Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 292351
AFDMPX

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

.UPDATE...
ISSUED AT 637 PM CDT MON SEP 29 2014

UPDATED TO INCLUDE 00Z 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 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 637 PM CDT MON SEP 29 2014

BKN/OVC UPPER-END MVFR CEILINGS SLOWLY STARTING TO DISSIPATE THIS
EVENING AS HIGH PRES NUDGES IN FROM THE NE AND UPR LEVEL RIDGING
MOVES IN FROM THE W. THIS WILL RESULT IN SCATTERING OUT OF CLOUDS
THRU THIS EVE INTO THE OVERNIGHT HRS...BUT TRAPPING OF MOISTURE
UNDERNEATH THE INVERSION OVERNIGHT. 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 HAVE OPTED TO RUN WITH 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.
WINDS WILL VEER AROUND TO SE BY TMRW AFTN...THEN INCRS TO ARND
15G25KT.

KMSP...WAS ABLE TO INITIALIZE AS VFR BASED ON LATEST CLOUD/OB
TRENDS AND AM EXPECTING TO RUN WITH AN ENTIRELY VFR FCST FOR MSP
THRU TMRW EVE...BUT THERE ARE A COUPLE AREAS OF LOWER CONFIDENCE.
FIRST IS IN THE PRE-DAWN HRS THAT SOME LOW-END MVFR CEILINGS COULD
DEVELOP...ROUGHLY IN THE 09Z-13Z TIME PERIOD. SECONDLY...THAT ONCE
THE PRECIP BEGINS AFTER 02Z-03Z TMRW EVE...THAT SOME CEILINGS
COULD DROP INTO UPPER-END MVFR RANGE AND PRECIP MAY DROP VSBY INTO
MVFR RANGE. NOT LOOKING FOR ANYTHING BELOW BKN020 NOR 4SM FOR TMRW
EVE.

/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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