389
FXUS63 KUNR 201715
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1015 AM MST FRI DEC 20 2024
KEY MESSAGES
- MILDER TEMPERATURES RETURN FROM WEST TO EAST OVER THE NEXT TWO DAYS,
WITH ABOVE NORMAL TEMPERATURES LIKELY FOR MOST OF THE AREA
TOMORROW THROUGH MUCH OF NEXT WEEK.
- MOSTLY DRY CONDITIONS ARE ANTICIPATED THROUGH NEXT WEEK, WITH
ONLY PASSING, SLIGHT CHANCES OF ISOLATED MEASURABLE
PRECIPITATION.
DISCUSSION
(TODAY THROUGH THURSDAY)
ISSUED AT 128 AM MST FRI DEC 20 2024
WATER VAPOR IMAGERY COMBINED WITH NIGHTTIME MICROPHYSICS RGB IMAGERY
TONIGHT SHOWS PATCHES OF CIRRUS DRIFTING OVER THE REGION IN
NORTHWEST FLOW ALOFT. THE CLIPPER SYSTEM THAT BROUGHT STRONG WINDS
TO THE REGION OVER THE PAST 24 HOURS HAS SHIFTED SOUTHEASTWARD AND
IS NOW CENTERED OVER THE OH VALLEY/GREAT LAKES. ANOTHER TROUGH IS
EVIDENT APPROACHING THE NORTHERN ROCKIES/PLAINS, WITH A CORRIDOR OF
ENHANCED DEEP MOISTURE AHEAD OF THE TROUGH EXTENDING FROM THE EAST
PACIFIC THROUGH SOUTHERN AB. MODEST SHORTWAVE RIDGING IS EVIDENT
NOSING NORTHEASTWARD THROUGH THE GREAT BASIN. LATEST SURFACE
ANALYSIS SHOWS HIGH PRESSURE CENTERED OVER ND, WITH RIDGING
EXTENDING SOUTHWARD THROUGH THE CENTRAL PLAINS, WITH WEAK TROUGHING
FROM WESTERN AB SOUTHWARD THROUGH NORTH CENTRAL WY. IT'S A CHILLY
NIGHT AREA-WIDE, PARTICULARLY ACROSS OUR EAST, WHERE SOME
TEMPERATURES ARE BELOW ZERO AT THIS HOUR.
SURFACE TROUGH SHIFTS EASTWARD TODAY AS PARENT MIDLEVEL DISTURBANCE
RAPIDLY TRANSLATES EAST-SOUTHEASTWARD FROM THE PACIFIC NORTHWEST
THROUGH THE NORTHERN ROCKIES AND INTO THE NORTHERN PLAINS.
ASSOCIATED DEEP Q-VECTOR CONVERGENCE AND ISENTROPIC ASCENT LARGELY
SKIRTS OUR FAR NORTH, WITH BETTER LARGE-SCALE SUPPORT FOR
PRECIPITATION TO OUR NORTH AND EAST. AS SUCH, MAIN SENSIBLE WEATHER
IMPACT WITH THE PASSAGE OF THE TROUGH FOR US WILL LIKELY BE
INCREASING SOUTH/SOUTHEASTERLY WINDS OWING TO A TIGHTENING PRESSURE
GRADIENT AND ACCOMPANYING 2-4 MB/3 HR PRESSURE FALLS. THE TROUGH
PASSAGE WILL DO LITTLE TO STYMIE THE EXPANSION OF LOW-LEVEL THERMAL
RIDGING INTO THE AREA, WITH 850 MB TEMPERATURES PROBABLY TO LIKELY
(60-90% CHANCES) EXCEEDING 10C BY SATURDAY EVENING ACROSS MUCH OF
THE AREA BASED ON LATEST LREF PROBABILITIES. THOUGH NOT QUITE AS
WARM THEREAFTER, EPS/GEFS/GEPS PROBABILITIES ALL SUGGEST THAT 2-M
TEMPERATURE ANOMALIES OF 5-10F OR GREATER ARE LIKELY TO DEFINITE FOR
MOST OF THE AREA THROUGH CHRISTMAS EVE, AND EVEN LONGER FOR OUR
EASTERN 2/3RDS.
A SECOND SHORTWAVE WITH A BETTER SIGNAL OF Q-VECTOR CONVERGENCE
CROSSES THE REGION EARLY SUNDAY, MAINLY ACROSS FAR NORTHWESTERN SD.
THOUGH PROBABILITIES FOR MEASURABLE PRECIPITATION HAVE DECREASED
SOMEWHAT OVER THE PAST 24 HOURS, LREF PROBABILITIES OF OVER 0.01" OF
PRECIPITATION ON SUNDAY REMAIN CLOSE TO 40% ALONG THE SD/ND BORDER,
DECREASING TO NEAR 0 ALONG THE I-90 CORRIDOR. ANY AMOUNTS SHOULD BE
VERY LIGHT, WITH PROBABILITIES FOR OVER 0.1" OR MORE OF
PRECIPITATION LIMITED TO LESS THAN 5%. ALTHOUGH A COUPLE MORE
PASSING CHANCES FOR PRECIPITATION WILL IMPACT THE AREA THROUGH
CHRISTMAS DAY, ODDS CERTAINLY FAVOR A BROWN CHRISTMAS FOR MOST THIS
SEASON.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z SATURDAY)
ISSUED AT 1014 AM MST FRI DEC 20 2024
VFR CONDITIONS WILL CONTINUE THROUGH THE PERIOD. ISOLATED LIGHT
SNOW SHOWERS OR FLURRIES WILL BE POSSIBLE OVER NORTHWESTERN SOUTH
DAKOTA THIS AFTERNOON.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION/KEY MESSAGES...SHERBURN
AVIATION...10
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