732  
FXUS63 KGRB 291107  
AFDGRB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREEN BAY WI  
607 AM CDT WED MAR 29 2017  
 
UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE  
   
SHORT TERM...TODAY...TONIGHT
 
AND THURSDAY  
ISSUED AT 332 AM CDT WED MAR 29 2017  
 
SATELLITE IMAGERY SHOWS MID TO HIGH LEVEL CLOUDS ASSOCIATED WITH  
A STRONG STORM SYSTEM TRACKING FORM THE CENTRAL PLAINS TO THE MID  
MISSISSIPPI VALLEY REGION WILL INCREASE ACROSS THE AREA TODAY.  
THIS STORM SYSTEM WILL LIKELY PRODUCE SEVERE WEATHER ACROSS THE  
CENTRAL AND LOWER MISSISSIPPI VALLEY REGION THE NEXT FEW DAYS. FOR  
THIS AREA, AVAILABLE OBSERVATIONS AND WEB CAMS THIS MORNING NOT  
SHOWING ANY LOW STRATUS OR FOG THIS MORNING SO FAR. FOG AND  
STRATUS WAS NOTED ACROSS SOUTHEAST WISCONSIN, AND ACROSS FAR  
EASTERN UPPER MICHIGAN WORKING INTO THE FAR NORTHERN PORTION OF  
LAKE MICHIGAN. WILL WATCH TO SEE IF THERE IS ANY EXPANSION WHICH  
COULD IMPACT PART OF THE AREA THIS MORNING.  
 
OTHERWISE FOCUS WITH THIS FORECAST IS THE RAIN/SNOW MIX POTENTIAL  
STARTING TONIGHT AS THE NORTHERN PRECIPITATION REGION OF THE  
STORM SYSTEM WORKS INTO CENTRAL AND EAST CENTRAL WISCONSIN, AND  
THEN FURTHER NORTHWARD THURSDAY. THE LEADING EDGE OF THE  
PRECIPITATION IS ALREADY INTO IOWA AT 3 AM, SO WILL CONTINUE THE  
TREND OF LIGHT RAIN WORKING INTO CENTRAL WISCONSIN LATER BY THIS  
AFTERNOON. BOUNDARY LAYER TEMPERATURES SUGGESTS PRECIPITATION WILL  
START OUT AS LIGHT RAIN ACROSS CENTRAL AND EAST CENTRAL  
WISCONSIN LATE TODAY INTO THIS EVENING, BUT THEN TURN TO A MIX AS  
EVAP COOLING SATURATES THE COLUMN TO MOSTLY SNOW. TO COMPLICATED  
SNOW AMOUNT TOTALS, WILL BE DEALING WITH THE WARM GROUND AND SNOW  
MELT ON IMPACT. PRECIPITATION WILL LIKELY TURN TO MOSTLY SNOW BY  
EARLY THURSDAY MORNING. WILL ISSUE A SPS FOR A HEADS UP FOR THE  
MORNING COMMUTE. TREND OF THESE MODELS HAVE BEEN TO EDGE UP THE  
SNOWFALL TOTALS, AND IF THIS TREND CONTINUES, HEADLINES MAY BE  
NEEDED FOR PART OF THE AREA.  
 
THURSDAY WILL CONTINUE TO BE CHALLENGING WITH PRECIPITATION TYPE  
ACROSS THE AREA. BOUNDARY LAYER TEMPS INCREASE ENOUGH TO PRODUCE  
A MIX AND PERHAPS CHANGE TO MAINLY RAIN FOR THE DAY. LFQ OF AN  
UPPER JET NUDGES INTO EAST CENTRAL WISCONSIN THURSDAY MORNING, SO  
LIFT INTO THE HIGHER SNOW GROWTH MAY PRODUCE PERIODS OF SNOW.  
LOWERED MAX TEMPS A LITTLE FOR THURSDAY DUE TO THE PRECIPITATION.  
   
LONG TERM
 
THURSDAY NIGHT THROUGH TUESDAY  
ISSUED AT 332 AM CDT WED MAR 29 2017  
 
MODELS CONTINUE TO SHOW AN ACTIVE SPLIT FLOW ACROSS THE CONUS WITH  
AN UPPER RIDGE OVER THE EXTREME EASTERN PACIFIC INTO WESTERN  
CANADA AND A SERIES OF SYSTEMS DROPPING SOUTHEAST INTO THE  
SOUTHWEST CONUS BEFORE MOVING NORTHEAST ACROSS THE REST OF THE  
CONUS. THE FIRST SYSTEM WILL ALREADY BE STARTING TO PULL AWAY FROM  
THE GREAT LAKES AT THE BEGINNING OF THE EXTENDED FORECAST WITH  
SYSTEM #2 EXPECTED TO IMPACT THE GREAT LAKES DURING THE MONDAY  
NIGHT-TUESDAY TIME FRAME. PRECIPITATION TYPE COULD AGAIN BECOME A  
NIGHTTIME ISSUE WHEN TEMPERATURES FALL CLOSE TO THE FREEZING MARK.  
 
THE FIRST SYSTEM IS EXPECTED TO SLOWLY MOVE EAST-NORTHEAST FROM  
THE MID-MS VALLEY TO JUST NORTH OF THE LOWER REACHES OF THE OHIO  
RIVER VALLEY THURSDAY NIGHT. OTHER THAN NORTH-CENTRAL WI, WE  
SHOULD STILL SEE PRECIPITATION LINGER OVER THE REST OF NORTHEAST  
WI THROUGH AT LEAST THURSDAY EVENING WITH LIGHT RAIN BECOMING  
MIXED WITH LIGHT SNOW OR LIGHT FREEZING RAIN AS TEMPERATURES BEGIN  
TO FALL. LITTLE OF ANY ACCUMULATION OF SNOW OR ICE IS ANTICIPATED,  
BUT WILL HAVE TO WATCH FOR POSSIBLE ICING ON AREA ROADS AS ANY  
PONDING OF WATER COULD FREEZE AS TEMPERATURES DROP BELOW FREEZING.  
MIN TEMPERATURES ARE FORECAST TO BE IN THE MIDDLE TO UPPER 20S  
NORTH-CENTRAL WI, LOWER TO MIDDLE 30S ELSEWHERE.  
 
DUE TO THE OVERALL SLOW MOVEMENT OF THIS SYSTEM (ONLY FORECAST TO  
REACH CENTRAL/EASTERN OH BY 00Z SATURDAY), IT IS NOT UNCONCEIVABLE  
THAT A LITTLE LIGHT RAIN OR MIXED PRECIPITATION COULD CARRY OVER  
INTO FRIDAY MORNING OVER PARTS OF EAST-CENTRAL WI BEFORE FINALLY  
PULLING AWAY IN THE AFTERNOON. A WEAK RIDGE OF IS THEN EXPECTED TO  
MOVE TOWARD THE WESTERN GREAT LAKES LATER ON FRIDAY AND BRING  
DECREASING CLOUDS FROM NORTHWEST TO SOUTHEAST THROUGH THE DAY,  
ALTHOUGH THIS CLEARING LINE MAY NOT MAKE IT TO EAST-CENTRAL WI  
UNTIL LATE AFTERNOON. NORTHEAST WI WILL STILL BE DEALING WITH A  
PREVAILING NORTHEAST WIND, THUS MAX TEMPERATURES TO RANGE FROM THE  
LOWER 40S NEAR LAKE MI, TO THE UPPER 40S NORTH-CENTRAL WI WHERE  
THE SUN TO ARRIVE FIRST.  
 
THE SURFACE RIDGE REMAINS OVER THE REGION FRIDAY NIGHT, BRINGING  
MOSTLY CLEAR TO PARTLY CLOUDY SKIES, LIGHT WINDS AND SEASONAL  
TEMPERATURES. LOOK FOR MINS TO BE IN THE MIDDLE 20S NORTH TO  
AROUND 30 DEGREES SOUTH. QUIET WEATHER CONDITIONS WILL CONTINUE  
INTO SATURDAY AS THE SURFACE RIDGE STARTS TO SLIDE TO OUR EAST.  
DEPENDING ON THE TIMING OF A WEAK NORTHERN STREAM SHORTWAVE TROUGH  
(THE GFS IS FASTER THAN OTHER MODELS), THERE COULD BE AN INCREASE  
IN CLOUDS ACROSS THE AREA. DO NOT HAVE ENOUGH CONFIDENCE ON THE  
TIMING OF THIS FEATURE TO JUSTIFY CARRYING ANY POPS AT THIS TIME  
AND PREFER TO REMOVE THE PREVIOUS POPS PLACED OVER THE FAR NORTH.  
MAX TEMPERATURES FOR SATURDAY SHOULD BE IN THE MIDDLE 40S NEAR  
LAKE MI, MAINLY LOWER TO MIDDLE 50S ELSEWHERE.  
 
NORTHEAST WI TO BE ON THE WESTERN FRINGES OF THE RETREATING  
SURFACE RIDGE WHILE UPPER HEIGHTS ALSO BUILD DURING THE LATTER  
HALF OF THE UPCOMING WEEKEND. GENERALLY PARTLY CLOUDY SKIES ARE  
EXPECTED WITH TEMPERATURES SLIGHTLY ABOVE NORMAL. THIS WOULD TAKE  
MAX TEMPERATURES ON SUNDAY INTO THE UPPER 40S NEAR LAKE MI, LOWER  
TO MIDDLE 50S MOST OTHER LOCATIONS. THERE COULD BE A FEW UPPER 50S  
WEST OF THE FOX VALLEY IF MORE SUN CAN WIN OUT OVER THE CLOUDS.  
 
FORECAST BECOMES MORE COMPLEX EARLY NEXT WEEK AS A SOUTHERN STREAM  
SYSTEM IS PROGGED TO MOVE FROM THE SOUTHERN PLAINS NORTHEASTWARD  
THROUGH THE OH/TN VALLEYS TOWARD THE NEW ENGLAND STATES. THE MAIN  
ISSUE IS A TRAILING NORTHERN STREAM SHORTWAVE TROUGH AND WHETHER  
THESE TWO SYSTEMS WILL STAY APART OR ATTEMPT TO PHASE. IF THESE  
SYSTEMS STAY APART, PRECIPITATION POTENTIAL FOR NORTHEAST WI  
MONDAY AND TUESDAY WOULD BE MINIMAL AS THE SOUTHERN SYSTEM WOULD  
PASS TOO FAR TO OUR SOUTH. IF THESE SYSTEMS DO INTERACT WITH ONE  
ANOTHER, WE WOULD BE IN FOR A STRETCH OF UNSETTLED WEATHER BOTH  
MONDAY AND TUESDAY. THE CONSENSUS OF MODELS WOULD FAVOR KEEPING  
THE SYSTEMS SEPARATE, HOWEVER EITHER SOLUTION IS STILL PLAUSIBLE.  
THEREFORE, HAVE KEPT A LOW CHANCE POP IN THE FORECAST FOR NOW BOTH  
MONDAY AND TUESDAY. OBVIOUSLY, TEMPERATURES WOULD BE COMPLETELY  
DEPENDENT ON WHICH SOLUTION ENDS UP BEING CORRECT WITH MAX  
TEMPERATURES EITHER IN THE 40S WITH RAIN OR 50S WITH SUN.  

 
   
AVIATION
 
FOR 12Z TAF ISSUANCE  
ISSUED AT 607 AM CDT WED MAR 29 2017  
 
MAINLY VFR CONDITIONS WERE OCCURRING ACROSS THE REGION EARLY THIS  
MORNING AND WILL LIKELY CONTINUE INTO THIS AFTERNOON. THERE IS A  
REGION OF IFR CONDITIONS DUE TO FOG LOCATED OVER NORTHERN LAKE  
MICHIGAN AND DRIFTING SOUTH. AT 6 AM, THE FOG AND STRATUS WAS  
ABOUT 15 TO 20 MILES OFFSHORE OF GILLS ROCK. OTHERWISE AS RAIN  
WORKS NORTH ACROSS THE STATE THIS AFTERNOON, LOOK FOR MVFR CIGS  
SPREADING NORTH WITH FURTHER DETERIORATION OF CONDITIONS TONIGHT  
AS A RAIN AND SNOW MIX DEVELOP.  
 

 
   
GRB WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM.....TDH  
LONG TERM......KALLAS  
AVIATION.......TDH  
 
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