Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 222331
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
631 PM CDT FRI MAY 22 2015

.UPDATE...
ISSUED AT 622 PM CDT FRI MAY 22 2015

CLEAR TO PARTLY CLOUDY SKIES THIS EVENING WITH DIMINISHING WINDS
WEST. AN UPPER LEVEL LOW PRESSURE SYSTEM OVER THE DESERT SOUTHWEST
WILL LIFT NORTHEAST INTO THE SOUTHERN ROCKIES TONIGHT...WHILE
UPPER LEVEL RIDGING HOLDS ON OVER THE NORTHERN PLAINS. MODELS HAVE
TRENDED SLOWER WITH SHOWERS MOVING INTO THE AREA ON SATURDAY. HAVE
KEPT TONIGHT DRY AS PREVIOUSLY FORECAST...AND SLOWED THE INTRUSION
OF SHOWERS FROM SOUTH TO NORTH SATURDAY MORNING. OTHERWISE NO
SIGNIFICANT UPDATES TO THE GOING FORECAST.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 241 PM CDT FRI MAY 22 2015

CURRENTLY...A SURFACE HIGH PRESSURE RIDGE AXIS EXTENDED FROM SOUTHERN MINNESOTA
NORTHWESTWARD FROM SOUTHEAST NORTH DAKOTA TO NORTHWESTERN NORTH DAKOTA AND INTO
SASKATCHEWAN. SOUTHWEST OF THIS AXIS WINDS WERE OUT OF THE SOUTHEAST AT 15 TO
25 MPH WITH HIGHER GUSTS. NORTHEAST OF THIS LINE THE SOUTH/SOUTHEAST WINDS
WERE AT 5 TO 15 MPH. AT UPPER LEVELS...THE SATELLITE WATER VAPOR LOOP INDICATED
AN UPPER LEVEL LOW/SHORTWAVE IMPULSE OVER SOUTHWESTERN NEBRASKA MOVING NORTHWARD.
THE MAIN UPPER LEVEL LONGWAVE TROUGH REMAINED OVER THE WEST COAST...WITH THE UPPER
JET ROUNDING THE TROUGH BASE OFF THE SOUTHERN CALIFORNIA COAST.

THE MODELS CONTINUED TO DIFFER REGARDING THE MOVEMENT AND TIMING OF THE MAIN
UPPER LEVEL FEATURES. THE GFS IS MOST AGGRESSIVE REGARDING
BRINGING THE MAIN UPPER LEVEL ENERGY NORTHWARD AND INTO SOUTHERN
NORTH DAKOTA SATURDAY MORNING. THE ECMWF BRINGS THE UPPER LEVEL
ENERGY NORTHWARD...BUT THE STRENGTH OF THE IMPULSE IS WEAKER THAN
THAT OF THE GFS...AND WOULD INDICATE ANY RAINFALL WOULD BEGIN A
BIT LATER SATURDAY MORNING. THE NAM IS WEAKEST AND SLOWEST OF ALL
AND SUGGESTS LITTLE TO NO PRECIPITATION DURING THE DAY SATURDAY.

THE CONSENSUS WAS TO GO WITH A BLEND OF THE ECMWF AND SOME OF THE MODEL
ENSEMBLES...AND BACKED OFF ON PRECIP AMOUNTS THAT WERE EARLIER FORECAST FOR
THE DAYTIME SATURDAY PERIOD.

THE LATEST THINKING IS THAT THE CHANCE OF SHOWERS WOULD BEGIN AROUND DAYBREAK
IN FAR SOUTHWEST AND SOUTH CENTRAL NORTH DAKOTA...WITH CHANCES OF SHOWERS IN THE
SOUTHERN 2/3 OF WESTERN AND CENTRAL NORTH DAKOTA DAYTIME SATURDAY. ALSO LIGHTER
PRECIPITATION AMOUNTS...LESS THAN 0.10" FOR THE SATURDAY DAYTIME PERIOD.

THE MENTION OF THUNDERSTORMS WAS TAKEN OUT FOR SATURDAY...AS LATEST MODELS
INDICATED MUCH LESS INSTABILITY AND FORCING EARLY ON IN THIS LARGE-SCALE
SYSTEM AFFECTING MUCH OF THE WESTERN AND CENTRAL US SATURDAY.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 241 PM CDT FRI MAY 22 2015

CONSENSUS AMONGST THE LONG TERM MODELS SHOW A POTENT JET STREAK
EJECTING THROUGH THE BASE OF A SOUTHWEST LONGWAVE TROUGH SATURDAY
NIGHT...PUSHING INTO THE CENTRAL/NORTHERN HIGH PLAINS SUNDAY. THE
EVOLUTION/PLACEMENT OF A NEARLY VERTICALLY STACKED LOW REMAINS
UNCERTAIN. HOWEVER MODELS AGREE THAT LIKELY POPS WARRANTED IN THE
FAR SOUTH SATURDAY NIGHT...WHICH GRADUALLY EXPAND NORTH SUNDAY
THROUGH MONDAY. THE GFS IS THE MOST AGGRESSIVE WITH THE SYSTEM IN
TERMS OF PRECIPITATION AMOUNTS AND RESULTANT UPPER LOW TRACKING
ACROSS CENTRAL NORTH DAKOTA. THE ECMWF IS THE LEAST AGGRESSIVE WITH
THE UPPER/SURFACE LOW FARTHER SOUTH AND AND EAST. THE CANADIAN GEM IS
IN MIDDLE. THUS USED A BLEND OF THE MODEL SUITE IN COMBINATION WITH
QPF FROM WPC. THIS PLACES THE HIGHEST PRECIPITATION AMOUNTS FROM THE
WEEKEND INTO TUESDAY MORNING OF AROUND 1.25 INCHES IN THE SOUTHWEST.
THE REST OF SOUTHERN NORTH DAKOTA SHOULD SEE AROUND 1 TO 1.20
INCHES. TOTAL RAINFALL TAPERS OFF TO THE NORTH WITH THE FAR NORTH
AROUND A HALF INCH OF PRECIPITATION. OVERALL THIS SHOULD BE A DECENT
PRECIPITATION PRODUCER SATURDAY NIGHT THROUGH MONDAY NIGHT.
THEREAFTER AN UNSETTLED PATTERN CONTINUES WITH DAILY CHANCES FOR
SHOWERS AND THUNDERSTORMS THROUGH FRIDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 622 PM CDT FRI MAY 22 2015

VFR CONDITIONS EXPECTED TONIGHT WITH A SOUTHEAST SURFACE FLOW.
MVFR CEILINGS WILL BEGIN TO MOVE NORTH THROUGH THE FORECAST AREA
ON SATURDAY. BROUGHT MVFR CEILINGS AND SHOWERS INTO KDIK AND KBIS
16-18Z SATURDAY...WITH VFR SHOWERS INTO KJMS AROUND 21 UTC
SATURDAY. WILL KEEP MENTION OF MVFR CEILINGS AND SHOWERS OUT OF
NORTHERN TAF SITES KISN AND KMOT THROUGH THE FORECAST PERIOD.
SOUTHEAST SURFACE FLOW WILL CONTINUE THROUGH SATURDAY.

&&

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

$$

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


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