000
FXUS63 KMPX 242055
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
355 PM CDT FRI MAY 24 2013

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 355 PM CDT FRI MAY 24 2013

SURFACE CYCLONE AND ASSOCIATED TROUGH NOTED ON IR SATELLITE IMAGERY
FROM SOUTHERN ALBERTA INTO EASTERN WYOMING. WARM FRONT ASSOCIATED
WITH THIS SYSTEM CURRENTLY FIRING UP SHIELD OF MAINLY LIGHT
SHOWERS AND ISOLATED THUNDERSTORMS OVER FAR EASTERN SODAK AND
WESTERN QUARTER OF OUR CWA. USED A COMBO OF HRRR...GFS40 305K
ISENTROPIC ANAL...AND THETA E ADVECTION TO PAINT PICTURE OF
FORWARD PROGRESSION ACROSS REMAINDER OF CWA DURING THE OVERNIGHT.
FAIRLY DRY COLUMN TO CONTEND WITH OVER MUCH OF THE FA THIS
AFTERNOON AND EVENING...THUS AM EXPECTING MAINLY LIGHT PCPN FOR
THIS FIRST WAVE OF ACTIVITY. ALTHOUGH K INDICES AND 850 LI`S
INDICATING LITTLE CHANCE OF THUNDER ATTM...DECIDED TO INCLUDE
ISOLATED CHANCE MOST AREAS INTO TOMORROW AFTN DUE TO FAIR AMOUNT
OF LIGHTNING NOTED ON CURRENT 0.5 REFLECTIVITY. AS PREVIOUSLY
ADVERTISED CHANCES FOR WIDESPREAD CONVECTIVE ACTIVITY DECREASE
MARKEDLY AFTER ABOUT 25/15Z TIME FRAME...AS WARM FRONTAL BOUNDARY
STALLS OVER NE MINNESOTA BY LATE SATURDAY MORNING. DECIDED TO
INCREASE SATURDAY`S HIGHS BY ONE CATEGORY CONSIDERING LIMITED PCPN
POTENTIAL AND POSSIBILITY OF MUCH LESS CLOUD COVER THEN CURRENTLY
FORECAST. FOCUS FOR ANY CONVECTIVE ACTIVITY ON SATURDAY AFTERNOON
DEFINITELY NOTED OVER FAR SOUTHERN MINNESOTA...WITH BEST UPPER
LEVEL SUPPORT VIA 250MB WEAK TO MODERATE DIVERGENCE OVER THIS
REGION. LEFT SLGT POPS OVER REMAINDER OF CWA TOMORROW AFTN DUE TO
FAIRLY ROBUST 850-500MB LAPSE RATES.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 355 PM CDT FRI MAY 24 2013

THETA E ADVECTION BLOSSOMS FROM SOUTHWEST INTO CENTRAL MN ON
SATURDAY NIGHT INTO SUNDAY...WHEN BOTH GFS AND NAM MODELS FORECAST A
SHORTWAVE TO CARVE THROUGH THE MID LEVEL RIDGE. EXPECT TO SEE
SCATTERED SHOWERS AND THUNDERSTORMS DEVELOPING...WITH THE HIGHEST
COVERAGE OVER SOUTHWEST MN WHERE 850 MB MOISTURE TRANSPORT IS
SLIGHTLY ENHANCED. HIGH TEMPERATURES ON SUNDAY WILL LIKELY MAX
OUT IN THE UPPER 50S AND LOWER 60S...AS THE WARM FRONT REMAINS TO
THE SOUTH OF THE AREA AND EXTENSIVE CLOUD COVER AND SHOWERS
PERSIST.

YET MORE WEAK SHORTWAVES RIDE NORTH OF THE WARM FRONT ON MEMORIAL
DAY...AND CONTINUE THE POSSIBILITY OF SCATTERED SHOWERS AND
THUNDERSTORMS. SHOULD SEE TEMPS MODERATE SLIGHTLY FOR THE
HOLIDAY...ALTHOUGH IT WILL STILL BE ON THE COOL SIDE WITH UPPER
60S TO MID 70S.

ON TUESDAY...THE AFOREMENTIONED WARM FRONT WILL BEGIN TO LIFT
NORTH...AND ENTER THE FORECAST AREA FROM WEDNESDAY THROUGH
THURSDAY. THIS WILL SIGNAL THE ARRIVAL OF SLIGHTLY WARMER
TEMPERATURES AND AN INCREASE IN HUMIDITY...WITH HIGHS IN THE 75 TO
80 DEGREE RANGE. THE ARRIVAL OF THE FRONT WILL ALSO YIELD AN
INCREASING THREAT FOR SEVERE WEATHER AND EXCESSIVE RAINFALL FOR
THURSDAY AND FRIDAY. FORECAST PRECIPITABLE WATER VALUES INCREASE TO
OVER 1.5 INCHES...WHICH ILLUSTRATES THE POTENTIAL FOR A DOUSING
RAINFALL EVENT. THE SEVERE WEATHER POTENTIAL IS SOMEWHAT UNCERTAIN
DUE TO THE DIFFERENCES IN THE MODELS WITH THE EVOLUTION OF THE
WESTERN TROUGH...AND THE DEGREE OF SURFACE CYCLOGENESIS THAT
ENSUES OVER THE NORTHERN PLAINS TOWARD THE END OF NEXT WEEK.
HOWEVER...IF THE 24.12Z GFS SHEAR AND INSTABILITY PROGS WERE TO
PAN OUT...THERE WOULD BE A FAIRLY HIGH THREAT FOR SEVERE WEATHER
AND TORNADOES ACROSS CENTRAL AND SOUTHERN MN ON THURSDAY
AFTERNOON/EVE. WILL CONTINUE TO MONITOR AND REFINE OVER THE NEXT
FEW MODEL RUNS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY MORNING)
ISSUED AT 115 PM CDT FRI MAY 24 2013

SCATTERED SHOWERS AND THUNDERSTORMS BREAKING OUT OVER EASTERN
SODAK AND SE SODAK AS TAFS ARE SENT. AREA LINES UP FAIRLY WELL
WITH GFS40 305K ISENTROPIC ANAL AND FAIRLY ROBUST 250MB DIVERGENCE
COUPLET. VFR CIGS AND VSBYS SHOULD PAN OUT THROUGH MOST OF INITIAL
SIX HOURS OF TAF PERIOD...WITH OCNL MID RANGE MVFR CIGS/VSBSYS
ERUPTING DURING THE EVENING HOURS OVER MN AIRPORT SITES. MUCH OF
THE INITIAL FORCING SHOULD END ACROSS MOST OF THE REGION BY 12Z.
LOOK FOR LIGHT TO MDT SE FLOW THROUGH END OF PERIOD ALL SITES
AS SURFACE GRADIENT TIGHTENS AHEAD OF DEVELOPING SURFACE CYCLONE
OVER WESTERN NE. INSTABILITY ASSOCIATED WITH A WARM FRONTAL
BOUNDARY ASSOCIATED WITH THIS SYSTEM WILL IGNITE ADDITIONAL
CONVECTIVE ACTIVITY ON SATURDAY. WITH THAT SAID DUE LATER PORTION
OF FORECAST PERIOD COULD ENTAIL WIDELY SCT CONVECTION. DECIDED
BEST OPTION DUE TO LACK OF UPPER LEVEL SUPPORT AND EXACT LOCATION
OF FRONTAL BOUNDARY WAS A PROB30 GROUP AT MOST LOCALES. SURFACE
CYCLONE WILL ONLY SLIGHTLY MOVE EAST BY SUNDAY MORNING...WITH
BEST CHANCE FOR MVFR CIGS/VSBYS ASSOCIATED WITH T-STORMS/-SHRAS
SHIFTING TO MAINLY KAXN AND KRWF SATURDAY NIGHT INTO SUNDAY
AFTN.

KMSP...IR SATELLITE IMAGERY CLEARLY INDICATES MAINLY A SHROUD
OF SCT-BKN CIRRUS ALMOST UP TO THE SODAK BORDER. DRY ATMOSPHERIC
COLUMN PRECLUDED ANY MENTION OF CONVECTION PRIOR TO 01Z. SLOW
PROGRESSION OF ACTIVITY OVER SODAK AND LACK OF ANY SIGNIFICANT
PARCEL ASCENT HAS PROMPTED LATE EVENING MENTION OF -SHRA IN
TAF. LACK OF NEAR ZERO OR BELOW 850MB LI`S ALSO NEGATES MENTION OF
THUNDER FOR ENTIRE PERIOD. LOOK FOR TEMPORARY PERIODS OF MVFR
CIGS/VSBYS ASSOCIATED WITH PRECIPITATION...WITH MVFR CIGS BECOMING
MORE WIDESPREAD LATE IN THE TAF PERIOD. ALTHOUGH BEST CHANCE FOR
CONVECTION WILL BE SEEN TONIGHT...LOOK FOR SCT BOUTS OF SHOWERS
/ISOLATED THUNDERSTORMS RIGHT INTO MONDAY.

/OUTLOOK FOR KMSP/
SAT...CHC MVFR OR LOWER CIGS. CHC SHRA/TSRA. WINDS SE 10-15 KTS.
SUN...CHC MVFR OR LOWER CIGS. CHC SHRA/TSRA. WINDS SE 10-15 KTS.
MON...CHC MVFR OR LOWER CIGS. CHC SHRA/TSRA. WINDS SE 10 KTS.

&&

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

$$

SHORT TERM...AJZ
LONG TERM...LS
AVIATION...AJZ