446 
FXUS63 KBIS 261801
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
101 PM CDT THU SEP 26 2013

.UPDATE...
ISSUED AT 101 PM CDT THU SEP 26 2013

GRADIENT FLOW HAS NOT RESPONDED AS PREVIOUSLY EXPECTED. THE
SURFACE LOW CONTINUES TO LIFT FARTHER NORTH INTO CANADA THAN HIGH
PRESSURE CAN BUILD INTO WESTERN NORTH DAKOTA. THEREFORE...SUSTAINED
SURFACE WINDS HAVE ONLY INCREASED TO AROUND 20 KNOTS EARLY THIS
AFTERNOON.

IN ADDITION...THE LATEST MODEL GUIDANCE CONTINUES TO BACK OFF ON
WIND SPEEDS THIS AFTERNOON AS GRADIENT FLOW IS WEAKER THAN
PREVIOUSLY EXPECTED. SUSTAINED WIND SPEEDS ARE EXPECTED TO BE UP
TO 25 MPH THIS AFTERNOON WITH 35 MPH GUSTS...WHICH IS BELOW WIND
ADVISORY CRITERIA. AS A RESULT...DECIDED TO CANCEL THE WIND
ADVISORY FOR SOUTHWESTERN INTO NORTH CENTRAL NORTH DAKOTA THIS
AFTERNOON.

ALSO REMOVED AFTERNOON CONVECTION BASED ON CURRENT RADAR
OBS/TRENDS. THE UPDATED PRODUCTS HAVE BEEN SENT.

UPDATE ISSUED AT 949 AM CDT THU SEP 26 2013

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE TO LIFT
NORTH OUT OF NORTH CENTRAL NORTH DAKOTA THIS MORNING. NONE OF THIS
ACTIVITY SHOULD BE SEVERE. ALL THUNDERSTORM ACTIVITY WILL BE OUT
OF THE CWA BY THIS AFTERNOON.

HIGH PRESSURE BUILDING INTO WESTERN NORTH DAKOTA AND LOW PRESSURE
LIFTING INTO MANITOBA WILL GENERATE WINDY CONDITIONS ACROSS
WESTERN AND NORTH CENTRAL NORTH DAKOTA THIS AFTERNOON. THE LATEST
MODEL PROGS HAVE BACKED OFF ON THE SUSTAINED WIND SPEED FORECAST
THIS AFTERNOON. HOWEVER...STILL THINK MARGINAL WIND ADVISORY
CONDITIONS WILL BE ACHIEVED IN SOME SPOTS. THEREFORE...MAINTAINED
THE CURRENT TEMPORAL AND AREAL RESOLUTION OF THE WIND ADVISORY
THIS AFTERNOON.

THE REMAINING FORECAST ELEMENTS ARE ON TRACK. THE UPDATED PRODUCTS
HAVE BEEN SENT.

UPDATE ISSUED AT 651 AM CDT THU SEP 26 2013

LOW PRESSURE SITUATED OVER CENTRAL NORTH DAKOTA WITH SCATTERED
SHOWERS AND THUNDERSTORMS LIFTING FROM EAST CENTRAL INTO NORTHEAST
NORTH DAKOTA...AND SHOWERS EXTENDING BACK INTO CENTRAL NORTH
DAKOTA JUST AHEAD OF THE LOW. COLD NORTHERLY FLOW HAS MOVED INTO
WESTERN NORTH DAKOTA WITH IFR CLOUDINESS SPREADING EAST ACROSS
WESTERN NORTH DAKOTA. UPDATED WEATHER POPS TO MATCH WITH LATEST
RADAR IMAGERY...AND EXTRAPOLATING NORTHEAST THROUGH THE MORNING.
LIMITED MENTION OF THUNDER TO THE EAST CENTRAL AND FAR NORTH
CENTRAL. INCREASED SKY COVER OVER THE WEST THROUGH THE MORNING TO
ACCOUNT FOR THE LOW STRATUS. EXPECT THIS TO DISSIPATE BY LATE
MORNING AND AFTERNOON WITH STRONG SUBSIDENCE MOVING INTO WESTERN
NORTH DAKOTA.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 249 AM CDT THU SEP 26 2013

MAIN CONCERN TODAY WILL BE THUNDERSTORMS EARLY THIS MORNING
FOLLOWED BY A WIND ADVISORY SOUTHWEST THROUGH NORTH CENTRAL. HAVE
UTILIZED A BLEND OF ALL MODELS...BUT SPECIFICALLY THE HRRR FOR
AREAL COVERAGE OF PRECIPITATION THIS MORNING AND NAM/GFS FOR THE
WIND ADVISORY. 

THE LATEST WATER VAPOR IMAGERY ALONG WITH SPC MESOSCALE ANALYSIS
CONTINUES TO SHOW THE H3 JET STREAK WORKING ITS WAY THROUGH
WYOMING AND INTO SOUTH DAKOTA. UPPER DIVERGENCE FIELD ASSOCIATED
WITH THE LEFT EXIT REGION CENTERED OVER CENTRAL/NORTHERN NORTH
DAKOTA AS ISOLATED THUNDERSTORMS CONTINUE TO ESCALATE UPWARDS.
SURFACE LOW PRESSURE IN SOUTHERN SOUTH DAKOTA WILL BEGIN TO MOVE
NORTH ALONG A COLD FRONT WHICH IS NOW LOCATED FROM NEAR OXBOW
SASKATCHEWAN...SOUTH TO MINOT AND INTO LEMMON SOUTH DAKOTA. AS THE
JET STREAK AND UPPER DIVERGENCE FIELD SHIFT FURTHER NORTH THROUGH
THE MORNING...THE SURFACE LOW WILL DEEPEN AS IT ENTERS SOUTHERN 
SASKATCHEWAN THIS AFTERNOON. A TIGHT PRESSURE GRADIENT WILL
ENSUE...RESULTING IN A MARGINAL WIND ADVISORY EVENT. WITH SUSTAINED
WINDS VERY NEAR 30 MPH AND GUSTS TO 40 MPH OVER A FAIRLY LARGE
AREA...DECIDED TO ISSUE A WIND ADVISORY FOR THE SOUTHWEST AND
NORTH CENTRAL ZONES. WINDS WILL INCREASE FIRST ACROSS THE SOUTHWEST
LATE THURSDAY MORNING...THEN TRANSLATE INTO NORTH CENTRAL BEGINNING
IN THE EARLY AFTERNOON. WINDS WILL THEN DIMINISH FROM SOUTH TO
NORTH THURSDAY EVENING.

AS FAR AS SHOWERS AND THUNDERSTORMS...THERE WILL BE A DIMINISHING
EFFECT AS THE SURFACE LOW MOVES FROM SOUTH TO NORTH TODAY. MAIN
INSTABILITY WASHES OUT BY 18Z IN THE NORTH AND HAVE ENDED THE
THUNDERSTORM THREAT IN THE GRIDDED FORECAST AT THAT TIME. DRY
WEATHER COMMENCES CENTRAL AND SOUTH TODAY INTO EARLY TONIGHT. THE
NEXT ROUND OF SHOWERS BEGINS IN THE SOUTHWEST EARLY TONIGHT AND
GRADUALLY EXPANDS NORTHEAST OVERNIGHT. 

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 249 AM CDT THU SEP 26 2013

THE MAIN FORECAST ISSUE IN THE LONG TERM PERIOD WILL BE 
PRECIPITATION CHANCES AND PLACEMENT FRIDAY THROUGH SATURDAY MORNING. 
THERE IS STILL SOME DISAGREEMENT AMONG THE DETERMINISTIC MODELS WITH 
PRECIPITATION ACROSS NORTH DAKOTA ON FRIDAY. HOWEVER...THERE IS MUCH
BETTER AGREEMENT FRIDAY NIGHT INTO SATURDAY MORNING.

WE BEGIN THE LONG TERM PERIOD ON FRIDAY WITH AN UPPER LEVEL TROUGH 
OVER THE NORTHERN AND CENTRAL ROCKIES. SHEARED VORTICITY ALONG THE 
LEADING EDGE OF THE TROUGH EXTENDS ACROSS EASTERN MONTANA AND 
WESTERN NORTH DAKOTA. THE ECMWF IS SHOWING A BROAD AREA OF LIGHT TO 
MODERATE RAIN LIFTING SOUTHWEST TO NORTHEAST ACROSS THE FORECAST 
AREA...WHILE THE GFS/GEM CONTINUE TO INDICATE TWO SEPARATE AREAS OF 
PRECIPITATION...ONE OVER THE WESTERN DAKOTAS ASSOCIATED WITH THE 
UPPER LEVEL TROUGH...AND ANOTHER OVER EASTERN NORTH DAKOTA 
ASSOCIATED WITH THE SURFACE SYSTEM...AND A DRY SLOT OVER CENTRAL 
NORTH DAKOTA. DUE TO CONTINUED DIFFERENCES...WILL SETTLE ON A BROAD
BRUSH OF CHANCE TO HIGH CHANCE POPS UNTIL THERE IS BETTER MODEL
AGREEMENT. EITHER WAY IT WILL BE QUITE COOL AND CLOUDY WITH
SCATTERED LIGHT RAIN AND HIGHS MAINLY IN THE 50S.

THERE IS BETTER MODEL AGREEMENT AS THE KICKER SHORTWAVE ROUNDS THE 
BASE OF THE UPPER TROUGH AND LIFTS INTO THE CENTRAL PLAINS FRIDAY 
NIGHT. STRONG 2D FRONTOGENESIS SETS UP OVER THE EASTERN DAKOTAS 
FRIDAY NIGHT AS THE SURFACE LOW TRACKS FROM THE CENTRAL PLAINS INTO 
NORTHERN MINNESOTA BY SATURDAY MORNING. THIS RESULTS IN AN ENHANCED 
BAND OF DEFORMATION RAIN OVER FAR SOUTH CENTRAL NORTH DAKOTA THROUGH 
THE JAMES RIVER VALLEY AND INTO EASTERN NORTH DAKOTA. 

THE RAIN WILL EXIT THE JAMES RIVER VALLEY SATURDAY MORNING WITH 
CLEARING SKIES OVER WESTERN NORTH DAKOTA. WE WILL NEED TO MONITOR 
FOR POSSIBLE FROST HIGHLIGHTS ACROSS THE WEST ON SATURDAY MORNING 
WITH LOWS POSSIBLY FALLING INTO THE MID TO UPPER 30S IF SKIES
CLEAR AND WINDS SUBSIDE.

UPPER LEVEL RIDGING BUILDS OVER THE AREA THROUGH THE REMAINDER OF 
THE WEEKEND WITH TEMPERATURES WARMING INTO THE 70S BY SUNDAY AND 
MONDAY. A QUASI-ZONAL FLOW THEN TAKES SHAPE THROUGH MID WEEK WITH 
THE STORM TRACK SITUATED NORTH OF THE BORDER. THUS MAINLY DRY 
CONDITIONS ARE EXPECTED EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 101 PM CDT THU SEP 26 2013

MVFR CIGS WILL GRADUALLY IMPROVE TO VFR FROM SOUTH TO NORTH THIS
AFTERNOON. VFR CONDITIONS ARE EXPECTED TO CONTINUE OVER WESTERN
AND CENTRAL NORTH DAKOTA TONIGHT. MVFR CONDITIONS WILL SPREAD 
FROM SOUTHWEST TO NORTHEAST FRIDAY MORNING AS SHOWERS DEVELOP.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

UPDATE...TM
SHORT TERM...KS
LONG TERM...TWH
AVIATION...TM