Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 182104
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
304 PM CST TUE NOV 18 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 304 PM CST TUE NOV 18 2014

COMPACT SHORTWAVE EVIDENT ON WATER VAPOR IMAGERY DIVING SOUTH
ACROSS LAKE WINNIPEG IS THE FEATURE OF INTEREST IN THE SHORT TERM.
LOOKING OUT TO OUR WEST...YOU WILL FIND A WARM FRONT DRAPED OUT
FROM N-S ACROSS THE CENTRAL DAKOTAS...WITH YET ANOTHER ARCTIC COLD
FRONT SWEEPING SE ACROSS WRN NODAK.

WAA OUT AHEAD OF THE SYSTEM HAS RESULTED IN AN EXTENSIVE BANK OF
CLOUDS BETWEEN 2K AND 4K FEET ACROSS THE UPPER MS VALLEY THIS
AFTERNOON. PRETTY MUCH THE ENTIRE DEPTH OF THESE CLOUDS IS WITHIN
IN THE DENDRITIC SNOW GROWTH ZONE...WHICH MEANS THEY HAVE BEEN
EFFICIENT AT PRODUCING FLURRIES AND LIGHT SNOW. THIS SNOW IS NOT
EXPECTED TO ACCUMULATE...WITH LIGHT ACCUMULATIONS EXPECTED WHEN
THE WINNIPEG WAVE ARRIVES.

BOTH SHORT TERM HI-RES CAMS AND DETERMINISTIC MODELS ARE SIMILAR
IN THEIR DEPICTION OF THE EVOLUTION OF THE WINNIPEG WAVE TONIGHT.
AS IT WORKS OVER TO CHICAGOLAND BY WEDNESDAY MORNING. WE WILL SEE
A QUICK HIT OF FORCING CENTERED ON THE 285K ISENTROPIC SFC DROP
DOWN WITH THE WAVE. THERE IS GOOD AGREEMENT AMONGST THE CAMS ON
THEIR HANDLING OF THIS QUICK SNOW BURST...WHICH CONVENIENTLY
MATCHED UP WELL WITH THE EXISTING FORECAST. ONLY REAL CHANGE TO
THE GOING POP FORECAST FOR TONIGHT WAS TO SPEED UP THE ARRIVAL OF
THE LIKELY AND BETTER POPS. NOT EXPECTING MUCH SNOW WITH
THIS...BUT HAVE SNOW TOTALS TONIGHT RANGING FROM A HALF TO ONE
INCH NORTHEAST OF THE MN RIVER.

TEMPERATURES FOR THE SHORT TERM WILL BE TRICKY WITH THE FRONT
COMING ACROSS THE AREA LATE TONIGHT AND EARLY WEDNESDAY MORNING.
WE WILL LIKELY SEE A SLIGHT DROP IN TEMPERATURES AFTER
SUNSET...BUT MUCH OF THE NIGHT WILL FEATURE RISING TEMPS...WITH
STRONG CAA BEHIND THE COLD FRONT KEEPING TEMPERATURES EITHER
STEADY OR SLOWLY FALLING THROUGH THE DAY WEDNESDAY. EXPECT MANY
LOCATIONS TO REACH THEIR HIGHS TODAY AT AROUND
MIDNIGHT...ESPECIALLY FOR WRN MN...WITH TEMPERATURES TOMORROW NOT
WANDERING TOO FAR FROM THE HIGH MARKS WE SEE OVERNIGHT.

FINAL ISSUE WILL BE THE STRONG WINDS. SEEING MID CHANNEL MIX DOWN
WINDS IN THE CAA LATE TONIGHT AND THROUGH THE DAY WEDNESDAY
PEAKING INTO THE LOW 30 KTS IN WRN MN AND CLOSER TO 25 KTS IN ERN
MN. AS A RESULT EXPECT WIND GUSTS TO AROUND 35 MPH FROM WEST
CENTRAL INTO SOUTH CENTRAL MN LATE TONIGHT THROUGH THE DAY ON
WEDNESDAY. THIS SHOULD BE ABLE TO BLOW THE SNOW AROUND SOME
MORE...BUT WITH NO SIGNIFICANT NEW SNOW EXPECTED SINCE OUR BLOWING
SNOW EVENT YESTERDAY...WE DO NOT THINK BLOWING SNOW WILL BE
REDUCING VISIBILITIES ENOUGH TO WARRANT ANY HEADLINES AT THIS TIME.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 304 PM CST TUE NOV 18 2014

VERY COMPLEX AND INTERESTING WEATHER PATTERN THIS WEEKEND AS TWO
PRIMARY SHORTWAVES DEVELOP SURFACE CYCLONES ACROSS THE CONUS. HOW
THESE TWO FEATURES INTERACT REMAINS TO BE SEEN...BUT AT THIS TIME IT
APPEARS THAT THE UPPER MIDWEST WILL BE SPARED FROM SIGNIFICANT
SNOWFALL LATE THIS WEEKEND AND EARLY NEXT WEEK.

BY WEDNESDAY EVENING MN/WI WILL BE ON THE TAIL END OF ANOTHER
CLIPPER SYSTEM WITH NW WINDS AND SEASONABLY COOL TEMPERATURES. H850
TEMPS OF -15 TO -17C WILL DEVIATE LITTLE BY THURSDAY MORNING. THE
ABSENCE OF COLD AIR ADVECTION WILL LIMIT THE MECHANICAL MIXING
OVERNIGHT AND WIND GUSTS SHOULD SUBSIDE QUICKLY AFTER SUNSET. IN
ADDITION SURFACE HIGH PRESSURE WILL BUILD IN WHICH WILL ALSO SUPPORT
LIGHT WINDS...CLEAR SKIES...AND SUBSTANTIAL RADIATIONAL COOLING.
THEREFORE DECREASED TEMPS SLIGHTLY FOR EARLY THURSDAY
MORNING...ESPECIALLY ACROSS THE WEST. TEMPERATURES SHOULD REBOUND
INTO THE MID TEENS BY THURSDAY AFTERNOON WITH AMPLE SUNSHINE. WARM
AIR ADVECTION WILL KEEP THURSDAY NIGHT LOWS IN THE SINGLE DIGITS
ALONG THE MINNESOTA RIVER VALLEY...BUT CALM WINDS WILL ALLOW THEM TO
DROP TO NEAR -5F ACROSS WESTERN WI. OTHER THAN THAT DID NOT MAKE
NOTEWORTHY CHANGES TO THE BLENDED FORECAST GUIDANCE.

LOOKING AHEAD...A SOUTHERN STREAM SHORTWAVE WILL TRACK ACROSS THE
TEXAS PANHANDLE OVER THE WEEKEND. MEANWHILE A POWERFUL JET WILL MOVE
ONSHORE IN THE PACIFIC NORTHWEST. A SHORTWAVE IN THE LEFT EXIT
REGION OF THIS JET WILL MOVE ACROSS THE INTERNATIONAL BORDER AND
DEVELOP A LEE SIDE CYCLONE OVER EASTERN MONTANA. ADIABATIC WARMING
WITH THIS SECONDARY FEATURE WILL ACT TO RELAX THE LOW LEVEL
TEMPERATURE GRADIENT ACROSS THE CENTRAL CONUS...THUS INHIBITING
THE AFOREMENTIONED TEXAS SHORTWAVE FROM SPINNING UP A SIGNIFICANT
WINTER CYCLONE AND TRACKING IT NORTH TOWARD MN/WI. INSTEAD...WARM
AIR ADVECTION AHEAD OF THIS SOUTHERN WAVE WILL BRING ABOVE NORMAL
TEMPERATURES EAST OF THE MISSISSIPPI RIVER...WITH WIDESPREAD RAIN
OF AROUND AN INCH ACROSS THE OHIO RIVER VALLEY CENTERED AROUND THE
SUNDAY TIMEFRAME.

CLOSER TO HOME...THE TRANSITION FROM NORTHWEST FLOW TO ZONAL FLOW
WILL BRING WARMER AIR ACROSS THE REGION BEGINNING FRIDAY. FORECAST
SOUNDINGS SHOW OVERCAST SKIES...WITH POTENTIALLY SOME LIGHT FREEZING
DRIZZLE INTO FRIDAY NIGHT. WARM AIR ADVECTION WILL CONTINUE AS THE
AFOREMENTIONED NORTHERN SHORTWAVE TRACKS ALONG THE INTERNATIONAL
BORDER. FORECAST HIGHS FOR BOTH SATURDAY AND SUNDAY SHOULD ECLIPSE
THE FREEZING MARK ACROSS THE ENTIRE REGION. IN ADDITION...THE
DEVELOPING STORM TO THE SOUTH...AND THE ONE TO THE NORTH WILL LEAD
TO A RELAXED PRESSURE GRADIENT MEANING LIGHTER WINDS BOTH THOSE
DAYS. BY EARLY NEXT WEEK THE SOUTHERN SHORTWAVE TAKES OVER AND A
SUB-980MB SURFACE CYCLONE WILL DEVELOP ACROSS THE GREAT LAKES...BUT
AT THIS TIME IT APPEARS THAT 1) THE SYSTEM WILL BE WARM ENOUGH TO
PRODUCE MAINLY RAIN...AND 2) THE HEAVIEST PRECIP WILL BE WELL TO THE
EAST OF THE FORECAST AREA.

IN SUMMARY...IT SEEMS THE MODEL DISCREPANCIES STEM FROM THE STRENGTH
OF THE NORTHERN SHORTWAVE. AT THIS TIME TRENDED TOWARD THE STRONGER
SOLUTION BASED OFF THE GFS/GEM/FIM...WHICH WOULD KEEP THE RAPID
INTENSIFICATION OF THE CENTRAL CONUS STORM EAST OF THE FORECAST
AREA...WITH PERHAPS ONLY SOME LIGHT WRAP AROUND SNOW ON MONDAY. THE
ECMWF 18.12 IS MUCH WEAKER WITH THE NORTHERN WAVE AND TAKES IT
SOUTHEAST INTO THE GREAT PLAINS VS TRANSLATING IT EASTWARD LIKE THE
OTHER GUIDANCE. ALTHOUGH THIS SOLUTION GENERATES MORE PRECIP ACROSS
THE EASTERN CWA...THE MAJORITY OF IT FALLS AS RAIN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1154 AM CST TUE NOV 18 2014

2500-4500 FT CLOUD DECK ON LEADING EDGE OF WAA IS LOCATED MOSTLY
WITHIN THE DENDRITIC SNOW GROWTH ZONE...SO EXPECT OCNL -SN AT ALL
BUT THE WRN MN TERMINALS TO CONTINUE THROUGH MUCH OF THE
AFTN...THOUGH VIS WILL REMAIN MOSTLY VFR WITH ONLY A TEMPO VIS DOWN
TO 4SM POSSIBLE. NOT MUCH HAS CHANGED WITH EXPECTATION FOR
SHORTWAVE CURRENTLY UP BY LAKE WINNIPEG...OTHER THAN SNOW LOOKS TO
ARRIVE A COUPLE OF HOURS FASTER THAN WHAT THE PREVIOUS TAF
HAD...SO ONLY MADE MINOR TIMING SHIFTS FROM WHAT IS IN THE 12Z
TAFS. COLD FRONT JUST NOW ENTERING NW NODAK HAS A FAIRLY EXTENSIVE
STRATUS DECK BETWEEN 015 AND 025 IN ITS WAKE...SO THAT SHOULD BE
WHAT WE ARE DEALING WITH FOR MUCH OF THE DAY WED. IN
ADDITION...LIKE TODAY...MUCH OF THIS CLOUD LAYER WILL BE WITHIN
THE PREFERRED DENDRITIC GROWTH ZONE...SO EXPECT ANOTHER DAY ON
WEDNESDAY TO FEATURE OCNL FLURRIES AND -SHSN. NAM FORECAST
SOUNDINGS STILL SHOWING MID CHANNEL MIX DOWN WINDS NEAR 30KTS IN
WRN MN AND 25 KTS IN ERN MN...SO STILL HAVE HIGH CONFIDENCE IN THE
BREEZY NW WINDS EXPECTED IN THE WAKE OF THE FRONT.

KMSP...WILL LIKELY SEE SOME FLURRIES THROUGH THE AFTERNOON
TODAY...AND MAY EVEN GET A VIS DOWN TO 4 OR 5 MILES...BUT SNOW
TODAY SHOULD HAVE MINIMAL IMPACTS. SNOW ARRIVING TONIGHT STILL
LOOKS TO BE SHORT LIVED WITH MINIMAL AMOUNTS...THOUGH A QUICK HALF
INCH OF DRY FLUFFY SNOW LOOKS PLAUSIBLE.

/OUTLOOK FOR KMSP/
THU...VFR. WINDS WNW 5-10 KTS.
FRI...VFR. WINDS SSE 10-15 KTS.
SAT...CHC MVFR CIGS. WINDS S 5-10 KTS.


&&

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

$$

SHORT TERM...MPG
LONG TERM...JRB
AVIATION...MPG






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