901
FXUS63 KABR 232003
AFDABR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
203 PM CST MON DEC 23 2024
KEY MESSAGES
- FOG, SOME OF WHICH IS DENSE, OVER THE REGION WILL PERSIST
OVERNIGHT INTO TUESDAY BEFORE ANY IMPROVEMENT IS EXPECTED.
VISIBILITY OF A QUARTER MILE OR LESS CAN BE EXPECTED AT TIMES
TONIGHT INTO TUESDAY.
- THERE IS AROUND A 30% CHANCE OF LIGHT RAIN FORECAST FRIDAY
INTO EARLY SATURDAY OVER MAINLY EASTERN SD AND WESTERN MN.
- TEMPERATURES WILL RUN AROUND 5 TO 20 DEGREES ABOVE NORMAL
THROUGH NEXT SUNDAY.
SHORT TERM /THIS EVENING THROUGH TUESDAY NIGHT/
ISSUED AT 200 PM CST MON DEC 23 2024
AT 1 PM CST, COUNTIES WEST OF THE MISSOURI RIVER VALLEY ARE
GENERALLY SUNNY (CLOUD/FOG FREE), WHILE THE FORECAST AREA EAST OF
THE MISSOURI RIVER VALLEY IS PRETTY MUCH ENTIRELY SOCKED IN UNDER
LOW CLOUDS. A PORTION OF CORSON AND DEWEY COUNTIES ARE ON THE
WESTERN EDGE OF THE LOW LEVEL COLD DOME THAT HAS BUILT DOWN OVER THE
REGION WITH SURFACE HIGH PRESSURE, AND THERE IS A SWATH OF LOW
CLOUDS/DENSE FOG THROUGH THAT INTERFACE BETWEEN WARMER AIR TO THE
WEST AND COLD AIR TO THE EAST. SWINGING SOUTHEASTWARD ALONG THAT
INTERFACE, DENSE FOG AND LOW CLOUDS EXTEND DOWN TO BLUNT AND OVER TO
GANN VALLEY. FURTHER EAST IN THE CWA, THE NORTH-COMPONENT WIND IS
ENHANCING UPSLOPE-INDUCED FOG ON THE NORTHERN PORTION OF THE PRAIRIE
COTEAU/SISSETON HILLS REGION, WHICH HAS BEEN SLOWLY ADVECTING
SOUTHWARD ACROSS THAT AREA OF THE CWA TODAY. OUT WEST WHERE IT'S
SUNNY, WINDS ARE LIGHT AND TEMPERATURES ARE WARMING THROUGH THE 30S
AND 40S. FURTHER EAST, WHERE IT'S CLOUDY, TEMPERATURES HAVE BEEN
EITHER GENERALLY HOLDING STEADY IN THE UPPER TEENS TO MID 20S (DUE
TO THE ONGOING LOW LEVEL CAA), OR HAVE BEEN SLOWLY RISING (WHERE
THERE HASN'T BEEN ALL THAT MUCH FOG TO CONTEND WITH). AGAIN, DENSE
FOG, THAT DEVELOPED/MOVED OVER THE CWA EARLIER THIS MORNING, HAS
BEEN MOVING AROUND TODAY, SPREADING OUT SOUTHWARD AND EASTWARD. A
DENSE FOG ADVISORY WAS ISSUED EARLIER TODAY, AND HAS BEEN FOLLOWING
THE DENSE FOG AROUND THE CWA.
WITH THE AMOUNT/DEPTH OF LOW LEVEL MOISTURE STUCK IN THIS SHALLOW
COLD AIRMASS UNDERNEATH A RATHER PRONOUNCED LOW LEVEL THERMAL
INVERSION, FULLY EXPECTING SATURATION (LOW CLOUDS) TO PERSIST UNTIL
SOMETHING (A FRONTAL BOUNDARY/LOW LEVEL JET??) CAN COME ALONG TO MIX
OUT THE INVERSION AND/OR INTRODUCE ENOUGH LOW LEVEL DRY AIR TO DRY
OUT THE BL. WITH LIGHT WINDS EXPECTED TO LAST INTO, AT LEAST,
TUESDAY AS WELL, THE FOG POTENTIAL, IN ADDITION TO THE LOW CLOUDS,
IS GOING TO PERSIST TOO.
THERE IS AN UPPER LEVEL SHORTWAVE TRYING TO PUSH EAST THROUGH THE
UPPER LEVEL RIDGE COVERING MUCH OF THE WESTERN HALF OF THE CONUS;
WORKING ACROSS THE NORTHERN PLAINS TOWARD MORNING WHILE BEING
DAMPENED OUT BY THE UPPER LEVEL RIDGE. NOT LOOKING LIKE MUCH OF A
PRECIPITATION THREAT ACROSS THE WESTERN THIRD OF FORECAST ZONES
TUESDAY MORNING. BUT, DID LEAVE IN SOME SEMBLANCE OF THE SLIGHT
CHANCE POPS FROM THE PREVIOUS SHIFT.
LONG TERM /WEDNESDAY THROUGH MONDAY/
ISSUED AT 200 PM CST MON DEC 23 2024
WEDNESDAY, AN UPPER-LEVEL TROUGH STARTS TO PUSH THE UPPER-LEVEL
RIDGE OUT OF SD. THE PRESSURE GRADIENT OVER THE STATE CREATES SOME
STRONGER WINDS THAT ARE PUSH TO THE SURFACE. SURFACE WINDS AND GUSTS
INCREASE INTO THE AFTERNOON OVER CENTRAL AND EASTERN SD, LIKELY TO
REACH UP AROUND 25KTS AND DECREASE INTO THE EVENING. THE UPPER-LEVEL
TROUGH HAS AN AREA OF LOWER PRESSURE TO THE SOUTH OVER CO, THOUGH
THE MODELS VARY THE LOCATION, TIMING, AND TRACK OF THIS LOW. AS THE
TROUGH MOVES OVER SD, AND MOVES THE LOW TO THE EAST/NORTHEAST, THE
UPPER-LEVEL FLOW OVER SD SPLITS. THIS CREATES ANOTHER AREA OF LOW
PRESSURE AT THE SURFACE OVER WESTERN/CENTRAL SD OVERNIGHT THURSDAY
INTO FRIDAY MORNING. THE MODELS VARY IF PRECIPITATION WILL DEVELOP
BEHIND THIS LOW, AS THOSE WITH MID-LEVEL MOISTURE OVER CENTRAL SD
HAVE PRECIPITATION DEVELOPING AT THE SURFACE, HOWEVER THE MODELS
WITHOUT THE MOISTURE DO NOT DEVELOP PRECIPITATION. AS THIS IS A NEW
DEVELOPMENT IN THE MODELS AND THERE IS UNCERTAINTY IF THERE WILL BE
MID-LEVEL MOISTURE OVER SD FOR PRECIPITATION TO DEVELOP, THE POP
VALUES HAVE BEEN INCREASED SLIGHTLY.
THE PRECIPITATION OVER CENTRAL SD MOVES EAST DURING THE DAY AND
MERGES INTO THE PRECIPITATION OVER EASTERN SD FRIDAY
AFTERNOON/EVENING. THERE IS SLIGHT VARIATION IN THE TIMING OF THE
PRECIPITATION LEAVING SD, AS THE MODELS VARY BETWEEN OVERNIGHT
FRIDAY TO SOMETIME DURING THE DAY SATURDAY. THE MID-LEVELS HAVE A
SMALL AREA OF WAA MOVING THROUGH SD OVERNIGHT THURSDAY THROUGH
SATURDAY. THIS MAINLY AFFECTS THE PRECIPITATION TYPE OCCURRING OVER
NORTH CENTRAL SD OVERNIGHT INTO FRIDAY, AS THE ECMWF P-TYPE CHART
SHOWS THE MEMBERS WITH PRECIPITATION OCCURRING HAVE A MIX OF MEMBERS
WITH SNOW/FREEZING RAIN THAT TRANSITIONS TO RAIN LATER IN THE DAY
FRIDAY. AREAS TO THE EAST IN NORTHEASTERN SD HAVE PRECIPITATION
FRIDAY AFTERNOON OVERNIGHT INTO SATURDAY MAINLY AS RAIN, THOUGH
THERE ARE A COUPLE OF MEMBERS OF THE ECMWF SHOWING FREEZING RAIN OR
SNOW.
AFTER THE MODELS MOVE THE UPPER-LEVEL TROUGH AND LOW OUT OF SD
SATURDAY EVENING, THE FLOW OVER THE STATE IS FROM THE NORTHWEST AS
AN UPPER-LEVEL RIDGE STARTS TO MOVE FROM THE WEST TOWARDS SD. AN
UPPER-LEVEL SHORTWAVE THEN STARTS TO SUPPRESS THE RIDGE AND MOVES
OVER SD MONDAY. THE MODELS VARY THE TIMING AND LOCATION OF THIS LOW
AS WELL AS THE ASSOCIATED SURFACE LOW AND ITS PRECIPITATION.
THE TEMPERATURE SPREAD IN THE MODELS AS WELL AS CLUSTER MEMBERS ARE
FAIRLY SMALL THROUGH FRIDAY, BUT THEY START TO INCREASE SUNDAY INTO
MONDAY AS THE MODELS VARY THE TYPE OF TEMPERATURE ADVECTION THAT
MOVES THROUGH SD. SURFACE TEMPERATURES THROUGH SUNDAY WILL BE 10-20
DEGREES WARMER THAN NORMAL. A MAJORITY OF MODELS HAVE A LITTLE BIT
OF COOLING OCCURRING INTO MONDAY, LOWERING TEMPERATURES. THE SURFACE
TEMPERATURES WILL STILL BE 5-10 DEGREES WARMER THAN NORMAL ON MONDAY
DESPITE THIS COOLING.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1202 PM CST MON DEC 23 2024
TERMINALS KABR,KATY,KPIR,KMBG
IT IS HIGHLY PROBABLE THAT BETWEEN NOW AND 00Z THIS EVENING, KPIR
WILL REMAIN VFR AND KMBG, KABR AND KATY WILL REMAIN IFR. KMBG MAY
CONTINUE TO BOUNCE IN AND OUT OF MVFR/IFR RANGE.
LATER TONIGHT AFTER 00Z, ALL FOUR TERMINALS WILL BE UNDER THE
INFLUENCE OF SUB-VFR STRATUS, WITH KMBG, KABR AND KATY LIKELY
EXPERIENCING LIFR (POSSIBLY VLIFR) VSBYS IN DENSE (FREEZING?)
FOG. THESE CONDITIONS WOULD PERSIST INTO CHRISTMAS EVE MORNING.
ABR WATCHES/WARNINGS/ADVISORIES
SD...DENSE FOG ADVISORY UNTIL 6 PM CST /5 PM MST/ THIS EVENING FOR
SDZ003-004-007>009-011-016-021-023-034>036-051.
MN...NONE.
SHORT TERM...DORN
LONG TERM...VERNON
AVIATION...DORN
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