Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 300125
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
825 PM CDT WED APR 29 2015

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 310 PM CDT WED APR 29 2015

A VERY BENIGN SHORT TERM PERIOD IS IN STORE FOR THE AREA...AS
SURFACE HIGH PRESSURE SLOWLY DRIFTS SOUTHEAST. AN AREA OF MID/HIGH
CLOUDS OVER NORTHEASTERN MINNESOTA WILL DRIFT SOUTH AND EAST ACROSS
EAST CENTRAL MINNESOTA AND WEST CENTRAL WISCONSIN THIS EVENING...BUT
OTHERWISE MOSTLY CLEAR SKIES WILL PREVAIL.

WITH RESPECT TO TEMPERATURES...EXPECT THE BULK OF THE FORECAST AREA
TO STAY ABOVE FREEZING...WITH LOWS TONIGHT PRIMARILY IN THE UPPER
30S TO LOWER 40S RANGE. A FEW MID 30S ARE POSSIBLE UP NEAR
LADYSMITH...WHERE PATCHY FROST APPEARS POSSIBLE.

HIGHS THURSDAY SHOULD MODERATE A FEW DEGREES FROM TODAY...GIVEN LESS
LLVL COLD AIR ADVECTION AND H85 TEMPS REACHING +10C ACROSS WESTERN
MINNESOTA. EXPECT HIGHS IN THE MID 60S /WEST CENTRAL WI/ TO MID 70S
/WEST CENTRAL MN/.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 300 PM CDT WED APR 29 2015

THE EXTENDED PERIOD CAN BE CHARACTERIZED AS WETTER AND MORE
UNSTABLE...ESPECIALLY BY SUNDAY AND EARLY NEXT WEEK. THIS WILL
LEAD TO TWO POSSIBLE WX CONCERNS. FIRST...THE POSSIBILITY OF SVR
WX SUNDAY AFTN. THE SECOND...THE POSSIBILITY OF HEAVY RAINFALL
AMOUNTS...ESPECIALLY ALONG THE IA/MN BORDER AS A FRONTAL BOUNDARY
STALLS SOUTH OF THE IOWA BORDER.

THE MEAN UPPER FLOW WILL BECOME MORE ZONAL BY FRIDAY AS THE UPPER
LOW ACROSS THE GREAT LAKES MOVES SOUTHEAST...AND A STRONG STORM
SYSTEM BREAKS DOWN THE WEAK UPPER RIDGE ACROSS THE NORTHERN
PLAINS. MODELS ARE FAIRLY CONSISTENT ON THE EVOLUTION OF THE
SHRTWV AND ASSOCIATED WEAK FRONTAL BOUNDARY MOVING ACROSS MN EARLY
FRIDAY. THE BEST MOISTURE CONVERGENCE AND MEAN RH FIELDS BLW 50H
OCCURS ACROSS WC MN BEFORE 12Z FRIDAY...AND TRANSLATES
EASTWARD...BUT WEAKENS BY THE AFTN IN EC/SC MN AND WC WI.
HOWEVER...THERE REMAINS ENOUGH CONTINUITY FOR INTRODUCING LIKELY
POPS IN A SHORT PERIOD FROM WEST TO EAST FROM MIDNIGHT IN WC
MN...TO EC MN BY 15-18Z. INSTABILITY REMAINS MARGINAL FOR ANY TYPE
OF ORGANIZED CONVECTION...SO ISOLD TSRA ARE THE BEST BET.

THIS FRONTAL BOUNDARY WILL STALL SOMEWHERE ACROSS IA FRIDAY NIGHT
...BEFORE WASHING OUT AS A SFC LOW BEGINS TO DEVELOP ACROSS THE
HIGH PLAINS. THE MOISTURE ASSOCIATED WITH THE OLD FRONTAL BOUNDARY
IN IOWA WILL SURGE BACK NORTHWARD ALONG WITH STRONGER MOISTURE
ADVECTION ACROSS THE PLAINS AS THE GULF OPENS UP. THIS WILL SET
THE STAGE FOR TSRA SUNDAY.

UNCERTAINTY REMAINS ON THE FRONTAL LOCATION AND ASSOCIATED SFC LOW
SUNDAY...PLUS IF ANY TSRA DEVELOP SATURDAY NIGHT...LEADING TO MORE
CLOUD COVER FOR SUNDAY AND LIMITING INSTABILITY. CURRENT MODELS
HAVE AN AVERAGE OF MLCAPE OF 1000-2000 J/KG SUNDAY AFTN ACROSS
SOUTHERN MN. THE EC IS FURTHER NORTH ACROSS CENTRAL MN WHERE
MOISTURE CONVERGENCE IS MAXIMIZED NEAR THE SFC LOW AND FRONTAL
BOUNDARY. EVEN THE GFS/GEM WHICH ARE FURTHER SOUTH...STILL HAVE
MUCH HIGHER CAPE VALUES THAN IN PREVIOUS MODEL RUNS IN THE PAST
FEW DAYS. ALTHOUGH SHEAR VALUES /30 KTS OR GREATER/ FROM THE 0-6KM
LAYER ARE HIGHER IN CENTRAL MN...AND WEAKER SOUTH/SE ACROSS
MN/WI...THERE REMAINS ENOUGH CONFIDENCE TO CONSIDER SVR TSRA
SUNDAY AFTN/EVENING. LATER SHIFTS WILL NEED TO MONITOR THE LATEST
SPC OUTLOOK ON THIS DEVELOPING STORY. IN ADDITION...THE LATEST
CIPS DETERMINISTIC MODEL GUIDANCE /GFS/ FOR MUCAPES/EFFECTIVE
SHEAR PARAMETERS DO HIGHLIGHT SC/SE/EC MN AND PARTS OF WC WI
SUNDAY AFTN/EVENING ON ORGANIZED SVR WX.

ALTHOUGH THERE IS A HIGH PROBABILITY OF TSRA SUNDAY
AFTN/EVENING...THE FRONTAL BOUNDARY ASSOCIATED WITH THE POTENTIAL
SVR WX WILL MOVE SOUTH INTO IOWA BY MONDAY.

A SERIES OF SHRTWV WILL LIKELY MOVE ACROSS THE NORTHERN TIER OF
THE CONUS PAST SUNDAY AS THE MEAN UPPER FLOW REMAINS ZONAL. THERE
IS A STRONG CORRELATION OF THE SYNOPTIC SCALE PATTERN ON WHAT MAY
BE A HEAVY RAINFALL EVENT DEVELOPING EARLY NEXT WEEK. SEVERAL OF
THE HEAVY RAINFALL PARAMETERS WHICH INCLUDE 1000-500MB MEAN
RH/850-300MB WINDS/850MB DEW PTS/WINDS AND SFC DEW PTS TO CONSIDER
AREAS ALONG AND NORTH OF THE OLD FRONTAL BOUNDARY MONDAY...TO SEE
SEVERAL WAVES OF SHRA/TSRA STARTING MONDAY. ALTHOUGH WE NEED
RAINFALL ACROSS THE REGION...ESPECIALLY CONSIDERING THE
DROUGHT...WE DO NOT NEED TOO MUCH RAINFALL IN A SHORT PERIOD OF
TIME. WILL MONITOR FOR THE POTENTIAL OF THIS SCENARIO AS WE GET
CLOSER TO THIS WEEKEND.

TEMPS WILL REMAIN NEAR OR SLIGHTLY ABV NORMAL BASE ON THE OVERALL
MEAN FLOW/THERMAL PROFILE OF THE 50H AND 85H.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 825 PM CDT WED APR 29 2015

HIGH CONFIDENCE IN VFR CONDITIONS AND SLOWLY VEERING WINDS THAT
WILL REMAIN LIGHT THROUGH THE TAF PERIOD.

KMSP...

HIGH CONFIDENCE IN VFR CONDITIONS AND SLOWLY VEERING WINDS THAT
WILL REMAIN LIGHT THROUGH THE TAF PERIOD.

/OUTLOOK FOR KMSP/
FRI...VFR. CHANCE -SHRA. WINDS SW 5-10 KTS.
SAT...VFR. WINDS SW 7-10 KTS.
SUN...-SHRA WITH MVFR POSSIBLE. WINDS S 5-10 KTS.

&&

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

$$

SHORT TERM...LS
LONG TERM...JLT
AVIATION...CLF


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