Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 290515
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1215 AM CDT WED OCT 29 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 238 PM CDT TUE OCT 28 2014

MAIN SHORT TERM CONCERN IS EXTENT OF LOW CLOUDS THROUGH THE FIRST
HALF OF THE PERIOD AND THEN TEMPERATURES.

THE UPPER LOW IS LIFTING OFF TO THE EAST PER TREND ON THE WATER
VAPOR LOOP. STILL HAVE A LOBE OF VORTICITY CIRCULATING OVER THE NORTH
AND WILL PIVOT/DROP SOUTH AND EAST INTO TONIGHT.  LAYERED CLOUDS OVER
MUCH OF THE STATE GIVING WAY TO LIFTING STRATOCUMULUS DECK OVER THE
DAKOTAS.  EROSION VERY SLOW WITH ONLY MINOR HOLES DEVELOPING TO THE
WEST.  IT WILL BE SLOW TO CLEAR INTO OUR CWA INTO TONIGHT. WILL TRY
AND TREND TO SCATTERED LATE IN THE WEST.  STILL SOME LIGHT -SHRA OR
DRIZZLE MOVING ACROSS THE EASTERN CWA INTO THE EVENING. WILL CARRY
SOME SMALL CHANCE POPS IN THE NORTHEAST CWA.  TEMPERATURES ALOFT
WILL BE COOL ENOUGH FOR A POSSIBLE RAIN/SNOW MIX INTO THE EVENING AS
WELL. THE BRISK WEST/NORTHWEST WINDS WILL SLOWLY DIMINISH FROM WEST
TO EAST AS WELL...AS THE SURFACE HIGH BUILDS EAST INTO MINNESOTA.

TEMPERATURES ARE EXPECTED TO REMAIN ON THE COOL SIDE ONCE AGAIN FOR
WEDNESDAY...WITH 40S COMMON.  NEXT WEAK CLIPPER MOVES ACROSS THE
DAKOTAS DURING THE DAY WITH PERHAPS SOME MID CLOUDS DEVELOPING INTO
WESTERN MN DURING THE AFTERNOON.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 238 PM CDT TUE OCT 28 2014

WEDNESDAY NIGHT AND THURSDAY...A SUBTLE RIPPLE IN NORTHWEST UPPER
LEVEL FLOW IS BECOMING BETTER DEFINED AND MORE AGREED ON BY THE
MODEL GUIDANCE AT THIS TIME. THIS WAVE WILL BE SLIDING SOUTHEAST
THROUGH NORTH DAKOTA EARLY WEDNESDAY EVENING. TAKING A LOOK AT THE
FORCING WITH THIS FEATURE...UPPER AND LOWER LEVELS ALIGN NICELY TO
PRODUCE MODEST LIFT MOVING INTO WEST CENTRAL MN WEDNESDAY NIGHT
AND CONTINUING TOWARD THE SOUTHEAST PORTION OF MN BY THURSDAY
MORNING. A 100 KNOT UPPER LEVEL JET STREAK WILL BE PRESENT
FROM EASTERN MONTANA THROUGH NEBRASKA...OFFERING UPPER LEVEL
DIVERGENCE IN THE LEFT EXIT REGION OF THIS JET MOVING INTO WESTERN
MN. MEANWHILE...POSITIVE VORTICITY ADVECTION WILL BE MOVING
THROUGH AS WELL IN ASSOCIATION WITH THE UPPER LEVEL SHORTWAVE. LOW
LEVEL WARM AIR ADVECTION WILL AID IN THE DEVELOPMENT JUST OUT
AHEAD OF THE VORT MAX. THE QUESTION WITH THIS SUBTLE WAVE IS
MOISTURE. THE MID LEVELS WILL BE QUITE DRY PRIOR TO THE ARRIVAL OF
THIS WAVE. SATURATION IS LIKELY BUT WILL TAKE SOME TIME...AND
WITH THE QUICK MOVING PACE OF THIS FEATURE...LIGHT QPF IS IN THE
FORECAST...UNDER ONE TENTH OF AN INCH.

THURSDAY THROUGH SATURDAY...TWO MAIN FEATURES TO DISCUSS IN THIS
PERIOD; AN UPPER LEVEL TROUGH TO DIG SOUTH FROM NORTHERN CANADA
AND A STRONG CANADIAN HIGH TO FOLLOW. THE MAIN IMPACT WILL BE THE
COLDEST AIR OF THE SEASON SO FAR. THE UPPER LEVEL TROUGH /WHICH IS
CURRENTLY ANALYZED AS A CLOSED LOW/ IS APPARENT IN FAR NORTHERN
CANADA ALONG THE NORTHERN SHORES OF NUNAVUT IN CURRENT SATELLITE
IMAGERY. THIS FEATURE WILL DIVE SOUTH-SOUTHEAST OVER THE COMING
DAYS AND BRING A PUNCH OF COLD AIR WITH IT. BY THURSDAY
NIGHT...STRONG COLD AIR ADVECTION WILL BE ONGOING AS THE AXIS OF
THE POSITIVELY TILTED UPPER LOW MOVES INTO THE WESTERN GREAT LAKES
REGION. 850H TEMPS NEAR AND POSSIBLY COLDER THAN -10C ARE CURRENTLY
ANTICIPATED TO DIVE INTO NORTHERN MN/WI BY FRIDAY MORNING. THE
CYCLONIC FLOW AND LOW LEVEL MOISTURE WITH THIS TROUGH WILL ALLOW
CLOUDS TO LINGER THURSDAY...WITH EVEN A FEW VERY LIGHT SHOWERS
POSSIBLE NORTHEAST OF THE TWIN CITIES. MEANWHILE...JUST UPSTREAM
OF THIS WAVE WILL BE A STRONGLY AMPLIFIED RIDGE OVER THE ROCKY
MOUNTAINS. AN AREA OF SURFACE HIGH PRESSURE WILL HAVE DEVELOPED IN
NORTHERN CANADA AND SANK SOUTH THROUGH THURSDAY AND BE LOCATED
JUST DOWNSTREAM OF THE UPPER RIDGE AXIS. THE AMPLIFYING UPPER
RIDGE WILL HELP STRENGTHEN THIS HIGH AND ALLOW IT TO SINK DIRECTLY
INTO THE UPPER MIDWEST BY FRIDAY MORNING. THE COLDEST SURFACE
TEMPERATURES FRIDAY MORNING WILL GREATLY DEPEND ON HOW QUICKLY THE
LOW LEVEL MOISTURE IS SCOURED OUT AND BY WHERE THE WINDS GO CALM
OVERNIGHT. CONFIDENCE CONTINUES TO INCREASE IN THE PLACEMENT AND
TIMING OF THE COLD AIR SO FORECAST LOWS FOR FRIDAY ARE BELOW
FREEZING ACROSS THE ENTIRE FA...WITH THE COLDEST LOWS EXPECTED IN
WESTERN MN IN CLOSEST PROXIMITY TO THE CENTER OF THE SURFACE HIGH.
TEMPERATURES THERE ARE CURRENTLY FORECAST TO FALL INTO THE MID
20S...BUT COULD EASILY SEE A FEW READINGS NEAR 20 IF WINDS TRULY
GO CALM. WITH SUCH A COOL AIR MASS IN PLACE AND TEMPERATURES
STARTING SO LOW...KNOCKED ANOTHER DEGREE OF THE FORECAST HIGHS FOR
FRIDAY DESPITE ABUNDANT SUNSHINE. TEMPERATURES AROUND 40 FOR HIGHS
LOOK LIKE A FAIR BET.

SO...HALLOWEEN EVENING WILL BE CHILLY...WITH LATE AFTERNOON TEMPS
IN THE UPPER 30S...AND QUICKLY FALLING TO THE LOWER 30S AFTER
DARK. WINDS WILL BE FAIRLY LIGHT AT THAT TIME AS THE SURFACE HIGH
ADVANCES EASTWARD...SO THIS IS GOOD NEWS FOR THOSE HOPING TO SPEND
THE EVENING OUTDOORS. BY SATURDAY MORNING...THE AXIS OF THE HIGH
PRESSURE SHOULD SLIDE INTO WISCONSIN...MEANING THE EASTERN PORTION
OF THE FA WILL BE LIKELIEST TO SEE THE COLDEST LOWS THAT MORNING.
LOW TO MID 20S LOOK LIKELY SATURDAY MORNING IN WESTERN
WISCONSIN...WITH SLIGHTLY WARMER TEMPS IN WESTERN MN THANKS TO A
LITTLE SOUTHERLY WIND.

BEYOND SATURDAY...A STRONG LOW PRESSURE SYSTEM IS STILL EXPECTED
TO DEVELOP JUST WEST OF THE DAKOTAS SATURDAY NIGHT...AND WILL
ADVANCE NORTHEAST TOWARD HUDSON BAY. WITH THIS DEVELOPING
LOW...AND THE DEPARTING HIGH...THIS WEEKEND LOOKS QUITE WINDY FOR
MOST. TEMPERATURES REBOUND TO NEAR NORMAL ON SUNDAY WITH STRONG
SOUTHERLY FLOW BRINGING WARMER AIR TO THE REGION. THE GFS/EC SEEM
TO HAVE FAIR AGREEMENT IN THE DEVELOPMENT OF THE AFOREMENTIONED
LOW...BUT HANDLING IT INTO EARLY NEXT WEEK SHOWS SOME DIFFERENCES.
THE LATEST EC HAS COME IN QUITE A BIT DRIER IN THE WARM SECTOR
WHICH MEANS OUR FA COULD BE SHUT OUT OF ANY PRECIP FROM THIS
SYSTEM. THE GFS HOWEVER DOES WANT TO PRODUCE WAA PRECIP LATE
SUNDAY NIGHT IN OUR AREA. THE EC KEEPS ALL OF ITS WARM SECTOR
PRECIP TO THE SOUTHEAST OF US AS WE MAY BE WITHIN THE DRY SLOT.
WENT WITH A BLEND OF GUIDANCE WHICH STILL INDICATES POPS FOR OUR
AREA...BUT MUCH IS TO BE SORTED OUT WITH THE EVOLUTION OF THIS
SYSTEM BEFORE WE CAN DEFINITIVELY SAY IT WILL BE EITHER WET OR DRY
SUNDAY NIGHT THROUGH MONDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1159 PM CDT TUE OCT 28 2014

MAIN CONCERN IS WHEN MVFR/IFR CIGS BECOME VFR WEDNESDAY...WITH
SHRA POSSIBLE LATE IN THE TAF PERIOD AT KAXN.

HIGH CONFIDENCE THAT MVFR CIGS WILL CONTINUE FOR
KAXN/KSTC/KRHN/KEAU THRU THE NEXT 6 HRS...WITH MOST AREAS HOLDING
BLW 3K UNTIL AFT 18Z. CONFIDENCE IS LOW ON WHEN THE MVFR CIGS LIFT
TO VFR ACROSS EASTERN MN/WESTERN MN WEDNESDAY AFTN. WHEN THE CYCLONIC
FLOW BECOMES ANTI-CYCLONIC IN MN WILL BE KEY ON WHEN THE CLDS
BEGIN TO BREAK UP AND LIFT TO VFR. BASED ON THE LATEST MODEL
INFORMATION...THE SFC RIDGE WILL NOT MOVE ACROSS THE AREA UNTIL
AFT 18Z...WITH THE EXCEPTION OF KAXN. THEREFORE...MVFR CIGS WILL
LIKELY CONTINUE. THE NEXT SYSTEM WILL RAPIDLY MOVE TO THE SE WED
NIGHT AND POSSIBLY HAVE -SHRA AT KAXN BY THE END OF THE TAF
PERIOD. INTRODUCE VCSH FOR NOW. WNW/NW WINDS WILL DECREASE
OVERNIGHT AND BECOME WEST/WSW BY THE AFTN...THEN MORE SW/S DURING
THE EVENING.

KMSP...

HIGH CONFIDENCE WITH MVFR CIGS /2K TO 2.5K/ CONTINUING THRU THE
NEXT 6 HRS...WITH LOW CONFIDENCE ON WHEN THE MVFR CIGS RISE TO VFR
OR SCATTER OUT BY THE AFTN. WILL CONTINUE THE SAME TREND WITH MVFR
CIGS UNTIL 18-21Z OR HIGH BASED MVFR CIGS. THERE COULD BE A PERIOD
OF VFR OR SCT030 AFT 18Z IF BOUNDARY LAYER MOISTURE MIXING OUT
FASTER. SFC WINDS WILL CONTINUE GUSTY UNTIL 9Z...WITH A SLOW TREND
OF WNW WINDS DECREASING TO 7=9 KTS BY THE MID/LATE MORNING. AFT 18Z
WINDS WILL BE W/WSW UNDER 6 KTS...BECOMING MORE SW/S LATE IN THE
EVENING.

/OUTLOOK FOR KMSP/

THU...VFR. WINDS VARIABLE 5 KTS BECOMING NW.
FRI...VFR. WINDS N 5-10 KTS.
SAT...VFR. WINDS SE 10-15 KTS.

&&

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

$$

SHORT TERM...DWE
LONG TERM...SPD
AVIATION...JLT




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