Area Forecast Discussion
Issued by NWS Aberdeen, SD

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318
FXUS63 KABR 132037
AFDABR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
237 PM CST SAT FEB 13 2016

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 235 PM CST SAT FEB 13 2016

FAIRLY ACTIVE SHORT TERM FORECAST FOR THE AREA AS TWO FEATURES
WILL COMBINE TO PRODUCE MODERATE TO OCCASIONALLY HEAVY SNOWFALL
OVER THE CWA. THE STRONG SHORTWAVE THAT WILL SLIDE SOUTHEAST
ACROSS SOUTHWEST SOUTH DAKOTA IS STILL LOCATED IN CENTRAL MONTANA
AT THIS TIME...AND IS LEADING TO A COUPLE AREAS OF PRECIPITATION
IN EASTERN MONTANA (ONE ALONG THE WARM FRONT AND ANOTHER TIED TO
THE SHORTWAVE AND COLD FRONT). CLOSER TO THE AREA...SEEING
PRECIPITATION JUST TO THE WEST OF THE MISSOURI RIVER THAT IS
SLOWLY MOVING EAST-SOUTHEAST. THIS PRECIPITATION IS DUE TO THE
INITIAL AREA OF MID-LEVEL WARM AIR ADVECTION AHEAD OF THE WARM
FRONT STRETCHING SOUTH-SOUTHEAST THROUGH FAR WESTERN SOUTH DAKOTA.
WEBCAMS SHOW THAT THE PRECIPITATION TOWARDS HAAKON/STANLEY
COUNTIES IS IN THE FORM OF RAIN AND WITH SURFACE TEMPERATURES IN
THAT AREA AROUND OR ABOVE FREEZING...DON/T THINK THERE IS TOO MUCH
FREEZING RAIN OCCURRING AT THIS POINT. FARTHER NORTH...RAP
ANALYSIS SOUNDINGS INDICATE THE WARM NOSE ALOFT WEAKENS WHICH
SHOULD TRANSITION THE PRECIP TO SNOW THE FARTHER NORTH YOU HEAD.
OVER THE REST OF THE AREA...CLOUDS HAVE BEEN LOWERING WITH THE
INCREASING LOW LEVEL MOISTURE AND DEPARTING SURFACE RIDGE.
TEMPERATURES ARE STILL FAIRLY COLD OVER NORTHEAST SD...WHERE 2PM
TEMPERATURES RANGE FROM THE UPPER SINGLE DIGITS AT K8D3 TO 13 AT
KABR AND THEN 17 AT KMBG.

MODELS CONTINUING TO STRUGGLE WITH THE TRACK/EVOLUTION OF THE
SHORTWAVE IN MONTANA...WHICH LEADS TO SOME UNCERTAINTY IN THE
FORECAST SNOWFALL OVER N.C./N.E. SOUTH DAKOTA THIS EVENING INTO
THE OVERNIGHT HOURS. LATEST RUNS OF THE RAP AND 12Z GLOBAL
MODELS HAVE TRENDED THE TRACK OF THE STRONGEST FORCING A LITTLE
FARTHER TO THE SOUTHWEST AND IN SOME CASES ONLY BARELY BRUSHING
SOUTHWESTERN SD. WHILE THAT BEST FORCING SLIDES SOUTHWEST OF
MUCH OF THE AREA...STILL HAVE SOME SUPPORT FROM THE UPPER TROUGH
AND ESPECIALLY FROM THE WARM AIR ADVECTION / ISENTROPIC ASCENT
ALONG AND AHEAD OF THAT TROUGH THROUGH THE EARLY OVERNIGHT
HOURS. FAIRLY STRONG LIFT WITH THE WAA (AND SEEN IN THE 700MB
OMEGA) WITH FAVORABLE 850-500MB Q-VECTOR DIVERGENCE.
THEREFORE...EXPECT TO SEE A FAIRLY QUICK HITTING (4-7HR PERIOD)
AREA OF PRECIPITATION MOVING THROUGH THE AREA...ESPECIALLY THIS
EVENING INTO THE EARLY OVERNIGHT HOURS. MODELS HAVE TRENDED QPF
AMOUNTS TO THE NORTH WITH THE MOST RECENT RUNS...SOME EVEN
SHOWING 12HR QPF AMOUNTS EXCEEDING 0.6IN BETWEEN
MOBRIDGE/ABERDEEN. THAT POTENTIAL (LIKELY SOMEWHAT CONVECTIVELY
DRIVEN WITH 750-500MB LAPSE RATES AROUND 7 C/KM) WILL NEED TO BE
WATCHED THROUGH THE EVENING AND IF IT SETS UP AS SHOWN WITH SOME
OF THE HIGHER RES RUNS...MAY NEED TO UPGRADE A FEW COUNTIES TO
WARNINGS. WITH THAT FARTHER NORTH TREND...EXPECT A LITTLE LESS
IMPACT FOR THE SOUTHWESTERN CWA...BUT STILL THINK THE POTENTIAL
FOR FREEZING RAIN THROUGH THE FIRST PART OF THE EVENING BEFORE
TRANSITIONING TO SNOW FOR A BRIEF PERIOD BEFORE ENDING. THAT
NORTHWARD SHIFT SHOULD KEEP SNOWFALL AMOUNTS BELOW 2 INCHES FROM
PIERRE AND SOUTHWEST (WHERE SOME AREAS WILL STAY MAINLY RAIN).

AS FOR SNOWFALL AMOUNTS OVER THE NORTH CENTRAL AND
NORTHEAST...HAVE A GENERAL 3-6 INCHES WITH SNOW RATIOS
INCREASING FROM AROUND 10-1 AROUND THE MISSOURI RIVER TO THE
12-14 TO 1 RANGE OVER THE NORTHEAST. OVER THE NORTHEAST...A GOOD
PORTION OF THE LIFT IS AT OR ABOVE THE DGZ...WHICH WILL LIKELY
LEAD TO MORE COLUMNS IN THE SNOW PROCESS AND MORE POTENTIAL FOR
COMPACTING (ALONG WITH AGGREGATION AS THE SNOW FALLS THROUGH THE
CLOUD LAYER BELOW THE DGZ). THUS...DIDN/T WANT TO GO MUCH HIGHER
THAN THE PREVIOUSLY MENTIONED VALUES ...ALTHOUGH RATIOS COULD
BRIEFLY INCREASE IF THE FORCING ALIGNS A LITTLE LOWER AND IN THE
DGZ. WITH THE HIGHER QPF AND RATIOS...HAVE NEAR WARNING SNOWFALL
AMOUNTS (5.5-6IN) OVER MCPHERSON/EDMUNDS/BROWN/MARSHALL/DAY
COUNTIES. WITH THE VARIABILITY IN THE MODEL RUNS TODAY...DIDN/T
HAVE ENOUGH CONFIDENCE TO UPGRADE TO A WARNING AT THIS POINT AND
THE EVENING SHIFT WILL NEED TO MONITOR FOR A POSSIBLE UPGRADE. IN
ADDITION...WITH THE SNOW OCCURRING LATE THIS EVENING AND DURING
THE EARLY OVERNIGHT HOURS...THOUGHT THE IMPACTS WOULD BE LOWER
THAN IF IT OCCURRED DURING THE DAY.

ONE OTHER ITEM TO MENTION WILL BE THE GUSTY SOUTH-SOUTHEAST
WINDS INITIALLY THIS EVENING AHEAD OF THE TROUGH (GUSTS TO
25-30MPH). THAT WILL LEAD TO PATCHY/AREAS OF BLOWING SNOW AND
WILL CONTINUE TO MENTION THAT IN THE FORECAST/WSW.

FOR THE REST OF THE PERIOD...THE SNOW WILL DIMINISH FROM WEST TO
EAST LATE TONIGHT AND THROUGH THE DAY ON SUNDAY (LARGELY OVER
THE EASTERN HALF/THIRD OF THE CWA). A BROAD SURFACE TROUGH WILL
BE OVER THE AREA AND LIMIT THE WINDS AND IN TURN ANY BLOWING SNOW
CONCERNS. IN ADDITION...WITH THE WARM AIR OVER THE
AREA BEHIND THE WARM FRONT THAT MOVED THROUGH...HIGHS WILL RISE
INTO THE MID/UPPER 20S OVER THE FAR EAST TO THE LOWER 40S ALONG
AND WEST OF THE MISSOURI RIVER.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 235 PM CST SAT FEB 13 2016

LOW TEMP FORECAST FOR SUNDAY NIGHT IS A BIT TRICKY. AREA WILL STILL
BE IN A RELATIVELY MILD AIR MASS WITH 925MB TEMPS AROUND 0C TO +2C
AND A LIGHT WEST TO SOUTHWEST SFC WIND. ALTHOUGH...WILL HAVE TO KEEP
IN MIND THE FRESH COAT OF SNOW THAT WILL BE OVER MUCH OF THE AREA.
THERE WILL BE SOME DEGREE OF CLOUD COVER AS WELL...SO TRYING TO
FIGURE OUT WHICH VARIABLES HAVE THE BIGGEST IMPACT ON TEMPS IS
TRICKY.

WILL THEN BE WATCHING THE NEXT PIECE OF SHORTWAVE ENERGY WHICH WILL
BE DROPPING SOUTHEAST THROUGH THE AREA MONDAY NIGHT. HAVE INCREASED
POPS FOR THIS EVENT AS MODELS ARE IN PRETTY GOOD AGREEMENT ON TIMING
AND PLACEMENT OF QPF. AGAIN...COULD BE DEALING WITH MIXED PRECIP
ISSUES AS THERE WILL BE WARM AIR IN PLACE.

YET ANOTHER WAVE MOVES THROUGH TUESDAY NIGHT BUT IS LOOKING RATHER
WEAK AT THIS POINT. SUPERBLEND GAVE SLIGHT CHANCE POPS AND THIS
LOOKS GOOD FOR THE TIME BEING. ONLY CHANGE HERE WAS TO REMOVE THE
SLIGHT CHANCES THEY INITIAL GAVE ON TUESDAY AND HELD THINGS OFF TO
TUESDAY NIGHT PER MODEL DATA.

TEMPS THROUGHOUT THE PERIOD STAY ON THE MILD SIDE...ESPECIALLY BY
THURSDAY WHEN MODELS TRY TO BRING IN SOME VERY MILD AIR. 925MB TEMPS
AROUND +20C SHOW UP IN THE MODELS OVER SOUTHWEST AND SOUTH CENTRAL
SD. SUPERBLEND TEMPS HAVE READINGS AS WARM AS THE 60S OVER THE
SOUTHWEST CWA ON THURSDAY.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1149 AM CST SAT FEB 13 2016

EXPECT DETERIORATING CONDITIONS FROM WEST TO EAST THROUGH THE
AFTERNOON AND EVENING ACROSS THE REGION...AS A STORM SYSTEM
SLIDES EAST-SOUTHEAST ACROSS THE AREA. HAVE ALREADY STARTED TO
SEE SOME REDUCTIONS IN VISIBILITY AT KMBG AND EXPECT
VISIBILITIES TO FALL TO LOW END IFR AT ALL THE SITES AS THE
HEAVIEST SNOW MOVES THROUGH. COULD BRIEFLY SEE LIFR VISIBILITIES
FIRST OVER THE WEST LATE THIS AFTERNOON THROUGH LATE EVENING AND
THEN AT KABR/KATY BETWEEN 02-08Z (COMBINATION OF THE HEAVY SNOW
AND BLOWING SNOW BEFORE WINDS DIMINISH). EXPECT VISIBILITIES TO
RAPIDLY IMPROVE OVER THE WEST AFTER MIDNIGHT AS THE SYSTEM SHIFTS
TO THE EAST (VFR CONDITIONS WEST BY MID MORNING)...ALTHOUGH MVFR
CONDITIONS WILL PREVAIL THROUGH SUNDAY MORNING OVER THE EAST.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY UNTIL 6 AM CST /5 AM MST/ SUNDAY FOR SDZ003-
     004-009-015-016-033>036-045-048-051.

     WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO NOON CST SUNDAY
     FOR SDZ005>008-010-011-017>023-037.

MN...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO NOON CST SUNDAY
     FOR MNZ039-046.

&&

$$

SHORT TERM...SRF
LONG TERM...TDK
AVIATION...SRF



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