Severe Thunderstorm Warning 68, NWS Aberdeen, SD

AREA FORECAST DISCUSSION FOR CENTRAL/NORTHCENTRAL AND NORTHEAST
SOUTH DAKOTA AND WEST CENTRAL MINNESOTA
NATIONAL WEATHER SERVICE ABERDEEN SD
320 PM CST MON JUN 18 2001

COLD FRONT HAS SWEPT INTO WESTERN SD THIS AFTERNOON AND CONTINUES
PRESSING SOUTH AND EAST. OUTFLOW BOUNDARIES ASSOCIATED WITH EARLIER
CONVECTION ARE ALSO MOVING SOUTH ACROSS THE EASTERN PORTION OF THE
STATE. SPEED MAX EVIDENT IN WATER VAPOR IMAGERY IS MOVING OUT OF
WY INTO SW SD THIS AFTERNOON AND SHOULD INTERACT WITH SFC BOUNDARIES
TO DEVELOP TSTMS ACROSS ERN SD IN MN THIS AFTERNOON AND EVENING.
BEST PRESSURE FALLS EXIST ACROSS MN WHILE SFC LOW HAS BEEN ANALYZED
EAST OF YKN. THIS LOW SHOULD TRACK TO THE NNE INTO THE BEST PRESSURE
FALLS THIS EVENING. UPPER LEVEL VORT MAX REMAINS TO THE NORTH ACROSS
ND BUT ENOUGH ENERGY SHOULD SLIDE INTO NRN PORTIONS OF THE STATE
TO BOOST STORMS. 1800 UTC SOUNDING SHOWS SFC BASED CAPE OF ALMOST
1300 J/KG WITH LI OF -4. INSTABILITY IS MOSTLY ALOFT THOUGH AS LOW
LEVEL BACKED INTO THE NE ON THE NORTHWEST SIDE OF THE SFC BOUNDARY
ACROSS SE SD. FCST SOUNDING FROM EARLIER ETA RUN IS MUCH MORE
FAVORABLE...ESPECIALLY ACROSS THE FAR EAST WHERE CAPE VALUES
INCREASE TO FCST LEVELS OF ALMOST 3500 J/KG WITH LI OF -7. LOW
LEVEL SHEAR NO IMPRESSIVE THOUGH...ONLY 17 M/S AHEAD OF COLD FRONT.
WILL MENTION SHOWERS AND THUNDERSTORMS ACROSS THE EASTERN SECTIONS
THIS EVENING. LESSER AMOUNTS TO THE WEST. CYCLONIC FLOW REMAINS IN
PLACE THROUGH WEDNESDAY BUT MOST SIGNIFICANT SHORT WAVE ENERGY
PASSES OUT OF THE REGION BY EARLY TUE. MINOR WAVES ROTATING AROUND
UPPER LOW WILL BRING PERIODS OF CLOUDS TO THE REGION WITH SHOWERS
POSSIBLE WEDNESDAY. CLEARING SHOULD BEGIN WEDNESDAY NIGHT.

.EXTENDED FORECAST DISCUSSION...
SUMMERLIKE PATTERN TO DEVELOP DURING EXTENDED PERIOD...AS ZONAL FLOW
AMPLIFIES. UPPER TROF DIGS INTO NORTHERN PACIFIC...AS WELL AS OVER
THE ERN CONUS. THIS CAUSES UPPER RIDGE TO BULGE NORTHWARD OVER
CENTRAL CONUS THRU PERIOD. THIS RIDGE MEANDERS EAST...AND AXIS WILL
BE EAST OF AREA BY END OF PD...PLACING CWA IN SW FLOW ALOFT. AT THE
SFC...HIGH PRESSURE BUILDS IN OVER REGION...PUSHING MOISTURE
SOUTHEAST AND KEEPING COLUMN DRY. THIS HOLDS THRU FRIDAY...WHEN SFC
FLOW RETURNS SOUTHERLY AND MOISTURE BEGINS TO WORK BACK IN. NCEP
ENSEMBLES/AVN ENSEMBLES SUGGEST CHANCE OF TSRA POSSIBLE BY SUNDAY IN
WEST...AND IN EAST AS LOW LEVEL FLOW INCREASES OFF GULF...AND MEAN
SFC TROF IN LEE OF ROCKIES MOVES EAST. MRF HINTING AT E-W ORIENTED
WRM FRONT LIFTING NORTH ON SUN...ONLY ADDING TO CONFIDENCE OF TSRA
THREAT SUN/MON.

.ABR...NONE.

FAUCETTE/BINAU

SDZ003>007-009>011-015-016-181700-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ABERDEEN SD
1101 AM CDT MON JUN 18 2001

...SEVERE THUNDERSTORM WATCH HAS BEEN ALLOWED TO EXPIRE...

THE SElVERE THUNDERSTORM WATCH THAT WAS IN EFFECT FOR PORTIONS OF
NORTH CENTRAL AND NORTHEAST SOUTH DAKOTA HAS BEEN ALLOWED TO EXPIRE.

FAUCETTE