Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 231112
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
612 AM CDT SAT AUG 23 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 350 AM CDT SAT AUG 23 2014

WE HAVE BEEN WATCHING AN IMPRESSIVE THUNDERSTORM COMPLEX RACE NORTH
ACROSS NEBRASKA OVERNIGHT IN ASSOCIATION WITH A SHORTWAVE ROTATING
NNE AROUND THE BASE OF A DEEP TROUGH CENTERED OVER IDAHO.
HOWEVER...DO NOT GET TOO EXCITED ABOUT THE PROSPECTS ABOUT ANYONE IN
THE MPX CWA SEEING MUCH OF THIS PRECIP TODAY...AS THIS WAA PRECIP
LOOKS TO LARGELY GO AROUND THE MPX CWA. MOST CAMS SHOW TWO
CONCENTRATED AREAS THIS MORNING HEADING EAST ACROSS IOWA...WITH THE
OTHER BATCH OF WIDESPREAD THUNDERSTORMS TO HEAD NORTH ACROSS THE
DAKOTAS. THE IOWA AREA IS IN RESPONSE TO AIR GETTING FORCED UP OVER
THE REMNANTS OF A COLD FRONT...WHICH AT 3 AM WAS LOCATED JUST SOUTH
OF OMAHA TO THE QUAD CITIES...WHICH IS MORE OR LESS THE AXIS WHERE
THE HRRR HAS A SWATH OF HIGHER QPF FALLING. THE DAKOTAS BULLSEYE IS
RESPONSE THE NOSE OF A 40 KT ESE ORIENTED LLJ THAT WILL BE WORKING
NORTH IN CONJUNCTION WITH THE STRONG SHORTWAVE CURRENTLY OVER
CENTRAL NEB. WITH THAT SAID...ACTIVITY OUT THERE NOW LOOKS LIKE IT
SHOULD HAVE ENOUGH MOMENTUM TO AT LEAST SNEAK UP TO AREAS SOUTH/WEST
OF THE MN RIVER. OTHERWISE...FOR MUCH OF THE MPX AREA...THE BAND OF
STORMS WE SEE COMING NORTH NOW WILL NOT DO MUCH MORE THAN BRING A
BAND OF ALTOCU THROUGH THE AREA.

FOR THIS AFTERNOON...ATTENTION TURNS TO THE SEVERE POTENTIAL OUT IN
WRN MN. BY THE AFTERNOON...THE BROAD SFC CYCLONE CURRENTLY SPLAYED
OUT ACROSS THE CENTRAL HIGH PLAINS WILL HAVE CONSOLIDATED INTO A
1000 MB LOW NEAR THE CENTRAL ND/SD BORDER. THIS WILL HELP PULL THE
FRONT IN IOWA BACK NORTH AS A WARM...WITH IT PUSHING INTO SW MN
AFTER 00Z. WILL HAVE TO WAIT A WHILE FOR SFC BASED CONVECTION TO
FIRE GIVEN EXTENT OF RAIN/CLOUD COVER EXPECTED ACROSS THE DAKOTAS
THIS MORNING..BUT EXPECT ENOUGH HEATING TO OCCUR THIS AFTERNOON TO
ALLOW FOR STORMS TO DEVELOP NEAR THE SURGING WARM FRONT ALONG THE
COTEAU IN SE SODAK AROUND 21Z...AS BOTH THE NMM/ARW SHOW. THIS
ACTIVITY SHOULD THEN TRACK NNE...TOWARD WEST CENTRAL AND NORTHWEST
MN DURING THE EVENING...AND IT IS THIS POTENTIAL ACTIVITY THAT
GIVES US THE SLIGHT RISK FOR TODAY FROM THE SPC. CERTAINLY
INSTABILITY AND SHEAR ARE ADEQUATE TO SUPPORT SURFACE BASED
SUPERCELLS AND THEREFOR ALL MODES OF SEVERE WEATHER. HOWEVER...FOR
AS FAR EAST AS MN...SHEAR VECTORS WILL BE MORE PARALLEL THAN
PERPENDICULAR TO THE FORCING...WHICH WOULD FAVOR THE CONGEALING OF
ACTIVITY INTO CLUSTERS/LINES...WHICH IS WHAT IS SEEN WITH NMM/ARW
REFLECTIVITY FORECASTS. THIS WOULD FAVOR THE HIGHEST TORNADO THREAT
BEING ACROSS THE DAKOTAS...WHERE STORMS ARE MORE LIKELY TO BE
DISCRETE...WITH WRN MN DEALING MORE WITH A POTENTIAL WIND/HAIL
THREAT.

FROM THE FLOOD TREAT...PWATS WILL INCREASE BACK TO AROUND 1.75
INCHES...SO CERTAINLY WILL SEE HEAVY RAIN WITH THIS ACTIVITY.
HOWEVER...CURRENT EXPECTATIONS ARE THAT ACTIVITY WILL BE PROGRESSIVE
ENOUGH TO KEEP ANY CONCENTRATED SWATHS OF HIGH QPF DOWN IN THE 1-2
INCH RANGE AS OPPOSED TO BEING UP IN THE 3-6 INCH RANGE LIKE WE WERE
SEEING LAST WEEK.

FOR TONIGHT...BEST UPPER FORCING WILL BE STAYING NW OF THE MPX
CWA...SO ACTIVITY THAT MOVES INTO WRN MN WILL HEAD FOR NW/NC MN...SO
CUT BACK CONSIDERABLY ON POPS...KEEPING THE ERN 2/3RDS OR SO OF THE
CWA DRY. MAY STILL BE TOO FAR EAST WITH POPS TONIGHT...BUT WE SHOULD
SEE SOMEWHAT OF AN EWRD PUSH WITH ACTIVITY TONIGHT AS COLD POOLS GET
GENERATED. EVEN IF IT DOES NOT RAIN...IT WILL BE A MUGGY NIGHT...AS
LOWER 70 DEWPS COME UP WITH THE WARM FRONT. WILL LIKELY MAKE IT
TOUGH FOR MUCH OF THE MN CWA TO DIP BELOW 70 SUNDAY MORNING...WHICH
WILL HAVE IMPLICATIONS ON THE POTENTIAL NEED FOR ANY HEAT HEADLINES
SUNDAY. NOT WORRIED ABOUT FOG TONIGHT EITHER...AS GRADIENT WILL
REMAIN STRONG THROUGH THE NIGHT...SO WILL BE ANOTHER NIGHT LIKE
TONIGHT WHERE WE JUST WATCH ANY STRATUS THAT SURVIVES THE DAY TODAY
EXPAND AGAIN OVERNIGHT.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 350 AM CDT SAT AUG 23 2014

THERE IS DEFINITELY SOME SPREAD IN THE MODEL GUIDANCE AS WE HEAD
THROUGH THE LATTER PORTION OF THE FORECAST... BUT THE GENERAL
SCENARIO SUGGESTS A TRANSITION FOR WESTERN RIDGE/EASTERN TROUGH TO
MORE OF A ZONAL PATTERN BY THE END OF THE WEEK. THIS SHOULD ALLOW
FOR TEMPERATURES TO TREND FROM ABOVE NORMAL TO NEAR NORMAL AS THE
WEEK UNFOLDS... WITH PCPN CHANCES BEING A BIT TOUGH TO PIN DOWN
DEPENDING UPON WHERE THE MAIN BAROCLINIC ZONE SETS UP. GIVEN THE
SPREAD IN DETERMINISTIC AND ENSEMBLE GUIDANCE... A CONSENSUS
APPROACH IS THE MOST SENSIBLE COURSE OF ACTION... SO STUCK CLOSE
TO A MULTI-MODEL BLEND.

THE MAIN FORECAST ISSUES LOOK TO BE THE POTENTIAL FOR EXCESSIVE
HEAT/HUMIDITY SUNDAY... THEN THE POSSIBILITY OF SIGNIFICANT PCPN
OVER THE SOUTHERN PORTION OF THE AREA LATE MONDAY THROUGH
WEDNESDAY AS THE FRONTAL BOUNDARY HANGS UP SOMEWHERE NEAR THE
MINNESOTA/IOWA BORDER. SUNDAY STILL LOOKS TO HAVE THE POTENTIAL
FOR VERY WARM TEMPERATURES ACROSS THE AREA... ALONG WITH HIGH
DEWPOINTS. AT THIS POINT... APPARENT TEMPERATURE FORECASTS PEAK
AROUND 100 OVER A PORTION OF THE AREA SUNDAY AFTERNOON WITH
FORECAST HIGHS IN THE LOW 90S AND DEWPOINTS NEAR 70. WET BULB
GLOBE TEMPERATURES JUMP INTO THE LOWER TO MIDDLE 80S AS WELL...
ALSO INDICATING THE POTENTIAL FOR HEAT RELATED ISSUES FOR PEOPLE
WHO MAY BE OUTDOORS ON SUNDAY. THERE WILL CERTAINLY BE A
SIGNIFICANT NUMBER OF PEOPLE OUTDOORS IN THE METRO AREA ON SUNDAY
WITH THE GREAT MINNESOTA GET TOGETHER IN FULL SWING... SO THE
POSSIBILITY OF EXCESSIVE HEAT/HUMIDITY WILL NEED TO BE MONITORED
IN SUBSEQUENT FORECASTS. AT THIS POINT... THERE IS STILL SOME
UNCERTAINTY IN CLOUD COVER AND WHETHER WE/LL MIX AS WELL AS SOME
GUIDANCE SUGGESTS AND/OR SEE MORE LOW LEVEL EVAPORATIVE COOLING
THAN ANTICIPATED. SO... WILL HIGHLIGHT THE POSSIBILITY IN THE
HAZARDOUS WEATHER OUTLOOK AND OTHER SERVICES... BUT HOLD OFF ON
ANY ACTUAL HEADLINES AT THIS POINT. PCPN CHANCES ON SUNDAY LOOK TO
BE CONFINED TO THE WESTERN/NORTHERN PORTION OF THE AREA UNTIL
LATE AFTERNOON AND/OR EVENING WHEN THE COLD FRONT FINALLY STARTS
TO WORK ITS WAY EAST ACROSS THE AREA. AT THAT POINT... THE MAIN
LARGE SCALE FORCING WILL BE TO OUR NORTH... SO PCPN MAY BE
SCATTERED IN NATURE WITH MORE WIDESPREAD ACTIVITY WITH THE
SHORTWAVE AND TRIPLE-POINT TO OUR NORTH AND THE SECONDARY WARM
ADVECTION/INSTABILITY NOSE TO OUR SOUTH. DEEP LAYER SHEAR WILL BE
BEST TO OUR NORTH... SO ANY SEVERE POTENTIAL LOOKS TO BE CAPE-
DRIVEN WITH MAINLY MULTI-CELL WIND/HAIL STORMS BEING THE CONCERN.

CHANCES FOR PCPN WILL PUSH EAST SUNDAY NIGHT WITH THE FRONT...
THEN WE/LL SEE HIGH PRESSURE BUILD OVER MUCH OF THE AREA.
HOWEVER... THE FRONTAL BOUNDARY LOOKS TO HANG UP TO OUR SOUTH/EAST
MONDAY INTO WEDNESDAY... NECESSITATING THE INCLUSION OF POPS OVER
MUCH OF THE AREA DURING THAT TIME FRAME... WITH BETTER CHANCES
SOUTH AND LOW CHANCES NORTH. THE FAR SOUTHERN PORTION OF THE AREA
HAS SOME POTENTIAL TO SEE SIGNIFICANT RAINFALL OVER THAT PERIOD OF
TIME... BUT MUCH WILL DEPEND ON WHERE SUCCESSIVE ROUNDS OF
SHRA/TSRA DECIDE TO TRACK... AND IT IS TOO EARLY TO GET A GOOD
HANDLE ON THAT EVOLUTION. WE SHOULD SEE HIGH PRESSURE...
SUBSIDENCE... AND DRIER AIR WORK INTO THE ENTIRE AREA FROM THE
NORTHWEST WEDNESDAY NIGHT THROUGH THE REMAINDER OF THE FORECAST
PERIOD... WITH DRY WEATHER PREDOMINATING. HOWEVER... THE 00Z ECMWF
IS A BIT SLOWER IN SHOWING THIS EVOLUTION IN COMPARISON TO ITS
PREVIOUS RUNS OR THE 00Z GFS... SO WE/LL NEED TO SEE HOW THINGS
EVOLVE IN SUBSEQUENT FORECASTS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 544 AM CDT SAT AUG 23 2014

WINDS HAVE STAYED UP ENOUGH THROUGH THE NIGHT TO KEEP THIS
MORNINGS ISSUE AS ONE OF STRATUS. GIVEN THE STRONGER WINDS...WE
WILL SEE THESE CLOUDS CLEAR OUT MORE QUICKLY THAN WE DID
YESTERDAY...BUT WILL STILL BE STUCK WITH IFR/MVFR CIGS THROUGH
MUCH OF THE MORNING. AREA OF TSRA ENTERING SW MN WILL STRUGGLE TO
MAKE IT MUCH FARTHER INTO THE STATE AS THE LLJ SLIDES MORE EAST
ACROSS IOWA...KEEPING ACTIVITY TODAY MAINLY ALONG I-90...WITH A
SECOND BATCH REMAINING OUT IN THE DAKOTAS. FOR THIS
AFTERNOON...EXPECT STORMS TO DEVELOP ACROSS ERN SODAK AND HEAD NE
TOWARD WEST CENTRAL MN. AXN LOOKS TO BE MOST SUSCEPTIBLE TO TSRA
THIS EVENING...WITH BEST CHANCES REMAINING NORTH OF RWF AND WEST
OF ALL OTHER TERMINALS. WILL ALSO HAVE A WARM FROM WORKING ACROSS
SW MN OVERNIGHT...WITH THE THREAT FOR MORE IFR/LIFR STRATUS
EXISTING AHEAD OF THIS BOUNDARY...WITH MAINLY MVFR HZ/BR IN THE
WARM SECTOR. AT THIS POINT...ONLY RWF LOOKS TO DEFINITELY SEE THE
WARM SECTOR...WHILE THE WI TERMINALS WILL REMAIN OUT AHEAD OF IT.
AXN/STC/MSP WILL HAVE THE BOUNDARY NEARBY BY THE END OF THE
NIGHT...BUT GIVEN THE DEGREE OF LOW LEVEL MOISTURE
AROUND...DECIDED TO GO WITH THE IDEA OF ANOTHER ROUND OF LOW
STRATUS TO START SUNDAY.

KMSP...DESPITE WHAT RADAR LOOKS LIKE TO THE SW...CONFIDENT THAT
MSP WILL SEE NOTHING MORE THAN SOME SPRINKLES THIS MORNING...AS
THIS ACTIVITY IS STARTING TO FAVOR IOWA BASED ON CLOUD TOP
TEMPERATURES WARMING OVER MN AND REMAINING COLD OVER IA. STRATUS
WILL BE EASIER TO CLEAR OUT TODAY GIVEN THE STRONGER WINDS.
TONIGHT...GIVEN WHERE FORCING IS GOING...CONFIDENT IN ANY TSRA
ACTIVITY REMAINING NW OF MSP. WILL BE VERY MOIST AGAIN...AND GIVEN
WHAT WE HAVE SEEN THE LAST FEW MORNINGS WITH STRATUS...DECIDED TO
GO WITH THE TREND OF LOW STRATUS RETURNING TO START OF SUNDAY.
HOWEVER...SUNDAY SHOULD SEE IT CLEAR OUT EVEN FASTER...AS A WARM
FRONT LOOKS TO QUICKLY CLEAR THE FIELD IN THE MORNING...WITH A
RATHER TOASTY WARM SECTOR MOVING IN IN ITS WAKE.

/OUTLOOK FOR KMSP/
SUN NIGHT...VFR. CHANCE MVFR/TSRA. WINDS BCMG W 5-10 KTS.
MON...VFR. WINDS W 5-10 KTS.
TUE...SHRA/TSRA AND MVFR LIKELY BY AFTERNOON. WINDS NE 5-10 KTS.

&&

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

$$

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






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