Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 311954
AFDMPX

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

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 252 PM CDT SUN AUG 31 2014

SVR WX PARAMETERS REMAIN FAVORABLE FOR LARGE HAIL/DAMAGING WINDS
THIS AFTN/EARLY EVENING. THE MAIN PROBLEM IS AFTN CAP /BASED ON
18Z KMPX SOUNDING/ WHICH HAS SUPPRESSED MOST OF THE CONVECTION
ACROSS SOUTHERN MN EARLY THIS AFTN. IN ADDITION...THE MAIN SHRTWV
AND UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE JET CORE MOVING
ACROSS COLORADO...IS NOT EXPECTED TO MOVE ACROSS NE/IA/MN UNTIL
LATER THIS EVENING. A STRONGER STORM NORTH OF KOMA AS OF 19Z IS A
REFLECTION OF A STRENGTHENING LLJ AHEAD OF THIS JET ENERGY MOVING
OUT OF COLORADO.

SHORT TERM MESOSCALE CONVECTIVE PARAMETERS /HRRR/RUC/ HAVE
DEPICTED THAT THE SHRA/TSRA ACROSS SOUTHERN MN SHOULD BE MOVING
ACROSS EASTERN MN/WESTERN WI BY 00Z...WITH MOST OF THE
STRONGER/SVR ACTIVITY FORMING SOUTH ACROSS IOWA. IN
ADDITION...THESE SAME MESOSCALE CONVECTIVE PARAMETERS HAVE ANOTHER
LINE OF SHRA/TSRA FORMING WEST OF THE TWIN CITIES ARND 2-4Z ALONG
AND AHEAD OF THE APPROACHING SFC FRONT. THIS MAY BE THE MAIN
PLAYER TONIGHT...AS SAID BEFORE...THE AFTN CAP WILL LIKELY HOLD
FOR A FEW MORE HRS...SETTING THE STAGE FOR AN EVENING EVENT.
OTHERWISE...SHRA/TSRA SHOULD CONTINUE TO FORM ALONG AND AHEAD OF
THIS SFC FRONT LATER THIS EVENING AND MOVE EASTWARD DURING THE
OVERNIGHT HRS. BY MORNING...MOST OF THE ACTIVITY SHOULD BE EAST OF
MPX FA...WITH ONLY RESIDUAL SHRA IN WC WI.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 252 PM CDT SUN AUG 31 2014

TUESDAY-WEDNESDAY...THE FIRST COUPLE DAYS OF THE EXTENDED PORTION
WILL BE DOMINATED BY GENERALLY ZONAL FLOW ALOFT WHILE SFC HIGH
PRES OVER THE CENTRAL PLAINS SHIFTS E INTO THE OHIO VALLEY. THIS
WILL SPELL A WEAK PRES PATTERN OVER THE UPR MISS RIVER VALLEY
REGION WITH WEAK SUPPORT ALOFT. HOWEVER...THE RELATIVELY WEAK
INFLUENCE OF HIGH PRESSURE AS IT STAYS S OF THE REGION MEANS THAT
THERE WILL BE FAIRLY INEFFECTIVE CAPPING WITHIN A CONTINUED DEEPLY
MOIST ENVIRONMENT. WEAK BUCKLES IN THE ZONAL FLOW CAN EASILY SPARK
ISOLD SHOWERS AND POSSIBLY EVEN A HANDFUL OF TSTMS ACRS THE REGION
DURING THIS PERIOD SO SPOTTY SLGT CHC POPS ARE MAINTAINED IN THE
FCST. MUCH OF THE FCST AREA WILL REMAIN DRY...BUT ANY LOCATIONS
THAT DO SEE SOME PRECIP WILL NOT RECEIVE MUCH IN THE WAY OF QPF.
OTHERWISE...TEMPS AND DEWPOINTS WILL GO ON A SLIGHT INCREASING
TREND AS WINDS SHIFT FROM WLY TO SLY ON THE BACKSIDE OF THE
DEPARTING HIGH PRES AREA.

WEDNESDAY NIGHT-THURSDAY NIGHT...A LARGE LONGWAVE TROUGH DROPPING
OUT OF THE GULF OF ALASKA MON WILL MOVE ONSHORE THE PAC NW
REGION TUE EVE AND SLOWLY MAKE ITS WAY INTO THE CENTRAL CONUS
DURING THE MIDDLE PORTION OF THE WEEK. THIS TROUGH WILL PICK UP A
DEVELOPING LOW PRES CENTER OVER MT...SHIFTING IT INTO THE DAKOTAS
AND EVENTUALLY NRN MN BY MIDDAY THU. THE COMBINATION OF THE
DIGGING TROUGH AND THIS LOW PRES CENTER DEEPENING OVER THE ERN
DAKOTAS AND MN WILL CREATE ADDITIONAL POTENTIAL FOR SCATTERED
SHOWERS AND THUNDERSTORMS FOR MUCH OF THE AREA LATE WED THRU THU
NIGHT. THE FRONT LOOKS TO STALL OUT OVER CENTRAL MN THU...SO THIS
MAY ALTER THE DURATION OF HAVING POPS IN THE FCST OVER THE NEXT
FEW DAYS WORTH OF MODEL RUNS.

FRIDAY-SUNDAY...THOUGH THE SFC REFLECTION OF THE LOW PRES SYSTEM
LOOKS TO BE E OF THE WFO MPX CWFA BY DAYBREAK FRI MRNG...THE
ASSOCIATED TROUGH AXIS ALOFT WILL BE DRAGGING ITS WAY THROUGH THE
REGION DURG THE DAY ON FRI. THIS MAY LEAD TO SOME SHOWERS WITH THE
RELATIVE CORE OF THE SYSTEM STILL PASSING THRU. BEHIND THESE
DISTURBANCES AT THE SFC AND ALOFT...MORE PRONOUNCED NW FLOW ALOFT
WILL DOMINATE THRU THE WEEKEND WHILE HIGH PRES SLOWLY SHIFTS SE.
THIS COMBINATION WILL ALLOW FOR A DRYING OUT PERIOD FOR NEXT
WEEKEND ALONG WITH COOLER AND LESS HUMID CONDITIONS. HIGHS WILL
DROP BACK TO THE UPR 60S AND LWR 70S BY NEXT WEEKEND WITH LOWS
FALLING INTO THE UPR 40S AND LWR 50S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1155 AM CDT SUN AUG 31 2014

LOW CONFIDENCE IN TSRA/SHRA DEVELOPMENT AFT 21Z WITH SHORT TERM
MODELS HAVING PROBLEMS WITH THE CONVECTION ALREADY DEVELOPING NEAR
KRWF/KFRM AS OF 17Z. WILL USE REGIONAL RADAR AND MOVEMENT TRENDS
FOR THE FIRST 3 HRS AS THIS LINE BECOMES MORE ORGANIZED AND MOVES
OFF TO THE NE. KRWF/KSTC WILL BE MOST IMPACTED IN THE SHORT TERM.
ELSEWHERE...TSRA/SHRA SHOULD HOLD OFF UNTIL AFT 21Z...WITH A
BETTER CHC AFT 00Z AS THE MAIN UPPER WAVE AND SFC FRONT MOVES
CLOSER TO THE AREA. WINDS WILL BE GUSTY THIS AFTN FROM THE
S/SW...WITH A MORE SW/WSW BY THE LATE AFTN IN WC/SW MN AND
DECREASE TO LESS THAN 10 KTS. EC MN/WC WI WILL LIKELY SEE THE
GUSTY WINDS UNTIL 00Z FROM THE S/SSW.

AM CONCERN WITH AREAS FROM SC/EC MN...EASTWARD ACROSS WC WI AFT 2Z
AS A LARGE AREA OF CONVECTION IS EXPECTED TO DEVELOP. WILL
ADJUST AS NECESSARY BUT IFR/MVFR CIGS/VSBYS FOR KRNH/KEAU LOOK
MORE LIKELY OVERNIGHT.

KMSP...

BASED ON THE LATEST REGIONAL RADAR MOST OF THE ACTIVITY SHOULD
HOLD OFF TO THE WEST UNTIL AFT 20-21Z...WITH A PERIOD OF VCTS FROM
20-23Z...BUT LOW CONFIDENCE ON AREAL EXTENT. A BETTER CHC OF
WIDESPREAD ACTIVITY IS EXPECTED AFT 2Z...WITH A PERIOD OF HEAVY
SHRA/TSRA AND LOW VSBYS. AFT 6Z...CHC/S OF SHRA/TSRA
DIMINISH...BUT MVFR CIGS AND/OR VSBYS MAY DEVELOP BEHIND THE SFC
FRONT...ESPECIALLY DURING THE TYPICAL 09-14Z TIME FRAME. IF MVFR
CIGS DEVELOP...DO NOT EXPECT VFR CONDS UNTIL AFT 16-18Z ON MONDAY.

/OUTLOOK FOR KMSP/

MON...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...JLT
LONG TERM...JPC
AVIATION...JLT





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