Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 171110
AFDMPX

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

.UPDATED FOR 12Z AVIATION DISCUSSION...
ISSUED AT 603 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 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 603 AM CDT SUN AUG 17 2014

STRATUS AND FOG CONTINUE ACROSS THE REGION THIS MORNING...WITH
CONDITIONS EXPECTED TO IMPROVE ON A TIME SCALE SIMILAR TO
YESTERDAY. AN AREA OF SHOWERS AND THUNDERSTORMS WILL DRIFT
EASTWARD AND AFFECT KAXN AND KSTC...WITH LOWER CONFIDENCE THAT IT
WILL AFFECT KMSP AND KRNH. THE LOW LEVEL MOISTURE WILL CAUSE
IFR/LIFR CONDITIONS TO RETURN MONDAY MORNING AHEAD OF THE NEXT
SYSTEM EXPECTED TO BRING WIDESPREAD RAINFALL.

KMSP...
LOW CEILINGS SHOULD REMAIN BELOW 1700FT THROUGH MID MORNING...AND
NOT EXPECTED TO IMPROVE TO VFR UNTIL 18Z. AT TIMES COULD SEE
CEILINGS DROP BELOW 1000FT OVER THE NEXT COUPLE OF HOURS. A FEW
THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON...BUT CONFIDENCE IN
COVERAGE TO LOW TO DO ANYTHING BUT VCTS. LOOKING AHEAD...ANOTHER
ROUND OF RA/TSRA WILL ARRIVE ON MONDAY...SO INCLUDED THE PROB30.

/OUTLOOK FOR KMSP/

MON...VFR/MVFR WITH TSRA LIKELY. WINDS S 5-10 KTS.
TUE...VFR/MVFR WITH TSRA POSSIBLE. WINDS NW 5-10 KTS.
WED...VFR. WIND VRB AT 5KTS.

&&

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

$$

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





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