470  
FXUS63 KMPX 281715  
AFDMPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN  
1215 PM CDT FRI APR 28 2017  
   
UPDATE
 
 
ISSUED AT 1207 PM CDT FRI APR 28 2017  
 
UPDATED TO INCLUDE 18Z AVIATION DISCUSSION BELOW.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 425 AM CDT FRI APR 28 2017  
 
EARLY MORNING WATER VAPOR IMAGERY TOGETHER WITH GFS 500MB HEIGHTS  
AND WINDS SHOWED A POSITIVELY TILTED TROUGH WITH A VERY STRONG  
UPPER LEVEL JET READY TO MANIFEST ITSELF IN A POWERFUL SYNOPTIC  
CYCLONE THAT WILL BRING EXTENSIVE HEAVY RAIN AND FLOODING ACROSS  
THE CENTRAL CONUS THIS WEEKEND. IN THE MEAN TIME EXPECT SURFACE  
HIGH PRESSURE TO BUILD ACROSS THE UPPER MIDWEST A BRING A BRIEF  
WINDOW OF DRY CONDITIONS OVER MINNESOTA AND WISCONSIN. WINDS WILL  
BE LIGHT AND TEMPERATURES WILL REMAIN COOL WITH FRIDAY'S HIGHS 10  
TO 15 DEGREES BELOW THE SEASONAL AVERAGE FOR LATE APRIL.  
 
FROM A PURE METEOROLOGICAL STANDPOINT, ONE HAS TO APPRECIATE THE  
WEATHER THAT WILL BEGIN TO UNFOLD OVER THE NEXT 36 HOURS. A  
POWERFUL SUPER-POSITIONED UPPER LEVEL JET CRASHING ON SHORE THE  
WEST COAST IS ALREADY SHOWING ITS HAND WITH THE PRECIPITATION  
DEVELOPING OVER THE CENTRAL PLAINS. DOWNSTREAM A RESIDUAL ARTIFACT  
IN THE FORM OF A LOW LEVEL THERMAL GRADIENT DRAPED EAST/WEST  
ALONG I-70 WAS LEFT OVER FROM THE CYCLONE CURRENTLY IN ONTARIO CA.  
THIS THERMAL GRADIENT WILL BE THE CATALYST FOR TRAINING  
THUNDERSTORMS WHICH WILL LIKELY CAUSE SIGNIFICANT FLOODING ACROSS  
MISSOURI AND ILLINOIS. BY THE TIME SATURDAY MORNING ROLLS AROUND  
SHOULD SEE A LINE OF CONVECTION FROM CENTRAL KANSAS UP THROUGH THE  
ILLINOIS AND OHIO RIVER VALLEYS. MEANWHILE THE UPPER MIDWEST WILL  
HAVE HIGH CLOUDS AND NORTHEAST WINDS SATURDAY MORNING  
   
LONG TERM
 
(SATURDAY THROUGH THURSDAY)  
ISSUED AT 425 AM CDT FRI APR 28 2017  
 
THE FOCUS IN THE LONG TERM REMAINS A STORM SYSTEM THAT WILL MOVE  
NORTHEAST ACROSS THE REGION FROM SUNDAY THROUGH MONDAY.  
DETERMINISTIC GUIDANCE FOR THE MOST PART IS NOW IN GREAT AGREEMENT  
WITH THE LOCATION AND TIMING OF THIS SYSTEM. EVEN THE GEFS IS  
PRACTICALLY ON TOP OF THE ECMWF/GFS SOLUTIONS. THE ONE OUTLIER IS  
THE CANADIAN, WHICH IS FURTHER NORTH AND WEST. THIS SEEMS TIED TO  
A SECONDARY UPPER LOW TRYING TO PHASE IN ON MONDAY FROM SOUTHERN  
SASKATCHEWAN. THE ECMWF HAS HAD THIS IDEA AS WELL THE PAST FEW  
RUNS, BUT NOT AS DEEP ON TONIGHTS RUN.  
 
RAIN WILL BEGIN SPREADING INTO FAR SOUTHERN MINNESOTA AHEAD OF THE  
STORM SYSTEM BY LATE IN THE DAY SATURDAY AND THEN CONTINUE  
EXPANDING NORTH AND EAST ON SUNDAY. THIS IS A LONG DURATION EVENT  
WITH LIKELY TO CATEGORICAL POPS FROM SUNDAY THROUGH MONDAY. IT'S A  
VERY DYNAMIC SYSTEM WITH PLENTY OF MOISTURE TO WORK WITH. THERE  
ARE TWO CONCERNS WITH THIS PRECIPITATION EVENT. THE FIRST IS HOW  
MUCH RAIN AND THE SECOND IS WHERE AND HOW MUCH SNOW. CONFIDENCE  
REMAINS HIGH ON WIDESPREAD RAIN AMOUNTS IN THE 1.25 TO 1.75 INCH  
RANGE, WITH THE HIGH END AMOUNTS ACROSS SOUTHERN MN INTO EAST  
CENTRAL MN (TWIN CITIES). FORTUNATELY IT'S SPREAD OUT OVER TWO  
DAYS, BUT SOME HYDRO ISSUES ARE CERTAINLY POSSIBLE WITH THE WET  
SOIL CONDITIONS IN PLACE ALONG WITH STANDING WATER BEING REPORTED  
HERE AND THERE.  
 
THE OTHER ISSUE IS THE POTENTIAL FOR ACCUMULATING SNOW.  
CONFIDENCE HAS INCREASED ON THIS WITH REGARDS TO THE LOCATION.  
HOWEVER AMOUNTS COULD GET OUT OF HAND LATE SUNDAY NIGHT AND EARLY  
MONDAY. WITH THE AGREEMENT IN THE MODEL SOLUTIONS, TEMPERATURE  
PROFILES ARE BEST FOR SNOW FROM SOUTHWEST THROUGH CENTRAL INTO  
NORTHEAST MN AND NORTHWEST WI. FOR OUR AREA, THIS WOULD BE CANBY  
AND REDWOOD FALLS ON NORTHEAST THROUGH ALEXANDRIA, STAPLES, ST.  
CLOUD, LITTLE FALLS AND CAMBRIDGE. RIGHT NOW, WE HAVE 2 TO 4  
INCHES OF SNOW ACCUMULATION FOR THESE AREAS. THE GFS WOULD SUGGEST  
6 TO 10 INCHES OF SNOW POSSIBLE IN THIS AREA. THE GEFS  
PROBABILITIES FOR 2-4 INCHES ARE IN THE LIKELY CATEGORY FOR  
BASICALLY THIS SAME AREA. WE'LL CERTAINLY NEED TO KEEP AN EYE ON  
THIS FOR POTENTIAL HEADLINES AS WE HEAD FORWARD. MAIN CHANGES  
AGAIN OVERNIGHT TO THE FB GRIDS WERE TO LOWER HIGH TEMPERATURES  
ACROSS SOUTHERN MN ON SUNDAY AND ACROSS ALL OF MN ON MONDAY WITH  
UPPER 30S IN PLACE FOR THE SNOW AREA. THIS MAY STILL BE TOO WARM  
WITH SOME SOLUTIONS SUGGESTING ONLY MIDDLE 30S. WE ENDED UP WITH A  
NICE TEMPERATURE GRADIENT FROM WEST TO EAST ON MONDAY FROM THE  
UPPER 30S IN WESTERN MN TO 50 AT EAU CLAIRE. OTHER CHANGES  
INCLUDED MORE WIDESPREAD CATEGORICAL POPS ALONG WITH INCREASING  
THE NORTH WINDS ON MONDAY.  
 
THIS SYSTEM WILL EXIT THE REGION ON TUESDAY. TWO MINOR SHORT WAVES  
WILL MOVE THROUGH IN THE NORTHWEST FLOW FOR WEDNESDAY AND THURSDAY  
WITH SOME SMALL CHANCES FOR SHOWERS. AFTER THAT, THE PATTERN  
BEGINS TO CHANGE WITH MASSIVE RIDGING ALOFT SPREADING INTO THE  
CENTER OF THE COUNTRY, BRING A BIG WARM UP HEADING INTO NEXT  
WEEKEND.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)  
ISSUED AT 1207 PM CDT FRI APR 28 2017  
 
HIGH PRESSURE DROPPING IN FROM THE NORTHWEST WILL KEEP THE FRONTAL  
SYSTEM AND ASSOCIATED PRECIPITATION TO THE SOUTH OF ALL TAF SITES  
THROUGH TOMORROW. HIGH CLOUDS FROM THE SYSTEM WILL BE THE MAIN  
IMPACT, KEEPING CEILINGS IN PLACE. THOUGH THERE ARE SOME ISOLATED  
POCKETS OF MVFR-LEVEL CLOUDS (SUCH AS KRWF AT INITIALIZATION  
TIME), THOSE INSTANCES ARE EXPECTED TO BE FEW AND FAR BETWEEN TO  
IMPACT ANY OTHER SITES. THUS, HAVE MAINTAINED VFR CONDITIONS AT  
ALL SITES THROUGH TOMORROW. N WINDS AROUND 10 KNOTS WITH  
OCCASIONAL HIGHER GUSTS WILL PERSIST THROUGH THIS EVENING THEN  
DIMINISH CLOSER TO 5 KNOTS WHILE VEERING TO NNE THEN TO NE BY  
DAYBREAK TOMORROW.  
 
KMSP...VFR CONDITIONS EXPECTED THROUGHOUT THIS SET WITH HIGH  
CEILINGS LATER THIS AFTERNOON INTO THE EARLY MORNING HOURS. THERE  
MAY BE A FEW OCCASIONAL PERIODS OF FEW-SCT CLOUDS AT 2-3 KFT  
THROUGH THIS EVENING BUT NO LOWER CEILINGS ARE EXPECTED.  
 
/OUTLOOK FOR KMSP/  
SUN...MVFR/IFR WITH RA. WINDS NE 15-20G30KTS.  
MON...IFR/RA MIXING WITH SN AFTN/EVE. WINDS N 15-20G30KTS.  
TUE...MVFR CEILINGS POSSIBLE. NW 10-15 KTS.  
 

 
   
MPX WATCHES/WARNINGS/ADVISORIES
 
 
WI...NONE.  
MN...NONE.  

 
 

 
 
UPDATE...JPC  
SHORT TERM...JRB  
LONG TERM...RAH  
AVIATION...JPC  
 
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