Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 290515
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1215 AM EST THU JAN 29 2015

LATEST UPDATE...
AVIATION

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

ROADS COULD BE ICY ON THURSDAY MORNING AS LOW PRESSURE BRINGS A
WINTRY MIX OF PRECIPITATION LATE TONIGHT. TEMPERATURES SHOULD RISE
ABOVE FREEZING BY LATE MORNING AND CONDITIONS SHOULD IMPROVE. SOME
LIGHT SNOW IS EXPECTED DURING THE AFTERNOON WITH ACCUMULATIONS AN
INCH OR LESS. IT WILL TURN MUCH COLDER ON FRIDAY AND INTO THE
WEEKEND.

&&

.UPDATE...
ISSUED AT 955 PM EST WED JAN 28 2015

NO BIG CHANGES TO THE FORECAST. STILL EXPECTING A RAPID INCREASE
IN PCPN COVERAGE AS THE LOW LEVEL JET ARRIVES ALONG WITH DEEPER
LOW LEVEL MOISTURE. THIS WILL OCCUR BETWEEN 06-09Z. PCPN TYPE
SHOULD BE MAINLY FREEZING RAIN AND SLEET ALONG I-94. ALSO FREEZING
AND SLEET ALONG I-96 WHICH MAY START CHANGING OVER THE SNOW TOWARD
DAYBREAK. AND SNOW MIXED WITH SOME SLEET TOWARD HIGHWAY 10. THE
PEAK OF THE PCPN WILL COINCIDE WITH THE MORNING COMMUTE AND THE
ADVISORY STILL LOOKS GOOD WITH AROUND A TENTH OF AN INCH OF ICE
EXPECTED THROUGH MID DAY THURSDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 328 PM EST WED JAN 28 2015

KEPT THE HEADLINES AS IS. MAIN THREAT APPEARS TO BE LIGHT FREEZING
RAIN LATE TONIGHT WHICH WILL CAUSE ICY ROADS FOR THE THURSDAY
MORNING COMMUTE. WARM AIR ADVECTION IS ALREADY UNDERWAY AND
STRENGTHENS OVERNIGHT. AS THE VERY WARM AIR ACROSS THE PLAINS
ADVECTS EAST WE WILL SEE 850 MB TEMPS GO ABOVE 0C FOR BY 06Z FOR
ALL BUT THE FAR NORTHERN TIER. WE START OFF VERY DRY SO TEMPS WILL
DROP AS THE COLUMN SATURATES AND WE COULD SEE A QUICK BURST OF
SNOW AT THE ONSET BEFORE PRECIP GOES OVER TO IP AND FZRA. DO NOT
EXPECT MUCH QPF SO ICE AMOUNTS WILL BE LIMITED...BUT ENOUGH TO
CAUSE POTENTIAL TRAVEL PROBLEMS BEGINNING AFTER MIDNIGHT AND
CONTINUING THROUGH THE MORNING COMMUTE.

SOUTHERLY FLOW THROUGH THE MORNING SUGGESTS THAT SFC TEMPS SHOULD
WARM AS ANY FREEZING PRECIP BRINGS LATENT HEAT EFFECTS THAT ARE NOT
BEING OFFSET BY CAA NEAR THE SFC. SO EXPECT ICING ISSUES TO END
DURING THE MORNING. SFC LOW MOVES EAST AND COLD AIR ADVECTION ON
NORTHWEST FLOW BEGINS AFTER 18Z WITH PRECIP TRANSITIONING BACK TO
SNOW FROM NORTH TO SOUTH. SNOW ACCUMULATIONS AN INCH OR LESS AND
TEMPERATURES SHOULD NOT BE COLD ENOUGH TO ALLOW MUCH ACCUMULATION ON
ROADS...SO IMPACTS ARE EXPECTED TO BE MINOR.

SYNOPTIC SNOWS END BY EVENING WITH SOME NORTH TO NORTHWEST LAKE
EFFECT. INVERSION HEIGHTS ARE AOB 5KFT DURING THE EVENING SO LAKE
EFFECT SHOULD NOT BE HEAVY.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 328 PM EST WED JAN 28 2015

OVERALL MODELS ARE TRENDING FURTHER SOUTH WITH THE TRACK OF THE LOW
SATURDAY NIGHT THROUGH SUNDAY...SUGGESTING LOWER MICHIGAN WILL END
UP WITH LESS PRECIPITATION AND COLDER TEMPERATURES.  HIGH RES EURO
SUGGESTS A DRY FORECAST IS THE WAY TO GO FOR SUNDAY.  NOT READY TO
DROP POPS COMPLETELY...BUT THE PATTERN WE ARE IN HAS BEEN A DRY
ONE.  AS A RESULT I WILL LOWER POPS ON SUNDAY AND BACK OFF ON THE
QPF CONSIDERABLY.

LOOKING FURTHER AHEAD...STRONGER WARM AIR ADVECTION IS NOTED FOR
TUESDAY.  WITH AN ARCTIC AIRMASS IN PLACE...THAT SHOULD SUPPORT A
SOUTHWEST FLOW EVENT. POPS WERE INCREASED...ESPECIALLY WEST OF GRAND
RAPIDS.

I DID LOWER TEMPERATURES ESPECIALLY SUNDAY NIGHT AND MONDAY GIVEN
THE DOMINANCE OF THE ARCTIC AIR.  THE MODELS COMMONLY ARE TOO WARM
WITH THE NIGHTTIME LOWS DURING THESE EVENTS.

&&

.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 THURSDAY FOR MIZ037-043-
     044-050>052-056>059-064>067-071>074.

LM...NONE.
&&

$$

UPDATE...JK
SYNOPSIS...OSTUNO
SHORT TERM...OSTUNO
LONG TERM...MJS
AVIATION...MEADE
HYDROLOGY...OSTUNO





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