Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 290818
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
318 AM EST THU JAN 29 2015

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

.SYNOPSIS...
ISSUED AT 318 AM EST THU JAN 29 2015

A WINTRY MIX WILL CONTINUE TODAY.  SOME AREAS MAY SEE UP TO A TENTH
OF INCH OF ICE BY MID DAY.  THE PRECIPITATION WILL BE CHANGING OVER
TO MOSTLY SNOW BY THIS AFTERNOON.  AND AS COLDER AIR MOVES IN...SOME
LAKE EFFECT SNOW WILL DEVELOP TONIGHT AND CONTINUE INTO FRIDAY.
HOWEVER SNOW ACCUMULATIONS ARE EXPECTED TO BE LIGHT...GENERALLY AN
INCH OR TWO.  AFTER HIGHS IN THE 30S TODAY...IT WILL COOL TO ONLY
AROUND 20 BY FRIDAY.

A STORM SYSTEM WILL MOVE SOUTH OF THE AREA SUNDAY AND MONDAY.  WE
WILL HAVE TO KEEP AN EYE ON THIS AS IT MAY GIVE SOUTHWEST MICHIGAN
MORE SNOW.  EITHER WAY...IT WILL GET MUCH COLDER INTO NEXT WEEK WITH
DAYTIME HIGHS ONLY IN THE TEENS SUNDAY THROUGH WEDNESDAY.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 318 AM EST THU JAN 29 2015

WILL MAINTAIN THE HEADLINE AS IS.  THE WINTRY MIX WILL CONTINUE...
ALTHOUGH IT WILL TREND TOWARD MORE SNOW FROM NW TO SE THROUGH THE
MORNING.

COMPLICATED FORECAST DAY AS WE WILL SEE EBBS AND FLOWS IN THE PCPN
TODAY.  AS OF 08Z WE WERE SEEING AN AREA OF MIXED PCPN MOVING INTO
THE REGION.  THIS WAS ON THE NOSE OF THE LOW LEVEL JET.  IT WAS A
FAIRLY NARROW BAND THAT WAS MOVING NE AT 30 KNOTS.  SO THIS WON/T BE
OVER ANY ONE AREA FOR MUCH MORE THAN A COUPLE HOURS...BUT ENOUGH TO
PUT DOWN A LIGHT GLAZE AND IMPACT THE MORNING COMMUTE.

IT APPEARS WE WILL THAN HAVE A SHORT BREAK IN THE PCPN AROUND MID
MORNING...THEN THE DEFORMATION ZONE MOVES IN LATE MORNING/EARLY
AFTERNOON.  THIS SHOULD BE MOSTLY SNOW...WITH PERHAPS SOME MIX STILL
ALONG I-94.  FINALLY...ONCE THE DEEPER MOISTURE EXITS WE MAY SEE A
PERIOD OF FREEZING DRIZZLE AS THE DGZ BECOMES UNSATURATED.  THE
NORTHERN CWA APPEARS SETUP BEST FOR THIS AS SOME OMEGA IS STILL SEEN
WITHIN THE CLOUD LAYER.  THE FZDZ COULD LAST THROUGH THE LATTER HALF
OF THE AFTERNOON...BEFORE IT COMES AN END.  ALL-IN-ALL A MESSY DAY.
HOWEVER ANY ICE ACCUMULATION SHOULD REMAIN UNDER A TENTH OF AN
INCH.  SNOW ACCUMULATIONS SHOULD BE LESS THAN AN INCH ALONG I-96...
AND UP TO TWO INCHES TOWARD HIGHWAY 10.

WE WILL GET INTO A PERIOD OF LIGHT LAKE EFFECT SNOWS TONIGHT AND
FRIDAY AS -15C H8 AIR MOVES OVER THE LAKE.  THE MEAN LOW LEVEL FLOW
WILL BE 318-330 WHICH WILL FAVOR AREAS WEST OF U.S. 131.  INVERSION
LEVELS REMAIN LOW...4500 FT OR LESS...SO NOT EXPECTING ANYTHING
HEAVY.  AN INCH OR TWO CAN BE EXPECTED HERE...WHILE INLAND AREAS SEE
LESS THAN AN INCH.  IT WILL TURN SHARPLY COLDER WITH LOWS OF 10 TO
15 TONIGHT AND FRIDAY NIGHT...WHILE FRIDAY/S HIGHS WILL ONLY BE
AROUND 20.

A COLD FRONT WILL SLOWLY DROP IN FROM THE NW BY LATE SATURDAY.  THE
FRONT LOOKS FAIRLY MOISTURE STARVED...BUT COMBINED WITH SOME LAKE
ENHANCEMENT WE MAY BE ABLE TO SQUEEZE OUT UP TO AN INCH OF SNOW OVER
THE NW CWA AS IT COMES IN.  SW WINDS AHEAD OF THE FRONT WILL HELP
TEMPS APPROACH 30.

.LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 318 AM EST THU JAN 29 2015

LITTLE CHANGE TO THE PREVIOUS FORECAST EXCEPT TO LOWER POPS/QPF
FURTHER ON SUNDAY. CONFIDENCE IS GROWING THAT BEST PROSPECTS FOR
MEASURABLE SNOW LOOK TO BE SOUTH OF I-96...IF NOT SOUTH OF I-94.

NEXT NOTABLE CHANCE FOR SNOW IS TUESDAY WITH A BURST OF WARM
ADVECTION THAT IS PORTRAYED MORE AGGRESSIVELY BY THE GFS THAN THE
ECMWF. THIS WILL BE FOLLOWED BY A SIGNIFICANT INTRUSION OF COLD AIR
WEDNESDAY AND THURSDAY...WITH THE 29/00Z ECMWF DOWN TO -25C AT 850
MB BY THURSDAY MORNING. THIS WILL BE FAVORABLE FOR LAKE EFFECT
SNOW...BUT AMOUNTS SHOULD BE GREATLY CURTAILED BY UNFAVORABLE
MICROPHYSICS ASSOCIATED WITH THE VERY COLD AIR. ADVERTISED HIGHS
THURSDAY ARE CURRENTLY IN THE TEENS...BUT THIS MAY NEED TO BE
LOWERED IF THE ECWMF TRENDS CONTINUE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1215 AM EST THU JAN 29 2015

NO MAJOR CHANGES TO THE 06Z TAFS. IT CONTINUES TO LOOK LIKE AN
ICING EVENT DEVELOPING OVERNIGHT INTO THURSDAY MORNING WITH
FREEZING RAIN AND SLEET. EXPECT MODERATE ICING BETWEEN THE SFC AND
3000 FT AND ALSO BETWEEN 8000 AND 18000 FT. TEMPERATURES BETWEEN
3000 FT AND 8000 FT SHOULD BE MOSTLY ABOVE FREEZING WITH MAINLY
RAIN EXPECTED IN THAT LAYER. LOWERING FREEZING LEVELS AFTER 15Z-
18Z THURSDAY WILL LEAD TO PRECIP CHANGING TO MOSTLY ALL LIGHT SNOW
SHOWERS FROM NORTH TO SOUTH IN THE AFTERNOON.

OTHER ISSUE IS LOW LEVEL WIND SHEAR/TURBULENCE THROUGH 10Z TONIGHT
WITH 50 KT WINDS OUT OF THE SOUTHWEST IN THE 2000-4000 FT AGL
LAYER AND SFC WINDS OUT OF THE SOUTH-SOUTHEAST AT 12-16 KTS.

EXPECT NUMEROUS IFR CIGS/VSBYS BETWEEN 12Z AND 18Z THURSDAY AS
THE SFC LOW/TROUGH TRACKS ACROSS MI. CIGS/VSBYS IMPROVING AFTER
18Z THURSDAY WITH THE PASSAGE OF THE LOW ALTHOUGH WINDS
SHIFTING/INCREASING OUT OF THE NORTHWEST TO 15-25 KTS WITH SOME
GUSTS OVER 30 KTS POSSIBLE. THIS WILL LEAD TO MORE LOW LEVEL
TURBULENCE DEVELOPING.

RADAR MOSAIC AT MIDNIGHT SHOWS ECHOES DEVELOPING ACROSS NRN/ERN IL
SHIFTING THIS WAY. SHORT RANGE GUIDANCE HAS BEEN SUGGESTING THIS
AREA WILL EXPAND AND INCREASE IN INTENSITY OVER SW LWR MI THROUGH
09Z. HOWEVER IT STILL REMAINS QUESTIONABLE JUST HOW PERSISTENT AND
WIDESPREAD THIS AREA OF PRECIP WILL BE EARLY THURSDAY MORNING.

FCST SOUNDINGS CONTINUE TO SUPPORT PREDOMINATELY FREEZING RAIN
WITH SOME SLEET POSSIBLY MIXED IN FOR THE AZO/BTL/JXN TERMINALS
AND I-94 CORRIDOR REGION. MEANWHILE THE MKG/GRR/LAN TERMINALS ARE
CLOSER TO THE TRANSITION ZONE TO MOSTLY SNOW WHICH SHOULD BE JUST
NORTH OF THE I-96 CORRIDOR. SUSPECT THESE TERMINALS WILL SEE MORE
IN THE WAY OF A SNOW/SLEET/FREEZING RAIN MIXTURE... WITH LESS
FREEZING RAIN THAN TO THE SOUTH.

&&

.HYDROLOGY...
ISSUED AT 328 PM EST WED JAN 28 2015

COLD WEATHER WITH ONLY LIGHT PRECIPITATION SHOULD MEAN NO
SIGNIFICANT TRENDS IN THE RIVERS. ICE WILL FORM OVER THE WEEKEND
AS THE COLD INTENSIFIES.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
MIZ037-043-044-050>052-056>059-064>067-071>074.

LM...NONE.
&&

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...TJT
AVIATION...MEADE
HYDROLOGY...OSTUNO








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