Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 300403
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1103 PM CDT MON SEP 29 2014

.UPDATE...
ISSUED AT 1056 PM CDT MON SEP 29 2014

UPDATED TO INCLUDE 06Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 420 PM CDT MON SEP 29 2014

SHORT TERM CONCERNS ARE THE EXTENT OF CLEARING OVERNIGHT AND
THREAT OF LOW CLOUDS AND FOG OR PATCHY FROST DEVELOPING LATE.
THEN TIMING OF INCOMING TROUGH AND ASSOCIATED AREAS OF RAIN AND
THUNDER MAINLY DURING THE AFTERNOON OUT WEST.

SOME BREAKS IN THE OVERCAST AND DRYING TREND MAINLY ACROSS
NORTHWEST MN AND PORTIONS OF WEST CENTRAL WISCONSIN. NORTHEAST
FLOW CONTINUES TO DRAW MOISTURE IN FROM THE GREAT LAKES/ WILL HAVE
TO MONITOR THIS TREND INTO THE EVENING. THERE MAY LEFTOVER CLOUD
COVER ACROSS MUCH OF THE WESTERN CWA INTO THE NIGHT. THE FAR EAST
MAY CLEAR SOMEWHAT...AND IF IT DOES...THERE REMAINS A THREAT OF
LOWER STRATUS DEVELOPMENT AFTER MIDNIGHT. FOG MAY BE A PROBLEM AS
WELL...BUT MAY NOT DEVELOP LOWER VSBYS. AIR IS COLD ENOUGH FOR
SOME FROST POTENTIAL IN THE FAR NORTHEAST PORTION OF THE CWA...BUT
CONFIDENCE ON ANYTHING WIDESPREAD NOT HIGH ENOUGH TO INCLUDE FOR
NOW.

NEXT TROUGH IS PROGGED TO MOVE FROM THE FOUR CORNERS AREA AT THIS
TIME TO THE DAKOTAS BY TUESDAY EVENING. SYSTEM APPEAR QUITE
STRONG ON SATELLITE WATER VAPOR IMAGERY WITH SIG DRYING AT THE
BASE OF THE TROUGH. THIS LIFTS NORTHEAST AND BECOMES NEGATIVELY
TILTED INTO SOUTHEAST SOUTH DAKOTA BY 00Z WED. SHOULD SEE DECENT
RESPONSE WITH INCREASING MOISTURE/INSTABILITY OVER THE SOUTHWEST
PORTION OF THE CWA TUESDAY AFTERNOON. THUNDER THREAT INCREASES
SOUTHWEST INTO AFTERNOON AS WELL WITH STEEPENING LAPSE RATES AND
BEST LI`S INCREASING TO AROUND MINUS 4. BEST SEVERE THREAT REMAINS
TO THE SOUTHWEST OF THE CWA.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 420 PM CDT MON SEP 29 2014

SEVERAL BOUTS OF PRECIPITATION ARE EXPECTED DURING THE LONG TERM
PORTION OF THE FORECAST...AS A LARGE SCALE MID/UPPER TROUGH
DOMINATES CENTRAL NORTH AMERICA. TEMPERATURES WILL RANGE AROUND
NEAR NORMAL VALUES THROUGH MOST OF THE WORK WEEK...WITH COLDER AIR
FILTERING IN FOR FRIDAY AND THE START OF THE WEEKEND.

THE FIRST ROUND OF WIDESPREAD RAIN IS EXPECTED LATE TUESDAY...AS
THE TROUGH CURRENTLY NOTED OVER THE FOUR CORNERS REGION /ON 21Z
WATER VAPOR IMAGERY/ EJECTS NORTHEAST AND BECOMES NEGATIVELY
TILTED OVER THE NORTHERN PLAINS...SENDING A COLD FRONT ACROSS THE
AREA. WEST CENTRAL MN SHOULD SEE SHOWERS AND THUNDERSTORMS BY MID
AFTERNOON TUESDAY...REACHING THE WI BORDER BY SUNSET...THEN
SPREADING ACROSS WEST CENTRAL WISCONSIN OVERNIGHT. THE FORCING IS
FAIRLY PROGRESSIVE...SO RAINFALL AMOUNTS WITH THIS FIRST WAVE
SHOULDN/T BE MORE THAN ONE QUARTER TO ONE HALF INCH.

GIVEN THE AFOREMENTIONED NEGATIVELY-TILTED NATURE OF THE FIRST
WAVE...THE COLD FRONT WILL LOSE ITS EASTWARD PUSH. THEREFORE IT
WILL LIKELY BECOME SLOWED UP ACROSS WESTERN MN ON WEDNESDAY INTO
THURSDAY...AS A REINFORCING SOUTHERN STREAM SHORTWAVE ARRIVES.
HAVE THEREFORE MAINTAINED THE CHANCE POPS FOR AREAS ALONG/EAST OF
INTERSTATE 35. ANOTHER ONE HALF INCH APPEARS POSSIBLE FOR THESE
AREAS...BRINGING TWO DAY TOTALS TO NEAR ONE INCH.

ON THURSDAY NIGHT AND FRIDAY...A NORTHERN STREAM WAVE DIPS
SOUTHEAST FROM CANADA...AND FACILITATES ONE MORE LOW CHANCE OF
PRECIPITATION /ALONG-NORTH OF INTERSTATE 94/ PRIOR TO OVERALL DRY
WEATHER ARRIVING FOR THE WEEKEND.

HIGH TEMPERATURES WILL MOSTLY BE IN THE 60S THROUGH THURSDAY...
WITH HIGHS IN THE 50S FOR FRIDAY AND SATURDAY AND LOWS IN THE 30S
FRIDAY NIGHT AS COLDER AIR WORKS IN BEHIND THE NORTHERN STREAM
WAVE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1056 PM CDT MON SEP 29 2014

ABLE TO INITIALIZE ALL SITES WITH VFR AND LOW-LVL SCT COVERAGE AS
HIGH PRES NUDGES IN FROM THE NE AND UPR LEVEL RIDGING MOVES IN
FROM THE W. HOWEVER...TRAPPING OF MOISTURE UNDERNEATH THE
INVERSION WITH NE WINDS OVERNIGHT WILL BRING IN SOME ADDITIONAL
LOW LEVEL MOISTURE AND THIS LOOKS TO BE CONDUCIVE TO LOW STRATUS
DURG THE PRE-DAWN HRS FOR ALL TAF SITES OUTSIDE THE MSP AREA.
CONFIDENCE IS NOT HIGH ENOUGH FOR PREVAILING GROUPS SO WILL USE
TEMPO GROUPS FOR THIS POSSIBILITY. KMSP LOOKS TO HAVE ONLY
SCATTERED COVERAGE OF SUB-1700 FT CLOUDS...BUT WILL MONITOR AND
ADJUST AS NEEDED. SKIES THEN EXPECTED TO HAVE MULTIPLE CU
SCATTERED LAYERS DURG THE DAY TMRW AHEAD OF THE NEXT LOW PRES
SYSTEM COMING OUT OF THE PLAINS FOR TMRW EVE. SOME -SHRA MAY MAKE
IT TO WRN MN LATE TMRW AFTN BUT THE BULK OF THE PRECIP WILL HOLD
OFF UNTIL AFTER 00Z TMRW EVE. HAVE INDICATED A POTENTIALLY HEAVIER
BAND OF PRECIP WITH TEMPO GROUPS THRU THE MN TAF SITES...BUT
CONFIDENCE NOT HIGH ENOUGH TO INCLUDE CB/TS ATTM. THAT SAID...THERE
IS STILL A CHC FOR SOME ISOLD TSTMS DURG THE WINDOW OF HEAVIER
RAINS. WINDS WILL VEER AROUND TO SE BY TMRW AFTN...THEN INCRS TO
ARND 15G25KT.

KMSP...AFTER INITIALIZING AS VFR BASED ON LATEST CLOUD/OB
TRENDS...AM EXPECTING TO RUN WITH AN ENTIRELY VFR FCST FOR MSP
THRU TMRW EVE...THEN CONDS LIKELY TO DETERIORATE TMRW EVE AS BANDS
OF RAIN MOVE ACRS THE AREA. FOR THIS MRNG...CONFIDENCE DROPS FOR THE
PRE-DAWN HRS IN THAT SOME LOW-END MVFR CEILINGS COULD
DEVELOP... ROUGHLY IN THE 09Z-13Z TIME PERIOD. NEXT...ONCE THE
PRECIP BEGINS AFTER 02Z-03Z TMRW EVE...THERE IS CONCERN THAT SOME
CEILINGS COULD DROP INTO UPPER-END MVFR RANGE AND PRECIP MAY DROP
VSBY INTO MVFR RANGE AND HAVE USED A TEMPO GROUP TO TRY TO
IDENTIFY BEST TIMING OF SUCH OCCURRENCE. NOT EXPECTING CONDITIONS
BELOW BKN020 NOR 4SM FOR TMRW EVE...BUT SUCH CONDITIONS CANNOT BE
COMPLETELY RULED OUT GIVEN HEAVY ENOUGH PRECIP.

/OUTLOOK FOR KMSP/
WED...MAINLY VFR. CHC MVFR IN SHRA/TSRA. WINDS S-SE 10-15 KTS.
THU...MAINLY VFR. CHC MVFR IN SHRA. WINDS W-NW 5-10 KTS.
FRI...VFR. SLGT CHC -SHRA. WINDS NW 10-20 KTS WITH HIGHER GUSTS.

&&

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

$$

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





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