187  
FXUS63 KGRR 210739  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
240 AM EST TUE FEB 21 2017  
 
LATEST UPDATE...  
SYNOPSIS/SHORT TERM/LONG TERM/CLIMATE/MARINE  
   
SYNOPSIS
 
 
ISSUED AT 240 AM EST TUE FEB 21 2017  
 
RAIN SHOWERS ASSOCIATED WITH A WEAK COLD FRONT WILL MOVE THROUGH THE  
AREA THROUGH THIS MORNING. THE SHOWERS WILL COME TO AN END AT MOST  
LOCATIONS BY AFTERNOON, AND CLEARING SKIES CAN BE EXPECTED.  
 
WE WILL SEE ONE MORE POTENTIAL RECORD WARM DAY ON WEDNESDAY AS  
ANOTHER SURGE OF WARMTH WILL MOVE UP OVER THE AREA AHEAD OF THE NEXT  
SYSTEM THAT WILL PASS THROUGH WEDNESDAY NIGHT INTO THURSDAY. A MUCH  
STRONGER SYSTEM WILL BEGIN TO MOVE IN LATE THURSDAY AND ON FRIDAY.  
THIS WILL BRING MORE WIDESPREAD RAINS AND A FEW STORMS, SOME OF  
WHICH COULD BECOME STRONG.  
 
COLDER AIR WILL MOVE IN FRIDAY NIGHT AND SATURDAY BEHIND THE SYSTEM.  
THIS WILL CHANGE RAIN SHOWERS OVER TO SOME LIGHT SNOW ACROSS THE  
AREA BEFORE THEY END ON SATURDAY. COOLER WEATHER CAN THEN BE  
EXPECTED THROUGH EARLY NEXT WEEK.  
 

 
   
SHORT TERM
 
(TODAY THROUGH THURSDAY)  
ISSUED AT 240 AM EST TUE FEB 21 2017  
 
OUR ITEMS OF INTEREST IN THE SHORT TERM ARE RAIN CHANCES FOR TODAY  
AND AGAIN WED NIGHT/THU, AND THE POTENTIAL FOR RECORD MAX TEMPS. NO  
REAL CHANGES HAVE BEEN MADE TO THE FCST.  
 
BAND OF RAIN SHOWERS TO OUR WEST AND SOUTHWEST ARE SLOWLY  
PROGRESSING TOWARD THE AREA ON SCHEDULE. MOISTURE TRANSPORT IS  
HOLDING ITS OWN SUPPORTING THESE SHOWERS, BUT WILL START TO WEAKEN  
AS IT MOVES THROUGH THE AREA. WE ARE STILL EXPECTING THAT THEY WILL  
EXIT MOST OF THE CWFA BY EARLY AFTERNOON. WE SHOULD SEE THE CLOUDS  
CLEAR OUT AND ALLOW TEMPS TO WARM BACK UP INTO THE 50S AND 60S.  
 
WE SHOULD STAY DRY THEN FOR TONIGHT AND WEDNESDAY, ALTHOUGH WE CAN  
NOT RULE OUT A SPRINKLE DURING THE TIME FRAME. WE WILL SEE THE COLD  
FRONT MOVING THROUGH TODAY RETURN NORTH AS A WARM FRONT LATER  
TONIGHT AND WED. MOISTURE IS QUITE LIMITED, SO WE ARE NOT REALLY  
EXPECTING ANYTHING.  
 
AS WE GET INTO THE WARM SECTOR ON WED, RECORD HIGHS WILL ONCE AGAIN  
BE LIKELY. SW FLOW WILL LIMIT THE HEATING POTENTIAL A BIT FOR AREAS  
DOWNWIND OF LAKE MICHIGAN. AREAS FURTHER S AND E WILL SEE MUCH  
BETTER WARMING WITHOUT THE INFLUENCE OF LAKE MICHIGAN. THE I-94  
CORRIDOR WILL HAVE A CHANCE OF TOUCHING 70 WITH H850 TEMPS OF AROUND  
10-11C NOSING IN.  
 
ANOTHER COLD FRONT WILL PUSH THROUGH PRIOR TO DAYBREAK THU MORNING.  
THE CHANCES OF RAIN ARE NOT ZERO WITH THIS, BUT MOISTURE IS RATHER  
LIMITED ONCE AGAIN FOR THE TIME BEING. THIS WILL CHANGE LATE THU  
AFTERNOON AND MORE SO AFTER THE SHORT TERM. THE FRONT WILL GET HUNG  
UP ONCE AGAIN AS THE MAIN LOW APPROACHES THE AREA, AND STARTS TO  
ADVECT MUCH BETTER MOISTURE FROM THE GULF OVER THE FRONT.  
   
LONG TERM
 
(THURSDAY NIGHT THROUGH MONDAY)  
ISSUED AT 240 AM EST TUE FEB 21 2017  
 
FORECAST CONCERNS CONTINUE TO DEAL WITH A FAIRLY STRONG STORM THAT  
IS PROGD TO MOVE ACROSS LAKE MICHIGAN AND CENTRAL LOWER MICHIGAN  
FRIDAY. BOTH THE ECMWF AND GFS SHOW SIMILAR STRUCTURE, TRACK AND  
TIMING WHICH IS LEADING TO HIGHER CONFIDENCE IN THE SOLUTION.  
 
GFS ENSEMBLE MEAN SHOWS A WARM FRONT MOVING NORTH ACROSS THE CWA BY  
12Z FRIDAY. THE SFC LOW IS PROGD TO MOVE FROM NORTHEAST IOWA AT 12Z  
TO NORTHERN LOWER BY 00Z SATURDAY. A 50 KT LLJ WILL DRAW ABUNDANT  
MOISTURE NORTH FROM THE GULF. AS THIS MOISTURE CROSSES THE NORTHWARD  
MOVING WARM FRONT THURSDAY NIGHT, SHOWERS WILL DEVELOP. ACROSS THE  
NORTHERN CWA WHERE SFC TEMPS WILL BE AOB FREEZING, SOME FREEZING  
RAIN IS POSSIBLE. THIS COULD LAST FOR 6 HOURS OR SO BEFORE WARMER  
AIR ARRIVES IN THE 12Z-15Z TIME FRAME.  
 
INSTABILITY QUICKLY INCREASES WITH LI'S FALLING TO -4C OR SO BY 18Z  
FRIDAY. STRONG DYNAMICS WITH RESPECT TO LIFT SUCH AS THE APPROACHING  
COLD FRONT, UPPER SHORT WAVE, AND THE ARRIVAL OF THE LEFT EXIT  
REGION OF THE UPPER JET WILL PROVIDE FAVORABLE CONDITIONS FOR  
CONVECTION. SHEAR VALUES AROUND 50 KTS STRONGLY POINT TOWARD  
ORGANIZATION. WHILE THIS DOESN'T LOOK LIKE A TORNADIC SITUATION...  
HODOGRAPHS ARE RATHER MEAGER... FRIDAY AFTERNOON COULD BE OUR FIRST  
SEVERE WX DAY OF THE YEAR WITH STRONG WIND THE MAIN THREAT AND 16Z-  
24Z THE MAIN TIME FRAME. IT'S ONLY TUESDAY, SO WE WON'T GET TOO  
CARRIED AWAY WITH THIS AS THE MODELS WILL CHANGE SOME BY FRIDAY.  
 
AFTER THE TRAILING COLD FRONT MOVES THROUGH LATE FRIDAY, COLDER AIR  
WILL FLOW INTO THE STATE. H8 TEMPS FALL FROM -12C SATURDAY MORNING  
TO -16C BY SUNDAY MORNING. WE HAVE SNOW SHOWERS IN THE GRIDS.  
MOISTURE APPEARS LIMITED WITH THIS SITUATION SO ACCUMS WILL BE  
LIMITED.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)  
ISSUED AT 1207 AM EST TUE FEB 21 2017  
 
A WEAK COLD FRONT WILL MOVE ACROSS LOWER MICHIGAN THIS MORNING.  
OBS ALONG THE FRONTAL BOUNDARY SHOW IFR/MVFR CONDITIONS AND WE  
EXPECT THOSE LOWER CIGS/VSBYS TO DEVELOP AFTER 10Z. NATIONAL RADAR  
SHOWS A LONG TRAIN OF ECHOS FROM LAKE SUPERIOR SOUTH TO THE GULF  
AND SOME OF THESE SHOWERS WILL WORK THEIR WAY UP AND THROUGH THE  
TAF SITES THIS MORNING. SKIES WILL CLEAR THIS AFTERNOON, BUT  
RESIDUAL MOISTURE NEAR THE GROUND MAY RESULT IN MORE FOG  
DEVELOPMENT TONIGHT.  
 

 
   
MARINE
 
 
ISSUED AT 240 AM EST TUE FEB 21 2017  
 
WE WILL NEED TO HOLD ON TO THE SMALL CRAFT ADVISORY FOR JUST A FEW  
MORE HOURS THIS MORNING. WINDS WILL BE COMING DOWN, BUT WAVES WILL  
TAKE A LITTLE LONGER TO COME DOWN SUFFICIENTLY BELOW THE 4 FT  
CRITERIA.  
 
THERE IS A CHANCE ANOTHER ADVISORY WILL BE NEEDED FOR THE WED TIME  
FRAME. THIS WILL BE JUST OUT AHEAD OF THE NEXT FRONTAL SYSTEM THAT  
WILL MOVE THROUGH THE AREA. WE ARE NOT SURE IF THE WINDS ALOFT WILL  
BE ABLE TO MIX DOWN. IT IS SOMETHING WORTH MONITORING.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 100 PM EST MON FEB 20 2017  
 
BASIN AVERAGE RAINFALL THROUGH TOMORROW IS EXPECTED TO BE RANGING  
FROM A COUPLE TENTHS OF AN INCH OVER THE GRAND AND KALAMAZOO RIVER  
BASINS TO PERHAPS A HALF INCH ACROSS THE WESTERN REACHES OF THE  
MUSKEGON RIVER BASIN. THIS RAINFALL SHOULD NOT LEAD TO ANY  
APPRECIABLE RISES ON THE MAIN STEM RIVERS. MORE SUBSTANTIAL  
RAINFALL IS POSSIBLE THURSDAY NIGHT THROUGH FRIDAY AS A  
STRENGTHENING STORM SYSTEM APPROACHES THE GREAT LAKES. THE  
PLACEMENT OF THIS HEAVIER RAINFALL IS STILL IN QUESTION, BUT  
MODELS ARE INDICATING AN INCH OR MORE POSSIBLE WHERE IT DOES SET  
UP. BOTH SMALL STREAM AND MAIN STEM RIVER RISES LOOK LIKELY IF  
THIS PATTERN HOLDS.  
 

 
   
CLIMATE
 
 
ISSUED AT 240 AM EST TUE FEB 21 2017  
 
THE RECORDS FOR OUR OFFICIAL SITES THROUGH WEDNESDAY ARE AS FOLLOWS:  
 
TUE 2/21 WED 2/22  
 
GRAND RAPIDS 66 - 1930 67 - 1930  
 
LANSING 62 - 1930 66 - 1930  
 
MUSKEGON 58 - 1930 55 - 1930  
 
OUR CURRENT THINKING IS THAT WE WILL COME UP JUST SHY OF ALL OF THE  
RECORDS FOR TODAY. A LITTLE EXTRA SUNSHINE, AND THEY COULD BE  
APPROACHED.  
 
THE RECORDS FOR WEDNESDAY DO LOOK IN JEOPARDY OF BEING BROKEN FOR  
THE MOST PART. THE MOST DIFFICULT ONE WILL BE GRAND RAPIDS, BUT IT  
WILL BE CLOSE.  
 

 
   
GRR WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LM...SMALL CRAFT ADVISORY UNTIL 11 AM EST THIS MORNING FOR  
LMZ844>849.  
 

 
 

 
 
SYNOPSIS...NJJ  
SHORT TERM...NJJ  
LONG TERM...04  
AVIATION...04  
HYDROLOGY...HOVING  
CLIMATE...NJJ  
MARINE...NJJ  
 
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