000
FXUS63 KFSD 150952
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
355 AM CST SUN FEB 15 2009
.DISCUSSION...
SURFACE HIGH PRESSURE DEPICTED OVER THE EASTERN DAKOTAS THIS
MORNING. ALOFT...WEAK SHORT WAVE MOVING FROM WESTERN NEBRASKA INTO
CENTRAL SOUTH DAKOTA WILL ATTEMPT TO PRODUCE LIGHT PRECIPITATION BUT
WILL FIGHT THE DRY AIR IN THE LOW LEVELS. HAVE OPTED TO MENTION
FLURRIES IN AN ARC FROM KHON TO KSUX WHERE LOW LEVELS APPEAR TO
APPROACH SATURATION FOR A BRIEF PERIOD THIS MORNING. AS SURFACE
HIGH SHIFTS EAST INTO IOWA AND MINNESOTA...SOUTHERLY FLOW WILL KICK
IN ACROSS WESTERN CWA ALLOWING FOR SLIGHTLY BETTER MIXING
CONDITIONS THAN AREAS FURTHER EAST THAT WILL REMAIN SHROUDED IN
CLOUDS MUCH OF THE DAY UNDER THE INFLUENCE OF WEAK NEBULOUS FLOW.
UPPER LEVEL TROUGH OVER THE WESTERN US DIGS AND BEGINS TO SHIFT EAST
INDUCING LEE-SIDE CYCLOGENESIS. THIS CAUSES THE PRESSURE GRADIENT
TO INCREASE THROUGHOUT SUNDAY NIGHT INTO MONDAY ACROSS THE NORTHERN
PLAINS. WARM AIR BEGINS TO FILTER INTO WESTERN CWA ON MONDAY
YIELDING TEMPERATURES IN THE 40S. COOLER AND BREEZY CONDITIONS
EXPECTED FURTHER TO THE EAST. AS OF RIGHT NOW...IT APPEARS AS
THOUGH WINDS WILL BE SHY OF CRITERIA BUT POTENTIALLY NOT BY MUCH.
PRESSURE FALLS REALLY INCREASE THROUGHOUT THE DAY ESPECIALLY EAST OF
THE JAMES RIVER VALLEY. WITH TIGHTENING GRADIENT ALOFT CAUSING 925
WINDS TO INCREASE TO 30-35 KNOTS...WINDS WILL BECOME BREEZY HOWEVER
WARM AIR ADVECTION SHOULD COUNTER BALANCE MIXING AND PRESSURE FALLS
SOME.
MONDAY NIGHT LOW PRESSURE SYSTEM ORGANIZES OVER EASTERN COLORADO AND
MOVES INTO THE PLAINS ON TUESDAY. MODELS WAFFLING ON AMOUNT OF WARM
AIR AHEAD OF THIS SYSTEM. NAM COOLEST OF THE SOLUTIONS...WITH ECMWF
THE WARMEST. HAVE SIDED CLOSER TO THE GFS WHICH IS MIDDLE OF THE
ROAD FOR THE TIME BEING. WITH WARM AIR ALOFT...PRECIP TYPE APPEARS
TO BE AN ISSUE DURING THE AFTERNOON HOURS. FORTUNATELY...AIR IN THE
LOWER LEVELS IS RELATIVELY DRY...AND AS IT SATURATES FROM ALOFT IT
WET BULBS DOWN TO SNOW BY TUESDAY EVENING SO ANY MIXED PRECIP
APPEARS TO BE RELATIVELY SHORT LIVED. DYNAMICS APPEAR TO BE MORE
FOCUSED ACROSS SOUTHERN HALF OF FORECAST AREA TUESDAY NIGHT AS OPEN
UPPER LEVEL WAVE SLIDES ACROSS CENTRAL PLAINS.
SECOND STRONGER WAVE MOVES DOWN FROM THE NORTH LATE IN THE DAY ON
WEDNESDAY...HOWEVER...MOISTURE APPEARS TO BE A CONCERN AS COLD AIR
WRAPS IN BEHIND SURFACE LOW SHIFTING INTO THE GREAT LAKES REGION.
ANY PRECIP THAT DOES FALL DURING THE DAY ON WEDNESDAY WILL BE TOUGH
TO MEASURE AS STRONG NORTH WINDS WILL CREATE POTENTIAL FOR
BLOWING/DRIFTING SNOW. MODELS DISAGREEING ON STRENGTH OF COLD AIR ON
WEDNESDAY INTO WEDNESDAY NIGHT...BUT WITH STRONG COLD AIR ADVECTION
THROUGHOUT THE DAY WENT WITH FALLING TEMPERATURES WEDNESDAY AND A
HANDFUL OF SUB ZERO TEMPS WEDNESDAY NIGHT INTO THURSDAY MORNING OVER
SOUTHWEST MINNESOTA WHERE MODELS SUGGEST 925 HPA TEMPS WILL FALL TO
-15 TO -20 C. IN ADDITION...AS PREVIOUS FORECASTER POINTED OUT...ANY
FRESH SNOW COVER FROM TUESDAY NIGHT INTO WEDNESDAY WILL AID IN LOW
LEVEL COOLING.
&&
.AVIATION...
CONDS WL BE PRIMARILY VFR THRU THIS EVENING. THE ONLY CONCERN IS
THERE COULD BE SOME PATCHY MVFR CIGS TODAY ALONG AND WEST OF A
KHON...KMHE TO KYKN LINE. IN ADDITION...A FEW FLURRIES COULD FALL IN
THESE AREAS...ESP THIS MORNING. BUT ANY VIS REDUCTION DUE TO -AN
WOULD BE MINIMAL AND SHORT LIVED.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
BT/MJF
000
FXUS63 KFSD 150342
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
915 PM CST SAT FEB 14 2009
.DISCUSSION...
PRESENT SATELLITE IMAGES AND OBS INDICATING LIGHT SNOW OVER NORTH
CENTRAL NEBRASKA WITH RETURN FLOW ON BACKSIDE OF THE SURFACE HIGH
POSITIONED OVER THE UPPER MIDWEST. WHOLE AREA HAS BEEN PUSHING
SLOWLY TO THE NORTHEAST THROUGH THE EVENING...THOUGH ECHOES ARE
BECOMING INCREASINGLY WEAKER AS THEY MOVE INTO DRIER AIR TO THE
NORTHEAST. WITH THAT IN MIND...STILL THINK ONLY FLURRIES WARRANTED
FOR OUR ZONES ALONG THE MISSOURI RIVER FOR THE OVERNIGHT HOURS.
TEMPERATURES HAVE BEEN SLOW TO FALL OFF OVER OUR SOUTHWEST TONIGHT
WITH INCREASING MID LEVEL CLOUDS INTO THE AREA...AND AM SOMEWHAT
CONCERNED THAT LOWS MAY NOT GET QUITE AS COLD AS WE PRESENTLY HAVE
FORECASTED OVER THESE AREAS. AT THIS POINT...DO NOT THINK THEY WILL
BE SIGNIFICANTLY WARMER...SO WILL LEAVE ALONE FOR NOW. OTHERWISE
CURRENT FORECAST OK WITH MINOR UPDATES ALREADY OUT. /JM
&&
.AVIATION...
EXPECTING INCREASING CLOUDS FROM THE SOUTHWEST THROUGH THE NIGHT
WITH LOWERING CEILINGS...AND A FEW FLURRIES POSSIBLE IN AREAS ALONG
THE MISSOURI RIVER. ANTICIPATE VFR CONDITIONS THROUGH THE NIGHT
HOWEVER...WITH PRESENT OBS INDICATING CEILINGS IN THE RANGE OF 6 TO
9 KFT ACROSS THE REGION.
&&
.PREV DISCUSSION...
WE HAVE THE SAME PRBLM WE HAVE HAD ON TNGTS FCST THAT THE MODELS
HAVE BEEN SHOWING LAST CPL DAYS. IN WEAK UPPER FLOW WITH WEAK SHRT
WV MOVG EWD TO THE S OF AREA...MID LVL MOISTURE STILL POISED TO
INCREASE OVER AREA FROM THE W/SW. EVENTUALLY SOME MARGINAL LOW
CLDS...MAYBE A FEW 3-5K FT CIGS...MAY GET ADVECTED INTO THE MO RVR
AREA SW/SRN CWA. WITH THIS MOISTURE WILL COME A FEW AREAS OF LGT
SNOW AT MID LVLS...BUT DRYNESS OF LWR AIR MAKES LAST NGTS CHANGE TO
JUST FLRYS ACRS SRN EDGE OF FCST AREA LOOK GOOD SO WILL KEEP IT AT
THAT. A STRAY FLAKE CUD REACH THE GROUND FRTHR N BUT DOESNT LOOK
WORTH MENTNG NOW. IT ADDS UP TO A GNRL INCRS IN CLDS...BUT WHETHER
THEY BECOME SEMISOLID OR THIN OUT LIKE TDAS BATCH IS A CLOSE CALL.
CLD CVR WILL ALSO AFFECT TEMPS AND WITH LGT WNDS VERY SLOW TO PICK
UP...WILL PRBLY ALLOW FOR A NICE LTL COOLING ERY THIS EVE AHEAD OF
MOST OF THE CLD INCRS. WILL STILL ALLOW FOR GUIDNCE TO BE JUST A TAD
TOO COOL ON TNGTS LOWS WITH LATER CLD INCRS. JUST A QUIET NGT WITH
SVRL MINOR DETAILS TO WATCH.
INCRG SSELY FLOW OF MODERATING AIR MOVG EWD OVER CWA FM SUN THRU
MON...WITH MAIN WARMING AND MIXING EXPCD IN SWRN CWA. LACK OF SNOW
COVER IN CWA AND INCRG SUN ANGLE SHOULD HELP OUT THE MODERATION NEXT
COUPLE FEW DAYS...SO UPPD THE TEMPS FM PREV FCST. LOWS FOR SUN NGT
ESP EAST OF I29 SHOULD BE ACHIEVED AROUND MIDN OR SO BEFORE THE SLY
FLOW KICKS IN. MON SHOULD BE ON THE WINDY SIDE WITH BRISK SLY WINDS
DVLPG AHEAD OF TROUGH OUT WEST. THIS SYSTEM IS A POTENTIAL SLEEPER
DEPENDING ON HOW MUCH THE NRN STREAM PHASES WITH STG SRN WAVE OUT
OF CALIFORNIA. EXPCT SOME PRETTY GOOD FRONTOGENESIS DVLPG W TO E IN
CWA LATE TUES THRU TUES NGT AND WITH EXPCD SELY INFLOW OF MOISTURE...
COULD BE A GOOD BAND OF PSBLY HEAVY SNOW ESP I90 NORTH TUES NGT...
BUT DVLPG SEWD THRU SRN CWA LATE TUES NGT AND WED MRNG. NEW ECMWF
SEEMS TO HAVE TOO MUCH EMPHASIS ON NRN STREAM WITH MAIN WAVE MOVG
SEWD OVER CWA WED AFTN...BUT KEPT THE POPS GOING ALL DAY WED. WENT
DRY AND COLD FM WED NGT THRU SAT AS A COLDER GENERALLY NWLY FLOW
DOMINATES AND THERE COULD BE NEW SNOW COVER IN THE AREA.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
RYRHOLM/WILLIAMS
000
FXUS63 KFSD 142131
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
330 PM CST SAT FEB 14 2009
.DISCUSSION...
WE HAVE THE SAME PRBLM WE HAVE HAD ON TNGTS FCST THAT THE MODELS
HAVE BEEN SHOWING LAST CPL DAYS. IN WEAK UPPER FLOW WITH WEAK SHRT
WV MOVG EWD TO THE S OF AREA...MID LVL MOISTURE STILL POISED TO
INCREASE OVER AREA FROM THE W/SW. EVENTUALLY SOME MARGINAL LOW
CLDS...MAYBE A FEW 3-5K FT CIGS...MAY GET ADVECTED INTO THE MO RVR
AREA SW/SRN CWA. WITH THIS MOISTURE WILL COME A FEW AREAS OF LGT
SNOW AT MID LVLS...BUT DRYNESS OF LWR AIR MAKES LAST NGTS CHANGE TO
JUST FLRYS ACRS SRN EDGE OF FCST AREA LOOK GOOD SO WILL KEEP IT AT
THAT. A STRAY FLAKE CUD REACH THE GROUND FRTHR N BUT DOESNT LOOK
WORTH MENTNG NOW. IT ADDS UP TO A GNRL INCRS IN CLDS...BUT WHETHER
THEY BECOME SEMISOLID OR THIN OUT LIKE TDAS BATCH IS A CLOSE CALL.
CLD CVR WILL ALSO AFFECT TEMPS AND WITH LGT WNDS VERY SLOW TO PICK
UP...WILL PRBLY ALLOW FOR A NICE LTL COOLING ERY THIS EVE AHEAD OF
MOST OF THE CLD INCRS. WILL STILL ALLOW FOR GUIDNCE TO BE JUST A TAD
TOO COOL ON TNGTS LOWS WITH LATER CLD INCRS. JUST A QUIET NGT WITH
SVRL MINOR DETAILS TO WATCH.
INCRG SSELY FLOW OF MODERATING AIR MOVG EWD OVER CWA FM SUN THRU
MON...WITH MAIN WARMING AND MIXING EXPCD IN SWRN CWA. LACK OF SNOW
COVER IN CWA AND INCRG SUN ANGLE SHOULD HELP OUT THE MODERATION NEXT
COUPLE FEW DAYS...SO UPPD THE TEMPS FM PREV FCST. LOWS FOR SUN NGT
ESP EAST OF I29 SHOULD BE ACHIEVED AROUND MIDN OR SO BEFORE THE SLY
FLOW KICKS IN. MON SHOULD BE ON THE WINDY SIDE WITH BRISK SLY WINDS
DVLPG AHEAD OF TROUGH OUT WEST. THIS SYSTEM IS A POTENTIAL SLEEPER
DEPENDING ON HOW MUCH THE NRN STREAM PHASES WITH STG SRN WAVE OUT
OF CALIFORNIA. EXPCT SOME PRETTY GOOD FRONTOGENESIS DVLPG W TO E IN
CWA LATE TUES THRU TUES NGT AND WITH EXPCD SELY INFLOW OF MOISTURE...
COULD BE A GOOD BAND OF PSBLY HEAVY SNOW ESP I90 NORTH TUES NGT...
BUT DVLPG SEWD THRU SRN CWA LATE TUES NGT AND WED MRNG. NEW ECMWF
SEEMS TO HAVE TOO MUCH EMPHASIS ON NRN STREAM WITH MAIN WAVE MOVG
SEWD OVER CWA WED AFTN...BUT KEPT THE POPS GOING ALL DAY WED. WENT
DRY AND COLD FM WED NGT THRU SAT AS A COLDER GENERALLY NWLY FLOW
DOMINATES AND THERE COULD BE NEW SNOW COVER IN THE AREA.
&&
.AVIATION...
VFR SHUD CONT MOST OF FCST AREA THRU 15/18Z. A FEW MVFR CIGS 2-3K FT
MAY SPREAD INTO MO RVR AREA AS FAR E AS YKN 15/06Z-12Z...BUT THIS IS
UNCERTAIN GIVE RELATIVELY DRY LO LVL AIR ARND. AT THIS TIME NO VSBY
REDUCTIONS EXPECTED WITH A FEW FLAKES PSBL FAR SRN FCST AREA THRU
15/18Z.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
RYRHOLM/WILLIAMS
000
FXUS63 KFSD 141637
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1035 AM CST SAT FEB 14 2009
.DISCUSSION...
OPAQUE TO SEMITRANSPARENT CLDS ARND THE LOW CLD/MID CLD INTERFACE
LVL SPREADIGN ACRS AREA AND THIS WILL CONT TDA WITH MORE CLDS
ARRIVING AS FCST BY EVENING. SOME OF THESE WILL THIN OUT A LTL BUT
UPDATED FOR A FEW MORE CLDS. LGT WNDS WILL CONT...AND FOR NOW FEEL
TEMPS SHUD BE ABLE TO REACH CLOSE TO ERYR FCST HIGHS.
&&
.AVIATION...
VFR SHUD CONT MOST OF FCST AREA THRU 15/18Z. HWVR A FEW MVFR CIGS
2-3K FT MAY SPREAD INTO MO RVR AREA AS FAR E AS YKN 15/06Z-12Z.
&&
.PREV DISCUSSION...
RELATIVELY SEASONABLE TEMPERATURES EXPECTED THIS WEEKEND AS CANADIAN
HIGH PRESSURE SETTLES OVER THE DAKOTAS. BATCH OF MID CLOUDS
ASSOCIATED WITH MESSY ZONAL FLOW ACROSS CENTRAL AND WESTERN SOUTH
DAKOTA WILL SHIFT EAST TODAY RESULTING IN OVERALL INCREASE IN CLOUD
COVER. THESE CLOUDS AND LIGHT NORTHERLY FLOW WILL LIMIT MIXING
SLIGHTLY. COLD AIR ADVECTION ACROSS EASTERN HALF OF FORECAST AREA
WILL ALSO AFFECT HIGHS AND HAVE KEPT TEMPERATURES TOWARDS THE COOL
SIDE OF GUIDANCE IN THE EAST.
RELATIVELY LIGHT FLOW CONTINUES TONIGHT AS HIGH PRESSURE CONTINUES
TO SHIFT EAST. WEAK RETURN FLOW BEGINS TO DEVELOP ON BACKSIDE OF
HIGH WITH WEAK ISENTROPIC LIFT DEVELOPING IN THE MID LEVELS. LIFT IS
RELATIVELY WEAK AND LOWER LEVEL SUBSIDENCE REMAINS. NAM DEVELOPS
LIGHT PRECIPITATION ALONG SOUTHERN EDGE OF CWA WHILE GFS REMAINS
DRY. GIVEN THE FORCING REMAINS RELATIVELY WEAK...CUT POPS BACK TO A
CHANCE OF FLURRIES WHICH STILL MAY BE OVER DONE.
SOUTHERLY FLOW INCREASES SUNDAY NIGHT INTO MONDAY AS LARGE UPPER
LEVEL TROUGH DEVELOPS OVER THE WESTERN US. SECOND NEARLY STATIONARY
UPPER LEVEL LOW OVER MANITOBA AND WESTERN ONTARIO. COLD FRONT
ASSOCIATED WITH NEARLY STATIONARY SYSTEM TO THE NORTH BEGINS TO
SHIFT THROUGH THE FORECAST AREA MONDAY NIGHT BUT GETS HUNG UP AS
WESTERN UPPER LEVEL TROUGH BEGINS TO BECOME DISORGANIZED AND SHIFTS
EAST INT THE PLAINS. THIS RESULTS IN FAIRLY RAPID SURFACE
CYCLOGENESIS OVER NORTHEASTERN COLORADO MOVING INTO THE PLAINS
TUESDAY NIGHT INTO WEDNESDAY. AS THIS WAVE MOVES INTO THE PLAINS
BEST CHANCES OF PRECIPITATION APPEAR ACROSS SOUTHERN HALF OF
FORECAST AREA WITH MIDLEVEL BOUNDARY HANGING ALONG AND SOUTH OF
I-90. UPPER LEVEL SUPPORT FOR THIS SYSTEM QUITE GOOD WITH 150+ KNOT
UPPER LEVEL JET STREAK EJECTING INTO THE CENTRAL PLAINS WITH
FORECAST AREA LOCATED IN LEFT FRONT. HAVE INCREASED POPS TUESDAY
NIGHT TO JUST SHY OF LIKELY ALONG AND SOUTH OF A LINE FROM
KYKN-KFSD-KMWM.
AS LOW SHIFTS EAST MUCH COOLER PATTER SETS UP AS SEMI PERMANENT
UPPER LEVEL TROUGH DEVELOPS OVER EASTERN US. THIS PLACES FORECAST
AREA UNDER THE INFLUENCE OF NORTHWEST FLOW. MODELS ADVERTISING -15
TO -20 C AIR AT 925 MB WORKING INTO FORECAST AREA. COOLED
TEMPERATURES SIGNIFICANTLY ON WEDNESDAY INTO THURSDAY...THOUGH DAY
SHIFT WILL LIKELY HAVE TO CONTINUE THE TREND.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
WILLIAMS
000
FXUS63 KFSD 140957
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
400 AM CST SAT FEB 14 2009
.DISCUSSION...
RELATIVELY SEASONABLE TEMPERATURES EXPECTED THIS WEEKEND AS CANADIAN
HIGH PRESSURE SETTLES OVER THE DAKOTAS. BATCH OF MID CLOUDS
ASSOCIATED WITH MESSY ZONAL FLOW ACROSS CENTRAL AND WESTERN SOUTH
DAKOTA WILL SHIFT EAST TODAY RESULTING IN OVERALL INCREASE IN CLOUD
COVER. THESE CLOUDS AND LIGHT NORTHERLY FLOW WILL LIMIT MIXING
SLIGHTLY. COLD AIR ADVECTION ACROSS EASTERN HALF OF FORECAST AREA
WILL ALSO AFFECT HIGHS AND HAVE KEPT TEMPERATURES TOWARDS THE COOL
SIDE OF GUIDANCE IN THE EAST.
RELATIVELY LIGHT FLOW CONTINUES TONIGHT AS HIGH PRESSURE CONTINUES
TO SHIFT EAST. WEAK RETURN FLOW BEGINS TO DEVELOP ON BACKSIDE OF
HIGH WITH WEAK ISENTROPIC LIFT DEVELOPING IN THE MID LEVELS. LIFT IS
RELATIVELY WEAK AND LOWER LEVEL SUBSIDENCE REMAINS. NAM DEVELOPS
LIGHT PRECIPITATION ALONG SOUTHERN EDGE OF CWA WHILE GFS REMAINS
DRY. GIVEN THE FORCING REMAINS RELATIVELY WEAK...CUT POPS BACK TO A
CHANCE OF FLURRIES WHICH STILL MAY BE OVER DONE.
SOUTHERLY FLOW INCREASES SUNDAY NIGHT INTO MONDAY AS LARGE UPPER
LEVEL TROUGH DEVELOPS OVER THE WESTERN US. SECOND NEARLY STATIONARY
UPPER LEVEL LOW OVER MANITOBA AND WESTERN ONTARIO. COLD FRONT
ASSOCIATED WITH NEARLY STATIONARY SYSTEM TO THE NORTH BEGINS TO
SHIFT THROUGH THE FORECAST AREA MONDAY NIGHT BUT GETS HUNG UP AS
WESTERN UPPER LEVEL TROUGH BEGINS TO BECOME DISORGANIZED AND SHIFTS
EAST INT THE PLAINS. THIS RESULTS IN FAIRLY RAPID SURFACE
CYCLOGENESIS OVER NORTHEASTERN COLORADO MOVING INTO THE PLAINS
TUESDAY NIGHT INTO WEDNESDAY. AS THIS WAVE MOVES INTO THE PLAINS
BEST CHANCES OF PRECIPITATION APPEAR ACROSS SOUTHERN HALF OF
FORECAST AREA WITH MIDLEVEL BOUNDARY HANGING ALONG AND SOUTH OF
I-90. UPPER LEVEL SUPPORT FOR THIS SYSTEM QUITE GOOD WITH 150+ KNOT
UPPER LEVEL JET STREAK EJECTING INTO THE CENTRAL PLAINS WITH
FORECAST AREA LOCATED IN LEFT FRONT. HAVE INCREASED POPS TUESDAY
NIGHT TO JUST SHY OF LIKELY ALONG AND SOUTH OF A LINE FROM
KYKN-KFSD-KMWM.
AS LOW SHIFTS EAST MUCH COOLER PATTER SETS UP AS SEMI PERMANENT
UPPER LEVEL TROUGH DEVELOPS OVER EASTERN US. THIS PLACES FORECAST
AREA UNDER THE INFLUENCE OF NORTHWEST FLOW. MODELS ADVERTISING -15
TO -20 C AIR AT 925 MB WORKING INTO FORECAST AREA. COOLED
TEMPERATURES SIGNIFICANTLY ON WEDNESDAY INTO THURSDAY...THOUGH DAY
SHIFT WILL LIKELY HAVE TO CONTINUE THE TREND.
&&
.AVIATION...
CONDS WL LIKELY STAY VFR THRU TODAY AND THIS EVENING.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
BT/MJF
000
FXUS63 KFSD 140238
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
830 PM CST FRI FEB 13 2009
.DISCUSSION...
HIGH PRESSURE CONTINUES TO BUILD INTO THE REGION THIS EVENING WITH
LATEST SAT IMAGES/OBS SHOWING ONLY A FEW MID AND HIGH CLOUDS
STREAMING ACROSS THE CWA. OTHER THAN SOME MINOR UPDATES FOR REAL
TIME TRENDS...PRESENT FORECAST LOOKING TO BE ON TRACK. MINOR UPDATES
ALREADY OUT. /JM
&&
.AVIATION...
VFR THROUGH TONIGHT.
&&
.PREV DISCUSSION...
DRY AIR IN THE LOW LEVELS OVERTOOK EVERYTHING AND SCOURED OUT ANY
MOISTURE IN THE MID LEVELS THAT TRIED TO FALL THIS AFTERNOON. EXPECT
THIS TREND TO CONTINUE AS THE UPPER LEVEL DISTURBANCE AND MID LEVEL
THERMAL BAND BOTH SHIFT EAST SOUTHEAST TONIGHT. HAVE REMOVED POPS
FROM NORTHWEST IOWA WITH SUBSIDENCE EXPECTED TO TAKE CONTROL. LIGHT
NORTH WINDS WILL DECREASE THROUGH THE NIGHT AS HIGH PRESSURE BUILDS
IN FROM THE NORTHWEST WITH A SLIGHT DECREASE IN CLOUDS. THIS WILL
LEAD TOWARDS SOME CHILLY LOWS...RANGING FROM 5 TO 10 ABOVE NORTH TO
10 TO 15 SOUTH.
SKY COVER WILL VARY A BIT SAT AS PATCHY MID LVL MOISTURE IS FORCED
EWD OVER AREA IN WEAKENING FLOW. NO EXCITEMENT ON TEMPS AS A BLEND
OF GUIDNCE SHOULD WORK FOR HIGHS SINCE THERE IS LTL SNOW
COVER...JUST THAT LTL BIT ON THE NRN/MAINLY NERN/ EDGE OF FCST AREA.
MODELS ARE PRETTY CONSISTENT ON APPCHG SHORT WAVE FOR SAT NGT INTO
SUN MRNG. WAVE MOVES MAINLY S OF AREA AND WEAKENS AS IT ARRIVES. A
FITTING SCENARIO FOR KEEPING JUST 20 PCT CHC OF LGT SNOW ACRS FAR
SRN FCST AREA DESPITE ENUF MID LVL MOISTURE TO INCREASE CLOUDS
EVERYWHERE.
THIS WEAK SYS WILL PASS BY SUN AFTN. MON THEN LOOKS LIKE A RELTVLY
MILD DAY AS EVEN MID LEVELS DRY OUT AND SUNSHINE BRINGS TEMPS UP TO
CLOSE TO OR ABV FREEZING. THIS IS PSBL IN PART BECAUSE APPCHG SYS
FOR TUE AND TUE NIGHT LOOKS GOOD BUT SLOWER THAN IT DID A DAY OR SO
AGO.
THIS FIRST PLAYER IN THIS SYS WILL BE THE CDFNT MODELS SHOW MOVG SWD
ACROSS AREA MON NGT AND ERY TUE TO SET UP A DECENT THERMAL RIBBON
JUST S OF FCST AREA TO HELP WITH LIFT AND PCPN EFFECIENCY. ALL
MODELS LOOKED AT HAVE PRETTY MUCH TARGETED OUR FCST AREA FOR A
DECENT CHC OF SNOW TUE AND TUE NGT...MAINLY TUE NGT IN ERN CWA.
MODEL UNCERTAINTIES AND TIMING QUESTIONS SUCH AS WE HAVE ALREADY
HAVE HAD WITH THIS SYS PREVENT ME FROM GOING LIKELY FOR ANY 12 HR
PD...BUT 50 PCT SEEMS REASNBL FOR NOW. EVEN IF THERMAL SUPPORT IS
WEAKER THAN ENVISIONED...EXPECT A PRETTY WDSPRD BAND OF LIGHT SNOW
TO DVLP. TEMPS MEANWHILE OF COURSE WILL COOL BACK FROM MONDAY BEHIND
CDFNT...NOT SHARPLY THO AS WE ARE IN A PATTERN RIGHT NOW PROHIBITIVE
OF TEMP EXTREMES EITHER WAY.
AFTER SYS MOVES OUT BY ERY WED...THE REST OF WED THRU FRI PD LOOKS
BLAND WITH SEASNBLY COLD TEMPS AND NO PCPN. GFS NOW COING WITH ECMWF
IDEA OF DVLPG NWRLY FLOW WHICH U CUD TRY TO SQUEEZE A FEW FLRYS OUT
OF BUT LTL ELSE.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
08/WILLIAMS
000
FXUS63 KFSD 132123
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
325 PM CST FRI FEB 13 2009
.DISCUSSION...
DRY AIR IN THE LOW LEVELS OVERTOOK EVERYTHING AND SCOURED OUT ANY
MOISTURE IN THE MID LEVELS THAT TRIED TO FALL THIS AFTERNOON. EXPECT
THIS TREND TO CONTINUE AS THE UPPER LEVEL DISTURBANCE AND MID LEVEL
THERMAL BAND BOTH SHIFT EAST SOUTHEAST TONIGHT. HAVE REMOVED POPS
FROM NORTHWEST IOWA WITH SUBSIDENCE EXPECTED TO TAKE CONTROL. LIGHT
NORTH WINDS WILL DECREASE THROUGH THE NIGHT AS HIGH PRESSURE BUILDS
IN FROM THE NORTHWEST WITH A SLIGHT DECREASE IN CLOUDS. THIS WILL
LEAD TOWARDS SOME CHILLY LOWS...RANGING FROM 5 TO 10 ABOVE NORTH TO
10 TO 15 SOUTH.
SKY COVER WILL VARY A BIT SAT AS PATCHY MID LVL MOISTURE IS FORCED
EWD OVER AREA IN WEAKENING FLOW. NO EXCITEMENT ON TEMPS AS A BLEND
OF GUIDNCE SHOULD WORK FOR HIGHS SINCE THERE IS LTL SNOW
COVER...JUST THAT LTL BIT ON THE NRN/MAINLY NERN/ EDGE OF FCST AREA.
MODELS ARE PRETTY CONSISTENT ON APPCHG SHORT WAVE FOR SAT NGT INTO
SUN MRNG. WAVE MOVES MAINLY S OF AREA AND WEAKENS AS IT ARRIVES. A
FITTING SCENARIO FOR KEEPING JUST 20 PCT CHC OF LGT SNOW ACRS FAR
SRN FCST AREA DESPITE ENUF MID LVL MOISTURE TO INCREASE CLOUDS
EVERYWHERE.
THIS WEAK SYS WILL PASS BY SUN AFTN. MON THEN LOOKS LIKE A RELTVLY
MILD DAY AS EVEN MID LEVELS DRY OUT AND SUNSHINE BRINGS TEMPS UP TO
CLOSE TO OR ABV FREEZING. THIS IS PSBL IN PART BECAUSE APPCHG SYS
FOR TUE AND TUE NIGHT LOOKS GOOD BUT SLOWER THAN IT DID A DAY OR SO
AGO.
THIS FIRST PLAYER IN THIS SYS WILL BE THE CDFNT MODELS SHOW MOVG SWD
ACROSS AREA MON NGT AND ERY TUE TO SET UP A DECENT THERMAL RIBBON
JUST S OF FCST AREA TO HELP WITH LIFT AND PCPN EFFECIENCY. ALL
MODELS LOOKED AT HAVE PRETTY MUCH TARGETED OUR FCST AREA FOR A
DECENT CHC OF SNOW TUE AND TUE NGT...MAINLY TUE NGT IN ERN CWA.
MODEL UNCERTAINTIES AND TIMING QUESTIONS SUCH AS WE HAVE ALREADY
HAVE HAD WITH THIS SYS PREVENT ME FROM GOING LIKELY FOR ANY 12 HR
PD...BUT 50 PCT SEEMS REASNBL FOR NOW. EVEN IF THERMAL SUPPORT IS
WEAKER THAN ENVISIONED...EXPECT A PRETTY WDSPRD BAND OF LIGHT SNOW
TO DVLP. TEMPS MEANWHILE OF COURSE WILL COOL BACK FROM MONDAY BEHIND
CDFNT...NOT SHARPLY THO AS WE ARE IN A PATTERN RIGHT NOW PROHIBITIVE
OF TEMP EXTREMES EITHER WAY.
AFTER SYS MOVES OUT BY ERY WED...THE REST OF WED THRU FRI PD LOOKS
BLAND WITH SEASNBLY COLD TEMPS AND NO PCPN. GFS NOW COING WITH ECMWF
IDEA OF DVLPG NWRLY FLOW WHICH U CUD TRY TO SQUEEZE A FEW FLRYS OUT
OF BUT LTL ELSE.
&&
.AVIATION...
VFR THROUGH TONIGHT.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
08/WILLIAMS
000
FXUS63 KFSD 131536 CCA
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
936 AM CST FRI FEB 13 2009
.DISCUSSION...
BAND OF MODERATE TO HEAVY SNOW MOVING INTO CENTRAL AND NORTHERN
PARTS OF NEBRASKA PRETTY MUCH WHERE IT SHOULD BE. THIS IS CLOSELY
FOLLOWING THE 1.5 PV ANOMALY AND COLLOCATED CLOSEST TO THE 700-650MB
FRONT. AS EXPECTED...MODELS HAD TROUBLE FIGURING THIS OUT YESTERDAY
AND WERE TRYING TO SATURATE CLOSER TO THE 800-850MB WHICH IS ALMOST
ALWAYS TOO LOW FOR A BANDED EVENT. THE 700-650MB LAYER IS ALSO WHERE
THE BETTER INSTABILITY IS AT...SO EXPECT SNOW PRODUCTION TO CONTINUE
TO FOLLOW THIS ELEVATION.
SO...THIS MEANS THAT OUR SOUTHERN AREA MAY HAVE TROUBLE GETTING MUCH
IN THE WAY OF MEASURABLE SNOW...WITH THE CURRENT HALF AN INCH OR SO
AROUND SUX LOOKING PRETTY GOOD. COOL...DRY AIR WILL CONTINUE TO
FILTER IN FROM THE NORTH SO THAT ANY WEAKER FORCING AND MOISTURE IN
THE MID LEVELS WILL RUN INTO ISSUES SATURATING TO THE SURFACE.
OTHERWISE...TEMPERATURES NOT TOO BAD BUT MAY END UP A BIT ON THE
COOL SIDE.
&&
.AVIATION...
MAINLY VFR THROUGH TONIGHT. IF SUX CAN SNEAK INTO A SNOW
BAND...CEILINGS AND VISIBILITIES COULD BRIEFLY FALL INTO A HIGHER
END MVFR.
&&
.PREV DISCUSSION...
IT APPEARS THAT THE BULK OF THE SNOW WITH SYS MOVING ACRS CNTRL
PLAINS WL REMAIN S OF CWA. THERE WILL BE A SHARP CUTOFF IN PRECIP
WITH VERY DRY AIR BLO H85 ACRS MOST OF CWA. PLENTY OF MID LEVEL
MOISTURE WL MAKE IT AS FAR N AS I90 BUT WILL HAVE A HARD TIME
SATURATING LOW LEVELS. WITH S/W A LTL FURTHER SOUTH THAN PROGGED
FELL ANY SNOW ACCUM WL REMAIN S OF A SUX-SLB LINE AND THIS MAINLY
DURING THE AFTN HOURS. EVEN THIS WL AMOUNT TO AN INCH OR LESS.
REST OF CWA WL SEE MID AND HIGH CLOUDS SPREAD NE ACRS THE CWA AND
WITH COLDER LOW LEVEL NNELY FLOW...TEMPS WL NOT BE AS WARM AS THU
AND PBLY CLOSE TO NORM.
SRN SYS WL PULL AWAY THIS EVE WITH SOME CLEARING EXPECTED FOLLOWED
BY SOME MID LEVEL MOISTURE AND WAA SPREADING W TO E LATER TONIGHT
INTO SAT. SO THIS WL LIKELY KEEP TEMPS FM FALLING OFF TO MUCH
TONIGHT...ESPEC WRN CWA AND ALSO WL KEEP TEMPS AT OR SLIGHTLY BLO
NORM ON SAT.
DID KEEP CHC OF S- ACRS FAR SRN CWA LATE SAT NITE AS SUN MORN WITH
S/W MOVING EWD ACRS NEB. NOT MUCH FORCING SO ANY SNOW WL LIKELY BE
LESS THAN ONE INCH. CLOUD COVER WL BE WDSPRD SAT NITE INTO SUN AND
WL KEEP TEMPS FM FALLING TOO FAR OR RISING TOO MUCH WITH LOW LEVEL
COLD AIR REMAINING IN PLACE.
WRMFNT WL LIFT INTO NRN CWA ON MON BUT WAA WL NOT BE THAT STRONG AND
WITH SSELY LOW LEVEL FLOW...WL NOT MIX OUT THAT WELL. SO ONLY EXPECT
TEMPS TO BE A FEW DEG ABOVE NORM S AND NR NORM N.
STILL LOOKING LIKE A DECENT POT FOR SNOW TUE AFTN INTO WED MORN AS
S/W DIGS ACRS SD/NEB. THIS SYS CUD BE STRONGER THAN PROG ESPEC WITH
DIGGING OF S/W WHICH ALL MODELS CONT TO PROG. WUD BE AN EFFICIENT
SYS WITH THE POTENTIAL TO PRODUCE MODERATE SNOW AMOUNTS.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
000
FXUS63 KFSD 131534
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
933 AM CST FRI FEB 13 2009
.DISCUSSION...
BAND OF MODERATE TO HEAVY SNOW MOVING INTO CENTRAL AND NORTHERN
PARTS OF NEBRASKA PRETTY MUCH WHERE IT SHOULD BE. THIS IS CLOSELY
FOLLOWING THE 1.5 PV ANOMALY AND COLLOCATED CLOSEST TO THE 700-650MB
FRONT. AS EXPECTED...MODELS HAD TROUBLE FIGURING THIS OUT YESTERDAY
AND WERE TRYING TO SATURATE CLOSER TO THE 800-850MB WHICH IS ALMOST
ALWAYS TO LOW FOR A BANDED EVENT. THE 700-650MB LAYER IS ALSO WHERE
THE BETTER INSTABILITY IS AT...SO EXPECT SNOW PRODUCTION TO CONTINUE
TO FOLLOW THIS ELEVATION.
SO...THIS MEANS THAT OUR SOUTHERN AREA MAY HAVE TROUBLE GETTING MUCH
IN THE WAY OF MEASURABLE SNOW...WITH THE CURRENT HALF AN INCH OR SO
AROUND SUX LOOKING PRETTY GOOD. COOL...DRY AIR WILL CONTINUE TO
FILTER IN FROM THE NORTH SO THAT AN WEAKER FORCING AND MOISTURE IN
THE MID LEVELS WILL RUN INTO ISSUES SATURATING TO THE SURFACE.
OTHERWISE...TEMPERATURES NOT TOO BAD BUT MAY END UP A BIT ON THE
COOL SIDE.
&&
.AVIATION...
MAINLY VFR THROUGH TONIGHT. IF SUX CAN SNEAK INTO A SNOW
BAND...CEILINGS AND VISIBILITIES COULD BRIEFLY FALL INTO A HIGHER
END MVFR.
&&
.PREV DISCUSSION...
IT APPEARS THAT THE BULK OF THE SNOW WITH SYS MOVING ACRS CNTRL
PLAINS WL REMAIN S OF CWA. THERE WILL BE A SHARP CUTOFF IN PRECIP
WITH VERY DRY AIR BLO H85 ACRS MOST OF CWA. PLENTY OF MID LEVEL
MOISTURE WL MAKE IT AS FAR N AS I90 BUT WILL HAVE A HARD TIME
SATURATING LOW LEVELS. WITH S/W A LTL FURTHER SOUTH THAN PROGGED
FELL ANY SNOW ACCUM WL REMAIN S OF A SUX-SLB LINE AND THIS MAINLY
DURING THE AFTN HOURS. EVEN THIS WL AMOUNT TO AN INCH OR LESS.
REST OF CWA WL SEE MID AND HIGH CLOUDS SPREAD NE ACRS THE CWA AND
WITH COLDER LOW LEVEL NNELY FLOW...TEMPS WL NOT BE AS WARM AS THU
AND PBLY CLOSE TO NORM.
SRN SYS WL PULL AWAY THIS EVE WITH SOME CLEARING EXPECTED FOLLOWED
BY SOME MID LEVEL MOISTURE AND WAA SPREADING W TO E LATER TONIGHT
INTO SAT. SO THIS WL LIKELY KEEP TEMPS FM FALLING OFF TO MUCH
TONIGHT...ESPEC WRN CWA AND ALSO WL KEEP TEMPS AT OR SLIGHTLY BLO
NORM ON SAT.
DID KEEP CHC OF S- ACRS FAR SRN CWA LATE SAT NITE AS SUN MORN WITH
S/W MOVING EWD ACRS NEB. NOT MUCH FORCING SO ANY SNOW WL LIKELY BE
LESS THAN ONE INCH. CLOUD COVER WL BE WDSPRD SAT NITE INTO SUN AND
WL KEEP TEMPS FM FALLING TOO FAR OR RISING TOO MUCH WITH LOW LEVEL
COLD AIR REMAINING IN PLACE.
WRMFNT WL LIFT INTO NRN CWA ON MON BUT WAA WL NOT BE THAT STRONG AND
WITH SSELY LOW LEVEL FLOW...WL NOT MIX OUT THAT WELL. SO ONLY EXPECT
TEMPS TO BE A FEW DEG ABOVE NORM S AND NR NORM N.
STILL LOOKING LIKE A DECENT POT FOR SNOW TUE AFTN INTO WED MORN AS
S/W DIGS ACRS SD/NEB. THIS SYS CUD BE STRONGER THAN PROG ESPEC WITH
DIGGING OF S/W WHICH ALL MODELS CONT TO PROG. WUD BE AN EFFICIENT
SYS WITH THE POTENTIAL TO PRODUCE MODERATE SNOW AMOUNTS.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
000
FXUS63 KFSD 130925
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
325 AM CST FRI FEB 13 2009
.DISCUSSION...
IT APPEARS THAT THE BULK OF THE SNOW WITH SYS MOVING ACRS CNTRL
PLAINS WL REMAIN S OF CWA. THERE WILL BE A SHARP CUTOFF IN PRECIP
WITH VERY DRY AIR BLO H85 ACRS MOST OF CWA. PLENTY OF MID LEVEL
MOISTURE WL MAKE IT AS FAR N AS I90 BUT WILL HAVE A HARD TIME
SATURATING LOW LEVELS. WITH S/W A LTL FURTHER SOUTH THAN PROGGED
FELL ANY SNOW ACCUM WL REMAIN S OF A SUX-SLB LINE AND THIS MAINLY
DURING THE AFTN HOURS. EVEN THIS WL AMOUNT TO AN INCH OR LESS.
REST OF CWA WL SEE MID AND HIGH CLOUDS SPREAD NE ACRS THE CWA AND
WITH COLDER LOW LEVEL NNELY FLOW...TEMPS WL NOT BE AS WARM AS THU
AND PBLY CLOSE TO NORM.
SRN SYS WL PULL AWAY THIS EVE WITH SOME CLEARING EXPECTED FOLLOWED
BY SOME MID LEVEL MOISTURE AND WAA SPREADING W TO E LATER TONIGHT
INTO SAT. SO THIS WL LIKELY KEEP TEMPS FM FALLING OFF TO MUCH
TONIGHT...ESPEC WRN CWA AND ALSO WL KEEP TEMPS AT OR SLIGHTLY BLO
NORM ON SAT.
DID KEEP CHC OF S- ACRS FAR SRN CWA LATE SAT NITE AS SUN MORN WITH
S/W MOVING EWD ACRS NEB. NOT MUCH FORCING SO ANY SNOW WL LIKELY BE
LESS THAN ONE INCH. CLOUD COVER WL BE WDSPRD SAT NITE INTO SUN AND
WL KEEP TEMPS FM FALLING TOO FAR OR RISING TOO MUCH WITH LOW LEVEL
COLD AIR REMAINING IN PLACE.
WRMFNT WL LIFT INTO NRN CWA ON MON BUT WAA WL NOT BE THAT STRONG AND
WITH SSELY LOW LEVEL FLOW...WL NOT MIX OUT THAT WELL. SO ONLY EXPECT
TEMPS TO BE A FEW DEG ABOVE NORM S AND NR NORM N.
STILL LOOKING LIKE A DECENT POT FOR SNOW TUE AFTN INTO WED MORN AS
S/W DIGS ACRS SD/NEB. THIS SYS CUD BE STRONGER THAN PROG ESPEC WITH
DIGGING OF S/W WHICH ALL MODELS CONT TO PROG. WUD BE AN EFFICIENT
SYS WITH THE POTENTIAL TO PRODUCE MODERATE SNOW AMOUNTS.
&&
.AVIATION...
AN AREA OF LOW PRESSURE WILL MOVE FROM EASTERN COLORADO INTO THE
CENTRAL PLAINS TODAY. A BATCH OF MID AND HIGH CLOUDS WILL SPREAD
ACROSS THE SOUTHERN HALF OF SOUTH DAKOTA...INTO SOUTHWEST MINNESOTA
AND NORTHWEST IOWA. FURTHER TO THE SOUTH NEAR KSUX...COULD SEE SOME
BRIEF MVFR CONDITIONS THIS AFTERNOON AS LIGHT SNOW DEVELOPS. VFR
CONDITIONS EXPECTED TO PREVAIL THROUGH FRIDAY NIGHT AS CANADIAN HIGH
PRESSURE BUILDS INTO THE DAKOTAS.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
000
FXUS63 KFSD 130245
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
845 PM CST THU FEB 12 2009
.DISCUSSION...
NO CHANGES TO GOING FORECAST TONIGHT. TEMPERATURES DROPPED QUICKLY
EARLY THIS EVENING AND ARE NOW LEVELING OUT. SHOULD SEE SLOW BUT
STEADY FALL THE REST OF TONIGHT UNDER MOSTLY CLEAR SKIES. CIRRUS
WILL INCREASE LATER TONIGHT FROM THE SW AS LOW PRESSURE BEGINS TO
MOVE INTO THE CNTRL PLAINS. INCREASING CLOUDS WILL HAVE LITTLE IF
ANY IMPACT ON TEMPERATURES.
&&
.AVIATION...
SFC HIGH PRESSURE AXIS IN PLACE ACROSS THE AREA TONIGHT...YIELDING
LIGHT WINDS AND CLEAR SKIES. SOME BKN MVFR PATCHES SHOULD REMAIN
INTO NE SD AND CNTRL MN. LOW PRESSURE TO DEEPEN LEE OF THE CNTRL
ROCKIES TONIGHT AND MOVE ACROSS THE CNTRL PLAINS FRIDAY. MAIN
PRECIPITATION WILL REMAIN S INTO NEB AND SRN IOWA...BUT NRN FRINGE OF
PRECIPITATION AND IFR COULD MAKE IT INTO SUX...OTHERWISE MAINLY VFR.
&&
.PREV DISCUSSION...
QUIET EVENING AHEAD WITH CLEAR SKIES AND DECREASING NORTH WINDS AS
HIGH PRESSURE LEAKS IN FROM THE NORTHWEST. WILL HAVE INCREASING
CLOUDS OVER THE SOUTHWEST LATE TONIGHT AS UPPER LEVEL WAVE IN THE
CENTRAL ROCKIES SPILLS ONTO THE PLAINS...BUT EXPECT THIS TO BE
MAINLY 20KFT OR HIGHER LEVEL STUFF. OTHERWISE...LOWS NOT TOO FAR
FROM GUIDANCE AND ENDED UP CLOSEST TO THE MET OUTPUT WHICH WAS A
LITTLE COLDER. THIS SEEMED REASONABLE GIVEN CLEAR SKIES EARLY AND
DECREASING WINDS.
MAIN SYSTEM DURING THE SHORT TERM TO AFFECT THE AREA WL OCCUR ON
FRIDAY. STRONG UPR CIRC CURRENTLY PUSHING TOWARD THE 4 CORNERS AREA
WL LIFT ENE INTO THE CNTRL PLAINS BY EARLY FRI. STRONG SLOPING
FRONTOGENETIC BNDRY SETS UP DURING THE MORNING HOURS...WITH DRY
WEDGE SOLIDLY IN PLACE BLO. SATURATION FROM THE MID LVL WL TAKE A
WHILE...INITIALLY WITH A FEW FLURRIES POSSIBLE EARLY TOWARD S CNTRL
SD AWAY FROM THE STRONGER DRY PUSH. HEADING TOWARD MIDDAY...EXPECT
TO SEE STREAKS OF ELEVATED SNOWFALL DEVELOP ALG THE MID LVL
FRONTOGENETIC AXIS...BATTLING A CONTINUED PUSH OF LOW LVL DRY AIR
FROM THE NORTH BLO FRONTAL BNDRY. EVENTUALLY...LIGHT TO MDT PCPN
SHUD DEVELOP QUITE RAPIDLY MIDDAY ACRS SRN CWA. STRENGTH OF
FRONTOGENESIS AND THE WKLY UNSTABLE LAYER ABOVE WOULD CERTAINLY
SUGGEST THAT PCPN WOULD BECOME BANDED...ESPLY DURING THE AFTN WHEN
THE STRONG PV FORCING RIDES ENE INTO THE AREA ACRS THE BNDRY.
ABSOLUTE ELEVATED INSTABILITY EXISTS SOUTH OF THE 7H BNDRY IN FAR
SERN NEBRASKA/SWRN IA...BUT CROSS SECTIONAL ANALYSIS SHOWS INDICATES
THAT THE EPV IS MUCH CLOSER TO THE FRONTAL BNDRY TOWARD THE 650 HPA
LVL WHICH SETS UP JUST S OF THE CWA...CONTAINS A SOMEWHAT MORE
DENDRITIC PROFILE...AND COLLOCATES WELL WITH THE BEST PV SUPPORT.
THERE IS ALSO A CURIOUS FRONTOGENETIC BNDRY WHICH DEVELOPS TO THE
NORTH OF THE MAIN AREA...IN A LITTLE OVERALL DRIER ENVIRONMENT...
BUT WOULD HINT AT ANOTHER WEAKER BAND POTENTIALLY DEVELOPING FROM
ELK POINT TOWARD KSPW. BULK OF SNOWFALL LOOKS TO BE DURING THE
AFTN...AND EXPECT A SHARP NRN CUTOFF TO PCPN. WITH WAVES LINGERING
DIV Q ALREADY PULLING E IN THE EARLY EVENING...AND DRY AIR
CONTINUING TO ERODE FROM THE N...EXPECT A RAPID TAPER OFF IN THE
EVNG ACRS FAR SERN AREAS. IF THERE WAS TO EVENTUALLY BE ANY
HIGHLIGHT NECESSARY...THE ONLY AREA THAT WOULD BE REMOTELY THREATENED
TO APPROACH ADVY LVL SNOWFALL WOULD BE FAR SOUTHERN PORTIONS OF
WOODBURY AND IDA COUNTIES...WHERE ARND 3 INCHES ARE EXPECTED.
AMOUNTS MAINLY 1 TO 3 INCHES EXPECTED SOUTH OF A CHEROKEE TO PONCA
LINE...DROPPING OFF RAPIDLY TO NOTHING WITHIN A COUNTY OR SO NORTH
OF THIS.
SATURDAY WL FOCUS ON RIDGING ALFT...WITH COOLER AIR DRIVING SWRD AS
SFC RIDGE NOSES SWRD INTO THE NRN PLAINS. BY SAT NIGHT...CLOUDS
INCREASE AS NEXT IN PARADE OF SYSTEMS WILL APPROACH THE REGION.
THIS WAVE IS VERY IMPRESSIVE ON WV IMAGERY OFF THE PAC COAST THIS
AFTN...AND MAY BE UNDERRATED IN THE MODEL WORLD. AS THE WAVE LIFTS
ENE WITHIN THE NRN/SRN STREAM CONFLUENCE SAT NIGHT...NICE LITTLE
PULSE OF PV/FRONTAL FORCING THRU SRN CWA. HOWEVER...ATM IS EVEN
DRIER OVERALL FOR THE SAT ROUND COMPARED TO FRI AFTER ANOTHER DAY OF
N TO NE FLOW. THEREFORE...EXPECT MEASURABLE THREAT TO BE QUITE
LOW...AND VERY RESTICTED TO MO VLY AREAS. SYSTEM SHEARS OUT ON
SUNDAY INTO VERY DRY AIRMASS...SO EXPECT ONLY SCATTERED FLURRIES TO
REMAIN A THREAT FROM CONSIDERABLE CLOUDINESS. OVERALL...LOW LVL
THERMAL STRUCTURE IS QUITE UNCHANGING THE NEXT THREE DAYS OVERALL...
SO DO NOT ANTICIPATED A GREAT DEAL OF DAY TO DAY CHANGE IN TMPS IN
THE BIG PICTURE. ANY CLEARING OF SKIES WITH RIDGE AXIS IN THE
NEIGHBORHOOD WITH HELP TO YIELD CHILLIER LOWS...AND THE N TO NE FLOW
WL DO THE UPSLOPING AREAS OF BUFFALO RIDGE NO FAVOR TO WARMING
DURING THE DAY.
FOR THE EXTENDED RANGE /MON THRU THU/ QUIET TO START...BUT CONSENSUS
IN SLNS IS ANOTHER COMPLEX WAVE SLIDING BY TUE INTO TUE NIGHT.
ENSEMBLES POINT SOMEWHAT AWAY FROM OPERATIONAL GFS BOTH 00Z AND 12Z
AS ON FRINGES OF ENSEMBLE SETS. 12Z GFS IS FAR TOO NRN STREAM
DOMINANT AND SEE NO REASON FOR FLOW TO CONSOLIDATE AS MUCH AS
QUICKLY...PERHAPS TOWARD NEXT WEEKEND. GENERALLY...WITH THE
UNCERTAINTY IN SPLIT FLOW...WENT WITH A CONTINUITY IDEA WHICH SEEMED
TO FIT THE HPC THOUGHTS AS WELL. INCREASING WAA AHEAD OF SYSTEM SHUD
ALLOW PCPN TO BREAK OUT MONDAY NIGHT AND EARLY TUE...WITH BEST
THREAT FOR PCPN RIGHT NOW LOOKING TO BE LTR TUE INTO TUE NIGHT.
SOME HINTS THAT COULD BE LOOKING AT A MIXED PCPN EVENT ACRS SRN
CWA...BUT ADJUSTED SFC LOW DEVELOPMENT SWRD ON TUE WHICH WOULD INFER
SOME SLIGHTLY COOLER OFF SFC TMPS.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
UPDATE...97
08/CHAPMAN
000
FXUS63 KFSD 122134
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
334 PM CST THU FEB 12 2009
.DISCUSSION...
QUIET EVENING AHEAD WITH CLEAR SKIES AND DECREASING NORTH WINDS AS
HIGH PRESSURE LEAKS IN FROM THE NORTHWEST. WILL HAVE INCREASING
CLOUDS OVER THE SOUTHWEST LATE TONIGHT AS UPPER LEVEL WAVE IN THE
CENTRAL ROCKIES SPILLS ONTO THE PLAINS...BUT EXPECT THIS TO BE
MAINLY 20KFT OR HIGHER LEVEL STUFF. OTHERWISE...LOWS NOT TOO FAR
FROM GUIDANCE AND ENDED UP CLOSEST TO THE MET OUTPUT WHICH WAS A
LITTLE COLDER. THIS SEEMED REASONABLE GIVEN CLEAR SKIES EARLY AND
DECREASING WINDS.
MAIN SYSTEM DURING THE SHORT TERM TO AFFECT THE AREA WL OCCUR ON
FRIDAY. STRONG UPR CIRC CURRENTLY PUSHING TOWARD THE 4 CORNERS AREA
WL LIFT ENE INTO THE CNTRL PLAINS BY EARLY FRI. STRONG SLOPING
FRONTOGENETIC BNDRY SETS UP DURING THE MORNING HOURS...WITH DRY
WEDGE SOLIDLY IN PLACE BLO. SATURATION FROM THE MID LVL WL TAKE A
WHILE...INITIALLY WITH A FEW FLURRIES POSSIBLE EARLY TOWARD S CNTRL
SD AWAY FROM THE STRONGER DRY PUSH. HEADING TOWARD MIDDAY...EXPECT
TO SEE STREAKS OF ELEVATED SNOWFALL DEVELOP ALG THE MID LVL
FRONTOGENETIC AXIS...BATTLING A CONTINUED PUSH OF LOW LVL DRY AIR
FROM THE NORTH BLO FRONTAL BNDRY. EVENTUALLY...LIGHT TO MDT PCPN
SHUD DEVELOP QUITE RAPIDLY MIDDAY ACRS SRN CWA. STRENGTH OF
FRONTOGENESIS AND THE WKLY UNSTABLE LAYER ABOVE WOULD CERTAINLY
SUGGEST THAT PCPN WOULD BECOME BANDED...ESPLY DURING THE AFTN WHEN
THE STRONG PV FORCING RIDES ENE INTO THE AREA ACRS THE BNDRY.
ABSOLUTE ELEVATED INSTABILITY EXISTS SOUTH OF THE 7H BNDRY IN FAR
SERN NEBRASKA/SWRN IA...BUT CROSS SECTIONAL ANALYSIS SHOWS INDICATES
THAT THE EPV IS MUCH CLOSER TO THE FRONTAL BNDRY TOWARD THE 650 HPA
LVL WHICH SETS UP JUST S OF THE CWA...CONTAINS A SOMEWHAT MORE
DENDRITIC PROFILE...AND COLLOCATES WELL WITH THE BEST PV SUPPORT.
THERE IS ALSO A CURIOUS FRONTOGENETIC BNDRY WHICH DEVELOPS TO THE
NORTH OF THE MAIN AREA...IN A LITTLE OVERALL DRIER ENVIRONMENT...
BUT WOULD HINT AT ANOTHER WEAKER BAND POTENTIALLY DEVELOPING FROM
ELK POINT TOWARD KSPW. BULK OF SNOWFALL LOOKS TO BE DURING THE
AFTN...AND EXPECT A SHARP NRN CUTOFF TO PCPN. WITH WAVES LINGERING
DIV Q ALREADY PULLING E IN THE EARLY EVENING...AND DRY AIR
CONTINUING TO ERODE FROM THE N...EXPECT A RAPID TAPER OFF IN THE
EVNG ACRS FAR SERN AREAS. IF THERE WAS TO EVENTUALLY BE ANY
HIGHLIGHT NECESSARY...THE ONLY AREA THAT WOULD BE REMOTELY THREATENED
TO APPROACH ADVY LVL SNOWFALL WOULD BE FAR SOUTHERN PORTIONS OF
WOODBURY AND IDA COUNTIES...WHERE ARND 3 INCHES ARE EXPECTED.
AMOUNTS MAINLY 1 TO 3 INCHES EXPECTED SOUTH OF A CHEROKEE TO PONCA
LINE...DROPPING OFF RAPIDLY TO NOTHING WITHIN A COUNTY OR SO NORTH
OF THIS.
SATURDAY WL FOCUS ON RIDGING ALFT...WITH COOLER AIR DRIVING SWRD AS
SFC RIDGE NOSES SWRD INTO THE NRN PLAINS. BY SAT NIGHT...CLOUDS
INCREASE AS NEXT IN PARADE OF SYSTEMS WILL APPROACH THE REGION.
THIS WAVE IS VERY IMPRESSIVE ON WV IMAGERY OFF THE PAC COAST THIS
AFTN...AND MAY BE UNDERRATED IN THE MODEL WORLD. AS THE WAVE LIFTS
ENE WITHIN THE NRN/SRN STREAM CONFLUENCE SAT NIGHT...NICE LITTLE
PULSE OF PV/FRONTAL FORCING THRU SRN CWA. HOWEVER...ATM IS EVEN
DRIER OVERALL FOR THE SAT ROUND COMPARED TO FRI AFTER ANOTHER DAY OF
N TO NE FLOW. THEREFORE...EXPECT MEASURABLE THREAT TO BE QUITE
LOW...AND VERY RESTICTED TO MO VLY AREAS. SYSTEM SHEARS OUT ON
SUNDAY INTO VERY DRY AIRMASS...SO EXPECT ONLY SCATTERED FLURRIES TO
REMAIN A THREAT FROM CONSIDERABLE CLOUDINESS. OVERALL...LOW LVL
THERMAL STRUCTURE IS QUITE UNCHANGING THE NEXT THREE DAYS OVERALL...
SO DO NOT ANTICIPATED A GREAT DEAL OF DAY TO DAY CHANGE IN TMPS IN
THE BIG PICTURE. ANY CLEARING OF SKIES WITH RIDGE AXIS IN THE
NEIGHBORHOOD WITH HELP TO YIELD CHILLIER LOWS...AND THE N TO NE FLOW
WL DO THE UPSLOPING AREAS OF BUFFALO RIDGE NO FAVOR TO WARMING
DURING THE DAY.
FOR THE EXTENDED RANGE /MON THRU THU/ QUIET TO START...BUT CONSENSUS
IN SLNS IS ANOTHER COMPLEX WAVE SLIDING BY TUE INTO TUE NIGHT.
ENSEMBLES POINT SOMEWHAT AWAY FROM OPERATIONAL GFS BOTH 00Z AND 12Z
AS ON FRINGES OF ENSEMBLE SETS. 12Z GFS IS FAR TOO NRN STREAM
DOMINANT AND SEE NO REASON FOR FLOW TO CONSOLIDATE AS MUCH AS
QUICKLY...PERHAPS TOWARD NEXT WEEKEND. GENERALLY...WITH THE
UNCERTAINTY IN SPLIT FLOW...WENT WITH A CONTINUITY IDEA WHICH SEEMED
TO FIT THE HPC THOUGHTS AS WELL. INCREASING WAA AHEAD OF SYSTEM SHUD
ALLOW PCPN TO BREAK OUT MONDAY NIGHT AND EARLY TUE...WITH BEST
THREAT FOR PCPN RIGHT NOW LOOKING TO BE LTR TUE INTO TUE NIGHT.
SOME HINTS THAT COULD BE LOOKING AT A MIXED PCPN EVENT ACRS SRN
CWA...BUT ADJUSTED SFC LOW DEVELOPMENT SWRD ON TUE WHICH WOULD INFER
SOME SLIGHTLY COOLER OFF SFC TMPS.
&&
.AVIATION...
VFR THROUGH TOMORROW. SOME LIGHT SNOW WILL BE POSSIBLE IN SUX AFTER
ABOUT 17Z WITH CEILINGS POSSIBLY DROPPING INTO THE MVFR CATEGORY.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
08/CHAPMAN
000
FXUS63 KFSD 121615
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1015 AM CST THU FEB 12 2009
.DISCUSSION...
FORECAST ON TRACK AND SEE LITTLE TO CHANGE. WINDS...AND SUBSEQUENTLY
THE TEMPERATURES...HAVE BEEN A LITTLE SLOWER TO RISE...SO ADJUSTED
FOR THIS...BUT THE OVERALL HIGH TEMPERATURES FORECAST SHOULD BE IN
LINE. HAVE ALSO DECREASED THE CLOUD COVER AS A WEAKENING AREA OF MID
CLOUDS SHOULD DIE OUT OVER THE NEXT COUPLE OF HOURS AND OTHER THAN
SOME SPOTTY AFTERNOON CU...DO NOT EXPECT MUCH OF AN INCREASE IN HIGH
CLOUDS UNTIL TONIGHT AHEAD OF TOMORROWS WAVE FOR NEBRASKA.
&&
.AVIATION...
VFR THROUGH TOMORROW.
&&
.PREV DISCUSSION...
LOW CLOUDS MAINLY NE OF A HON-FSD-SPW LINE AND SLOWLY PULLING OFF TO
THE EAST. WUD EXPECT THESE CLOUDS TO BE JUST AFFECTING FAR NERN CWA
BY 15Z. MID LEVEL CLOUDS NW OF CWA AT THE MOMENT WL SPREAD SEWD
DURING THE DAY. SOME DRIER AIR IN MID LEVELS OVR CWA SO WUD NOT
EXPECT TO BE CLOUDY AS THESE CLOUDS MOVE IN...BUT WUD EXPECT PC AS
NW FLOW SHUD BRING THEM INTO CWA TODAY. HIGH TEMPS SHUD BE SIMILAR
TO WED MOST PLACES WITH ONLY A DEG OR COOLER HIGHS EXPECTED.
TONIGHT SHUD BE RATHER QUIET WITH CLOUDS SPREADING NEEWD INTO SRN
CWA AHEAD OF NEXT SYS. LOWS TEMPS WL STILL REMAIN ABOVE NORMAL ACRS
THE CWA AS LACK OF SNOW COVER MOST PLACES WL HELP HOLD TEMPS UP.
DECENT S/W CONTS TO BE PROGGED TO MOVR ACRS NEB ON FRI AND INTO IA
BY FRI EVE. GFS AND CANADIAN A LTL FURTHER S THAN NAM/EC SOLUTION.
EITHER WAY...THIS SYS SHUD JUST AFFECT FAR SRN CWA MAINLY S OF A
YKN-SPW LINE. GFS SOLUTION WUD GIVE AN INCH OF SNOW AT BEST ACRS THE
FAR SOUTH WITH BOTH EC AND NAM MORE IN THE 2 TO 5 INCH RANGE. FOR
NOW WL NOT GO WITH ANY TYPE OF AN ADVY AS LATER FCSTS SHUD BE ABLE
TO PIN IT DOWN BETTER. STILL A HIGH POP SITUATION FOR THAT AREA AND
WL KEEP SNOW AMOUNTS IN THE 1 TO 3 INCH RANGE ACRS THE FAR SE. BULK
OF SNOW SHUD FALL IN THE AFTN AND THEN QUICKLY PULL AWAY IN THE EVE.
THIS FAST MOVEMENT IS ANOTHER REASON WHY IT MAY STAY BLO ADVY
CRITERIA. SHUD ALSO NOT BE MUCH WND ASSOCD WITH THIS SYS. WITH THE
EXPECTED CLOUD COVER ACRS CWA AND COLDER LOW LEVEL NNELY
FLOW...TEMPS BE COLDER WITH HIGHS GENLY NEAR NORM.
SHUD REMAIN COOLER THRU THE WEEKEND WITH WEAK NNELY LOW LEVEL FLOW
KEEPING LOW LEVELS COLDER. WEAK S/W SAT NITE INTO SUN WL HAVE A HARD
TIME PRODUCING MUCH IN THE WAY OF ANY SNOW WITH DRY LOW LEVELS. CUD
BE A FEW FLURRIES S OF I90 SAT NITE AND SUN WHERE LOW LEVELS WL NOT
BE QUITE AS DRY.
CUD BE MORE INTERSTING ON TUE/TUES NITE AS MODELS ARE NOW BECOMING
CLOSER IN AGREEMENT WITH DECENT S/W AND INVERTED TROF TRACKING EWD
ACRS THE CNTRL AND NRN PLAINS. CANADIAN...EC AND GFS ARE ALMOST
IDENTICAL...SO CUD BE A NICE LITTLE SNOW EVENT IF THEY PAN OUT TUE
INTO TUE NITE.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
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