Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 222109
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
309 PM CST THU JAN 22 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 415 AM CST THU JAN 22 2015

AREAS OF CLEARING...TOGETHER WITH LIGHT WINDS LET TO PRISTINE
COOLING CONDITIONS...WITH EARLY MORNING TEMPERATURES NEAR ZERO
ACROSS FAR WEST CENTRAL MINNESOTA. MEANWHILE TEMPERATURES REMAINED
IN THE MID 20S BENEATH OVERCAST SKIES IN EASTERN MN AND WESTERN WI.

THROUGHOUT THE DAY TODAY LOW CLOUDS WILL MEANDER ACROSS THE REGION
AS THE LOW LEVEL MOISTURE REMAINS TRAPPED BENEATH A STOUT INVERSION.
SOUTHWESTERLY FLOW WILL DEVELOP THIS AFTERNOON AS THE SURFACE RIDGE
MIGRATES EASTWARD AND IS REPLACES BY A TROUGH OF LOW PRESSURE. THE
CLIPPER SYSTEM DRIVING THIS SURFACE TROUGH WILL SKIRT ALONG THE
INTERNATIONAL BORDER. MID LEVEL CLOUDS WILL OVERSPREAD THE REGION
THURSDAY NIGHT AHEAD OF THE WAVE...BUT HAVE HELD OFF WITH POPS UNTIL
AFTER 09Z FRIDAY. ANY PRECIP THAT FALLS WILL BE VERY LIGHT...BUT THE
CONCERN IS FREEZING DRIZZLE/SLEET GIVEN THE WARM LAYER ALOFT AND SUB-
FREEZING SURFACE TEMPS.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 309 PM CST THU JAN 22 2015

BY FRIDAY NIGHT...THE TROUGH AXIS WILL BE THROUGH OUR AREA...AND
WINDS WILL HAVE TURNED NORTHWEST BY THE EVENING HOURS. ADDITIONAL
LOW LEVEL CLOUDINESS WILL OVERTAKE THE EASTERN HALF OF THE AREA
THROUGH THE NIGHT...WITH WESTERN MN HAVING MORE DRY AIR PRESENT IN
THE LOW LEVELS. ON SATURDAY MORNING...AN INITIAL SUBTLE WAVE AHEAD
OF OUR MAIN CLIPPER SYSTEM THAT IS EXPECTED SATURDAY NIGHT THROUGH
SUNDAY. HOWEVER...THERE IS ESSENTIALLY NO FORCING AT THIS TIME FRAME
AND WHILE LOW LEVEL SATURATION IS FORECAST IN THE MODEL
SOUNDINGS...AT THIS TIME EXPECTATIONS REMAIN GENERALLY FOR LOW CLOUD
COVER.

OUR MAIN CONCERN IN THE LONG RANGE FORECAST IS ON SATURDAY NIGHT
THROUGH SUNDAY AS A STRONG CLIPPER SYSTEM DIVES SOUTH TOWARD OUR
AREA. THERE IS MUCH TO BE SORTED OUT WITH THIS SYSTEM AT THIS POINT.
THE GFS HAS SHIFTED THE MAIN PRECIP AXIS TO THE EAST...AND HAS THE
HEAVIEST PRECIP AXIS RUNNING FROM THE ARROWHEAD TOWARD MILWAUKEE.
THIS SOLUTION WOULD SIDE SWIPE OUR AREA WITH LIGHT SNOW.  THE 12Z
NAM AND THE GEM SHIFTED EAST AS WELL SO CONFIDENCE HAS SLIGHTLY
INCREASED IN A MORE EASTERLY SOLUTION. THE PROBLEM CONFIDENCE WISE
IS THE ECMWF. IT IS HOLDING FIRM AS A WESTERN OUTLIER AND BRINGS THE
HEAVIEST PRECIP DIRECTLY THROUGH OUR CWA. TAKING A LOOK AT THE MID
AND UPPER LEVELS...THE ECMWF HAS A MUCH STRONGER 500MB TROUGH THAT
BECOMES A CLOSED LOW AS IT MOVES THROUGH OUR AREA. THE GFS ON THE
OTHER HAND HAS A FLATTER WAVE THAT DOES NOT CLOSE OFF AT 500MB AND
IS SLOWER.  THE NAM TENDS TO AGREE MORE WITH GFS SOLUTION WHICH IS
REFLECTED IN THE SIMILARITIES OF THE PRECIP FIELD. TAKING A LOOK AT
THE SREF PLUMES SHOWS A LARGE AMOUNT OF SPREAD IN THE VARIOUS
MEMBERS AS WELL.

SO...I DID NOT GET TOO AGGRESSIVE IN REDUCING POPS BASED ON THE
CONSENSUS OF AN EASTERN SHIFT IN MOST OF THE GUIDANCE EXPECT THE
ECMWF. EVEN WITH THE GUIDANCE THAT AGREES ON THE EASTWARD
SHIFT...TIMING DIFFERENCES REMAIN.  BUT THE MAIN HESITATION I HAD
WAS HOW MUCH TO TRIM THE POPS...ESPECIALLY IN WESTERN MN...DUE TO
THE WESTERN SOLUTION OF THE ECMWF.  THE ECMWF HAS BEEN FAIRLY
CONSISTENT...SO I`D LIKE TO SEE THE GFS/NAM/GEM KEEP SHOWING THIS
EASTERLY SOLUTION FOR A FEW MORE RUNS BEFORE GETTING AGGRESSIVE WITH
THE FORECAST. ITS STILL POSSIBLE FOR THE GFS/NAM/GEM CLUSTER TO
START MOVING THE WAY OF THE ECMWF AT THIS STAGE SO THE POINT
IS...EXPECT THIS FORECAST TO BE CHANGED/TWEAKED/FINE TUNED AS
CONFIDENCE IN THE GUIDANCE INCREASES.

BEYOND THE WEEKEND...BOTH THE EC/GFS INDICATE A WEAK CLIPPER MOVING
THROUGH AGAIN ON MONDAY-TUESDAY TIMEFRAME.  THE MAIN DIFFERENCES
THERE ARE TIMING...BUT A LIGHT SNOWFALL EVENT IS POSSIBLE DURING
THAT PERIOD.

AS FAR AS TEMPERATURES ARE CONCERNED...RELATIVELY WARM CONDITIONS
WILL PERSIST AS THE WESTERN RIDGE HOLDS STRONG AND WE REMAIN ALONG
THE UPPER JET EARLY NEXT WEEK. THE WESTERN RIDGE IS FORECAST TO
PUSH THE JET NORTHEAST OF US WEDNESDAY...AND ALLOW EVEN WARMER
TEMPERATURES TO MOVE TOWARD OUR AREA.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 539 AM CST THU JAN 22 2015

A WEAK RIDGE OF HIGH PRESSURE WILL DRIFT EASTWARD TODAY. LIGHT
WINDS WILL BECOME SOUTHWEST THIS AFTERNOON. MEANWHILE...VERY
LITTLE MIXING THIS MORNING WILL KEEP THE LOW CLOUDS IN PLACE
ACROSS MUCH OF THE REGION...WITH LITTLE CHANGE EXPECTED FROM THE
CURRENT CONDITIONS. THIS EVENING MID LEVEL CLOUDS WILL
INCREASE...WITH A CHANCE FOR A LIGHT WINTRY MIX ALONG I-94. AT
THIS TIME...CONFIDENCE WAS TO LOW TO MENTION IN THE TAF...BUT
LIGHT FREEZING RAIN IS POSSIBLE.

KMSP...
THERE IS A SMALL BREAK ON THE BACK SIDE OF THESE CLOUDS...SO
SHOULD SEE A BRIEF WINDOW OF VFR CONDITIONS FOR MID MORNING.
HOWEVER...HIRES MODELS SHOW LOW CLOUDS MOVING UP FROM THE
SOUTHWEST AROUND 18Z. THIS EVENING AND OVERNIGHT SHOULD SEE VFR
CONDITIONS. MENTIONED FREEZING RAIN/RAIN FOR FRIDAY MORNING.
ACCUMULATIONS WILL BE VERY LIGHT...BUT FORECAST SOUNDINGS SHOW THE
POSSIBILITY OF A LIGHT GLAZING.

/OUTLOOK FOR KMSP/
FRI...MVFR WITH -FZDZ/RA POSSIBLE EARLY. WINDS NW AT 10KT.
SATURDAY...VFR. WIND W AT 5-10KT.
SUNDAY...MVFR WITH -SN/IFR POSSIBLE. WIND NW AT 10G20KT SUNDAY.


&&

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

$$

SHORT TERM...JRB
LONG TERM...SPD
AVIATION...JRB


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