Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 301745
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1245 PM CDT WED JUL 30 2014

.UPDATE...
ISSUED AT 1233 PM CDT WED JUL 30 2014

UPDATED TO INCLUDE 18Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 429 AM CDT WED JUL 30 2014

MORE OF THE SAME TODAY INTO TONIGHT...AS THE LARGE SCALE PATTERN
REMAINS NEARLY IDENTICAL TO YESTERDAY...WITH NORTHWEST FLOW
DOMINATING LOCALLY ON THE WESTERN PERIPHERY OF THE EASTERN CONUS
LONGWAVE TROUGH.

THIS WILL MEAN ANOTHER DAY WITH CUMULUS CLOUDS DEVELOPING BY LATE
MORNING AND TEMPERATURES WARMING INTO THE UPPER 70S TO LOWER 80S.
THE SCATTERED SHOWER AND ISOLATED THUNDER THREAT WILL AGAIN BE
GENERALLY RESTRICTED TO AREAS ALONG AND EAST OF THE INTERSTATE 35
CORRIDOR...PRIMARILY AFFECTING WEST CENTRAL WISCONSIN COUNTIES.

TONIGHT SHOULD AGAIN BRING CLEARING SKIES AND WINDS DECREASING
BELOW 5 MPH...WITH LOWS IN THE MID 50S TO LOWER 60S.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 429 AM CDT WED JUL 30 2014

AT THE START OF THE PERIOD PERSISTENCE FORECASTING FROM THE PAST
FEW DAYS SHOULD YIELD FAIRLY ACCURATE RESULTS AS THE UPPER LEVEL
RIDGE AND SURFACE HIGH PRESSURE LEAD TO DRY CONDITIONS AND SUNNY
SKIES ONCE AGAIN ACROSS THE WESTERN CWA...WHILE THE JAMES BAY LOW
AND NORTHERN STREAM SHORTWAVES PROVIDE REPEATED CHANCES FOR
SHOWERS AND THUNDERSTORMS ACROSS THE EASTERN HALF OF THE CWA
DURING PEAK HEATING.

THE CURRENT UPPER LEVEL PATTERN SHOWS SIGNS OF BREAKING DOWN BY
THE WEEKEND IN THE SENSE THAT THE FLOW WILL BE LESS AMPLIFIED
MAINLY DUE TO THE POLEWARD REGRESSION OF THE AFOREMENTIONED UPPER
LEVEL LOW. WITHIN THIS ZONAL FLOW REGIME A SHORTWAVE WILL DRIVE A
LOW LEVEL FRONTAL BOUNDARY SOUTHWARD. THE GRADIENT WILL EVENTUALLY
BECOME EAST/WEST ORIENTED AS IT WEAKENS AND STALLS OUT ACROSS THE
NORTH CENTRAL CONUS. THE 30.00 GFS AND ECMWF AGREE CONSIDERABLY
WELL FOR THE UPPER LEVEL FLOW...BUT THE ECMWF DRIVES THE FRONT
FARTHER SOUTH...AND HAS HIGHER MOISTURE TRANSPORT WITH A STRONGER
NOCTURNAL LOW LEVEL JET BEGINNING SUNDAY NIGHT AND LASTING THROUGH
THE MIDDLE OF NEXT WEEK. THIS ECMWF SOLUTION WOULD FAVOR NOCTURNAL
MCS DEVELOPMENT AND WIDESPREAD HEAVIER RAINFALL ACROSS THE
SOUTHERN HALF OF THE CWA...WHILE THE GFS WOULD FOCUS THE
CONVECTION MORE ACROSS NORTHERN MN/WI AND HAS LIGHTER AMOUNTS.

AT THIS TIME DID NOT HAVE THE CONFIDENCE TO FAVOR ONE SOLUTION
OVER THE OTHER...BUT CONFIDENCE IS HIGH THAT WETTER WEATHER IS
ON TAP FOR NEXT WEEK. STORM MOTION WILL BE SLOW...AND POTENTIAL
FOR TRAINING THUNDERSTORMS EXISTS ALONG THE FRONTAL BOUNDARY SO
ISOLATED HEAVY RAINFALL AMOUNTS ARE EXPECTED NEXT WEEK.
HOWEVER...PWAT VALUES WILL GENERALLY HOOVER AROUND 1.5IN...AND THE
FREEZING LEVEL SITS AT AROUND 11KFT...WHICH SHOULD LIMIT THE
POTENTIAL FOR ANY TORRENTIAL RAINFALL/FLOODING AND KEEP MAX
RAINFALL AMOUNTS IN THE 1-3IN RANGE VS THE HIGHER AMOUNTS THAT
OCCURRED EARLIER THIS SUMMER. THE THREAT FOR SEVERE WEATHER IS
LIMITED DUE TO THE RELATIVELY WEAK WIND FIELDS H700-500 LAPSE
RATES IN THE 6-7C RANGE. HODOGRAPHS TO SHOW GOOD DIRECTIONAL
SHEAR...SO WONT RULE OUT SEVERE WEATHER AT THIS TIME...BUT IT
LOOKS TO BE MARGINAL AT BEST.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1233 PM CDT WED JUL 30 2014

NO CONCERNS AT MN TAF SITES...BOTH FROM A FOG AND PRECIP
STANDPOINT. MIDLVL CU CLOUDS WILL FILL IN THE SKIES THE REST OF
THE AFTN HOURS...THEN SKIES CLEAR OUT OVERNIGHT...FOLLOWED AGAIN
BY LATE MRNG MIDLVL CU CLOUDS ON THU. NW WINDS 5-10 KT THIS AFTN
DROP TO NEAR CALM OVERNIGHT THEN RESUME FROM THE NW IN THE 5-10 KT
RANGE TMRW.

WI TAF SITES WILL AGAIN BE SUBJECT TO PASSING -SHRA...AND POSSIBLY
ISOLD TSTMS...LATER THIS AFTN INTO THE EARLY EVE HRS. COVERAGE IS
NOT XPCTD TO BE AS MUCH AS YDA...BUT HAVING A STRAY SHWR/TSTM
DRIFT OVER THE TERMINAL CANNOT BE RULED OUT. NO CONFIDENT ENOUGH
AT TSTM DEVELOPMENT SO HAVE OMITTED CB/TS MENTION...BUT IT MAY BE
NEEDED LATER IN AN AMD. IN ADDITION...KEAU LOOKS TO AGAIN
POTENTIALLY HAVE PRE-DAWN FOG DEVELOPMENT. CONFIDENCE NOT HIGH
ENOUGH TO DROP CONDS DOWN TO IFR-OR-WORSE ATTM BUT DID INDICATE
THE POTENTIAL BY DROPPING VSBY INTO LOW-END MVFR.

KMSP...VFR CONDS XPCTD THROUGHOUT THIS SET WITH NO PRECIP XPCTD.
MIDLVL CU WILL AGAIN DEVELOP...LASTING THRU MID-EVENING BEFORE
DISSIPATING FOR OVERNIGHT. ADDITIONAL MIDLVL CU LAT TMRW MRNG.

/OUTLOOK FOR KMSP/
FRI...VFR. WINDS NW 5 KTS.
SAT...VFR. WINDS N 5 KTS.
SUN...MAINLY VFR. SLGT CHC OF MVFR IN SHWRS/TSTMS. WINDS SW 5-10
KTS.

&&

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

$$

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





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