Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 302321
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
521 PM CST FRI JAN 30 2015

.UPDATE...
ISSUED AT 506 PM CST FRI JAN 30 2015

UPDATED TO INCLUDE 00Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 306 PM CST FRI JAN 30 2015

THE SHORT TERM FORECAST IS QUIET WITH SEASONAL TEMPERATURES AND
LITTLE CHANCE FOR PERCIP. HIGH PRESSURE IS CURRENTLY SLIDING
SOUTHEAST OF THE FORECAST AREA AND A WEAK SURFACE TROUGH IS SLOWLY
MOVING EAST ACROSS THE DAKOTAS. THE AIR MASS JUST AHEAD OF THIS
TROUGH IS QUITE WARM WHERE TEMPS CLIMBED TO NEAR 50 TO OUR WEST THIS
AFTERNOON. THIS TROUGH WILL MOVE THROUGH TONIGHT...BUT THE FRONT IS
REALLY MORE OF AN OCCLUDED FRONT WITH THE COLDER AIR COMING IN
FAIRLY QUICKLY BEHIND THE FRONT. IN TERMS OF CLOUD COVER...CLEARING
TONIGHT SHOULD BE REPLACED BY A STRATUS DECK COMING IN FROM THE
NORTH WITH THE COLD AIR. 850MB TEMPS ARE EXPECTED TO -10C TO -12C BY
00-06Z.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 306 PM CST FRI JAN 30 2015

FOCUS THIS SHIFT IS AT THE BEGINNING OF THE LONG TERM
PERIOD...BEGINNING SATURDAY NIGHT. A COMPLICATED FORECAST
SITUATION IS EVOLVING AS A NORTHERN STREAM WAVE OVER BRITISH
COLUMBIA IS FORECAST TO PHASE WITH A SOUTHERN STREAM SYSTEM COMING
OUT OF THE SOUTHWESTERN CONUS. THE DETAILS WILL BE GREATLY
AFFECTED BY HOW THE SOUTHERN AND NORTHERN STREAM SYSTEMS
MERGE...AND WHEN. THE MODELS IN THE PAST HAVE STRUGGLED IN
PROPERLY HANDLING THIS TYPE OF INTERACTION AT TIMES...AND MOST OF
THE MOISTURE WILL COME WITH THE SOUTHERN STREAM SYSTEM.

THE CONSENSUS WAS A SHIFT NORTHWARD TODAY...SO INCREASED POPS FOR
THE SOUTHERN HALF OF THE AREA...WITH HIGH PROBABILITIES OF
ACCUMULATING SNOW ALONG THE IOWA BORDER. THE HEAVIEST AMOUNTS WILL
FALL SOUTH OF OUR AREA...BUT AT THIS TIME IT LOOKS AS IF WE`LL GET
CLIPPED WITH A FEW INCHES OF LIGHT SNOW ALONG THE IOWA BORDER.
WHERE I LACK CONFIDENCE IS IN THE MERGING OF THE NORTHERN AND
SOUTHERN STREAM WAVES BECAUSE THE NORTHERN WAVE WILL NEED TO
ACCELERATE AND MERGE WITH THE SOUTHERN WAVE BEFORE ITS EAST OF
IOWA. IF THIS OCCURS...THE NORTHERN WAVE IS STILL LIKELY TO BRING
LIGHT SNOW TO SOUTHERN AND SOUTHWESTERN MN...BUT WITH LIGHTER
AMOUNTS. IF THE MERGE CAN HAPPEN BEFORE THE SOUTHERN SYSTEM MOVES
TOO FAR EAST...AMOUNTS ALONG THE SOUTHERN THIRD OF THE STATE COULD
BE HIGHER DUE TO BETTER FORCING AND MORE ABUNDANT MOISTURE. PLENTY
OF TIME TO HASH OUT THE DETAILS OF THIS SYSTEM BUT FOR NOW
GENERALLY WENT FOR 1-3" ACROSS THE FAR SOUTH. THIS FORECAST LEANED
MOSTLY TOWARD THE ECMWF SOLUTION...BUT THE 18Z NAM ALSO CAME IN
AND BACKED OFF ON AMOUNTS IN OUR AREA FROM THE 12Z RUN.

LOOKING AHEAD...TEMPERATURES WILL COOL BEHIND THESE SYSTEMS WITH
SHORTWAVES MOVING THROUGH THE GENERAL UPPER MIDWEST REGION EVERY
FEW DAYS THROUGH THE END OF THE PERIOD. OPPORTUNITIES TO PICK UP
LIGHT SNOW REMAIN IN THE FORECAST FOR THOSE SYSTEMS.
OTHERWISE...NEAR TO SLIGHTLY BELOW NORMAL TEMPERATURES FOR MUCH OF
NEXT WEEK. THERE ARE INDICATIONS THOUGH THAT THE WESTERN CONUS
RIDGE WILL ADVANCE EAST AROUND NEXT WEEKEND AND PUSH US BACK TO
ABOVE NORMAL TEMPERATURES.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 506 PM CST FRI JAN 30 2015

OVERALL IT WILL BE A RELATIVELY QUIET PERIOD AVIATION-WISE...
ALTHOUGH THERE LOOKS TO BE A PERIOD OF LOWER CEILINGS ALONG WITH
VEERING WINDS THROUGH THE PERIOD. SURFACE TROUGH WILL MOVE THROUGH
TONIGHT... WITH MOISTURE POOLING ALONG THE TROUGH AXIS. SUBSIDENCE
WORKS IN BEHIND THAT... AND FOR A TIME IT LOOKS TO TRAP THE
MOISTURE AND BRING A PERIOD OF 010-020 CEILINGS TO THE AREA.
EXACTLY WHEN THAT OCCURS AND HOW LONG INTO SATURDAY THEY PERSIST
IS STILL SOMEWHAT QUESTIONABLE WITH QUITE A BIT OF VARIATION IN
THE MODEL GUIDANCE. AT THIS POINT... TWEAKED THINGS TO BE A BIT
MORE PESSIMISTIC WITH SLIGHTLY EARLIER ARRIVAL AND LATER DEPARTURE
OF THE LOW CEILINGS.

KMSP...HAVE MODERATE TO HIGH CONFIDENCE IN THE OVERALL TREND
DEPICTED IN THE TAF... BUT LOW TO MODERATE CONFIDENCE IN THE
TIMING OF THE PERIOD OF LOWER CEILINGS AS WELL AS THE ACTUAL
CEILING HEIGHTS. COULD EASILY SEE ARRIVAL/DEPARTURE OF LOWER
CEILINGS VARY BY +/- 3 HOURS FROM FORECAST VALUES... WITH CEILING
HEIGHTS POSSIBLY DIFFERENT BY +/-005 FT.

/OUTLOOK FOR KMSP/
SATURDAY OVERNIGHT...MVFR CEILINGS AND VISIBILITIES EXPECTED WITH
LIGHT SNOW... IFR POSSIBLE. NORTHEAST WIND 10 TO 20 KT.
SUNDAY...MVFR CEILINGS AND VISIBILITIES EXPECTED EARLY WITH LIGHT
SNOW. NORTH WIND 10 TO 15 KT.
SUNDAY NIGHT...VFR. VARIABLE WIND LESS THAN 10 KT.
MONDAY...VFR. SOUTHWEST WIND 5 TO 10 KT.
MONDAY NIGHT...MVFR CEILINGS POSSIBLE LATE. SOUTHWEST WIND 5 TO 10
KT.
TUESDAY...MVFR CEILINGS AND VISIBILITIES POSSIBLE WITH A CHANCE OF
SNOW. VARIABLE WIND LESS THAN 10 KT BECOMING NORTH AROUND 10 KT.

&&

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

$$

UPDATE...
SHORT TERM...CLF
LONG TERM...SPD
AVIATION...


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