Area Forecast Discussion
Issued by NWS Rapid City, SD

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 44 45 46 47 48 49 50
000
FXUS63 KUNR 010400
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
900 PM MST SAT JAN 31 2015

.UPDATE...
ISSUED AT 900 PM MST SAT JAN 31 2015

LATEST WATER VAPOUR LOOP SHOWED SHORTWAVE OVER SOUTHEAST MT AND
ANOTHER OVER CO...AND THEY ARE ON THEIR WAY TO PHASE EAST OF THE
CWA AND CREATE HAVOC. CLOSER TO HOME...SURFACE TROUGH AHEAD OF
NORTHERN STREAM SHORTWAVE WORKING ACROSS WESTERN SD WITH BAND OF
-SN ALLOWING -FZDZ TO END. WILL DROP ADVISORY ON SCHEDULE.

DEFORMATION ZONE SNOWS FROM SOUTHERN STREAM SHORTWAVE ON TRACK TO
AFFECT SOUTH CENTRAL SD OVERNIGHT WITH 2-5 INCHES OF
SNOW...LOCALLY HIGHER AMOUNTS SOUTHEAST IF KICR.

UPDATE ISSUED AT 426 PM MST SAT JAN 31 2015

LOSS OF SOLAR INSOLATION ABOVE ST/FG DECK IS ALLOWING FZDZ TO
ACCUMULATE ON ROADS IN/NEAR THE BLACK HILLS...WHERE BEST UPSLOPE
ENHANCED FREEZING DRIZZLE/FOG ARE OCCURRING. HAVE HOISTED AN
ADVISORY TO ACCOUNT.

ACTIVITY SHOULD QUICKLY TURN TO SNOW AS TROUGH CURRENTLY ACROSS
SOUTHWEST ND INTO CENTRAL WY SWEEPS ACROSS THE CWA EARLY THIS
EVENING.

&&

.SHORT TERM...THIS EVENING THROUGH SUNDAY NIGHT
ISSUED AT 148 PM MST SAT JAN 31 2015

POTENT WINTER STORM TAKING SHAPE ACROSS THE MID CONUS. PHASING
NORTHERN AND SOUTHERN STREAM UPPER TROUGHS WILL SUPPORT
CYCLOGENESIS ACROSS THE CENTRAL PLAINS...WITH A DEVELOPING
DEFORMATION ZONE NW OF THE LOW. THE FA WILL SEE INFLUENCE FROM
BOTH OF THESE SYSTEMS WITH THE NORTHERN COUNTERPART AFFECTING MOST
OF THE FA...WHILE SCENTRAL SD WILL SEE AN INFLUENCE FROM BOTH.
BACKDOOR COLD FRONT HAS SPREAD SW ACROSS THE FA...WITH FG AND
AREAS OF ZL IN ITS WAKE. EXPECTING FG AND ZL TO TAPPER OFF LATE
THIS AFTERNOON AND EARLY EVENING AS THERMAL PROFILES COOL AND ICE
NUCLEATION ENSUES. IN ADDITION...SEEDER FEEDER FROM DEVELOPING
SNOWS WILL ALSO SCOUR AVAILABLE NUCLEI. MAIN STORY WILL BE SNOWS
TONIGHT. STRONG UPPER JET STREAK ASSOCIATED WITH THE NORTHERN
STREAM SHORTWAVE WILL COMBINE WITH AN ASSOCIATED ARCTIC FRONT TO
SUPPORT SNOWS ACROSS MOST OF EH FA TONIGHT...SPREADING QUICKLY SE
FROM NW SD THIS EVENING. MUCH OF WESTERN SD AND PORTIONS OF NE WY
WILL SEE AROUND AN INCH TO 2 INCHES OF SNOW...POSSIBLY NEAR 3 IN
THE FAR NE NEAR LEMMON. THE NORTHERN BLACK HILLS AND FOOTHILLS
WILL ALSO SEE SOME UPSLOPE ENHANCEMENT...WITH CLOSER TO 3 INCHES
POSSIBLE THERE. MOST OF THE SNOW WILL FALL THIS EVENING...WITH
RESIDUAL LIGHT SNOW THE REMAINDER OF THE NIGHT.

A LITTLE DIFFERENT PROCESS EXPECTED OVER SCENTRAL SD. MASSIVE SW
CONUS UPPER LOW WILL EJECT INTO THE CENTRAL PLAINS AND CONTINUE TO
SUPPORT VIGOROUS CYCLOGENESIS IN THE EASTERN CENTRAL PLAINS AND
MIDWEST. MOIST CONVEYOR BELT ASSOCIATED WITH THIS PROCESS WILL
SUPPORT A STRENGTHENING DEFORMATION ZONE ACROSS CENTRAL NE INTO
SCENTRAL SD TONIGHT...WHERE LOCALLY ENHANCED SNOW RATES CAN BE
EXPECTED. IN ADDITION...PHASING NORTHERN STREAM IMPULSE WILL SUPPORT
A BRIEF STALL/PIVOT OF THE MOISTURE CONVEYOR BELT AND ASSOCIATED
DEFORMATION ZONE/FGEN...SUPPORTING A 2-4 HOUR EXTENSION OF DECENT
SNOWFALL. BOTTOM LINE EXPECTING 2-5 INCHES ACROSS MELLETTE...TODD
AND ESP TRIPP COUNTIES. LOCALLY HIGHER AMOUNTS COULD BE POSSIBLE IF
THE ENTIRE PROCESS SHIFTS A BIT FARTHER NW AND PAUSES LONGER. SNOW
WILL WIND DOWN QUICKLY SUNDAY MORNING WITH CLEARING SUNDAY AFTERNOON
MOST IF NOT ALL PLACES. A BRIEF SKIRT OF ARCTIC AIR WILL SUPPORT
MUCH COLDER TEMPERATURES ACROSS THE FA THROUGH SUNDAY. ACTIVE NW FLOW
WILL PERSIST WITH A LL BAROCLINIC ZONE REMAINING ACROSS THE FA. THE
NEXT IN A SERIES OF IMPULSES WILL ARRIVE LATE SUNDAY NIGHT...AND MAY
SUPPORT SNOW TOWARD DAWN MONDAY ACROSS THE FAR NW.

.LONG TERM...MONDAY THROUGH SATURDAY
ISSUED AT 148 PM MST SAT JAN 31 2015

NW FLOW ALOFT WILL CONTINUE OVER THE FORECAST AREA THROUGH THE
EXTENDED FORECAST PERIOD. A RELATIVELY WEAK SHORTWAVE WILL BRING A
CHANCE OF SNOW OR RAIN TO THE FORECAST AREA ON MONDAY AND TUESDAY.
A BETTER DEFINED UPPER TROUGH/JET STREAK WILL AFFECT THE AREA ON
TUESDAY NIGHT AS A COLD FRONT MOVES THROUGH AT THE
SURFACE...BRINGING A CHANCE OF SNOW TO THE AREA. AT THIS TIME IT
LOOKS LIKE THE BEST AREA FOR MEASURABLE SNOW ACCUMULATION WOULD BE
OVER PARTS OF NORTHEASTERN WYOMING AND SOUTHWESTERN SOUTH DAKOTA.
SNOW MAY LINGER INTO WEDNESDAY ACROSS THE SOUTHWESTERN CWA...BUT
DRY WEATHER IS THEN EXPECTED THROUGH THE REST OF THE WEEK AS A
RIDGE BUILDS OVER THE WESTERN CONUS.

THE TEMPERATURE FORECAST REMAINS TRICKY AS A SURFACE FRONTAL
BOUNDARY FLUCTUATES ACROSS THE FORECAST AREA WITH A WIDE VARIATION
IN TEMPERATURES ON EITHER SIDE OF THE BOUNDARY. AT THIS TIME IT LOOKS
LIKE HIGH TEMPERATURES WILL MAINLY BE SLIGHTLY WARMER THAN AVERAGE
ON MONDAY AND TUESDAY...ESPECIALLY ACROSS THE SOUTHWEST HALF OF THE
CWA. BELOW NORMAL TEMPS ARE EXPECTED ON WEDNESDAY AS THE BOUNDARY
SHIFTS SOUTH. WESTERLY WINDS WILL AID IN SIGNIFICANT WARMING FOR THE
END OF THE WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 900 PM MST SAT JAN 31 2015

WIDESPREAD IFR CONDITIONS DUE TO -SN/BR WILL IMPROVE FROM
NORTHWEST TO SOUTHEAST OVERNIGHT INTO SUNDAY. LOCAL LIFR
CONDITIONS WITH HEAVIEST BANDS OF SNOW...ESPECIALLY FROM ABOUT
MARTIN TO CHAMBERLAIN AND POINTS EAST.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY UNTIL 6 AM CST SUNDAY FOR SDZ046-047-049.
WY...NONE.

&&

$$

UPDATE...HELGESON
SHORT TERM...JC
LONG TERM...POJORLIE
AVIATION...HELGESON



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