Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 111705
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1105 AM MDT FRI APR 11 2014

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT
ISSUED AT 311 AM MDT FRI APR 11 2014

WATER VAPOR IMAGERY SHOWS WEAK RIDGING ACROSS THE NORTHERN HIGH
PLAINS ON THE BACKSIDE OF A DEPARTING SHORTWAVE PUSHING THROUGH
EASTERN NEB INTO WRN MN. THE NEXT UPPER WAVES ARE CROSSING THE
PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES. SURFACE ANALYSIS SHOWS
HIGH PRESSURE ACROSS THE NORTHERN PLAINS...AND LOW PRESSURE
DEVELOPING ACROSS ALBERTA INTO NRN MT.

SURFACE LOW WILL CROSS ERN MT AND INTO THE CWA THIS AFTERNOON. AHEAD
OF THE LOW...BREEZY SW WINDS WILL DEVELOP ACROSS NE WY AND SW
SD...WITH GOOD WARM AIR ADVECTION THROUGH THE DAY. MAX TEMPS TODAY
ARE EXPECTED TO REACH THE 60S TO MID 70S. A SERIES OF UPPER WAVES
WILL CROSS MT TO ND AND INTO NRN SD. MID/HIGH CLOUDS WILL INCREASE
THROUGH THE DAY...BUT DRY WEATHER WILL REMAIN TODAY AND TONIGHT. THE
ONLY EXCEPTION IS A SHOWER OR TWO MAY DEVELOP THIS EVENING ACROSS
FAR NW SD.

UPPER PATTERN SATURDAY WILL BECOME INCREASING CYCLONIC AS A BROAD
THROUGH SETS UP ACROSS THE WESTERN TO CENTRAL CONUS. SURFACE LOW
WILL SLIDE EAST OF THE REGION WITH A COLD FRONT WILL CROSSING THE
CWA THROUGH THE DAY. DRY WEATHER IS EXPECTED SAT MORNING...BUT
CHANCES FOR PRECIP WILL INCREASE INTO SATURDAY NIGHT. HIGHS WILL
RANGE FROM THE 50S OVER NW SD TO NE WY...TO MID 70S OVER SCNTRL SD. A
STRONG BAND OF FRONTOGENESIS WILL DEVELOP LATE SATURDAY INTO SAT
NIGHT ACROSS CNTRL NEB INTO SW/SCNTRL SD. THIS WILL BRING PRECIP TO
THE SRN CWA OVERNIGHT. SREF/FORECAST SOUNDINGS SHOW PRECIP WILL BE
MAINLY RAIN SAT EVENING OVER THE SD PLAINS...AND CHANGING TO SNOW
OVER NE WY/BLKHLS. PRECIP WILL THEN CHANGE TO SNOW LATE SAT NIGHT
THROUGH SW/SCNTRL SD. POTENTIAL SNOW AMOUNTS ARE STILL BEING WORKED
OUT...BUT IT LOOKS LIKE MUCH OF NE WY TO SW/SCNTRL SD MAY SEE 1-3
INCHES BY SUNDAY MORNING WITH LOCALIZED 3-5 INCHES. THE BLKHLS MAY
SEE 3-6 INCHES IF ENOUGH PRECIP REACHES FAR ENOUGH NORTH.

&&

.LONG TERM...SUNDAY THROUGH THURSDAY
ISSUED AT 311 AM MDT FRI APR 11 2014

ACTIVE WESTERLY FLOW WILL PREVAIL THROUGH THE PERIOD...AS SEVERAL
DISTURBANCES EMANATE FROM THE MEAN EASTERN PAC UPPER TROUGH.
STAUNCH WESTERN ATLANTIC RIDGING WILL SUPPORT SEMI-BLOCKING WITH A
SOUTHWARD BIAS OF COLD AIR EXPECTED INTO THE REGION THROUGH NEXT
WEEK...SUPPORTING GENERALLY BELOW SEASONAL AVERAGES PER TEMPS.
THIS PATTERN WILL SUPPORT AN INCREASED CHANCE FOR PRECIP ESP MID
WEEK GIVEN A WAVERING BAROCLINIC ZONE OVER OR NEAR THE
REGION...WITH THE EXPECTED LOW HEIGHT BIAS OVER THE NORTHERN
PLAINS. THERE WILL ALSO BE AN INCREASED POTENTIAL FOR SNOW ACCUMS
WITH ANY SYSTEM...GIVEN AVAILABLE COLD AIR WITH SUFFICIENT DEEP
LAYER MOISTURE PER PAC ORIGIN FLOW.

BUMPED POPS UP SUN MORNING WITH INCREASING CONFIDENCE IN THE
EXPECTED WEEKEND UPPER TROUGH. SNOW IS LIKELY OVER THE SW THIRD OF
THE FA...WITH ACCUMS LINGERING INTO SUN MORNING. OTHERWISE...THE
NEXT CHANCE FOR PRECIP WILL BE IN THE WED-THUR PERIOD WITH ACTIVE
WESTERLY FLOW RESUMING BEHIND A DEPARTING SFC RIDGE. STILL
UNCERTAINTY PER THE LOCATION OF THE PREFERRED BAROCLINIC ZONE/WAVE
STRENGTH/WAVE TRACK/AND WAVE EVOLUTION. HENCE...FEEL A GENERAL LOW
POP IS WARRANTED FOR NOW AND NOTHING HIGHER GIVEN LACK OF
APPRECIABLE FORECAST CONFIDENCE. AS PER TEMPS...KEPT THINGS
GENERALLY BELOW SEASONAL NORMS GIVEN SIGNALS FOR LOWER HEIGHTS OVER
THE REGION WITH TENDENCIES FOR WESTERN ATLANTIC BLOCKING DIRECTING
HIGH LATITUDE COLD AIR SOUTHWARD...FAVORING MIDDLE OF THE ROAD
GUIDANCE NUMBERS ATTM.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY)
ISSUED AT 1104 AM MDT FRI APR 11 2014

VFR CONDITIONS EXPECTED THROUGH THE PERIOD.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

SHORT TERM...13
LONG TERM...JC
AVIATION...HELGESON



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