Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 030542
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
1242 AM CDT THU SEP 3 2015

.UPDATE...
ISSUED AT 1242 AM CDT THU SEP 3 2015

MAIN CONCERN THIS UPDATE IS FOG POSSIBILITY...ESPECIALLY ACROSS
CENTRAL NORTH DAKOTA. DEWPOINT TEMPERATURES IN THE 60S TO LOWER 70S
WITH HUMID SOUTHEAST FLOW. RELATIVE HUMIDITY VALUES ALREADY REACHING
100 PERCENT SOME LOCALES. WENT WITH PATCHY FOG CENTRAL. ONLY
LIMITING FACTOR FOR MORE WIDESPREAD FOG WOULD BE THE SOUTHEAST WINDS
OF 5 TO 10 MPH THAT MAY BE ENOUGH TO KEEP SUFFICIENT MIXING TO LIMIT
WIDESPREAD NATURE OF FOG. OTHERWISE ADJUSTED CURRENT HOURLY
TEMPERATURE TRENDS. CURRENT FORECAST ON TRACK.

UPDATE ISSUED AT 943 PM CDT WED SEP 2 2015

NO CHANGES TO THE GOING FORECAST.

UPDATE ISSUED AT 754 PM CDT WED SEP 2 2015

MONTANA SHOWERS DISSIPATED AS THEY NEARED THE NORTH DAKOTA BORDER.
UPDATED TO DRY OUT THE FORECAST.

UPDATE ISSUED AT 441 PM CDT WED SEP 2 2015

WILL NEED TO DO A FORECAST UPDATE TO ACCOUNT FOR SHOWERS MOVING
FROM THE MILES CITY TO GLENDIVE AREA OF MONTANA TOWARD THE NORTH
DAKOTA BORDER. THE HRRR IS HANDLING THE PRECIPITATION THE BEST AS
COMPARED TO OTHER HI RES SHORT TERM MODELS. THE HRRR HAS THE
SHOWERS DEPICTED...AND BRINGS THEM INTO NORTH DAKOTA...EVEN INTO
THE CENTRAL PART OF THE STATE LATER.

KMLS ASOS HAD A WIND GUST OF 52 KNOTS...60 MPH...HOWEVER...THE
STATION REPORTED NO THUNDER AND THE LIGHTNING NETWORK SHOWED NO
LIGHTNING. SO...IT WAS A SHOWER THAT MIXED DOWN HIGHER WIND AND
LIKELY EVAPORATION ADDED TO THE DOWNWARD TRANSPORT. DOWNDRAFT CAPE
IS ANALYZED 1700-1800 UNITS ACROSS WESTERN NORTH DAKOTA.

WILL ADD POPS TO THE WEST AND MAY NEED TO BRING THEM INTO THE
CENTRAL PART OF THE STATE ON A LATER UPDATE. WILL THE ACTIVITY
HOLD TOGETHER AS DEPICTED BY THE HRRR...IS THE QUESTION.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)

ISSUED AT 330 PM CDT WED SEP 2 2015

MAIN CONCERNS THIS PERIOD WILL BE SOME PATCHY FOG TONIGHT...
AND TEMPERATURES AND SOME SLIGHT CHANCES FOR THUNDERSTORMS ALONG
A SLOWLY MOVING FRONTAL BOUNDARY ACROSS THE NORTHWEST ON THURSDAY.

TONIGHT...THE H500 FLOW REMAINS ORIENTED SOUTHWEST TO NORTHEAST.
EXPECT THE COLD FRONTAL BOUNDARY WHICH IS ALIGNED WITH THE FLOW
ALOFT TO ONLY MOVE SLOWLY EAST TONIGHT AND THURSDAY. THIS WILL
GIVE THE REGION ANOTHER OPPORTUNITY FOR VERY WARM TEMPERATURES
THURSDAY ALONG AND AHEAD OF THE FRONT. HIGHS CENTRAL SECTIONS WILL
BE CLOSE TO 100. RELATIVELY COOLER AIR...ALTHOUGH STILL IN THE
MID 80S...WILL MOVE INTO THE NORTHWEST. LOW LEVEL MOISTURE
POOLING ALONG THE JAMES RIVER VALLEY TONIGHT WILL FAVOR MUGGY
CONDITIONS AND SOME PATCHY FOG TONIGHT WITH DEWPOINTS AROUND 70.
ON THURSDAY THE HEAT INDEX VALUES WILL RISE TO NEAR 100 ACROSS THE
JAMES RIVER VALLEY BY AFTERNOON.

THE NAM/GFS BOTH DEVELOP SOME WEAK CONVECTION ALONG THE FRONTAL
BOUNDARY THURSDAY. THE WRF MODEL DOES TOO BUT IN THE AFTERNOON.
WILL ADD ISOLATED THUNDERSTORMS FAR WEST INTO THE NORTH CENTRAL
THURSDAY.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)

ISSUED AT 330 PM CDT WED SEP 2 2015

A SIGNIFICANT PATTERN CHANGE WILL IMPACT THE NORTHERN PLAINS FOR
THE UPCOMING HOLIDAY WEEKEND...WITH COOLER AND WETTER CONDITIONS.

STRONG UPPER LEVEL LOW DROPPING INTO THE PACIFIC NORTHWEST TODAY
WILL BECOME AN OPEN WAVE AND DEEPEN OVER THE WEST COAST THROUGH
SATURDAY. BY THURSDAY NIGHT EMBEDDED S/WV IMPULSES WILL BEGIN TO
APPROACH THE REGION...AND WHEN COUPLED WITH A SLOW MOVING SFC
BOUNDARY WILL RESULT IN CHANCES FOR SHOWERS/THUNDERSTORMS WEST TO
EAST DURING THE NIGHT. A PARTICULARLY STRONG EMBEDDED WAVE WILL
LIFT NORTHEAST ACROSS THE DAKOTAS LATE THURSDAY NIGHT/FRIDAY
MORNING AND MAY BRING MODERATE TO HEAVY RAIN TO PORTIONS OF NORTH
CENTRAL AND EASTERN NORTH DAKOTA DURING THAT TIMEFRAME.

FRIDAY-SATURDAY THE WEST COAST UPPER TROUGH BEGINS TO MOVE FARTHER
INLAND AND WILL DIRECT A SERIES OF SHORTWAVE ENERGY IMPULSES ACROSS
THE NORTHERN PLAINS. THE EXPECTED INCREASE IN CLOUD COVER AND CAA
IN THE WAKE OF THE SFC FRONT WILL RESULT IN MUCH COOLER
TEMPERATURES...WITH HIGHS DROPPING INTO THE 70S MOST AREAS BY
SATURDAY. SATURDAY NIGHT INTO SUNDAY THE BASE OF THE UPPER TROUGH
LIFTS NORTHEASTWARD ACROSS THE ROCKIES AND INTO THE NORTHERN
PLAINS...REACHING FAR SOUTH CENTRAL CANADA SUNDAY NIGHT. THIS
TIME PERIOD (FRIDAY-SUNDAY) WILL SEE VERY GOOD CHANCES FOR SHOWERS
AND THUNDERSTORMS. HEAVIEST PRECIPITATION FORECAST ACROSS THE
NORTH. TOTAL RAINFALL THURSDAY NIGHT THROUGH SUNDAY IS FORECAST TO
RANGE FROM AROUND HALF AN INCH SOUTHWEST...TO NEAR 2 INCHES NORTH.
HEAVIER AMOUNTS VERY POSSIBLE WITH THUNDERSTORMS. INSTABILITY NOT
OVERLY IMPRESSIVE SO WHILE A FEW STRONGER STORMS MAY FORM...THE
OVERALL SEVERE THREAT WILL BE MINIMAL.

MUCH COOLER IN THE WAKE OF THE STORM SYSTEM MONDAY...WITH FORECAST
HIGHS MID 60S TO LOW 70S. A QUASI-ACTIVE UPPER LEVEL ZONAL FLOW
SETS UP EARLY TO MID NEXT. THIS IS A DEVIATION FROM PREVIOUS
MODELS SO UNCERTAINTY RATHER HIGH AT THIS POINT. STILL LOOKS LIKE
A SLOW MODERATION IN TEMPERATURES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1242 AM CDT THU SEP 3 2015

LOW PRESSURE IN EASTERN MONTANA IS FORECAST TO MOVE EASTWARD TO THE
ND/MT BORDER BY DAYBREAK...AND INTO CENTRAL NORTH DAKOTA BY AROUND
00Z. SOUTHEAST WINDS EARLY THIS MORNING WILL CONTINUE TO BRING HUMID
AIR INTO THE REGION...WITH PATCHY FOG POSSIBLE TOWARD DAYBREAK.
ADDED TEMPO 3SM BR BETWEEN 10Z-14Z FOR NOW AT KMOT/KBIS/KJMS.
OTHERWISE VFR CONDITIONS AFTER 14Z EXPECTED. ISOLATED THUNDERSTORMS
POSSIBLE THIS AFTERNOON NORTHWESTERN ND BUT CHANCES TOO SMALL TO
MENTION IN TAFS. SCATTERED TSTMS POSSIBLE AFT 00Z AT
KISN/KDIK/KMOT.

&&

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

$$

UPDATE...JV
SHORT TERM...WAA
LONG TERM...NH
AVIATION...JV



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