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000
FXUS63 KBIS 240227
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
927 PM CDT THU MAY 23 2013

.UPDATE...
ISSUED AT 920 PM CDT THU MAY 23 2013

MAIN CONCERN THIS EVENING WILL BE THE WINDS AROUND AND IN THE
ADVISORY AREAS SOUTHWEST AND WEST CENTRAL. WITH THE PAST
HOUR...WINDS GUSTING TO NEAR 48 MPH AT BAKER MONTANA...40 AT
BUFFALO SOUTH DAKOTA...AND 37 MPH AT DICKINSON. THESE ARE ALL IN
OR NEAR THE ADVISORY SO WILL CONTINUE THE ADVISORY...PROBABLY
THROUGH THE TERMINATION AT 06Z/1 AM CDT. OTHERWISE...TONIGHT CLOUDS
ARE INCREASING WEST..AND CURRENT FORECAST LOOKS GOOD.

UPDATE ISSUED AT 645 PM CDT THU MAY 23 2013

STRONG WINDS CONTINUE SOUTHWEST EARLY THIS EVENING. CLOUDS ARE
INCREASING ACROSS THE WEST. WINDS STILL REMAIN ABOVE 25 MPH
ACROSS THE SOUTHWEST SO WILL KEEP THE WIND ADVISORY IN EFFECT
THROUGH MIDNIGHT. RAIN STILL EXPECTED TO HOLD OFF UNTIL THURSDAY
MORNING. OTHER THAN THE CLOUDS...CURRENT FORECAST TRENDING WELL.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 338 PM CDT THU MAY 23 2013

THE MAIN HIGHLIGHT OF THE SHORT TERM ARE STRONG WINDS THROUGH THE
EVENING SOUTHWEST AND THUNDERSTORMS ON FRIDAY.

DID EXTEND THE ONGOING WIND ADVISORY FOR SOUTHWEST NORTH DAKOTA
THROUGH 06 UTC TONIGHT. 12 UTC NAM/GFS BUFR SOUNDINGS CONTINUE TO
SUPPORT A STRENGTHENING WIND FIELD AFTER 00 UTC. WHILE LAPSE RATES
DO DECREASE TO NEAR ISOTHERMAL FROM BELOW 900 MB...IT APPEARS
THAT MOMENTUM TRANSFER WILL STILL BE SUFFICIENT FOR 35+ KT
GUSTS AFTER THE ORIGINAL 03 UTC EXPIRATION TIME.

FOR FRIDAY...A WEAK CONVERGENCE ZONE/MOISTURE GRADIENT IS
EXPECTED TO ESTABLISH ITSELF BETWEEN THE HIGHWAY 85 AND 83
CORRIDORS BY LATE IN THE AFTERNOON. MUCH UNCERTAINTY REMAINS IN
CAPPING IN A LOW LEVEL WARM AIR ADVECTION REGIME...HOWEVER...IF
SURFACE HEATING CAN OVERCOME THE CAPE....ML CAPE VALUES OF
800-1000 J/KG WITH 40 KTS OF DEEP LAYER SHEAR ARE AVAILABLE WHICH
COULD SUPPORT A LOW END...ISOLATED SEVERE THREAT...AGAIN IF
CAPPING CAN BE OVERCOME. OTHERWISE...ISOLATED TO SCATTERED SHOWERS
ARE EXPECTED IN LOW LEVEL WARM AIR ADVECTION ACROSS MUCH OF
CENTRAL NORTH DAKOTA THROUGH THE AFTERNOON...WHICH WEAK VERTICAL
INSTABILITY LIMITING THE THUNDER THREAT.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 338 PM CDT THU MAY 23 2013

FORECAST HIGHLIGHTS FOR THE EXTENDED PERIOD INCLUDE PRECIPITATION
CHANCES AND AMOUNTS AS WELL AS THE POSSIBILITY FOR SEVERE WEATHER.

THE SUITE OF 12Z MODEL GUIDANCE IS RELATIVE GOOD AGREEMENT REGARDING
THE OVERALL SYNOPTIC PATTERN ACROSS THE CONUS AND UNSETTLED PATTERN...BUT
DIVERGE/DISAGREE CONCERNING FORECAST PRECIPITATION CHANCES...AMOUNTS
AND PLACEMENT. THE EXTENDED PERIOD WILL START OUT WITH UPPER LEVEL
RIDING TAKING PLACE OVER THE CENTRAL CONUS WITH AN UPPER LEVEL CLOUD
LOW OVER THE WESTERN US. BY THE BEGINNING OF NEXT WEEK...THE RIDGE
AXIS WILL HAVE SHIFTED TO OUR EAST ALLOWING FOR SOUTHWEST FLOW TO
DEVELOP AHEAD OF THE CLOSED LOW OVER THE WESTERN US. THIS SOUTHWEST
FLOW WILL REMAIN IN PLACE FOR THE DURATION OF THE PERIOD...AS
MULTIPLE IMPULSES RIDE THE SOUTHWEST FLOW OVER THE NORTHERN PLAINS.
HAVE OPTED TO USE A BLEND OF GUIDANCE GIVEN THE DISAGREEMENT BETWEEN
12Z MODELS FOR PRECIP CHANCES AND UTILIZED WPC QPF FOR PRECIP
AMOUNTS.

THE POTENTIAL AND CONFIDENCE FOR SEVERE WEATHER THROUGHOUT THE
PERIOD REMAINS LOW. THE ENTIRE CWA IS OUTLINED IN THE GENERAL RISK
FOR DAY 3 BY THE SPC FOR SATURDAY. MIXED LAYER CAPE FOR SATURDAY
AFTERNOON WILL BE ON THE ORDER OF 2000 TO 2400 J/KG...HOWEVER...THE
0-6 KM BULK SHEAR WILL NOT BE SUFFICIENT. THE LIMITING FACTORS THAT
WILL COME INTO PLAY WILL BE THE UNFAVORABLE DYNAMICS AS AN UPPER
LEVEL RIDGE WILL BE OVERHEAD AND LIMITED MOISTURE (DEWPOINTS IN THE
50S. MOISTURE WILL BE ON THE INCREASE THROUGH THE REMAINDER OF THE
PERIOD...BUT ML CAPE WILL BE IN THE 1000 TO 1200 J/KG RANGE AND 0-6
KM BULK SHEAR WILL REMAIN LOW. WILL CONTINUE TO MONITOR THE
POTENTIAL FOR SEVERE OVER THE COMING DAYS. WILL CONTINUE THE MENTION
OF SEVERE POTENTIAL FROM THE MID SHIFT IN THE HAZARDOUS WEATHER
OUTLOOK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 920 PM CDT THU MAY 23 2013

MAIN HAZARD TO AVIATION FOR THE REMAINDER OF THURSDAY EVENING WILL
BE STRONG SURFACE WINDS PRIMARILY ACROSS THE SOUTHWEST. VFR
CONDITIONS EXPECTED THROUGH 12Z...HOWEVER LOWER CEILINGS WILL
PROGRESS ACROSS THE WEST...FROM KISN-KDIK-KMOT-KBIS AFTER 12Z AS A
LOW PRESSURE SYSTEM MOVES EAST INTO WESTERN NORTH DAKOTA ON
FRIDAY. KDIK WILL LIKELY SEE MVFR CONDITIONS. LOW LEVEL WIND SHEAR
THREAT WILL CONTINUE LATE THIS EVENING AND OVERNIGHT AT KDIK-KISN.
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE ON
FRIDAY...HOWEVER...DUE TO UNCERTAINTY AND LOW COVERAGE...LEFT OUT.

&&

.HYDROLOGY...
ISSUED AT 338 PM CDT THU MAY 23 2013

THE MAIN HYDROLOGY CONCERN IS THE POTENTIAL ACTIVE WEATHER PERIOD
FOR NEXT WEEK ACROSS WESTERN AND CENTRAL NORTH DAKOTA AND THE
POSSIBILITY OF WIDESPREAD MODERATE TO HEAVY RAINFALL FOLLOWING THE
RECENT HEAVY RAIN EVENT. MUCH UNCERTAINTY REMAINS IN PRECIPITATION
AMOUNTS AND HYDROLOGIC IMPACTS...HOWEVER...SEVERAL ROUNDS OF
THUNDERSTORMS ARE POSSIBLE THIS WEEKEND THROUGH NEXT WEEK.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 1 AM CDT /MIDNIGHT MDT/ FRIDAY FOR NDZ017-
018-031>033-040-041-043-044.

&&

$$

UPDATE...WAA
SHORT TERM...AYD
LONG TERM...LTH
AVIATION...WAA
HYDROLOGY...AYD