430
FXUS63 KFSD 181728
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1128 AM CST TUE DEC 18 2018
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 249 AM CST TUE DEC 18 2018
TEMPERATURES EARLY THIS MORNING STILL NEAR THEIR CLIMATOLOGICAL
HIGHS FOR THIS TIME OF YEAR, IN THE UPPER 20S AND 30S. GOES EAST
SATELLITE IMAGERY SHOWS A BROAD UPPER LOW SPINNING OVER THE
DESERT SOUTHWEST WITH HIGH LEVEL CLOUDS CURRENTLY FILTERING OVER
OUR AREA. THRU THE DAY, A WEAK PIECE OF ENERGY FROM THIS BROAD
TROUGH WILL SLIDE THROUGH THE AREA LARGELY JUST BRINGING AN
INCREASE IN MID/UPPER LEVEL CLOUD COVER. WITH SURFACE FLOW OUT OF
MORE OF A SOUTHWESTERLY TO WESTERLY DIRECTION, ALONG WITH
SEASONABLY WARM AIR ABOVE THE SURFACE, ANOTHER MILD AFTERNOON IS
EXPECTED. EVEN WITH THE INCREASING CLOUD COVER, CONTINUED THE
TREND OF LEANING ON THE UPPER ENDS OF GUIDANCE VALUES FOR
AFTERNOON HIGH TEMPERATURES AS MIXING POTENTIAL MAY HELP TO
COMPENSATE FOR ANY LOSS OF RADIATIONAL HEATING, ESPECIALLY GIVE
THE TIME OF YEAR/SUN ANGLE.
BY TONIGHT, THE MAIN UPPER LEVEL TROUGH BEGINS TO SLIDE EASTWARD.
ANY BREAKS IN THE UPPER LEVEL CLOUDS FROM TODAY WILL BE FILLED IN
WITH INCREASING CLOUD COVER ALONG WITH PERHAPS A BIT OF FOG IN NW
IOWA. THIS WILL ALSO WORK TO KEEP OVERNIGHT LOWS ON THE WARM SIDE
OF NORMAL AGAIN, OR GENERALLY IN THE 20S.
LONG TERM
(WEDNESDAY THROUGH MONDAY)
ISSUED AT 249 AM CST TUE DEC 18 2018
WEDNESDAY: MODELS CONTINUE TO ADVERTISE A NARROW BAND OF LIGHT
PRECIP SLIDE THROUGH WITH THIS TROUGH PASSAGE. WHILE SEVERAL
OPERATIONAL MODELS, ALONG WITH THEIR RESPECTIVE ENSEMBLE MEMBERS,
SHOW SOME VERY LIGHT QPF AMOUNTS, GIVEN A DRY LAYER IN THE LOWER
LEVELS OF THE ATMOSPHERE EXHIBITED IN THE FORECAST SOUNDINGS, AM
SKEPTICAL THAT WE SEE A WHOLE LOT MORE THAN SOME SPRINKLES. IN
EITHER CASE, WILL STILL MAINTAIN SOME LOW SLIGHT CHANCE POPS OVER
PORTIONS OF THE AREA FOR THE POTENTIAL THAT A FEW LOCATIONS PICK
UP A HUNDREDTH OF AN INCH OR TWO OF RAIN. IF THIS BAND OF PRECIP
CAN MAKE IT INTO OUR FAR WESTERN ZONES EARLIER ENOUGH IN THE
MORNING BEFORE TEMPERATURES WARM ABOVE FREEZING, CAN'T COMPLETELY
RULE OUT A VERY LIGHT WINTRY MIX BUT CONCERN AT THIS TIME IS
PRETTY LOW.
HIGH TEMPERATURES WEDNESDAY WILL BE SOMEWHAT TRICKY WITH CLOUD COVER
IN PLACE BUT ALSO WARMER 925 MB TEMPERATURES SURGING IN FROM THE
WEST. IF WE CAN MIX DOWN SOME OF THIS AIR WITH INCREASING WESTERLY
WINDS, TEMPERATURES COULD EASILY MAKE IT INTO THE 50S NEAR AND WEST
OF THE JAMES RIVER.
THURSDAY AND FRIDAY: AFTER THE MINOR SYSTEM ON WEDNESDAY, UPPER
LEVEL RIDGE BEGINS BUILDING TO OUR WEST BY THURSDAY AND SLIDES
EASTWARD BY FRIDAY. QUIET AND COOLER WEATHER EXPECTED, ALTHOUGH
TEMPERATURES STILL RUNNING 5-10 DEGREES ABOVE THEIR SEASONAL
NORMALS.
WEEKEND: A QUICK MOVING SHORTWAVE(S) WILL MOVE THROUGH THE REGION
ALTHOUGH MODELS IN DISAGREEMENT WITH THE DETAILS. THE GFS IS QUICKER
AND SOMEWHAT MORE ROBUST WITH AN INITIAL WAVE, PERHAPS BRINGING SOME
VERY LIGHT PRECIP TO MAINLY OUR NORTHERN COUNTIES SATURDAY, WHILE
THE EC/CANADIAN ARE SLOWER IN THE SATURDAY NIGHT/SUNDAY TIMEFRAME.
HAVE OPTED TO KEEP THE SLIGHT CHANCE BLENDED GUIDANCE UNTIL MORE
CONSISTENCY IS REALIZED. WHILE THE PRECIP CHANCES LOOK FAIRLY SLIM
CURRENTLY WITH THIS SYSTEM, WHAT LOOKS MORE CERTAIN IS THAT THIS
WILL DRAW IN SOME COOLER TEMPERATURES, MAINLY BACK INTO THE 30S FOR
AFTERNOON HIGHS.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1120 AM CST TUE DEC 18 2018
VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. MID TO HIGH CLOUDS
WILL BE ON THE INCREASE THIS AFTERNOON INTO WEDNESDAY AS A WEAK
SYSTEM MOVES THROUGH. A FEW SPRINKLES TO VERY LIGHT RAIN WILL BE
POSSIBLE ON WEDNESDAY THROUGHOUT THE DAY FROM WEST TO EAST.
ALTHOUGH CONFIDENCE REMAINS LOW TO MODERATE, AREAS OF FOG LOOK
POSSIBLE ACROSS NORTHWEST IOWA AND ADJACENT COUNTIES EARLY
OVERNIGHT INTO MID WED MORNING.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
SHORT TERM...KALIN
LONG TERM...KALIN
AVIATION...05
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