Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 172112
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
412 PM CDT SUN MAY 17 2015

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 412 PM CDT SUN MAY 17 2015

THUNDERSTORMS HAVE BECOME FAIRLY WIDESPREAD THIS AFTERNOON TO THE
EAST OF A COLD FRONT THAT IS ADVANCING EAST ACROSS MN. THE SFC LOW
DRIVING THIS FRONT WAS DOWN TO 995 MB AND SPINNING RATHER
AGGRESSIVELY ACROSS NE SODAK. BASED ON SFC PRESSURE FALLS...THIS LOW
WILL BE ON ITS WAY OFF TO THE ARROWHEAD TONIGHT. WE HAVE QUITE THE
CONTRAST IN AIRMASSES ACROSS THE SYSTEM...WITH SUMMER-LIKE AIR TO
ITS EAST WITH TEMPERATURES IN THE 70S AND DEWPS IN THE 60S...WHILE
WEST OF THE LOW...TEMPERATURES ARE DOWN IN THE MID 30S ACROSS NODAK.
IN FACT...IT IS COLD ENOUGH ON THE WRN EDGE OF THE PRECIP SHIELD
THAT WE ARE SEEING A RAIN/SNOW MIX THIS AFTERNOON.

FOR THE REST OF TODAY...LIKE THE IDEA THAT THE HRRR HAS BEEN RUNNING
WITH ALL DAY THAT MATCHES WELL WITH REALITY NOW. AND THAT IS FOR THE
WIDESPREAD DISCRETE CELLS TO CONTINUE THROUGH THE EVENING AHEAD OF
THE COLD FRONT. WE HAVE SEEN SBCAPE INCREASE TO BETWEEN 1000 AND
1500 J/KG...BUT WITH LITTLE CIN IN PLACE...WE ARE BASICALLY POPPING
CONVECTION AS SOON AS INSTABILITY DEVELOPS. MID-LEVEL LAPSE RATES
ARE PRETTY WEAK THOUGH...WHICH IS A BIG LIMITING FACTOR IN THE SVR.
STILL...FREEZING LEVELS HAVE DROPPED FROM ALMOST 12K FT AGL
YESTERDAY TO BETWEEN 8K AND 9K FEET TODAY...WHICH WILL CONTINUE TO
ALLOW FOR THE THREAT FOR MARGINALLY SVR HAIL THROUGH THE EVENING.
GIVEN THE DEPTH OF THE SYSTEM IN TO OUR NW...WE ARE SEEING LOTS OF
WIND THROUGH PRETTY MUCH THE WHOLE DEPTH OF THE ATMO...SO THESE
SHOWERS WILL LIKELY BE ABLE TO MIX SOME OF THAT DOWN...LEADING TO
SOME GUSTY WINDS AS WELL. TORNADO THREAT DOES NOT LOOK AS GOOD AS
YESTERDAY...WHEN WE HAD A WARM FRONT DRAPED ACROSS THE STATE...BUT
THE RAP HAS BEEN SHOWING 0-1 SHEAR INCREASING LATE THIS AFTERNOON
ACROSS ERN MN/WRN WI...WHERE THE BEST CHANCE FOR SEEING A BRIEF
TORNADO WOULD EXIST.

FOR TONIGHT...THE BIG THING WE WILL SEE IS STRONG CAA AS THE LOW
PUSHES TOWARD THE ARROWHEAD. THIS WILL LEAD TO SOME AGGRESSIVE
TEMPERATURE DROPS OVERNIGHT...WHERE LOWS IN WRN MN WILL FALL BACK
INTO THE MID 30S...OR ABOUT 35 DEGREES COLDER THAN THE HIGHS WERE
THIS AFTERNOON. IN ADDITION TO THE COLD AIR...WE WILL SEE WRAP
AROUND PRECIP DIP DOWN ABOUT AS FAR SOUTH AS A MADISON TO MILLE LACS
LAKE LINE. FORECAST SOUNDINGS IN THIS AREA ARE ALSO COLD ENOUGH TO
SHOW A RAIN/SLEET MIX DEVELOPING LATE TONIGHT. IN FACT...THE NAM
WOULD SAY THE P-TYPE AT AXN WILL BE ALL SLEET TOMORROW MORNING...SO
DID INTRODUCE A PRECIP MIX INTO THE GRIDS. BESIDE THE PRECIP...WINDS
WILL BE STRONG AS WELL. TOP OF THE CHANNEL MIX DOWN AT MOST SITES IN
MN IS OVER 40 KTS. WE ARE RIGHT ON THE CUSP OF NEEDING A WIND
ADVY...BUT DECIDED TO HOLD OFF ON ONE FOR NOW AND WILL LET THE
SEVERE POTENTIAL PLAY OUT BEFORE HOISTING A WIND ADVY.

FOR MONDAY...THERE IS NO WAY AROUND IT...IT WILL BE A RAW DAY. NAM
HAS H85 TEMPS DROPPING TO BETWEEN -5 AND -8C...WHICH IS BELOW THE
CLIMATOLOGICAL RECORD FOR H85 TEMPS FOR THE DAY AT STC/MPX. THROW IN
THE MOSTLY CLOUDY SKIES...AND HAVE HIGH CONFIDENCE IN HIGHS STAYING
IN THE 40S...WITH HIGHS ONLY IN THE 30S OUT TOWARD AXN. THESE VALUES
WILL BE IN THE 25 TO 35 DEGREES BELOW NORMAL RANGE.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 412 PM CDT SUN MAY 17 2015

THE AFOREMENTIONED STRONG COLD ADVECTION ON MONDAY WILL KEEP THE
LOCAL AREA COOL ON TUESDAY AS WELL WITH HIGHS LIKELY REMAINING IN
THE 50S. THE TROUGH MOVES EAST BY WEDNESDAY AND EAST COAST TROUGH
SHEARS OUT BEFORE ADVANCING OUT OF THE ROCKIES. THEREFORE WE
SHOULD SEE DRY WEATHER AND COOL TO MILD TEMPERATURES THROUGH THE
WEEK...WITH A SLOW WARMING TREND TIME. WE EXPECT TUESDAY AND
WEDNESDAY MORNINGS TO FALL INTO THE 30S ACROSS CENTRAL MN AND WEST
CENTRAL WI...SO WE COULD SEE A LITTLE FROST IF WE MANAGE TO
GET CLEARING AND THE WINDS STAY CALM. WEDNESDAY MORNING HAS A
BETTER CHANCE OF A CALM WIND AND AT LEAST PARTIAL CLEARING. THE
NEXT CHANCE FOR THUNDERSTORMS WILL LIKELY HOLD OFF UNTIL THE
WEEKEND WHEN ANOTHER TROUGH APPROACHES THE REGION FROM THE PLAINS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 125 PM CDT SUN MAY 17 2015

LIKE THE IDEA OF THE HRRR...WITH WIDESPREAD SHOWERS AND
THUNDERSTORMS DEVELOPING THIS AFTERNOON AS THE STACKED LOW MOVES
THROUGH MN WITH MARGINAL INSTABILITY BUT VIRTUALLY NO CIN. DECIDED
TO CONTINUE TREND OF HANDLING THIS SCENARIO WITH VC GROUPS AND
EXTENDED TEMPO GROUPS FOR THUNDER. HAVE HIGH CONFIDENCE IN STORMS
OCCURRING...JUST LOW CONFIDENCE ON TIMING/TRACKS OF THE NUMEROUS
STORMS THAT ARE EXPECTED. AS WE GET BEHIND THE COLD FRONT...LOW
STRATUS BACK OVER THE DAKOTAS WILL SWING THROUGH...WITH TIMING ON
ITS ARRIVAL NOT TOO DIFFERENT BETWEEN THE HRRR/SREF/NAM/LAMP...SO
MAIN ISSUE WITH THAT IS MORE HOW LOW WILL IT BE AS OPPOSED TO WHEN
WILL THOSE CLOUDS GET TO EACH AIRPORT. MAIN CHANGE MADE TO THE
PREVIOUS TAF WAS TO GO WITH MORE WINDS GIVEN STRENGTH OF MIXED
LAYER WINDS ON NAM SOUNDINGS...WOULD NOT BE SURPRISED TO SEE SOME
WIND GUSTS IN WRN MN TONIGHT THROUGH MON MORNING GET INTO THE 40S
KTS.

KMSP...ALREADY SEEING SHOWERS BUBBLE UP AT 18Z...AND THINKING
THIS THEME OF SCT SHOWERS/STORMS WILL BE WITH US THROUGH ABOUT 1Z.
TEMPO GROUP FOR THUNDER IS BASED ON WHEN THE HRRR BRINGS THE
GREATEST COVERAGE OF STORMS THROUGH. ALSO HAVE HIGH CONFIDENCE IN
MVFR CIGS RETURNING TONIGHT. THOUGH HAVE KEPT CIGS ABOVE 017...MAY
CIGS GET DOWN BETWEEN 010-015 DURING THE MORNING ON MONDAY. WINDS
COULD ALSO BE PROBLEMATIC MONDAY MORNING...WITH STRONG CROSS
WINDS EXPECTED IN THE EARLY MORNING BEFORE WINDS CONTINUE TO VEER
MORE TOWARD A 300 DIRECTION IN THE AFTERNOON.

/OUTLOOK FOR KMSP/
TUE...MVFR CIGS EARLY. WINDS N AT 10 KTS.
WED...VFR. WINDS NNE 5 KTS.
THU...VFR. WINDS NNW 5 KTS.


&&

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

$$

SHORT TERM...MPG
LONG TERM...CLF
AVIATION...MPG



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