Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 170913
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
413 AM CDT SUN AUG 17 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 413 AM CDT SUN AUG 17 2014

EARLY MORNING RADAR...IR...AND WATER VAPOR IMAGERY TOGETHER WITH RAP
OVERLAYS SHOW WEAKENING TRENDS WITH THE SLOW MOVING CONVECTION
ACROSS WEST CENTRAL MN. THE COMPACT SHORTWAVE THAT HAS DRIVEN THIS
CONVECTION OVER THE PAST 48 HOURS IS STARTING TO GET STRUNG OUT BY
THE INTERACTION WITH THE UPSTREAM PV ANOMALY OVER SOUTHERN
SASKATCHEWAN. AS A RESULT THE FORCING IS DISTRIBUTED ACROSS A LARGER
AREA...AND SHOULD CONTINUE TO SEE SHOWERS AND THUNDERSTORMS SLOWLY
SPREAD FROM WEST TO EAST ACROSS THE CWA TODAY. THE PRECIP WILL
REMAIN SCATTERED...AND THE WIND PROFILE OFF THE BUFR SOUNDINGS
SUGGEST THAT THE SLOW MOVING STORMS WILL BE CAPABLE OF ISOLATED
RAINFALL TOTALS ON THE ORDER OF 1-3 INCHES. THIS MATCHES UP WELL
WITH THE HOPWRF TOTAL ACCUMULATED PRECIP WHICH SHOWS 2-3 INCH
BULLSEYES ACROSS THE CWA. OF COURSE MATCHING UP THESE EXTREME VALUES
WITH THEIR EXACT LOCATION IS BEYOND THE SCOPE OF 2014
METEOROLOGY...SO HAVE BROAD BRUSHED THE QPF WITH AROUND 0.25 TO 0.50
INCHES OVER THE WEST/CENTRAL CWA THIS MORNING AND AFTERNOON.

IT WILL FEEL HUMID OUTSIDE AS MID 60 DEWPOINTS CONTINUE ACROSS MUCH
OF THE REGION...WITH A FEW LOWER 70S EXPECTED OVER THE SOUTHWESTERN
CWA. AS THE AFOREMENTIONED WEAKENING UPPER LEVEL WAVE AND ASSOCIATED
PRECIP SLOWLY DRIFT EASTWARD THIS EVENING...ANOTHER ROUND OF SHOWERS
AND THUNDERSTORMS SHOULD DEVELOP IN THE DAKOTAS AHEAD OF THE
SASKATCHEWAN PV ANOMALY. HIRES MODELS SUCH AS THE 17.00 WRFARW AND
WRFNMM DO NOT DEVELOP MUCH PRECIP AHEAD OF THIS WAVE...BUT RATHER
TIE IT TO THE DIURNAL HEATING ON MONDAY AFTERNOON. MEANWHILE THE
NSSLWRF BRINGS A WEAKENING LINE OF SHOWERS AND THUNDERSTORMS INTO
THE WESTERN CWA AFTER MIDNIGHT...BUT IT TOO DOES NOT MATCH UP WITH
THE CONCEPTUAL MODEL OF WIDESPREAD PRECIP SUNDAY MORNING ACROSS
WESTERN MN. THIS IS RATHER PUZZLING CONSIDERING THE LARGE SCALE
FORCING FOR ASCENT...AND PREVENTED INCREASING POPS BEYOND THAN THE
70 PERCENT CURRENTLY GOING ACROSS THE FAR WESTERN CWA AT 11Z MONDAY.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 413 AM CDT SUN AUG 17 2014

PRIMARY CONCERN REVOLVES AROUND STORMS MONDAY AND MONDAY NIGHT.
MODELS ARE IN DECENT AGREEMENT REGARDING SHORT WAVE DRIVING ESE ACROSS
SOUTHERN MN MONDAY MORNING AND INTO WESTERN WISCONSIN LATE MONDAY
AFTERNOON... WITH MAIN TROUGH AXIS ASSOCIATED WITH UPPER LOW
ARRIVING IN WESTERN MN MONDAY AFTERNOON. OF THESE TWO...THE
GREATEST AMOUNT OF MOISTURE THROUGHOUT THE COLUMN WILL BE ON
MONDAY WITH PRECIPITABLE WATER TOTALS GENERALLY AROUND 1.5 TO 1.6
INCHES. INTERESTINGLY...THE HIGH RES MODELS DO NOT PRODUCE TOO
MUCH PRECIP WITH THIS FIRST SURGE MONDAY MORNING AND MIDDAY...BUT
ARE MUCH MORE AGGRESSIVE WITH PRECIP LATER MONDAY AFTERNOON INTO
THE EVENING. MEANWHILE THE DETERMINISTIC ECMWF/NAM/GEM SHOWS MOST
PRECIP ON MONDAY MORNING AND MIDDAY. THERE IS STILL SOME TIME TO
SORT THIS OUT...SO HAVE MAINTAINED MID TO LIKELY POPS AT THIS
STAGE. TEND TO THINK THE GFS/GEM/NAM SOLUTION WILL BE MORE CORRECT
SINCE THE THERMODYNAMICS IN THE HIGH RES MODELS MAY WELL BE MORE
AFFECTED BY THE STORMS TODAY AND TONIGHT.

OTHERWISE...WEAK SHORT WAVE AROUND THE BACK SIDE OF THE UPPER LOW
COULD BRING SOME SHOWERS AND A FEW STORMS TO EASTERN MN AND
WESTERN WISC LATE MONDAY NIGHT AND TUESDAY.

WEAK RIDGING MOVES OVER THE AREA TUESDAY NIGHT AND WEDNESDAY...AND
THIS WILL BE THE ONLY TIME DURING THE WEEK WHEN DRY WEATHER IS IN
THE FORECAST. BROAD SW FLOW ARRIVES WEDNESDAY NIGHT AS LARGE
WESTERN TROUGH DEVELOPS AND AFFECTS MN/WI THROUGH NEXT WEEKEND.
THE ECMWF DOES NOT EXTEND THE WESTERN TROUGH AS FAR SOUTH AS THE
GFS... BUT EVEN IT STILL PICKS UP A COUPLE OF EMBEDDED SHORT WAVES
FROM THE SOUTHWEST AND BRINGS THEM TOWARD THE UPPER MIDWEST. GFS
DEFINITELY SHOWS THIS. THERE ARE TIMING DIFFERENCES WITH THESE...
BUT THE BOTTOM LINE IS LATE THIS WEEK WILL FEATURE A GOOD CHANCE
OF VERY WARM AND HUMID WEATHER ALONG WITH HEAVY RAIN ASSOCIATED
WITH A TROPICAL CONNECTION WITH PRECIPITABLE WATER VALUES
EXCEEDING TWO INCHES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1052 PM CDT SAT AUG 16 2014

CONFIDENCE REMAINS HIGH ON LOW MVFR/IFR CEILINGS DEVELOPING
OVERNIGHT ACROSS MUCH CENTRAL/SOUTHERN MN AND WESTERN WI.
THE CEILINGS ARE EXPECTED TO DEVELOP A LITTLE EARLIER THAN
YESTERDAY MORNING FROM KRWF THROUGH KMSP TO KEAU AS VERY MOIST LOW
LEVEL CONDITIONS PREVAIL. LOW CEILING FORECASTS FROM KAXN THROUGH
KSTC TO KRNH ARE A LITTLE TRICKY WITH A NEARLY STATIONARY FRONT
OVER THESE SITES ALONG WITH A FEW SHOWERS MEANDERING AROUND. IN
ADDITION...SHOWERS AND THUNDERSTORMS ARE FORECAST INTO KAXN AFTER
08Z AND KSTC BY 11Z ASSOCIATED WITH A DISTURBANCE NEAR FARGO.
STILL THINK THAT AROUND DAYBREAK IF NOT BEFORE THESE SITES WILL
DETERIORATE. THE LOW CEILINGS AT ALL SITES SHOULD PERSIST THROUGH
THE MORNING. SHOWER AND THUNDERSTORM CHANCES WILL SPREAD INTO
EASTERN MN AND WESTERN WI SUNDAY AFTERNOON/EVENING AS THE
AFOREMENTIONED DISTURBANCE IS ND MOVES THROUGH. LIGHT EASTERLY
WINDS OVERNIGHT AND FROM 6 TO 10 KNOTS ON SUNDAY.

KMSP...BKN-OVC010 DEVELOPING AROUND 10Z AND PERSISTING THROUGH
MID MORNING THEN MVFR THROUGH LATE MORNING. VFR IN THE AFTERNOON
BUT WITH A THREAT FOR MVFR CEILINGS...SCT SHRA/TSRA.

/OUTLOOK FOR KMSP/
SUN NIGHT...VFR. MVFR WITH TSRA POSSIBLE. WINDS SE 5-10 KTS.
MON...VFR/MVFR WITH TSRA LIKELY. WINDS S 5-10 KTS.
TUE...VFR/MVFR WITH TSRA POSSIBLE. WINDS NW 5-10 KTS.


&&

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

$$

SHORT TERM...JRB
LONG TERM...TDK
AVIATION...RAH






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