Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 192356
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
656 PM CDT SAT JUL 19 2014

.UPDATED FOR 00Z AVIATION DISCUSSION...
ISSUED AT 639 PM CDT SAT JUL 19 2014

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 333 PM CDT SAT JUL 19 2014

SFC ANALYSIS SHOWS A WEAK SFC CDFNT LINGERING
OVER NW MN WITH A WEAK PRE-FRONTAL SFC TROF WOBBLING OVER SRN-ERN MN
INTO NW WI. ALOFT...A WEAK SHORTWAVE TROF WITHIN FAIRLY ZONAL FLOW
WILL CONTINUE TO SHIFT EAST AND AWAY FROM THE AREA INTO THE GREAT
LAKES. THE COMBINATION OF THE PRE-FRONTAL TROF...DISTURBANCE ALOFT
AND A NARROW SWATH OF MOISTURE PRODUCED ISOLD -SHRA OVER CENTRAL-ERN
MN EARLY THIS AFTN...BUT NOTHING MORE THAN ONLY A FEW HUNDREDTHS OF
QPF. THE OTHER EFFECTS ARE MID- AND UPPER- LEVEL CLOUD COVER THAT
LOOKS TO LINGER OVERNIGHT INTO TMRW...ESPECIALLY DUE TO THE EXPECTED
EWD MOVEMENT OF THE AFOREMENTIONED CDFNT BEFORE IT DISSIPATES OVER
CENTRAL-NRN MN DURG THE DAY TMRW. ASIDE FROM ANY LINGERING SHWRS
THIS AFTN WHICH WILL SOON DISSIPATE...NO PRECIP IS EXPECTED THIS EVE
THRU LATE TMRW AFTN. THE MAIN EFFECTS WILL BE SLIGHTLY HIGHER MIN
TEMPS TNGT FOLLOWED BY SLIGHTLY HIGHER MAX TEMPS TMRW DUE TO A MORE
PRONOUNCED SLY FLOW AHEAD OF THE DISSIPATING CDFNT...PLUS AN
INCOMING WMFNT WHICH LOOKS TO PUSH THRU THE AREA DURG THE DAY TMRW.
H85 TEMPS WILL SLOWLY INCRS FROM THE MID-UPR TEENS DEG C TO THE UPR
TEENS TO LWR 20S DEG C...ADDING TO THE WARMER LOWER LEVELS IN PLACE
OVER THE AREA. MIN TEMPS TNGT WILL ONLY DROP TO THE MID-UPR 60S
WHILE HIGHS TMRW CLIMB TO MID 80S TO NEAR 90...WITH THE HIGHEST OF
THAT RANGE OUT IN WRN MN. THERE ALSO WILL BE A STRONG INCRS IN HEAT
INDEX VALUES ON SUNDAY AS THE DEEPER MOISTURE COLUMN...PRODUCING
DEWPOINTS IN THE UPR 60S TO LWR 70S...SHIFTS OVER THE REGION IN
CONJUNCTION WITH THE WMFNT. THIS WILL PUSH HEAT INDICES TO THE UPR
80S TO LWR 90S FOR WRN WI INTO ERN MN...AND TO THE MID-UPR 90S IN
CENTRAL-WRN MN.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 333 PM CDT SAT JUL 19 2014

THERE ARE A COUPLE CHANCES FOR PRECIP /POSSIBLY HEAVY/ OVER THE NEXT
FEW DAYS BEFORE COOLER/DRIER NORTH-NORTHEAST FLOW DEVELOPS TUESDAY
NIGHT INTO WEDNESDAY MORNING. THE HEAT IS STILL ON SUN-TUE WITH
TEMPS RUNNING 5-15 DEGREES ABOVE NORMAL AND HIGH AMOUNTS OF
HUMIDITY.

ALTHOUGH MOST OF THE THUNDERSTORM ACTIVITY SHOULD BE FOCUSED NORTH OF
THE FORECAST AREA SUNDAY NIGHT INTO MONDAY MORNING...WE INTRODUCED
POPS ACROSS EASTERN PORTIONS OF THE FORECAST AREA AFTER 06Z MONDAY.
SEVERAL RUNS OF THE ECMWF HAD BEEN HINTING AT AN MCS FORMING IN
EASTERN MN AND MOVING SOUTHEAST DOWN THE EAST SIDE OF A 850-300MB
THICKNESS RIDGE. THE 19.12Z ECMWF BACKED OFF ON QPF AND THE OTHER
MODELING SYSTEMS HAVEN`T BEEN TOO OPTIMISTIC IN DEVELOPING
ELEVATED/NOCTURNAL CONVECTION...BUT EVEN THE GFS HAS A DECENT
925-700MB MOISTURE TRANSPORT NOSE ACROSS THE EASTERN FORECAST AREA
BETWEEN 00-06Z TO GO ALONG WITH ABOVE NORMAL PRECIPITABLE WATER
VALUES. THERE IS NO STRONG TRIGGER...BUT THE MORE PRONOUNCED CAPPING
IS SOUTH OF HERE AND THE NORTHERN/EASTERN FORECAST AREA IS COOLER
ALOFT.

MONDAY STILL LOOKS LIKE OUR WARMEST DAY...BUT THERE IS STILL SOME
UNCERTAINTY AS TO WHETHER WE WILL BE CLOSER TO 90 OR 95. A MODEL
CONSENSUS BLEND GIVES KMSP AND MUCH OF SOUTHERN MINNESOTA HIGHS
CLOSER TO 94-95...BUT WE SHOULD ALSO HAVE DEWPOINTS IN THE MID 70S.
IT IS DIFFICULT TO GET BOTH MID 70 DEWPOINTS AND MID 90 HIGHS /IT
CAN AND CERTAINLY HAS HAPPENED BEFORE/. USING LAST NIGHTS NAM/GFS
RUNS WE COMPARED THE TOP 5 CIPS ANALOGS TO THE PATTERN AT 00Z
TUESDAY AND FOUND SOME INTERESTING RESULTS. THE OVERALL BEST PATTERN
MATCH TO BOTH THE NAM AND GFS WAS 08-02-2004. KMSP HIT 85 THAT
AFTERNOON. USING KMSP AS A PROXY...THE AVERAGE OF THE TOP FIVE OVERALL
ANALOGS TO THE NAM YIELDED AN AVERAGE HIGH OF 86...A HIGH OF 87.6
WHEN USING THE TOP FIVE 2-M DEWPOINT ANALOGS...AND 87.4 WHEN USING
850MB TEMPERATURE ANALOGS. THE GFS IS WARMER WITH THE OVERALL TOP
FIVE ANALOGS YIELDING A MEAN HIGH TEMPERATURE OF 89.3...90 WHEN
USING 2-M DEWPOINTS AS AN ANALOG...AND 94.2 WHEN USING 850MB
TEMPERATURE. THAT 94.2 /WHICH INCLUDED 07-07-1980: 98 AND
7-15-1988:102/ IS NOT SURPRISING GIVEN THE VERY WARM 850MB TEMP
FORECAST OFF THE GFS. BESIDES THAT SET OF YEARS...MOST OF THE
ANALOGS SUGGEST A TEMPERATURE CLOSER TO 90. THIS ALSO MAKES SENSE
GIVEN THE S-SE SURFACE WIND AND HUMID AIR MASS. THE OVERNIGHT SHIFT
DISCUSSED A HEAT EVENT ALMOST A YEAR AGO TO THE DAY /7-18-2013/.
THAT DAY DID INDEED HAVE A HIGH OF 94...HOWEVER WE STARTED THAT
MORNING IN THE 80S AND MIXED OUT DEWPOINTS INTO THE UPPER 60S. IT
LOOKS LIKE WE WILL MAINTAIN MID 70 DEWPOINTS ON MONDAY...WHICH
SHOULD KEEP HIGH TEMPS CLOSER TO 90...BUT THIS STILL EQUATES TO HEAT
INDEX VALUES NEAR 105. THE GFS MIX DOWN TEMP USING 875MB FOR THE TOP
OF THE MIXED LAYER YIELDS A HIGH OF 92. NOT A BAD STARTING POINT.

THE OVERNIGHT SHIFT HAD A GOOD DISCUSSION ON THE THUNDERSTORM/SEVERE
POTENTIAL MONDAY NIGHT INTO TUESDAY...BUT MORE LIKELY A HEAVY RAIN
EVENT /ESPECIALLY FOR CENTRAL AND NORTHERN MINNESOTA/. THERE IS
STILL UNCERTAINTY ON SYSTEM PLACEMENT EVEN WITH THE 12Z RUNS. COOLER
AND LESS HUMIDITY WILL SPREAD ACROSS THE FORECAST AREA BY WEDNESDAY
MORNING.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 639 PM CDT SAT JUL 19 2014

VFR CONDITIONS THROUGHOUT. THE ONLY EXCEPTION COULD BE SOME
REDUCED VISIBILITIES FROM FOG/HAZE...BUT MID LEVEL CLOUDS SHOULD
KEEP ANY RESTRICTIONS FROM BEING TOO WIDESPREAD. THE HOPWRF SHOWS
THIS AS WELL...WITH VERY LOW PROBABILITIES OF LESS THAN 5SM.
LOOKING AHEAD...SOUTHERLY WINDS WILL INCREASE ON SUNDAY. THE BEST
CHANCE FOR PRECIP WILL BE ACROSS NORTHERN MN

KMSP...
NO SIGNIFICANT CHANGES FROM THE ABOVE DISCUSSION. THERE IS A SMALL
CHANCE THAT VISBYS COULD GO MVFR FROM HAZE...BUT CONFIDENCE IS TOO
LOW TO INCLUDE IN THE TAF.

/OUTLOOK FOR KMSP/
MON...VFR WITH TSRA POSSIBLE LATE. WINDS S AT 10G15KTS.
TUE...VFR WITH IFR/TSRA POSSIBLE. WINDS SW AT 10TKS BECOMING N
LATE.
WED...VFR. WINDS NNE AT 10KTS.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...EXCESSIVE HEAT WATCH FROM MONDAY AFTERNOON THROUGH MONDAY
     EVENING FOR MNZ060>063-068>070.

WI...NONE.
&&

$$

SHORT TERM...JPC
LONG TERM...CLF
AVIATION...JRB





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