Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 090356
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1056 PM EST MON FEB 8 2016

LATEST UPDATE...
UPDATE

.SYNOPSIS...
ISSUED AT 305 PM EST MON FEB 8 2016

COLDER AIR WILL START FILTERING INTO THE AREA THIS EVENING AND WILL
REMAIN IN PLACE LIKELY THROUGH NEXT WEEKEND. THIS WILL START UP SNOW
SHOWERS TONIGHT. THE SNOW SHOWERS WILL BECOME MORE PERSISTENT LATER
TUESDAY AFTERNOON AND THEN LIKELY LAST INTO THURSDAY BEFORE
DIMINISHING. THE AREAS ALONG THE LAKESHORE WILL SEE MOST OF THE SNOW
THROUGH THIS PERIOD.

A REINFORCING SHOT OF VERY COLD AIR WILL MOVE IN FOR THE WEEKEND.
THIS WILL BRING MORE CHANCES OF SNOW SHOWERS ALONG THE LAKESHORE.
THE HEAVIER SNOW SHOWERS LIKELY WILL STAY OFFSHORE THIS WEEKEND.

&&

.UPDATE...
ISSUED AT 1056 PM EST MON FEB 8 2016

TWEAKED POPS TO REPRESENT MORE OF THE SYNOPTIC SET UP. THE LAKE
EFFECT REALLY DOES NOT KICK IN UNTIL AFTER 09Z OR SO.

MUCH OF THE SNOWFALL THIS EVENING WAS OCCURRING ALONG AND SOUTH OF
I-96 WITH AN AREA OF INSTABILITY. THIS TREND SHOULD CONTINUE...
ALTHOUGH THE INTENSITY OF THE SNOW WILL CONTINUE TO DIMINISH.
HOWEVER INCREASED POPS OVER THE NE CWA WHERE THE EFFECTS OF THE
UPPER LOW CONTINUES TO SPIN SNOW BACK WESTWARD. THIS LEAVES THE NW
CWA WITH THE LOWEST POPS THROUGH THE NIGHT. THE SNOW MAY INCREASE
IN THIS REGION AROUND OR SHORTLY AFTER DAYBREAK AS THE COLDER AIR
FINALLY ARRIVES AND THE LAKE EFFECT SNOWS DEVELOP.

WITH THIS SAID...THE SNOW WILL STAY LIGHT AND ACCUMS WILL STAY
LIGHT THE REST OF THE NIGHT. MOST AREAS WILL SEE LESS THAN AN
INCH OVERNIGHT...WITH SOME AREAS SOUTH OF I-96 AND ALONG THE
LAKESHORE PERHAPS SEEING AN INCH OR TWO.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 305 PM EST MON FEB 8 2016

WE ARE ISSUING A WINTER WEATHER ADVISORY FOR THE PERIOD FROM LATE
TUESDAY AFTERNOON THROUGH THE THU MORNING COMMUTE FOR LAKE EFFECT
SNOW SHOWERS THAT WILL BE PICKING UP IN INTENSITY FOR THE LAKESHORE
AND PORTIONS OF LAKE COUNTY.

A FEW SNOW SHOWERS HAVE BEEN CRAWLING ONSHORE ACROSS THE LAKESHORE
COUNTIES OVER THE PAST COUPLE OF HOURS. WE ARE EXPECTING THESE SNOW
SHOWERS TO CONTINUE THIS TREND A BIT THROUGH TONIGHT WITH RELATIVELY
LIGHT AMOUNTS. THE BEST SNOW AMOUNTS TONIGHT WILL BE ACROSS WRN VAN
BUREN COUNTY CLOSER TO THE CENTER OF THE UPPER LOW AND ASSOCIATED
LOW LEVEL CONVERGENCE WILL BE FOUND. WE ARE THINKING 1-3 INCHES
THERE WITH LESSER AMOUNTS ELSEWHERE. THE IMPACTS SHOULD BE SMALL
ENOUGH WE DID NOT INCLUDE THIS PERIOD IN THE ADVISORY.

THINGS WILL BE RELATIVELY QUIET THEN INTO TUE AFTERNOON AS WE
TRANSITION TO THE LAKE EFFECT EXPECTED BEGINNING LATER TUE
AFTERNOON. THERE WILL BE SOME LAKE EFFECT SNOW SHOWERS...BUT THEY
ARE NOT EXPECTED TO BE CAUSE TOO MANY ISSUES WITH THE BEST COLD AIR
ADVECTION YET TO OCCUR. DURING THIS PERIOD ALSO...THE ERN EDGE OF
THE CWFA COULD GET IN ON A LITTLE OF THE LIGHT SNOW ON THE FAR WRN
FLANK OF THE SFC LOW OVER THE ERN LAKES. THIS IS NOT FOR SURE...AND
ANY SNOW THAT WOULD OCCUR THERE WOULD LIKELY BE A DUSTING.

LATER TUE AFTERNOON IS WHEN WE EXPECT THE LAKE EFFECT SNOW SHOWERS
TO START BECOMING A NOTICEABLE FACTOR. THE FAVORED AREAS WILL BE
MAINLY ALONG THE LAKESHORE NORTH OF MUSKEGON AND NEAR HOLLAND AND
AREAS SOUTH. NW LAKE COUNTY WILL ALSO LIKELY SEE SOME HEALTHY
AMOUNTS. THE FLOW IS EXPECTED TO TRANSITION TO A NNW FLOW REGIME FOR
MUCH OF THE PERIOD WITH SOME SLIGHT FLUCTUATIONS WITH SHORT WAVES IN
THE UPPER FLOW. THE ADVISORY COUNTIES ARE BASED ON THE AREAS WHERE
THE PREDOMINATELY STRONGER LOW LEVEL CONVERGENCE SIGNALS ARE...WHICH
LINES UP WELL WITH THE NNW FLOW LAKE EFFECT FLOW REGIME.

OVER LAKE INSTABILITY WILL BE INCREASING WITH DELTA T/S INCREASING
TO AROUND THE LOWER 20S C BY TUE EVENING AND THEN PERSISTING THROUGH
WED NIGHT AND BEYOND. INVERSION HEIGHTS WILL BE INCREASING TO ALMOST
10K FEET BY LATE TUE NIGHT INTO WED. THE HEAVIEST LAKE EFFECT WILL
LIKELY COME DURING THAT TIME WITH A BETTER DEFINED SHORT WAVE THAT
WILL BE DROPPING INTO THE AREA. THE DGZ SHOULD BE FAVORABLE ALSO AS
IT WILL BE LOW...BUT STILL LIKELY IN THE CLOUD LAYER AND COINCIDING
WITH THE BETTER CONVERGENCE.

CONDITIONS WILL BECOME SLIGHTLY LESS FAVORABLE FOR LAKE EFFECT WED
NIGHT AS INVERSION HEIGHTS FALL A LITTLE...BUT THINGS SHOULD
CONTINUE ENOUGH THAT IMPACTS WILL BE FELT THU MORNING IN THE
FAVORED AREAS.


.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 305 PM EST MON FEB 8 2016

THE LONG TERM PATTERN WILL BE DOMINATED BY AN AIRMASS COLD ENOUGH
FOR LAKE EFFECT AND CYCLONIC LOW LEVEL FLOW. USUALLY THIS MEANS A
PROLONGED PERIOD OF SNOW SHOWERS...ESPECIALLY NEAR THE LAKESHORE.

AN ARCTIC FRONT DROPS SOUTHWARD THROUGH THE REGION FRIDAY INTO
FRIDAY NIGHT.  AT THE SAME TIME A WAVE OF LOW PRESSURE WILL BE
TRACKING ALONG IT. SNOW SHOWERS SHOULD INCREASE FOR MUCH OF THE
REGION AS THIS FRONT NEARS.  SOME IMPACTS POSSIBLE AS THE RISK FOR
SOME OF THESE SNOW SHOWERS TO BE LOCALLY HEAVY EXISTS.  THEN BEHIND
THE FRONT THE LOW LEVEL WINDS BECOME NORTHERLY AND DIVERGENT.
COMMONLY THIS CAUSES THE CLOUDS TO SCATTER OUT AND A DIMINISHING
TREND TO ANY SNOW SHOWER ACTIVITY.  THIS FLOW IN COMBINATION WITH
ARCTIC AIR IN PLACE SUPPORTS PUSHING THE MAIN SNOW BANDS OFFSHORE.
ON SATURDAY. IMPACTS FROM THE COLD ARE LIKELY TO HAPPEN AS SUB ZERO
TEMPERATURES LOOK LIKELY FOR MUCH OF THE REGION SATURDAY MORNING.

ON SUNDAY WARM AIR ADVECTION STARTS UP.  THE LOW LEVEL FLOW BECOMES
SOUTHWEST.  SOMETIMES THESE SETUPS LEAD TO ACCUMULATING SNOW ALONG
THE LAKESHORE.  WILL FEATURE RELATIVELY HIGH POPS GOING FOR THIS
POTENTIAL.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 652 PM EST MON FEB 8 2016

CONDITIONS THIS EVENING WILL RANGE FROM MVFR TO IFR WEST AND
SOUTH OF GRR WHERE SNOW SHOWERS OCCUR... TO VFR EAST OF GRR.
EVENTUALLY ALL THE TERMINALS SHOULD TREND INTO MVFR CATEGORY
OVERNIGHT AND TUESDAY WITH SOME OCNL IFR PERSISTING MAINLY WEST
AND SOUTH OF GRR. AN INCREASE IN WINDS IS FORECAST FOR TUESDAY...
WITH MOST AREAS SEEING SPEEDS OF 15-25 KTS BY 18Z OUT OF THE
NORTHWEST.


&&

.MARINE...
ISSUED AT 305 PM EST MON FEB 8 2016

WE HAVE EXTENDED THE SMALL CRAFT ADVISORY OUT THROUGH 00Z THU WITH
THIS FCST ISSUANCE. WE EXPECT WINDS TO INCREASE THIS EVENING AS LOW
PRESSURE STARTS TO SHIFT EAST OF THE AREA. WINDS WILL INCREASE TO
AROUND 25 TO 30 KNOTS AND SHOULD HOLD THERE THROUGH MUCH OF THE DAY
ON WED. THERE IS A CHC THAT WINDS COULD APPROACH GALES AT TIMES...
HOWEVER THIS SEEMS TO BE THE EXCEPTION RATHER THAN THE RULE.


&&

.HYDROLOGY...
ISSUED AT 1200 PM EST MON FEB 8 2016

COLDER TEMPERATURES (AS OPPOSED TO PRECIPITATION) WILL BE THE
HIGHLIGHT OF THE UPCOMING WEEK. DAYTIME HIGHS WILL CONSISTENTLY BE
BELOW FREEZING WITH NIGHTTIME TEMPERATURES INTO THE TEENS... AND
EVENTUALLY INTO THE SINGLE DIGITS BY THE END OF THE WEEK. STREAMS
AND RIVERS CONTINUE TO RUN HIGH. FORECAST TEMPERATURES AND HIGHER
RIVERS MAY CREATE SOME CONCERNS IN REGARDS TO ICE BUILD UP.
IN THE EVENT OF ICE FORMATION...FLUCTUATIONS COULD RESULT THROUGH
THE NEXT SEVERAL DAYS...POSSIBLY SENDING SOME LOCATIONS NEAR OR
OVER BANKFULL.

THE POSITIVE NOTE IS THAT PRECIPITATION OVER THE NEXT SEVERAL
DAYS WILL COME IN PERIODIC EPISODES. THE GREATEST TOTALS WILL
FAVOR LAKESHORE COUNTIES AND WILL BE IN THE FORM OF SNOW. FREEZING
TEMPERATURES WILL MINIMIZE RISK DUE TO RUNOFF...LIMITING THE RISK
MAINLY TO ICE JAM POTENTIAL.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY FROM 4 PM TUESDAY TO 10 AM EST THURSDAY
     FOR MIZ037-038-043-050-056-064-071.

LM...SMALL CRAFT ADVISORY UNTIL 7 PM EST WEDNESDAY FOR LMZ844>849.

&&

$$

UPDATE...JK
SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...MJS
AVIATION...MEADE
HYDROLOGY...JAM
MARINE...NJJ


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