Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 021556
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1056 AM CDT TUE SEP 2 2014

.UPDATE...
ISSUED AT 1036 AM CDT TUE SEP 2 2014

MORNING UPDATE CONSISTS OF ADDING IN SOME SLGT CHC POPS FOR THIS
AFTN MAINLY ALONG AND N OF THE I-94 CORRIDOR. SHORT-TERM MODELS...
SPECIFICALLY THE HRRR/HOPWRF/RAP COMBINATIONS...INDICATE MODEST
INSTABILITY WITHIN THE WNW-ENE FLOW ALOFT. SOME SAGGINESS IN THE
NRN FRINGES OF EXITING HIGH PRES HINT AT WEAK SFC CONVERGENCE
PERTURBATIONS...ALONG WITH SOME BUCKLING IN THE UPPER FLOW. THESE
INGREDIENTS MAY ALLOW FOR SOME ISOLD SHWRS...POSSIBLY EVEN A
TSTM...DURING THE MID-TO-LATE AFTN HOURS. MOST AREAS WILL REMAIN
DRY...AND COVERAGE WILL BE SPARSE SHOULD ANYTHING DEVELOP. QPF
WILL ALSO BE QUITE LOW...BUT THIS IS SIMPLY DECENT SHORT-TERM
MODEL AGREEMENT THAT THE DAY MAY NOT BE COMPLETELY AND SOLIDLY
DRY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 410 AM CDT TUE SEP 2 2014

A COOL AND DRY DAY IS EXPECTED ACROSS EASTERN MN AND WESTERN WI WITH
ISOLATED SHOWERS THIS MORNING MOVING EAST AND OUT OF THE FORECAST
AREA WITH TIME.

VAD WIND PROFILES FROM KABR...TO KMSP...TO ARX ARE ALL SHOWING
NORTHWEST FLOW FROM 2-10KFT THIS MORNING. THERE IS ONGOING WEAK
LOW-LEVEL COLD ADVECTION THIS MORNING WHICH SHOULD KEEP HIGH TEMPS
TODAY SLIGHTLY COOLER THAN YESTERDAY EVEN WITH EXPECTED AFTERNOON
SUNSHINE. THE HIGH CLOUDS THIS MORNING ARE THE REMNANTS OF A COMPLEX
OF THUNDERSTORMS THAT DEVELOPED IN SD/NE LAST EVENING. THE CLOUDS
ARE THINNING WITH TIME WITH NO NEW UPDRAFTS AND ARE ALSO MOVING
EAST AT GOOD CLIP /35-40KTS/. SO...THE CLOUDS SHOULD BE OUT OF THE
PICTURE QUICKLY THIS MORNING. PLEASANT TEMPERATURE-DEWPOINT
COMBINATION TODAY IS TYPICAL FOR EARLY SEPTEMBER WITH 70S OVER 50S.
THERE IS GOOD COVERAGE IN LIGHT SHOWERS ACROSS FAR SOUTHERN MN AND
IN NORTH CENTRAL IA EARLY THIS MORNING TIED TO PV ADVECTION AND THE
UPPER JET OVER IA. THE VORTICITY ADVECTON WILL ALSO QUICKLY MOVE
EAST OF THE FORECAST AREA THIS MORNING. THE LIGHTNING HAS REALLY
DROPPED OFF...WITH JUST A COUPLE STRIKES IN IA WHERE THERE ARE STILL
MUCAPE VALUES BETWEEN 500-1000J/KG. THE NORTHWEST FLOW WILL BE SHORT
LIVED...HOWEVER...WITH THE LOW LEVEL FLOW TURNING BACK TO THE
SOUTHWEST BY 12Z WEDNESDAY ACROSS WESTERN MN. THE WARM ADVECTION HAS
THE POTENTIAL TO GENERATE ISOLATED TO SCATTERED WEAK THUNDERSTORMS
LATE TONIGHT ACROSS THE WESTERN FORECAST AREA.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 410 AM CDT TUE SEP 2 2014

WARM AND HUMID WEATHER IN THE MIDDLE OF THE WEEK WILL GIVE WAY TO A
COOL CRISP FALL AIRMASS FOR THE WEEKEND. TEMPERATURES WILL RUN FROM
ROUGHLY 5 TO 10 DEGREES ABOVE NORMAL ON WEDNESDAY...TO 5 DEGREES
BELOW NORMAL OVER THE WEEKEND.

EARLY MORNING WATER VAPOR IMAGERY WITH GFS 02.00 500MB HEIGHTS AND
WINDS IDENTIFIED A VIGOUROUS SHORTWAVE CRAWLING DOWN THE BRITISH
COLUMBIA COAST. OVER THE NEXT 36 HOURS THIS PV ANOMALY WILL
TRANSITION EASTWARD ALONG THE INTERNATIONAL BORDER AND CAUSE A
SURFACE LOW TO DEVELOP OVER THE HIGH PLAINS...WITH THE WARM SECTOR
OVERSPREADING THE UPPER MIDWEST DURING THE DAY ON WEDNESDAY. A
SURFACE WARM FRONT WILL LIFT NORTHWARD...AND BOUNDARY LAYER
DEWPOINTS OF NEAR 70F WILL BECOME WIDESPREAD ACROSS SOUTHERN MN BY
WEDNESDAY EVENING.

PRECIP CHANCES WILL FOLLOW THIS WARM FRONT...BUT BY WEDNESDAY
AFTERNOON BUFR SOUNDINGS SHOW A STOUT CAP DEVELOPING ACROSS SOUTHERN
MN...SO HAVE BROKE POP GRIDS INTO 3HR BLOCKS TO BETTER DEPICT THE
TIMING AND LOCATION OF EXPECTED CONVECTION. THE 02.00 WRFARW AND
WRFNMM HAVE PRECIP FOCUSED NORTH OF THE WARM FRONT...SO FEEL
COMFORTABLE SHAVING OFF POPS FROM SOUTH TO NORTH THROUGHOUT THE DAY
ON WEDNESDAY. LATE WEDNESDAY EVENING THE BOUNDARY LAYER WILL
DECOUPLE AND SHOULD SEE AN MCS DEVELOP ON THE NOSE OF THE LOW LEVEL
JET ACROSS CENTRAL MN WHICH SHOULD SHIFT EAST SOUTHEAST OVERNIGHT.
VEERING WINDS IN THE EFFECTIVE LAYER WILL SUPPORT ORGANIZED
CONVECTION SO SUSPECT TO SEE A FEW STRONG/SEVERE STORMS...WITH THE
BEST CHANCES ALONG AND NORTH OF I-94.

THIS CONVECTION WILL EXIT THE REGION BY THURSDAY MORNING...AND
WILL SEE TEMPERATURES SURGE ACROSS SOUTHEASTERN MN AND WESTERN
WI AHEAD OF A COLD FRONT THAT IS FORECAST TO PASS THROUGH THE
REGION DURING THE DAY ON THURSDAY. FORECAST SOUNDINGS SHOW AN
EXTREMELY UNSTABLE ENVIRONMENT BY LATE AFTERNOON ACROSS
WISCONSIN...SO COULD SEE ANOTHER ROUND OF SEVERE STORMS IF THE
SURFACE CONVERGENCE ALONG THE FRONT IS ENOUGH TO BREAK THROUGH THE
CAP.

IN THE WAKE OF THIS FRONT IS A MUCH COOLER...DRIER AIRMASS. LOW
TEMPERATURES THURSDAY NIGHT WILL FALL INTO THE 40S ACROSS THE
NORTHWEST CWA. NORTHWEST FLOW AND SURFACE HIGH PRESSURE SUPPORT DRY
WEATHER THROUGH THE WEEKEND.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 620 AM CDT TUE SEP 2 2014

SHOWERS AND HIGH CLOUDS WILL CLEAR EASTERN MN AND WESTERN WI EARLY
THIS MORNING. HIGH CONFIDENCE IN A DRY FORECAST AND VFR CONDITIONS
THROUGH THE DAY AND MOST OF TONIGHT. ISOLATED TO SCATTERED SHOWERS
AND STORMS COULD BEGIN IMPACTING PORTIONS OF SOUTHWEST MN AND
APPROACH KRWF BY LATE TONIGHT.

KMSP...
LOW CHANCE FOR RAIN THROUGH THE PERIOD WITH VERY HIGH
CONFIDENCE IN VFR CONDITIONS.

/OUTLOOK FOR KMSP/
WED...VFR. CHC MVFR/TSRA. WINDS S 10-15 KTS.
THU...VFR. CHC MVFR/TSRA LATE. WINDS S 10-15 KTS BCMG W LATE.
FRI...VFR. WINDS NW 10 KNOTS.


&&

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

$$

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





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