Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KMPX 311109
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
609 AM CDT SUN AUG 31 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 245 AM CDT SUN AUG 31 2014

ALTHOUGH SUNDAY AND ITS POTENTIAL SEVERE WEATHER EVENT ARE
HERE...THE CAMS STILL LEAVE PLENTY OF QUESTIONS AS TO HOW THINGS
WILL EVOLVE LATER TODAY.

FOR THIS MORNING...INITIAL SURGE OF THE LLJ IS MOVING ACROSS THE
DAKOTAS OUT AHEAD OF SHORTWAVE THAT CAN BE SEEN ON WATER VAPOR
MOVING INTO CENTRAL SODAK. ALTHOUGH BEST FORCING AND MOST WIDESPREAD
THUNDERSTORM ACTIVITY CAN BE FOUND AT THE NOSE OF THE LLJ ACROSS
NODAK AND ON ITS WAY TO NW MN...ENOUGH THETA-E ADVECTION AND
ISENTROPIC LIFT IS PRESENT ON THE ERN FLANK OF THE LLJ TO GET SCT
CONVECTION DOWN INTO NE NEB. THE HRRR/HOPWRF/MPXWRF/NMM/ARW ALL SHOW
THIS BAND OF ISO/SCT SHOWERS WORKING ACROSS MN THROUGH THE
MORNING...SO WORKED SOME 20/30 POPS ACROSS MN THIS MORNING TO
ACCOUNT FOR THAT. EXPECT THIS ACTIVITY TO START WEAKENING AS IT
MOVES EAST ACROSS MN AND LIKELY WILL NOT MAKE IT INTO WI AS IT
ENCOUNTERS A PROGRESSIVELY DRIER AIRMASS /SEE 00Z SOUNDING FROM MPX
LAST NIGHT/.

IN THE WAKE OF THIS MORNING ACTIVITY...H85 TEMPS WILL BE INCREASING
TO AROUND 20C. LOOKING AT BUFKIT SOUNDINGS FROM ACROSS THE
AREA...THIS WILL PUT A DECENT CAP IN PLACE THAT LOOKS TO KEEP A LID
ON SURFACE BASED CONVECTION UNTIL ABOUT 00Z. WHERE WE ARE SEEING
SOME VARIABILITY THOUGH WITH THE CAMS IS WITH THE POTENTIAL FOR SOME
ELEVATED CONVECTION TO DEVELOP THIS AFTERNOON OUT AHEAD OF WHAT YOU
COULD CONSIDER THE MAIN SHOW FROM THE SEVERE WEATHER PERSPECTIVE.
THIS ELEVATED CONVECTION LOOKS TO BE TIED TO THE STRONG WAVE ON
WATER VAPOR CURRENTLY MOVING INTO WRN KS. THIS FEATURE HAS A FEW
STORMS ASSOCIATED WITH IT IN KANSAS THIS MORNING AND BY THE
AFTERNOON...THIS WAVE WILL BE NEAR THE MN/IA BORDER. THE CAMS THAT
ARE MOST BULLISH WITH THIS ACTIVITY ARE THE MPXWRF AND ARW...AND
ALTHOUGH IT ENDS AT 21Z...YOU GET A SENSE FROM THE HRRR REFLECTIVITY
FORECAST...IT MAY BE GOING THE SAME WAY IN THE NEXT COUPLE OF RUNS.
THE IMPACT OF THIS ACTIVITY ON THE FORECAST WAS TO SPREAD HIGHER
POPS A BIT FARTHER EAST LATE THIS AFTERNOON THAN THE POSITION OF THE
SFC FEATURES WOULD OTHERWISE SUGGEST.

AS FOR THE POTENTIAL SFC BASED CONVECTION...THE MAIN TREND SEEN WITH
THE CAMS AND 00Z DETERMINISTIC MODELS WAS DELAY ITS START
SOME...WHICH MAKE SENSE GIVEN THE CAPPING SEEN IN THE FORECAST
SOUNDINGS. CURRENT EXPECTATIONS ARE THAT SFC BASED CONVECTION WILL
DEVELOP AROUND 21Z NEAR OMAHA...WHERE INSTABILITY WILL BE
MAXIMIZED...WITH INITIATION ALONG THE FRONT UP IN MN COMING A BIT
CLOSER TO 00Z. GREATEST SEVERE THREAT REALLY LOOKS TO BE DOWN ACROSS
IOWA...WHERE THE COMBINATION OF AN IMPINGING WRLY MID LEVEL JET WITH
A 40-50 KT SWRLY LLJ LOOKS TO MAXIMIZE SHEAR. CAN NOT ARGUE WITH THE
DAY1 SEVERE PROBABILITIES...WHICH HAS THE GREATER SEVERE POTENTIAL
EXISTING FROM I-90 SOUTH. LOOKING AT THE 0-3/0-6 KM SHEAR OF 30-60
KTS WITH VECTORS ORIENTED MOSTLY PERPENDICULAR TO THE FRONT ACROSS
IOWA INDICATES THE POTENTIAL FOR GETTING A STRONG MCS WITH STRONG
WINDS ACROSS IOWA TONIGHT...WHICH IS WHAT THE NMM/ARW CERTAINLY SHOW
EVOLVING. STILL A GOOD DEGREE OF VARIABILITY WITH HOW THIS ACTIVITY
WILL EVOLVE ACROSS THE MPX CWA...WITH SOME SUGGESTION THAT WE MAY
SEE THE GREATEST THUNDERSTORM ACTIVITY SPLIT THE MPX CWA TO THE
NORTH AND SOUTH. CERTAINLY THE HRRR MSLP FORECAST SHOWS SOME MERIT
TO THIS POSSIBILITY...WITH TWO SFC LOWS NOTED BY 21Z. ONE UP IN NRN
MN AND THE OTHER IN WRN KS.

FOR TONIGHT...WE ARE ALSO SEEING THE NMM AND THE ARW TO A LESSER
EXTENT HANGING UP ACTIVITY BACK ACROSS THE CENTER OF THE MPX CWA AS
THEY BOTH DEVELOP A DEFORMATION BAND IN THE WAKE IN THE MAIN COLD
FRONT ACTIVITY. THIS LOOKS TO BE TIED TO THE MAIN SHORT WAVE
POSSIBLY MIXED WITH A BIT OF AN MCV MOVING ACROSS THE UPPER MS
VALLEY LATE TONIGHT. AS A RESULT...HELD ON TO CHANCE POPS A BIT
LONGER BACK ACROSS MOST OF THE MN PORTION OF THE MPX CWA IN THE WAKE
OF THE FRONT. THIS ACTIVITY WOULD NOT HAVE MUCH OF A SEVERE
THREAT...THOUGH IT WOULD SET UP MORE IN A WAY TO ALLOW FOR SOME
TRAINING OF STORMS ALONG A SW TO NE AXIS...SO IT COULD POSE MORE OF
A HYDRO THREAT IF IT MATERIALIZES.

TO SUMMARIZE...WE EXPECT A BAND OF NON-SEVERE SHOWERS/STORMS TO MOVE
ACROSS MN THIS MORNING. STILL A GOOD DEGREE OF UNCERTAINTY WITH
RESPECT THE AFTERNOON ACTIVITY...WITH THE POTENTIAL FOR A PREFRONTAL
TROUGH TO GET ELEVATED CONVECTION GOING BY EARLY AFTERNOON IN THE
EAST...WITH THE GREATEST SEVERE RISK EXISTING FROM ABOUT 6 PM TO
MIDNIGHT FROM SOUTH CENTRAL MN INTO IOWA AHEAD OF THE MAIN SFC COLD
FRONT. EVENTUALLY...A LINE OR TWO OF STORMS LOOKS TO FORM...WITH THE
MAIN SEVERE THREAT BEING DAMAGING STRAIGHT LINE WINDS.
HOWEVER...WHERE ACTIVITY INITIALLY DEVELOPS...IT WILL LIKELY BE
SUPER CELLULAR IN NATURE...WITH LARGE HAIL AND A FEW TORNADOES BEING
POSSIBLE AS WELL...BUT THIS THREAT LOOKS GREATEST FROM ERN NEB INTO
WRN IOWA.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 245 AM CDT SUN AUG 31 2014

THE LONGER TERM WILL INCLUDE SOME ADDITIONAL CHANCES FOR
SHRA/TSRA AS WE SEE THE LARGE SCALE PATTERN ONCE AGAIN BECOME MORE
ZONAL BY THE MIDDLE OF THE WEEK... BEFORE ANOTHER UPPER TROUGH
MOVES INTO THE CENTER OF THE COUNTRY TOWARD THE WEEKEND. THE
MEDIUM RANGE GUIDANCE IS IN FAIRLY GOOD AGREEMENT THROUGH
MIDWEEK... BUT DIVERGES A FAIR AMOUNT BY THE WEEKEND... WHICH
LEADS TO MORE UNCERTAINTY AND NECESSITATES THE INCLUSION OF CHANCE
POPS FOR SEVERAL DAYS.

SOME PCPN WILL LIKELY STILL BE ONGOING ACROSS THE EASTERN PORTION
OF THE AREA ON MONDAY AS THE FRONTAL BOUNDARY SLOWLY PUSHES EAST
INTO THE GREAT LAKES. COULD SEE A FEW SHRA/TSRA SNEAK BACK INTO
THE WESTERN AND CENTRAL PORTION OF THE AREA MONDAY NIGHT INTO
EARLY TUESDAY AS THE UPPER TROUGH/COLD POOL SWING THROUGH THE
REGION. THIS ACTIVITY WILL SHIFT NORTHEAST BY TUESDAY... WITH
RETURN FLOW BEGINNING TO SETUP BY TUESDAY NIGHT. CHANCES FOR
SHRA/TSRA LOOK TO RETURN FROM WEST TO EAST WEDNESDAY INTO THURSDAY
AS A SURFACE LOW SLOWLY TAKES SHAPE OVER THE PLAINS AHEAD OF THE
NEXT UPPER TROUGH... WITH A LONG PERIOD OF MAINLY WEAK ISENTROPIC
LIFT PROGGED ACROSS OUR AREA. THE SPEED WITH WHICH THE SURFACE LOW
MOVES THROUGH OUR AREA VARIES QUITE A BIT AMONGST THE GUIDANCE...
AND AT THIS POINT THERE IS TOO MUCH SPREAD IN THE ENSEMBLE
SOLUTIONS TO HAVE MUCH CONFIDENCE IN ANYTHING SPECIFIC. UNTIL THE
SURFACE LOW AND ASSOCIATED FRONTAL BOUNDARY MOVE THROUGH... WE/LL
CONTINUE TO HAVE A NEED FOR AT LEAST CHANCE POPS. THERE IS ALSO
UNCERTAINTY IN HOW FAR SOUTH THE BOUNDARY WILL BE DISPLACED ONCE
THE SURFACE LOW AND UPPER TROUGH MOVE EAST... WITH THE GUIDANCE
SHOWING VARYING AMPLITUDES OF THE UPPER TROUGH WHICH LEADS TO
DIFFERENCES IN HOW FAR SOUTH THE BOUNDARY IS DISPLACED AS THE
SURFACE HIGH BUILDS INTO THE AREA LATE FRIDAY INTO SATURDAY. AT
THIS POINT... KEPT SOME POPS OVER THE SOUTHERN PART OF THE AREA
INTO SATURDAY TO ACCOUNT FOR THE POSSIBILITY OF THE BOUNDARY
HANGING UP OVER NORTHERN IOWA.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 558 AM CDT SUN AUG 31 2014

EXTENSIVE FOG/LOW STRATUS THAT DEVELOPED OVER WI BENEATH THE SFC
HIGH HAS MANAGED TO WORK INTO ERN MN/WRN WI ON SOUTHEAST WINDS
THIS MORNING. AS WINDS CONTINUE TO BECOME MORE SRLY AND PICK UP IN
STRENGTH...WE SHOULD SEE THESE CLOUDS MIX OUT PRETTY QUICK THIS
MORNING. SHOWERS THAT SNUCK INTO WRN MN EARLY THIS MORNING WILL
CONTINUE TO SLOWLY FALL APPART AS THEY WORK ACROSS MN AND FEEL
VCSH MENTIONS AT MN TERMINALS IS ENOUGH FOR THIS MORNING. FOR THE
AFTERNOON...BEGINNING TO FAVOR THE HRRR/ARW TREND FOR STORMS
TODAY...WITH STORMS DEVELOPING NEAR THE MN/WI BORDER AROUND 20Z ON
A LEAD TROUGH...WITH THE MAIN COLD FRONTAL ACTIVITY NOT LOOKING TO
REALLY GET GOING IN MN UNTIL AFTER 00Z. BEHIND THIS
ACTIVITY...GFSLAMP IS WANTING TO DEVELOP LOW STRATUS...BUT 925-850
RH FORECASTS FROM THE NAM/GFS INDICATE THE STRATUS BEING FAVORED
FOR NRN MN...SO KEPT CIGS VFR TONIGHT.

KMSP...CONFIDENCE IS NOT AT THE CERTAIN LEVEL FOR MSP GETTING
STORMS THIS AFTERNOON...AS SEVERAL OF THE CAMS ARE SHOWING
AFTERNOON ACTIVITY MAINLY IMPACTING WI...WHILE STRONGER STORMS
TONIGHT STAY OFF TO THE SOUTH. IT IS THIS SECONDARY ACTIVITY
THOUGH THAT LOOKS TO HAVE THE GREATEST POTENTIAL FOR IMPACTING THE
FIELD...WHICH IS WHY THE TEMPO GROUP IS STILL THERE FROM 1-4Z.
MOVED THE VCTS MENTION UP TO 21Z TO ACCOUNT FOR UNCERTAINTY FOR
WHERE STORMS WILL DEVELOP ALONG THE PREFRONTAL TROUGH THIS
AFTERNOON. GIVEN STRENGTH OF WINDS...SHOULD NOT TAKE TOO LONG TO
MIX OUT LOW STRATUS THIS MORNING...WITH THAT LOOKING TO OCCUR
BETWEEN 14Z AND 15Z.

/OUTLOOK FOR KMSP/
MON...MVFR/TSRA ENDING EARLY. VFR BY AFTERNOON WINDS WNW 5-10 KTS.
TUE...VFR. WINDS WSW 5-10 KTS.
WED...VFR. CHC MVFR/TSRA LATE. WINDS S 5-10 KTS.

&&

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

$$

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






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.