Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 292018
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
118 PM MST THU JAN 29 2015

.SHORT TERM...THIS EVENING THROUGH FRIDAY NIGHT
ISSUED AT 117 PM MST THU JAN 29 2015

SPLIT FLOW WILL DOMINATE THROUGH THE PERIOD...WITH FAST MILD NW
FLOW OVER THE REGION. A WEAK SFC LOW AND ASSOCIATED MID LEVEL
IMPULSE WILL SUPPORT WAA WITH A THERMAL RIDGE TIMING OVER THE
REGION FRIDAY. WEAK FORCING AND LACK OF APPRECIABLE LL MOISTURE
WILL SUPPORT DRY WX WITH THIS SYSTEM...ALTHOUGH PLENTY OF CIRRUS
LOOK POSSIBLE WITH THIS SYSTEM...AS WELL AS INCREASING UPPER LEVEL
MOISTURE FROM A DEEP SW CONUS UPPER TROUGH THAT WILL REMAIN WELL
SOUTH OF THE REGION. NOT MUCH ADJUSTMENT MADE TO THE PREVIOUS
FORECAST GRIDS...SAVE AN UPTICK IN HIGHS FRIDAY. THERMAL RIDGE
TIMING WITH PEAK HEATING/LACK OF SNOW COVER/AND DECENT TO STRONG
INSOLATION SUPPORTS A TREND TO THE WARMER SIDE OF GUIDANCE. THIS
WILL SUPPORT HIGHS MAINLY IN THE UPPER 40S AND LOW 50S AT MOST
AREAS. A STRONGER NORTHER STREAM IMPULSE WITH AN ASSOCIATED LL
ARCTIC BUBBLE WILL SHIFT SE ACROSS THE SOUTHERN CANADIAN
PROVINCES. FRIDAY INTO FRIDAY NIGHT. THIS WILL SUPPORT A SOUTHWARD
BIAS TO THE NEARLY STALLED LL BAROCLINIC ZONE IN PLACE ACROSS THE
NORTHERN PLAINS...DIRECTING A BACKDOOR COLD FRONT INTO THE AREA
SAT MORNING. CURRENTLY...GUIDANCE SUGGEST ARRIVAL OF THIS FEATURE
MORE INTO THE LATE MORNING/AFTERNOON PERIOD. HOWEVER...GIVEN THE
TRACK RECORD OF THESE TYPES OF FEATURES IN THE AREA...AN EARLIER
ARRIVAL/STRONGER PUSH IS LIKELY. HAVE ADJUSTED FRIDAY NIGHT LOWS
FOR ANTICIPATION OF THIS...WITH A DOWNTREND ACROSS NW SD.

.LONG TERM...SATURDAY THROUGH THURSDAY
ISSUED AT 117 PM MST THU JAN 29 2015

A UNSETTLED AND COLDER PATTERN WILL SET UP FOR THE
WEEKEND AND AT LEAST THE FIRST HALF OF NEXT WEEK. MEDIUM RANGE
MODELS ARE COMING INTO BETTER AGREEMENT WITH TEMPERATURES AND THE
TIMING/INTENSITY OF SHORTWAVES...ALTHOUGH THERE ARE STILL SOME
DISCREPANCIES.

A CANADIAN COLD FRONT WILL PUSH THROUGH THE AREA EARLY SATURDAY...
BRINGING BELOW AVERAGE TEMPERATURES FOR THE WEEKEND...ESPECIALLY ON
SUNDAY. AN UPPER LEVEL DISTURBANCE BEHIND THE FRONT WILL BRING
INCREASING CHANCES FOR SNOW INTO SATURDAY NIGHT...WITH SNOW
DIMINISHING ON SUNDAY MORNING. A LIGHT ACCUMULATION OF
SNOW...GENERALLY AN INCH OR LESS...CAN BE EXPECTED IN MOST PLACES.
ACCUMULATIONS AROUND 2 INCHES OR SO ARE POSSIBLE ACROSS NORTH
CENTRAL SD.

THE TEMPERATURE FORECAST FOR THE FIRST HALF OF NEXT WEEK LOOKS VERY
UNCERTAIN AT THIS POINT AS FRONTAL BOUNDARY REMAINS ACROSS THE
REGION AND WILL LIKELY MEANDER INTO OR ACROSS THE CWA AT TIMES. A
BRIEF WARMUP IS STILL EXPECTED ON MONDAY AHEAD OF THE NEXT
SHORTWAVE. THE WAVE LOOKS A LITTLE STRONGER THAN PREVIOUSLY...SO
INCREASED POPS FOR TUESDAY. COOLER AIR WILL AGAIN DIVE SOUTHWARD
TUESDAY INTO WEDNESDAY...ALTHOUGH MODELS DISAGREE ON EXACTLY HOW FAR
WEST THE COLDEST AIR WILL REACH. THE GFS AND ECMWF BOTH HAVE WARMER
AIR MOVING BACK INTO THE REGION TOWARDS THE END OF NEXT WEEK.


&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z FRIDAY
ISSUED AT 117 PM MST THU JAN 29 2015

VFR CONDITIONS ARE EXPECTED THROUGH THE FORECAST PERIOD.

&&

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

$$

SHORT TERM...JC
LONG TERM...POJORLIE
AVIATION...POJORLIE






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