Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 210042
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
642 PM CST TUE JAN 20 2015

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 410 PM CST TUE JAN 20 2015

INITIAL SHORT TERM CONCERN REMAINS PTYPE AS THE UPPER TROUGH MOVES
INTO THE AREA.  CURRENT SURFACE OBS ARE SHOWING L-/UP IN THE AREAS
RECEIVING PRECIPITATION.  SOME SNOW IS ADVANCING EAST FROM SOUTH
DAKOTA HOWEVER AS INCREASING VERTICAL MOITION/FORCING MOVES IN.
THIS TREND IS EXPECTED TO CONTINUE INTO THE LATE AFTERNOON/EARLY
EVENING.

SURFACE TEMPERATURES WILL BE CRITICAL FOR THE THREAT OF FZDZ IN THE
EASTERN AREAS IN THE EARLY EVENING...BUT THE THREAT SEEMS TO BE LOW.
AS ICE IS INTRODUCED INTO THE COLUMN...SNOW SHOULD BE THE MAIN
THREAT.  SNOW ACCUMULATIONS APPEARS TO BE IN THE 1 TO 2 INCH
RANGE...MAINLY ALONG AND SOUTH OF I94 THROUGH 12Z WED.

THE INITIAL SOUTH DAKOTA WAVE DROPS SOUTHEAST AND WEAKENS OVERNIGHT
AS THE SECONDARY TROUGH...WHICH FOLLOWS THIS ONE...MOVES IN FOR
WEDNESDAY. THIS WILL CONTINUE THE THREAT OF LIGHT SNOW TO MAINLY
FOR THE WEST AND SOUTH INTO THE DAY WEDNESDAY. TEMPERATURES WILL
COOL ONLY SLIGHTLY FROM TODAYS VALUES OVER THE AREA.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 410 PM CST TUE JAN 20 2015

TWO MAIN CHANGES MADE IN THE LONG TERM WERE TO CONTINUE NUDGING BOTH
HIGHS AND LOWS UP...WHILE ALSO INCREASING POPS SATURDAY NIGHT/SUNDAY
AS BOTH THE GFS/ECMWF SHOW A POTENT CLIPPER MOVING THROUGH THE
AREA...WITH A HEALTHY BURST OF 3-5 INCHES OF SNOW LOOKING POSSIBLE.

TWO THEMES HAVE NOT CHANGED OVER THE LAST COUPLE OF DAYS IN THE
EXTENDED. ONE...THE UPPER RIDGE WILL BE AMPLIFYING AND WILL BE DOING
SO OVER THE INTER MOUNTAIN WEST. BY SETTING UP SO FAR EAST...WE WILL
BE MISSING THE ARCTIC AIR...BUT WILL BE WELL WITHIN AN ACTIVE NW
FLOW...WITH SHORTWAVES COMING THROUGH THE REGION ABOUT EVERY 24-36
HOURS.

MODEL AGREEMENT BETWEEN THE GFS/ECMWF IS PRETTY HIGH THROUGH
SATURDAY...BUT THEY BEGIN TO DIVERGE A BIT AFTER SUNDAY...WITH THE
GFS MORE AGGRESSIVE WITH SENDING ENERGY AROUND THE WRN RIDGE THAN
THE ECMWF.

THE MAIN WEATHER SYSTEM IN THE COMING WEEK WILL BE A CLIPPER COMING
DOWN SATURDAY NIGHT. THE GFS/ECMWF HAD REALLY ONLY MINOR PLACEMENT
AND STRENGTH DIFFERENCES...SO INCREASED POPS TO NEAR 50 PERCENT
SATURDAY NIGHT...WHEN THE BRUNT OF THE WAVE LOOKS TO COME THROUGH.
THERE IS A STRONG PV BOOT WITH THIS WAVE...WITH THE COMBINATION OF
STRONG WAA AND FGEN IN THE H85-H6 LAYER LOOKING TO PRODUCE A HEAVY
BURST OF SNOW FOR CLIPPER STANDARDS. BOTH THE ECMWF/GFS SHOW RUN
TOTAL QPFS ON THE ORDER OF 0.3 INCHES...SO THIS SHOULD PRETTY EASILY
TRANSLATE INTO 3-5 INCHES OF SNOW. WE STILL HAVE A FEW DAYS FOR
MODELS TO IRON OUT THE DETAILS...BUT FOR THE LAST 24 HOURS...BOTH
THE ECMWF AND GFS HAVE BEEN SIMILAR WITH DRIVING THIS BAND OF SNOW
SOMEWHERE BETWEEN WRN MN AND WRN WI...SO CONFIDENCE IS BEGINNING TO
INCREASE IN ACCUMULATING SNOW WITH THIS SYSTEM.

OTHER THAN THAT...SYSTEMS LOOK RELATIVELY MINOR. THERE IS STILL A
WAVE PROGGED TO GO ACROSS LAKE SUPERIOR ON FRIDAY. THOUGH THE BULK
OF THE PRECIP WILL BE NE OF THE MPX CWA...MODELS CONTINUE TO BRING
SOME LIGHT QPF INTO THE FAR NE MPX FRIDAY AFTERNOON...WHERE A SMALL
CHANCE OF A WINTRY MIX CONTINUES. THE SYSTEM COMING DOWN SATURDAY
NIGHT WILL LIKELY HAVE LIGHT SNOW LINGER INTO SUNDAY NIGHT ACROSS
THE EAST...BUT THE BOTH THE GFS/ECMWF ARE TRENDING DRY FOR THE FIRST
HALF OF NEXT WEEK.

FOR TEMPERATURES...WITH THE SYSTEM GOING OFF TO OUR NORTH ON
FRIDAY...WE WILL BE GETTING INTO ANOTHER WARM SW TO W FLOW THURSDAY
AND FRIDAY. AS A RESULT...BOOSTED TEMPS FOR BOTH DAYS...WITH FRIDAY
LIKELY TO YIELD SOME MORE HIGHS IN THE LOWER 40S OUT IN WRN MN.
GIVEN HOW TEMPERATURES PERFORMED OVER THE WEEKEND WHEN WE GOT INTO
SIMILAR LOW LEVEL FLOW...WE MAY STILL NEED TO GO HIGHER. EVEN THE
SYSTEM COMING DOWN FOR THE WEEKEND...WE LOOK TO BE JUST COLD ENOUGH
FOR ALL SNOW...AS HIGHS WILL CONTINUE TO BE IN THE LOW 30S INTO THE
WEEKEND. WHERE THE MODEL DIFFERENCES IN THIRD PARAGRAPH MANIFEST
THEMSELVES IS WITH THE TEMPERATURES FOR NEXT WEEK. THE FASTER GFS
SENDS ANOTHER LOW NORTH OF US ON TUESDAY...WITH MONDAY AND TUESDAY
BRINGING A RETURN TO MILD WRLY LOW LEVEL FLOW. THE SLOWER ECMWF
ALLOWS FOR A HIGH TO SETTLE OVER THE AREA MON/TUE...WITH WARMER SRLY
FLOW NOT SHOWING UP UNTIL THE THE MIDDLE OF NEXT WEEK. GIVEN THE
DISCREPANCIES...KEPT CLOSE TO A BLENDED FORECAST AT THIS POINT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 638 PM CST TUE JAN 20 2015

LOW CEILINGS WILL PREVAIL THROUGH THE PERIOD... ALTHOUGH THEY WILL
BE WORST AS THE UPPER LEVEL SHORTWAVE AND SNOW MOVES THROUGH
TONIGHT. VISIBILITIES WILL ALSO BE LOWEST FOR THE FIRST 6 TO 9
HOURS OF THE FORECAST... WITH SOME LOWER VISIBILITIES LINGERING
INTO WEDNESDAY WITH SOME LIGHT FOG. IMPROVEMENT CERTAINLY SHOULD
OCCUR AS WEDNESDAY PROGRESSES... BUT DON/T EXPECT THINGS TO GET
BETTER THAN MVFR THROUGH THE PERIOD.

KMSP...TAF REFLECTS GENERAL EXPECTATIONS IN TRENDS... WITH SOME
OCCASIONAL IFR FOR MUCH OF THE NIGHT BEFORE MORE SUBSTANTIAL
IMPROVEMENT OCCURS ON WEDNESDAY. TIMING OF WORST CONDITIONS AND
IMRPOVEMENT COULD CERTAINLY VARY BY +/- 3 HOURS... SO AMENDMENTS
ARE A GOOD POSSIBILITY THROUGH THE NIGHT DEPENDING ON HOW QUICKLY
THE BAND OF SNOW SHIFTS EAST.

/OUTLOOK FOR KMSP/
WEDNESDAY OVERNIGHT...MVFR CEILINGS LIKELY EARLY WITH A CHANCE OF
LIGHT SNOW. NORTHWEST WINDS 5 TO 10 KT.
THURSDAY...MAINLY VFR WITH MVFR CEILINGS POSSIBLE. WEST WINDS
AROUND 5 KT.
FRIDAY...MVFR CEILINGS LIKELY WITH LIGHT SNOW POSSIBLE. SOUTHWEST
WIND 5-10 KT.

&&

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

$$

SHORT TERM...DWE
LONG TERM...MPG
AVIATION...


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