Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 110002
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
702 PM CDT WED SEP 10 2014

.UPDATE...
ISSUED AT 656 PM CDT WED SEP 10 2014

UPDATED TO INCLUDE 00Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 408 PM CDT WED SEP 10 2014

EXTENSIVE LOW CLOUDINESS COVERS THE FA IN THE WAKE OF A LOW
PRESSURE STORM SYSTEM OVER THE CENTRAL GREAT LAKES AT MID
AFTERNOON. ONLY A FEW SPRINKLES REMAIN OVER FAR EASTERN AREAS OF
THE CWA AND THESE WILL BE GONE BY EVENING. THE LOW LEVEL FLOW WILL
REMAIN QUITE CYCLONIC THROUGH MUCH OF THE NIGHT ACROSS WI AND
THIS WILL LIKELY AID IN A SLOWER DISSIPATION/CLEARING OF THE LOW
CLOUDINESS. ANOTHER AREA THAT WILL SEE A SLOWER CLEARING IS ACROSS
SOUTHWEST AREAS OF MN. EVEN WITH THE LOSS OF THE LOW
CLOUDINESS...MID/HIGH LEVEL CLOUDS WILL BE ON THE INCREASE THROUGH
THE NIGHT AND EARLY THURSDAY AS A SHORT WAVE AND MID LEVEL
FRONTOGENESIS DROP SOUTH THROUGH THE NORTHERN PLAINS. THE MID
LEVEL FORCING REALLY INCREASES ACROSS NEBRASKA AND IOWA THURSDAY
AFTERNOON...SO THE THREAT FOR SHOWERS APPEARS TO BE MAINLY TO OUR
SOUTH WITH A DRY FORECAST CONTINUING FOR US.

LOW/HIGH TEMPERATURES WILL REMAIN WELL BELOW NORMAL IN THE SHORT
TERM. LOWS TONIGHT IN THE UPPER 30S TO LOWER 40S WILL BE SOME 10
TO 15 DEGREES BELOW NORMAL...WHILE HIGHS ON THURSDAY IN THE
MIDDLE TO UPPER 50S WILL BE 15 TO 20 DEGREES BELOW NORMAL.
ALTHOUGH TEMPERATURES ARE FORECAST WELL BELOW NORMAL...NO RECORD
LOWS OR RECORD LOW HIGHS ARE IN JEOPARDY.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 408 PM CDT WED SEP 10 2014

A FAIRLY QUIET AND BENIGN LONG TERM PERIOD IS IN STORE...WITH
MINOR CHANCES FOR SOME LIGHT RAIN THU NIGHT INTO FRI AND AGAIN
SUN INTO MON. TEMPERATURE WISE...WE WILL START OUT WELL BELOW
NORMAL...WITH HIGHS IN THE 50S...BUT WILL SEE THEM BACK UP TO NEAR
AND A LITTLE ABOVE NORMAL BY THE MIDDLE OF NEXT WEEK.

THE MEAN WEATHER PATTERN THIS PERIOD WILL FEATURE RIDGING WEST AND
TROUGHING EAST...WITH A MAINLY ZONAL FLOW THROUGH MONDAY... GIVING
WAY TO NW FLOW NEXT WEEK. WHEN IN THE ZONAL FLOW...WE WILL SEE A
COUPLE OF SHORTWAVES TRAVERSE THE AREA FRIDAY AND MONDAY /HENCE
THE SMALL PRECIP CHANCES/. THE NW FLOW NEXT WEEK WILL DRY US
OUT...BUT THE SLOW EASTWARD CREEP OF THE WRN RIDGE WILL ALLOW FOR
TEMPERATURES TO RETURN BACK TO NEAR NORMAL BY THE END OF THE
PERIOD.

THURSDAY NIGHT INTO FRIDAY...WE ARE STILL DEALING WITH TWO CAMPS
IN THE MODELS. THE SLOWER/STRONGER ECMWF AND THE WEAKER/FASTER
NAM/GFS/GEM. WHAT IS INTERESTING...WHEN DOING RUN-TO-RUN
COMPARISONS...ALL MODELS HAVE MAINTAINED CONSISTENCY AMONGST
THEMSELVES AND HAVE LOCKED ON TO THERE RESPECTIVE SOLUTIONS AND
HAVE YET TO BUDGE. THE OFFENDING WAVE SHOWS UP NICELY ON WATER
VAPOR THIS AFTERNOON AND IS RESPONSIBLE FOR THE EARLY SEASON SNOW
STORM THE FOLKS UP IN CALGARY ARE ENJOYING TODAY. THIS WAVE WILL
WORK ACROSS THE DAKOTAS THU NIGHT AND ACROSS THE UPPER MIS VALLEY
ON FRIDAY. THE ECMWF CONTINUES SHOWING THIS WAVE TAKING ON A MORE
NEUTRAL TILT OVER MN...ALLOWING FOR THE SLOWER PROGRESSION...WHILE
THE OTHER DETERMINISTIC MODELS KEEP A POSITIVE TILT TO THE WAVE
UNTIL IT REACHES THE GREAT LAKES SATURDAY. NO MATTER WHAT SOLUTION
WORKS...THEY BOTH HAVE THE SAME ISSUE...AND THAT IS VERY DRY LOW
LEVEL AIR IN PLACE WITH MSLP VALUES EXPECTED TO BE UP AROUND 1030
MB ACROSS THE UPPER MIS VALLEY /ASSOCIATED WITH A 1035 MB HIGH
OVER WRN NEB/. IN ALL CASES...PV ADVECTION OUT AHEAD OF THE WAVE
ALONG WITH FGEN UP AROUND THE H6 LEVEL WILL GENERATE PLENTY OF MID
LEVEL SHOWERS...THE QUESTION IS DOES ANY OF THAT ACTUALLY REACH
THE GROUND. THE SLOWER ECMWF SOLUTION KEEPS THE FORCING AROUND
LONG ENOUGH TO ALLOW FOR THE PRECIP TO REACH THE GROUND. SREF
PROBS FOR AT LEAST 0.01" OF PRECIP DO GET OVER 60% FROM SC MIN
INTO WRN WI...INDICATING THAT A GOOD DEAL OF THE INDIVIDUAL
MEMBERS OF THE SREF HAVE SOME FLAVOR OF THE ECMWF FORECAST WITH
THEM. FOR THIS FORECAST...LEANED TOWARD THE DRY AIR WINNING...SO
LOWERED POPS SOME IN EACH PERIOD...CONFINING THEM TO SOUTH CENTRAL
MN LATE THU NIGHT AND WORKING THEM UP INTO ERN MN/WRN WI FRIDAY.

THE NEXT PRECIP CHANCES WILL COME SUNDAY INTO MONDAY. SUNDAY WILL
BE THE RESULT OF A WEAKENING COLD FRONT WORKING ACROSS THE AREA.
MODELS CONTINUE TO SHOW THE DEEPEST MOISTURE REMAINING NORTH OF
THE AREA...BUT ENOUGH LOOKS TO GET DOWN HERE TO KEEP SOME 20 POPS
GOING SUNDAY NORTH OF I-94. SUNDAY NIGHT INTO MONDAY...A SYSTEM
VERY SIMILAR TO THU NIGHT/FRI LOOKS TO COME THROUGH...SO CONTINUED
TO ALLOW SOME 20 POPS TO WORK ACROSS SRN MN INTO WI. AFTER
THAT...NW FLOW ALOFT LOOKS TO BRING AN END TO MARGINAL PRECIP
CHANCES FOR THE REST OF THE WEEK.

FINAL ISSUE THIS PERIOD WILL COME SATURDAY MORNING WITH FROST
POTENTIAL. WE LOOK TO CLEAR OUT FRIDAY NIGHT WITH A SFC RIDGE
MOVING OVER HEAD. DEWPS WILL HAVE FALLEN BACK INTO THE 30S...SO
THE DRY AIR...CLEAR SKIES...AND LIGHT WINDS WILL ALLOW FOR IDEAL
COOLING CONDITIONS. KNOCKED LOWS BACK A COUPLE OF DEGREES FRIDAY
NIGHT...WITH LOWS RANGING FROM 33 OUT TOWARD LADYSMITH...WITH 39
FOR THE HEAT ISLAND. STILL HAVE PLENTY OF TIME TO MAKE DECISIONS
ON FROST HEADLINES...BUT WOULD NOT BE SURPRISED IF WE EVENTUALLY
NEED ONE COME FRIDAY NIGHT. HOWEVER...DID TAKE THIS FIRST STEP
THAT DIRECTION TODAY BY ADDING FROST INTO THE GRIDS ANYWHERE WHERE
THE CURRENT FORECAST LOW IS 36 OR LESS SATURDAY MORNING.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 656 PM CDT WED SEP 10 2014

ALL SITES WILL START OUT AS MVFR IN RESPONSE TO LOW LEVEL MOISTURE
CIRCULATING AROUND A DEPARTING LOW PRES SYSTEM OVER THE GREAT
LAKES. CEILINGS WILL GRADUALLY LIFT THROUGH THE EVENING HOURS...
EVENTUALLY HITTING VFR LEVELS BY THE EARLY MORNING HOURS. AM
EXPECTING ALL SITES TO REMAIN VFR FROM ROUGHLY 06Z ONWARDS THROUGH
THU EVE. ONLY KEAU MAY BE LAGGING BEHIND THAT TIME. A WEAK
DISTURBANCE APPROACHING FROM THE DAKOTAS TMRW MAY TRY TO SPREAD
SOME -SHRA INTO WRN MN BUT CHCS ARE TOO LOW FOR MENTION ATTM.
WINDS WILL REMAIN FROM THE N THROUGHOUT THIS TAF PERIOD WITH
SPEEDS GRADUALLY SETTLING DOWN TO 10 KT OR LESS BY LATE EVENING.

KMSP...MVFR CEILINGS THRU THIS EVENING...BUT WILL LOOK FOR
CEILINGS TO REMAIN ABOVE THE 1700 FT THRESHOLD. CEILINGS TO RISE
ABOVE 3000 FT BY LATE EVENING AND REMAIN VFR THROUGHOUT THE REST
OF THIS TAF PERIOD. BKN/OVC SKIES WILL CONTINUE TO PREVAIL.

/OUTLOOK FOR KMSP/
FRI...VFR. CHC -SHRA. WINDS NW AT 5-10 KNOTS.
SAT...VFR. WINDS SW 5-10 KNOTS.
SUN...VFR. WINDS SW 10 KNOTS.

&&

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

$$

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






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