803  
FXUS63 KGRR 290255  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
955 PM EST WED JAN 28 2015  
 
LATEST UPDATE...  
UPDATE  
   
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 00Z TAFS THROUGH 00Z THURSDAY EVENING)  
ISSUED AT 755 PM EST WED JAN 28 2015  
 
AVIATION IMPACTS DEVELOPING TONIGHT AND CONTINUING THURSDAY  
MORNING. THE MAIN ISSUE IS A MEDIUM TO HIGH CONFIDENCE ICING EVENT  
DUE TO SLEET AND FREEZING RAIN BETWEEN ROUGHLY 06Z AND 15Z. EXPECT  
MODERATE ICING BETWEEN THE SFC AND 3000 FT, AND ALSO BETWEEN 8000  
AND 16000 FT, DURING THIS TIME. 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 SNOW SHOWERS FROM NORTH TO  
SOUTH IN THE AFTERNOON.  
 
OTHER ISSUE IS LOW LEVEL WIND SHEAR/TURBULENCE BETWEEN ROUGHLY 02Z  
AND 10Z TONIGHT AS WINDS INCREASE TO 50 KT OUT OF THE SOUTHWEST IN  
THE 2000-4000 FT AGL LAYER. THE SFC WINDS DURING THIS TIME WILL BE  
OUT OF THE SOUTH-SOUTHEAST AT 12-16 KTS.  
 
LAST BUT NOT LEAST 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.  
 
THE PATTERN FOR THIS EVENT LOOKS VERY SPRINGLIKE. IN THE WARM  
SECTOR OF THIS SYSTEM... TEMPERATURES TODAY IN PARTS OF THE  
CENTRAL PLAINS WERE IN THE 70S. THIS AIR MASS... ACCOMPANIED BY  
PWATS NEAR 0.80... WILL BE PUSHING RAPIDLY NORTH TONIGHT AND  
INTERACTING WITH A SHALLOW COLD AND DRY AIR MASS OVER MI. SFC DEW  
POINTS WERE ONLY AROUND 10F IN MI AT 7 PM. THE CONTRAST ACROSS THE  
WARM FRONT IS BOUND TO RESULT IN SOME INTERESTING WEATHER IN TERMS  
OF PRECIPITATION TYPES... ALTHOUGH OVERALL COVERAGE/INTENSITY/AMOUNT  
OF PRECIPITATION IS STILL SOMEWHAT IN QUESTION AT THIS HOUR.  
 
LATEST SHORT RANGE GUIDANCE SUPPORTS DEVELOPMENT OF CONVECTIVE  
PRECIPITATION BETWEEN 06Z AND 09Z OVER SOUTHWEST LOWER MICHIGAN  
ON THE NOSE OF THE LOW LEVEL JET. FCST SOUNDINGS OVERNIGHT 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 FROM 1 AM TO 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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