405  
FXUS63 KMPX 172122  
AFDMPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN  
322 PM CST THU JAN 17 2019  
   
SHORT TERM
 
(THIS EVENING THROUGH FRIDAY NIGHT)  
ISSUED AT 322 PM CST THU JAN 17 2019  
 
THE PIECE OF ENERGY EXPECTED TO BRING SNOW ACROSS SOUTHERN  
MINNESOTA FRIDAY HAS REACHED THE WESTERN ROCKIES THIS AFTERNOON.  
SNOW WILL BEGIN OVER MONTANA AND THE WESTERN DAKOTAS THIS EVENING,  
SPREADING EAST TO SOUTHWESTERN MINNESOTA BY EARLY FRIDAY MORNING  
AND ACROSS THE REMAINDER OF SOUTHERN MINNESOTA DURING THE MID  
MORNING. THIS BAND WILL BE FRONTOGENESIS DRIVEN AND A DEEP DGZ  
LAYER WILL HELP SUSTAIN DECENT RATES FOR MOST OF THE DAY SOUTH OF  
THE MN RIVER. THE QUESTION IS, AND ALWAYS SEEMS TO BE, HOW FAR  
NORTH THE SNOW WILL GET BEFORE DRY AIR WINS OUT. GLOBAL GUIDANCE  
AND EVEN THE ENSEMBLES HAVE SHIFTED NORTH TODAY, WITH ALL BUT THE  
NAM SUPPORTING 1 TO 2 INCHES EVEN UP TO THE METRO. THIS IS STILL  
AN UNLIKELY SCENARIO GIVEN THE DEGREE OF DRY AIR IN THE BOUNDARY  
LAYER. THE GRADIENT WILL ALMOST CERTAINLY BE TIGHTER THAN THOSE  
MODELS INDICATE. STILL, CANNOT COMPLETELY IGNORE THE RECENT TREND,  
SO DID INCREASE POPS SOME UP TO I-94, WITH A DRY FORECAST  
REMAINING NORTH OF THAT CORRIDOR. THE SNOW WILL EXIT TO THE  
SOUTHEAST FRIDAY EVENING.  
 
TOTAL ACCUMULATIONS WILL DEPEND ON A NUMBER OF FACTORS AND IS  
PARTICULARLY SENSITIVE DUE TO THE UNUSUALLY WIDE RANGE OF  
POTENTIAL SNOW RATIOS. GIVEN HOW COLD THE ATMOSPHERE IS AND HOW  
DEEP THE DGZ IS, RATIOS OF 15-17:1 SEEM REASONABLE. HOWEVER, IF  
THE AREA OF BEST LIFT IS TRANSIENT AND SNOW PRODUCTION BECOMES  
LESS EFFICIENT, RATIOS MAY BE LOWER THAN THAT DUE TO SMALLER FLAKE  
SIZE. QPF ACROSS THE FAR SOUTH IS IMPRESSIVE AND RANGES FROM  
1/3-1/2 INCH. IF THOSE RATIOS DO MATERIALIZE, THEN IT SHOULDN'T BE  
MUCH OF AN ISSUE TO GET 5 TO 8 INCHES SOUTHWEST OF THE MN RIVER.  
CONVERSELY, IF RATIOS ARE MORE 12:1 OR SO, THEN WE MAY BE TALKING  
CLOSER TO 3 TO 7 INCHES. UPGRADED PARTS OF THE ADVISORY TO A  
WINTER STORM WARNING FOLLOWING COLLABORATIVE EFFORTS WITH WPC AND  
THE SURROUNDING OFFICES AND EXPECTED THE ADVISORY SLIGHTLY  
NORTHWARD AS WELL.  
   
LONG TERM
 
(SATURDAY THROUGH THURSDAY)  
ISSUED AT 322 PM CST THU JAN 17 2019  
 
OVERALL, THE LONG TERM PERIOD STILL LOOKS TO BE COOLER THAN  
NORMAL WITH WIDESPREAD LIGHT SNOW LOOKING LIKELY FOR NEXT WEEK.  
 
BY SATURDAY, WE'LL BE IN THE WAKE OF THE DEPARTING SYSTEM WITH  
NORTHERLY FLOW AND TEMPERATURES A SOLID 10 TO 20 DEGREES BELOW  
NORMAL. THE MORNING WILL START OUT COLD, WITH TEMPS BELOW ZERO IN  
WESTERN AND CENTRAL MN, AND WIND CHILLS HOVERING NEAR THE -25  
DEGREE MARK TO START THE DAY ACROSS MUCH OF WESTERN MN.  
 
BY LATE SATURDAY NIGHT, AN APPROACHING 850MB TROUGH WITH DECENT  
THETA-E ADVECTION AND ISENTROPIC LIFT ALONG WITH AN UPPER LEVEL  
VORT MAX WILL SLIDE SOUTHEAST ACROSS MUCH OF WESTERN/SOUTHWESTERN  
MN AND BRING ABOUT AN INCH OR SO OF SNOW TO THAT AREA.  
 
THEN ATTENTION TURNS TO A POSITIVELY TILTED UPPER TROUGH THAT  
WILL DIG ACROSS THE WESTERN CONUS ON MONDAY. A SURFACE CYCLONE  
WILL EMERGE ACROSS CO AND TRANSLATE EASTWARD THROUGH TUESDAY. AN  
INVERTED TROUGH EXTENDING NORTHWARD INTO MN WILL BE SUPPORTED BY  
UPPER LEVEL VORTICITY ADVECTION AND DECENT DIFFERENTIAL DIVERGENCE  
THANKS TO THE LEFT EXIT REGION OF A STRENGTHENING JET MOVING  
THROUGH THE REGION. THIS STILL LOOKS LIKE A LIGHT SNOW EVENT  
ACROSS A BROAD AREA.  
 
DEEP NORTHWEST FLOW LOOKS TO FOLLOW INTO MIDDLE OF NEXT WEEK WITH  
BELOW NORMAL TEMPERATURES AND THE OPPORTUNITY FOR A QUICK-MOVING  
CLIPPER SYSTEM TO MOVE THROUGH LATE NEXT WEEK.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)  
ISSUED AT 1256 PM CST THU JAN 17 2019  
 
MVFR CONTINUES ACROSS WI EARLY THIS AFTERNOON, AND HAS MOVED BACK  
INTO THE KAXN AREA. OTHERWISE, PARTLY CLOUDY SKIES BETWEEN THESE  
AREAS. VFR CONDITIONS WILL RETURN AREA WIDE LATER TODAY OR THIS  
EVENING BEFORE SNOW ADVANCES EASTWARD ACROSS SOUTHERN MN FRIDAY  
MORNING WITH IFR CONDITIONS.  
 
KMSP...VFR THROUGH THE PERIOD IS LIKELY. IT REMAINS TO BE SEEN  
WHETHER THE SNOW WILL REACH MSP FRIDAY, THE NORTHERN EDGE WILL BE  
CLOSE. MVFR CONDITIONS WOULD ACCOMPANY THE SNOW WITH THE STEADIEST  
LIKELY REMAINING SOUTH.  
 
/OUTLOOK FOR KMSP/  
FRI NIGHT...VFR. WIND NE 7 KTS.  
SAT...VFR. WIND NNW 15G25 KTS.  
SUN...MVFR PSBL. WIND LIGHT & VRBL.  
 

 
   
MPX WATCHES/WARNINGS/ADVISORIES
 
 
WI...NONE.  
MN...WINTER STORM WARNING FROM 6 AM TO 10 PM CST FRIDAY FOR MNZ074-  
082-083-091>093.  
 
WINTER WEATHER ADVISORY FROM 6 AM TO 10 PM CST FRIDAY FOR MNZ067-  
075>077-084-085.  
 
WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM CST FRIDAY FOR MNZ054-  
056-064-065-073.  
 

 
 

 
 
SHORT TERM...BORGHOFF  
LONG TERM...SPD  
AVIATION...BORGHOFF  
 
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