Area Forecast Discussion
Issued by NWS Rapid City, SD

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

000
FXUS63 KUNR 271713
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1113 AM MDT WED APR 27 2016

.UPDATE...
ISSUED AT 1020 AM MDT WED APR 27 2016

HAVE UPDATED FOR A WINTER WEATHER ADVISORY OVER NWRN SD THROUGH
THIS EVENING. STRONG ISENTROPIC LIFT AND FRONTOGENESIS COUPLED
WITH AMPLE MOISTURE WILL MAINTAIN SNOW OWING TO DYNAMIC AND WET-
BULB COOLING WHERE PRECIP RATES ARE GREATEST.

UPDATE ISSUED AT 922 AM MDT WED APR 27 2016

HAVE UPDATED THE FORECAST TO INCREASE SNOWFALL AMOUNTS OVER PARTS
OF CNTRL AND NWRN SD. WEBCAMS AND SHORT-TERM GUIDANCE SUGGEST AT
LEAST 1-2 INCHES LIKELY. VERY DIFFICULT CALL BASED ON TIME OF DAY
AND WARM ADVECTION FROM THE NORTHEAST WORKING AGAINST DYNAMIC AND
WET-BULB COOLING. SEVERAL HI-RES MODELS INDICATE MORE THAN 1 FOOT
OF SNOW...BUT THAT SEEMS UNREALISTIC GIVEN THE COMPETING FACTORS
NOTED ABOVE.

&&

.SHORT TERM...TODAY THROUGH THURSDAY NIGHT
ISSUED AT 301 AM MDT WED APR 27 2016

UPPER LEVEL ANALYSIS HAS STRONG CLOSED LOW ACROSS WESTERN KANSAS
WITH LARGE PLUME OF CLOUD COVER AND MOISTURE LIFTING NORTH ACROSS
CENTRAL SOUTH DAKOTA. AT THE SURFACE...LOW PRESSURE IS LOCATED
ACROSS NORTH CENTRAL KANSAS WITH HIGH PRESSURE OVER SOUTHERN
CANADA. TEMPERATURES ACROSS THE FORECAST AREA AT 3AM ARE IN THE
30S TO MID 40S...WITH WINDS OUT OF THE NORTH TO NORTHEAST.

TODAY AND TONIGHT...UPPER LEVEL LOW LIFTS NORTHEAST INTO EASTERN
NEBRASKA THIS AFTERNOON...AS THE MAIN PRECIP BAND SHIFTS WESTWARD
ACROSS SOUTH DAKOTA. WIDESPREAD RAIN...WITH SOME RAIN/SNOW MIX IN
AREAS...IS EXPECTED TODAY FOR MUCH OF THE AREA. THE EXCEPTION WILL
BE ACROSS NORTHEAST WYOMING...WHERE CLOUD COVER AND LESSER CHANCES
OF ACCUMULATING PRECIP WILL OCCUR. ACROSS THE SD PLAINS...RAINFALL
AMOUNTS WILL RANGE FROM AN INCH ACROSS FAR SOUTH CENTRAL SOUTH
DAKOTA...TO A QUARTER INCH ACROSS THE BLACK HILLS AREA. DRIEST
AREAS WILL BE FROM FAR SOUTHWEST SD INTO NORTHEAST WYOMING. LIGHT
ACCUMULATIONS OF SNOW WILL BE POSSIBLE...WHERE DYNAMIC COOLING
OCCURS WITH THE HEAVIER PRECIP BANDS...AND ALSO ACROSS THE BLACK
HILLS WHERE COOLER TEMPERATURES ARE IN PLACE. HIGH TEMPERATURES
ACROSS THE AREA WILL REMAIN MOSTLY IN THE 30S...WITH SOME LOW 40S
IN SOUTHERN AREAS...AND WHERE PRECIP IS LIGHTER. UPPER LOW SHIFT
INTO IOWA TONIGHT...AS HEAVIEST PRECIP CONTINUES ACROSS MAINLY
NORTHWEST INTO SOUTH CENTRAL SOUTH DAKOTA. ANOTHER 1 TO 2 INCHES
OF SNOWFALL WILL BE POSSIBLE ACROSS THE HIGHER ELEVATIONS OF THE
BLACK HILLS. LOWS WILL FALL INTO THE UPPER 20S TO MID 30S.

THURSDAY...UPPER LOW WILL WEAKEN AND SHIFT EAST...WITH WEAK
RIDGING MOVING ACROSS THE CENTRAL PLAINS. PRECIP CHANCES WILL BE
MARKEDLY LESS...BUT CLOUDY SKIES AND COOL TEMPERATURES WILL
PERSIST. HIGH TEMPERATURES WILL BE A LITTLE WARMER...IN THE 40S.
THE NEXT UPPER LOW WILL APPROACH THE AREA THURSDAY NIGHT...WITH
PRECIP CHANCES INCREASING TOWARDS FRIDAY MORNING. LOWS THURSDAY
NIGHT WILL FALL INTO THE MID 20S TO MID 30S.

.LONG TERM...FRIDAY THROUGH TUESDAY
ISSUED AT 301 AM MDT WED APR 27 2016

MEAN TROUGHING AND COOL/WET CONDS WILL CONTINUE THROUGH THE
WEEKEND. INDICATIONS REMAIN FOR MEAN LONG WAVE RIDGING OVER
WESTERN NOAM BY EARLY NEXT WEEK...AS A STRONG/DEEP UPPER TROUGH
SHIFTS EAST IN THE NORTHERN PAC. MUCH UNCERTAINTY WRT TO THE
STRENGTH/TRACK OF THESE FEATURES WHICH WILL HAVE A SIG IMPACT OF
THE EVOLUTION OF THE AFOREMENTIONED WESTERN NOAM RIDGE AND
POTENTIAL BLOCKING PATTERN...ALTHOUGH WARMER/DRIER WEATHER LOOK
CERTAIN BY NEXT WEEK. WEAK REX TYPE BLOCKING IS INDICATED IN MODEL
PROGS...WHICH WOULD FAVOR A WEAK/MEAN UPPER TROUGH SOMEWHERE FROM
THE PLAINS TO THE CENTRAL ROCKIES.

ANOTHER TROUGH WILL EJECT INTO THE PLAINS BY FRI...SETTING THE STAGE
FOR MORE CHANCES FOR PRECIP AS WELL AS SOME LIGHT SNOW ACCUMS INTO
SUN. FORECAST MODELS HAVE SHIFTED SLIGHTLY WEST WITH THE TRACK OF
THIS SYSTEM...PLACING BETTER CHANCES FOR PRECIP FURTHER NW. IN
ADDITION...THIS SYSTEM LOOKS TO STALL OVER THE CENTRAL PLAINS
SAT...WITH A COUPLE BANDS OF PRECIP ROTATING AROUND THE UPPER
LOW...SUPPORTING A COUPLE DECENT CHANCES FOR RAIN/AND SOME SNOW.
EASTERN PORTIONS OF THE FA LOOK TO SEE THE BEST CHANCES FOR
PRECIP...ESP SCENTRAL SD. SOME SNOW ACCUMS WILL BE POSSIBLE ONCE
AGAIN OVER MAINLY THE WESTERN HALF...ESP THE BLACK HILLS. THIS WILL
HIGHLY DEPEND ON THE AMOUNT OF CAA AND WETBULB EFFECTS ASSOCIATED
WITH THIS SYSTEM...ALTHOUGH MODELS HAVE TRENDED SLIGHTLY COLDER IN
THE SAT NIGHT PERIOD. COOL CONDS WILL CONTINUE THROUGH THE
WEEKEND...WITH HIGHS MAINLY IN THE 40S AND LOWS IN THE 30S.

CONTINUED INDICATION TOWARD STAUNCH WESTERN NOAM RIDGING AND
POTENTIAL BLOCKING EARLY NEXT WEEK...WHICH COULD LEAVE THE REGION
UNDER A WEAK NEGATIVE HEIGHT ANOMALY...ALTHOUGH WARMER AND MUCH
DRIER THAN THE CURRENT PATTERN. OVERALL...TEMPS WILL BE WELL BELOW
SEASONAL NORMS THROUGH THE WEEKEND...WITH A WARM UP NEXT WEEK.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z THURSDAY
ISSUED AT 1111 AM MDT WED APR 27 2016

WIDESPREAD IFR CONDITIONS WILL CONTINUE THROUGH THURSDAY MORNING
WITH AREAS OF -RA/-SN/BR. LOCAL LIFR CONDITIONS ARE EXPECTED IN
THE BANDS OF HEAVIEST PRECIPITATION OR OVER THE HIGHER TERRAIN OF
THE BLACK HILLS DUE TO FOG.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT FOR SDZ001-
     002-013-014.

WY...NONE.
&&

$$

SHORT TERM...15
LONG TERM...JC
AVIATION...MLS



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.