000 
FXUS63 KFSD 161451
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
955 AM CDT WED APR 16 2008

.DISCUSSION...
DEEP UPR TROUGH THRU WRN U.S. NOW STARTING TO PUSH INFLUENCE INTO 
NRN PLAINS...CUTTING SHORT THE SIGNIFICANT WARMUP FROM YDA. INITIAL
WAVE LIFTING THRU ND WITH TAIL BACK TO IMPULSE IN SWRN SD. SFC WAVE
NOW IN SWRN MN...WITH CDFNT SWRD THRU NERN NEBRASKA.  PLENTY OF 
CHALLENGES TODAY AS CDFNT MOVES THRU CWA. WINDS TROUBLESOME EARLIER 
WITH SOME 50+ MPH GUSTS IN JAMES VALLEY SHORTLY AFTER FROPA...BUT 
MAIN PRESSURE RISES OF 6-7 HPA/3H NOW WKNG AND FOCUSING MUCH MORE S
THRU NEBRASKA. THEREFORE...WNDS SHUD BECOME MORE DRIVEN BY MIXING
FOR STRENTGH AS DAY WEARS ON...OF WHICH SPEEDS ARE MORE SUPPORTIVE
THRU DEEP LYR OF A GUSTY 20 TO 35 MPH.  TEMPERATURES ALSO AN 
INTERESTING QUANDRY AS NUMERICAL GUIDANCE SEVERAL DEGREES WARMER 
THAN SUPPORTED BY FULL ADIABATIC MIXING. INSPECTION OF GRIDDED MODEL 
DATA REVEALS ABOUT 2-3F SUPERADIABATIC IN NEAR SFC LAYER. WHILE THAT 
IS A DISTINCT POSSIBILITY IN PRE GREENUP TIMES...TDA DOES NOT SEEM 
TO BE THAT TYPE OF DAY. ALSO HAVE ISSUES WITH POTENTIAL RAIN/VIRGA 
COOLED POOL TO NW AND WHAT FORMATION OF CLOUDS WOULD DO TO TMPS AS
STRATOCU DECK DEVELOPS THRU THE AFTN.  PULLED TMPS BACK CLOSER TO 
WHAT 900-875 HPA MIXING WOULD SUGGEST MIDDAY AND THRU AFTN...WHICH
RESULTING IN SOMEWHAT COOLER MAX FCST FOR NWRN 1/2 TO 2/3 OF CWA.
WHILE BULK OF PCPN THREAT SHUD REMAIN TO NW OF AREA...PV LOBE 
SLIDING BY MIDDAY NW COULD ENHANCE LIFT ENOUGH TO GENERATE A FEW
LIGHT SHOWERS...MAINLY ACRS FAR NWRN CWA THRU EARLY AFTN AS SHEARS 
PAST...BUT DO NOT EXPECT TO AFFECT ANY MORE TO THE SE THAN THAT. 
UPDATED GRIDS/PFM ISSUED...AND ZFP TO FOLLOW SHORTLY.

&&

.AVIATION...
CDFNT AT 15Z HAS MOVED THROUGH ALL TAF SITES...CLEARING KSUX AREA
AS OF 13Z. STRATOCU DEVELOPMENT BEHIND THE FRONT LKLY TDAY WITH CAA. 
BORDERLINE MVFR CIGS LKLY TO DEVELOP ESPLY FOR KHON...BEFORE MIXING 
TO HIGHER VFR LEVELS DURING THE AFTN. PCPN CHCS LOOK WEAK AT BEST 
FOR KHON AND NON EXISTENT FOR KSUX/KFSD WITH POSTFRONTAL LIFT...WITH
MOISTURE NOT EXTENDING FAR INTO THE MID LVLS. WINDY AGAIN TDA...THIS 
TIME FM THE NW...WITH MIXED OUT GUSTS TO 25 TO 30 KTS THRU THE AFTN.

&&

.PREV DISCUSSION...
FRONTAL PASSAGE AND INCREASED CLOUD COVER TO MAKE FOR COOLER 
TEMPERATURES TODAY...BUT RIGHT AROUND NORMAL FOR THIS TIME OF YEAR. 
IT WILL BE ANOTHER WINDY DAY BUT NOT NEARLY AT WINDY AS YESTERDAY. 
STILL...SUSTAINED WINDS IN THE 20 TO 25 MPH RANGE WILL BE COMMON 
WITH GUSTS 30 TO 35 MPH. IT IS POSSIBLE A FEW LOCATIONS COULD REACH 
WIND ADVISORY BRIEFLY BUT NO WIDESPREAD WIND ADVISORY EXPECTED. 
CHANCES FOR PRECIPITATION ON THE LOW SIDE TODAY. UPPER FORCING WEAK 
AND NOT MUCH IN THE WAY OF MID LEVEL MOISTURE. ANY MEASURABLE 
PRECIPITATION SHOULD BE WEST AND NORTH OF THE CWA THIS MORNING. 

BETTER CHANCES FOR PRECIPITATION LATE TONIGHT AND TOMORROW INTO NW 
ALONG THE NRN EDGE OF A LOW LEVEL JET. SOME S/WV ENERGY AHEAD OF 
DEVELOPING CUT OFF LOW IS ALSO EXPECTED TO AID IN LIFT. QUESTION 
WILL BE THE EXACT POSITION OF JET AND S/WV. MAIN CHANCES FOR 
PRECIPITATION INTO THE FAR SE PORTIONS OF THE CWA NEAR STORM LAKE. 

CUT OFF LOW TO SLOWLY MOVE ACROSS THE CNTRL PLAINS THROUGH THE 
LATTER PORTIONS OF THE WEEK AND EARLY WEEKEND. MODELS VARY SOME ON 
THE TRACK OF THE LOW...WHICH WILL HAVE AN IMPACT ON PRECIP CHANCES 
AND TEMPERATURES. 00Z GFS TRENDED SLIGHTLY FARTHER N WITH THE LOW 
AND IS A GOOD DEAL FARTHER N THAN THE ECMWF. TRENDED TEMPERATURES 
SLIGHTLY COOLER IN THE E FOR THU...FRI...AND SAT BUT PROBABLY NOT 
COOL ENOUGH SHOULD THE 00Z GFS ACTUALLY VERIFY. MAY ALSO HAVE TO ADD 
SOME BETTER CHANCES FOR RAIN SHOWERS IN THE EAST THIS WEEKEND SHOULD 
GFS PAN OUT.  LIEBL

&&


.FSD WATCHES/WARNINGS/ADVISORIES...

IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.

&&

$$

CHAPMAN