Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 301131
AFDMPX

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

.UPDATE...FOR 12Z 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 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 632 AM CDT WED JUL 30 2014

THE ONLY CONCERNS TODAY ARE MORNING FOG AND STRATUS OVER WEST
CENTRAL WI...BUT THAT WILL BURN OFF BY 15Z. VFR CONDITIONS ARE
THEN EXPECTED THROUGH THE REMAINDER OF THE PERIOD. TODAY WILL
FEATURE ANOTHER DAY WITH DIURNALLY-DRIVEN CUMULUS CLOUD
DEVELOPMENT AND NORTHWEST WINDS AROUND 10KTS...WITH ISOLATED
SHOWERS AND TS POSSIBLE OVER WEST CENTRAL WI. HAVE INCLUDED A VCSH
MENTION AT KEAU. OTHERWISE...SKIES CLEAR AGAIN THIS EVE AND WINDS
DECREASE TO AOB 5 KTS. COULD SEE SOME FOG DEVELOPMENT AGAIN
TONIGHT...PRIMARILY OVER WEST CENTRAL WI...ESPECIALLY IN LOCATIONS
THAT RECEIVE PRECIP TODAY.

KMSP...
FOG JUST EAST OF MSP BURNS OFF BY 14Z...THEN CUMULUS CLOUDS
DEVELOP AGAIN TODAY AS NORTHWEST WINDS INCREASE TO 10 KTS. COULD SEE
THE DECK GO BROKEN THIS AFTERNOON...BUT KEPT IT AT SCATTERED SINCE
THAT SHOULD PREVAIL AND THE LEVEL WILL BE VFR. SKIES CLEAR AFTER
00Z AND WINDS DECREASE BELOW 5 KTS.

/OUTLOOK FOR KMSP/
THU...VFR. WINDS NW 5-10 KTS.
FRI...VFR. WINDS NW 5 KTS.
SAT...VFR. WINDS N 5 KTS.

&&

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

$$


SHORT TERM...LS
LONG TERM...JRB
AVIATION...LS





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