Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 131123
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
423 AM MST SAT FEB 13 2016

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
ISSUED AT 327 AM MST SAT FEB 13 2016

UPPER TROUGH CONTINUES ACROSS THE ERN HALF OF THE CONUS WITH NW FLOW
OVER THE NRN PLAINS. A STRONG FAST MOVING SHORTWAVE IS CROSSING THE
CASCADES INTO THE NRN ROCKIES ATTM. CANADIAN HIGH PRES IS SITTING
ACROSS THE UPPER MIDWEST WITH A STRONG BAROCLINIC ZONE OVER THE
CNTRL TO ERN DAKOTAS. WARM AIR ADVECTION HAS BEGUN OVER THE CWA AS
THE FRONTAL BOUNDARY SLIDES E/NE. TEMPS AT 800MB HAVE RISEN ABOVE
FREEZING ACROSS MOST OF THE CWA...AND WILL DO SO INTO CNTRL SD OVER
THE NEXT 3 TO 6 HOURS. TEMPS WILL WARM ABOVE FREEZING TODAY ACROSS
NE WY TO MUCH OF WRN SD...HOWEVER FREEZING TEMPS ARE PROGGED ACROSS
PTNS OF NW/NCNTRL SD THROUGH MUCH OF TODAY. AS THE SHORTWAVE PUSHES
THROUGH THE REGION TODAY...PRECIP WILL DEVELOP ESPECIALLY ACROSS THE
NRN HALF OF THE AREA. WARM LOW LEVELS SHOW THIS WILL FALL AS RAIN.
CONCERN IS LINGERING SUB-FREEZING TEMPS ACROSS THE NRN PARTS OF
THE CWA WILL RESULT IN A PERIOD OF FREEZING RAIN ESPECIALLY
THROUGH THE AFTERNOON. WILL KEEP WINTER WEATHER ADVISORY ISSUED
YESTERDAY BUT HAVE EXPANDED IT ACROSS HARDING COUNTY WITH THE
SREF/HRRR SHOWING PRECIP POTENTIALLY BEGINNING LATE THIS MORNING
WHEN SURFACE TEMPS ARE STILL BELOW FREEZING. BEHIND THE SHORTWAVE
...SUB-FREEZING LOW LEVELS WILL QUICKLY PUSH BACK INTO THE REGION
ENDING THE THREAT FOR FREEZING RAIN AS IT BECOMES ALL SNOW IN THE
AFTERNOON/EVENING. PARTS OF NW/CNTRL SD COULD SEE 1 TO 3 INCHES
OF ACCUMULATION BEFORE PRECIP ENDS DURING THE OVERNIGHT HOURS.
WITH LOW LEVEL INSTABILITY THAT DEVELOPS...MAY EVEN A FEW
LIGHTNING STRIKES. MODELS SHOWING 700-850MB WINDS REACHING 50KT
BRIEFLY NEAR THE FRONTAL BOUNDARY WHICH WOULD CREATE A SHORT
PERIOD OF STRONG WINDS FOR NOT MORE THAN AN HOUR OR SO.

W/NW WINDS WILL CONTINUE ACROSS THE AREA SUNDAY AS LOW PRESSURE SITS
EAST OF THE AREA. WARMER TEMPS NEAR THE SURFACE WILL ALLOW HIGHS TO
REACH THE UPPER 30S TO UPPER 40S...HOWEVER COOLER 700MB TEMPS WILL
RESULT IN INSTABILITY IN THE LOW LEVELS WHICH WILL ALLOW FOR
UPSLOPING TO DEVELOP ACROSS THE NRN/WRN BLKHLS. PRECIP WILL BE RAIN
EXCEPT SOME SNOW AT THE HIGHEST ELEVATIONS. THIS LIGHT PRECIP WILL
LINGER INTO SUNDAY NIGHT.

.LONG TERM...MONDAY THROUGH FRIDAY
ISSUED AT 327 AM MST SAT FEB 13 2016

EASTERN NOAM TROUGH WILL BREAKDOWN IN THE PERIOD...ALLOWING MEAN
RIDGING TO SPREAD EAST INTO CENTRAL NOAM. THIS WILL RESULT IN A
TREND TO VERY MILD/DRY CONDS BY MID WEEK AS STAUNCH WAA SPREADS
INTO THE NORTHERN PLAINS. BEFORE THIS OCCURS...ANOTHER NW FLOW
IMPULSE WILL ADVECT ACROSS THE NORTHERN PLAINS...SUPPORTING RA/SN
SHOWERS MON INTO TUE. VERY WARM WEATHER CAN BE EXPECTED BY WED AND
ESP THUR. HIGHS ACROSS THE FA THUR LOOK TO APPROACH AND PASS 70 AT
SOME LOCATIONS...ESP IN THE LEE OF THE BH WHERE DOWNSLOPING WILL
BE IN PLACE AHEAD OF A DEEP SFC CYCLONE THAT WILL ADVECT EAST
THROUGH THE REGION SPURRED BY AMPLIFIED ACTIVE FLOW OVER THE
EASTERN PAC. THUR-FRI LOW PRESSURE SYSTEM MAY ALSO SUPPORT ANOTHER
HIGH WIND EVENT IN THE REGION TOWARD THE END OF THE WORK WEEK
GIVEN PROGGED CAA/PRESSURE RISE COUPLET. ACTIVE JET ACROSS THE PAC
LOOKS TO SUPPORT MILD ZONAL FLOW THROUGH THE MIDDLE/END OF NEXT
WEEK...KEEPING ARCTIC AIR BOTTLED UP IN NORTHERN CANADA AS RIDGING
REMAINS CONFINED TO LOWER LATITUDES.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 417 AM MST SAT FEB 13 2016

WIDESPREAD MVFR/IFR CIGS WILL CONTINUE OVER WESTERN AND CENTRAL
SOUTH DAKOTA THIS MORNING IN ESE UPSLOPE FLOW. MVFR/IFR
CONDITIONS WILL PERSIST THROUGH TODAY ACROSS NORTHWEST INTO SOUTH
CENTRAL SOUTH DAKOTA WITH A WINTRY MIX OF SNOW AND FREEZING
RAIN...WHILE CONDITIONS WILL IMPROVE IN SOUTHWEST SOUTH DAKOTA
THROUGH THIS AFTERNOON.

A LOW PRESSURE SYSTEM WILL FORCE A SFC TROUGH INTO THE REGION
THIS AFTERNOON...WITH GUSTY SHRA EXPECTED OVER NE WY INTO FAR
WESTERN SD. SOME THUNDER IS POSSIBLE...ALTHOUGH COVERAGE WILL BE
VERY ISOLD. GUSTS OF 35 TO 45 KNOTS WILL BE POSSIBLE AS A LINE OF
SHRA ADVECTS ACROSS NE WY AND FAR WESTERN SD THIS AFT/EVE. CONDS
WILL TREND HIGH END MVFR TO VFR ALL PLACES THIS EVE AND OVERNIGHT.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY FROM 8 AM THIS MORNING TO 8 PM MST THIS
     EVENING FOR SDZ001-002-014.

WY...NONE.
&&

$$

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


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