGATIVE
TILT SHORTWAVE AND SFC OCCLUSION LIFT NORTH THROUGH THE STATE. SFC
DEW POINTS OF 45 TO 50 MOVING OVER THE SNOW COVER SHOULD LEAD TO
AREAS OF FOG SUNDAY NIGHT.

THE SFC LOW DEEPENS TO 975 MB AS IT TRACKS NORTH ACROSS ERN WI INTO
UPR MI LATE SUNDAY NIGHT AND EARLY MONDAY. WE SHOULD SEE SOME
STRONG/GUSTY WINDS ON THE BACK SIDE OF THE SYSTEM MONDAY AND TUESDAY
WITH H8 TEMPS FALLING QUICKLY TO AROUND -12C. SEVERAL INCHES OF LAKE
ENHANCED SNOW APPEAR LIKELY MONDAY NIGHT AND TUESDAY WHEN DEEP
MOISTURE AND LIFT IS PROGGED TO IMPACT THE REGION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1236 PM EST THU NOV 20 2014

SNOW SHOWERS WILL CONTINUE THROUGH THE EVENING BEFORE TAPERING
AFTER MIDNIGHT. WIDE VARIABILITY IS EXPECTED IN VSBYS AS THE SNOW
SHOWERS MOVE IN AND OUT. WINDS WILL GRADUALLY DIMINISH LATER THIS
EVENING BUT GENERALLY REMAIN OUT OF THE WEST...BEFORE BECOMING
SOUTHWEST LATE TONIGHT.

&&

.MARINE...
ISSUED AT 310 AM EST THU NOV 20 2014

THE GALE WARNING REMAINS IN EFFECT THROUGH 7 AM AND WILL BE
FOLLOWED BY A SMALL CRAFT ADVISORY FOR THE REST OF THE DAY THROUGH
TONIGHT. WNW WIND SPEEDS WILL RAMP BACK UP THIS AFTERNOON BUT
SHOULD STAY BELOW GALE FORCE LATER TODAY.


&&

.HYDROLOGY...
ISSUED AT 310 AM EST THU NOV 20 2014

NO HYDRO ISSUES THROUGH FRIDAY WITH UNSEASONABLY COLD WEATHER AND
PCPN IN THE FORM OF SNOW. A STRONG SYSTEM WILL BRING A MODERATING
TREND OF TEMPERATURES AND WINDY CONDITIONS SUNDAY WITH RAIN. THE
COMBINATION OF RAIN AND MELTING SNOW MAY CAUSE SOME RIVER LEVELS
TO RISE TO NEAR ACTION STAGE.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY UNTIL 7 AM EST FRIDAY FOR MIZ037-038-043-
     044-050-056-057-064-065-071-072.

     WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR MIZ058-
     059-066-067-073-074.

LM...SMALL CRAFT ADVISORY UNTIL 7 AM EST FRIDAY FOR LMZ844>849.

&&

$$

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





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