Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 060538
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
1238 AM CDT FRI MAY 6 2016

.UPDATE...
ISSUED AT 1237 AM CDT FRI MAY 6 2016

MAIN CONCERN THIS UPDATE IS ARRIVAL OF THE COLD FRONT JUST ENTERING
NORTHWESTERN NORTH DAKOTA. LOOKING LIKE WINDS BECOME
NORTHWESTERLY...BUT DO NOT BEGIN INCREASING FOR A FEW HOURS BEHIND
THE FRONTAL PASSAGE. STILL SOME AREAS IN SASKATCHEWAN WITH REDUCED
VISIBILITY - LIKELY DUE TO SMOKE FROM LARGE FIRES IN NORTHERN
ALBERTA/SASKATCHEWAN. SWIFT CURRENT HAD BEEN REPORTING VISIBILITIES
OF 2-3 MILES BUT NOT SEEING OTHER SURROUNDING STATIONS WITH
VISIBILITY REDUCTIONS. WILL BE MONITORING FOR FUTURE UPDATES.
OTHERWISE BLENDED CURRENT OBSERVATIONS WITH TEMPERATURE TRENDS AND
NO BIG CHANGES FOR THE OVERNIGHT HOURS.

UPDATE ISSUED AT 943 PM CDT THU MAY 5 2016

MOST OF THE CUMULUS AND ISOLATED...HIGH-BASED SHOWERS /AND A LONE
STORM THAT OCCURRED IN WILLIAMS COUNTY EARLIER/ ARE DIMINISHING
WITH THE ONSET OF NOCTURNAL COOLING AND STABILIZATION. THAT IS IN
LINE WITH OUR LATE AFTERNOON FORECAST UPDATE. THE MAIN QUESTION
GOING FORWARD WILL BE WHAT /IF ANY/ SHOWER POTENTIAL EXISTS OVER-
NIGHT. RECENT OPERATIONAL HRRR SIMULATIONS CONTINUE TO BE TOO
AGGRESSIVE WITH CONVECTIVE DEVELOPMENT COMPARED TO REALITY...AND
THE 18 UTC GFS AND 00 UTC NAM ARE AT ODDS OVER SHOWER POTENTIAL.
THAT PROVIDED LOW ENOUGH CONFIDENCE FOR US TO KEEP A DRY FORECAST
GOING OVERNIGHT...THOUGH THAT WILL NEED TO BE RE-EVALUATED LATER.
THE ONE CHANGE WE DID MAKE WITH THIS UPDATE WAS TO INCREASE LOWS
BY 2-4 F IN MOST AREAS BASED ON MID-EVENING TEMPERATURE TRENDS.

FINALLY...ONE OTHER ISSUE THAT WE WILL NEED TO CONTEND WITH FOR
LATER FORECAST RELEASES IS HOW THICK SMOKE FROM CANADIAN FIRES MAY
BE FRIDAY. OBSERVATIONS IN SASKATCHEWAN HAVE SHOWN VISIBILITIES
AS LOW AS 4SM FOR SEVERAL HOURS BEHIND THE COLD FRONT THAT WILL
CROSS THE AREA. THUS...IT/S POSSIBLE THICKER LOW-LEVEL SMOKE MAY
IMPACT PARTS OF WESTERN AND CENTRAL ND LATE TONIGHT AND FRIDAY.
AT THE VERY LEAST IT SEEMS REASONABLE TO BELIEVE THE SMOKE WILL BE
SENSIBLE VIA SMELL FRIDAY.

UPDATE ISSUED AT 755 PM CDT THU MAY 5 2016

WE WILL LET THE RED FLAG WARNING EXPIRE AS SCHEDULED AT 8 PM CDT
/01 UTC/...AS WINDS IN EAST CENTRAL ND HAVE DIMINISHED TO AROUND
10 MPH. HUMIDITIES ARE AT OR ABOVE 20 PERCENT AS OF 0050 UTC AND
THEY WILL CONTINUE A SLOW RISE WITH THE ONSET OF DIURNAL COOLING.

UPDATE ISSUED AT 551 PM CDT THU MAY 5 2016

WE HAVE ADDED A SLIGHT CHANCE OF A SHOWER OR THUNDERSTORM TO THE
FORECAST THROUGH MID EVENING IN NORTHWEST ND. A HIGH-BASED SHOWER
DEVELOPED NORTHWEST OF WILLISTON NEAR 2230 UTC...AND EVEN THOUGH
THE ENTLN TOTAL LIGHTNING PLOT HAS NOT YET SHOWN ANY IN-CLOUD OR
CLOUD-TO-GROUND STRIKES...THE STEEP LAPSE RATES AND WEAK MLCAPE
/UP TO 250 J/KG PER THE SPC MESOANALYSIS/ IN THAT AREA SUGGEST A
RUMBLE OR TWO OF THUNDER IS POSSIBLE. VISIBLE SATELLITE IMAGERY
THROUGH 2245 UTC SHOWS CUMULUS ALL ALONG A WEAK SURFACE PRESSURE
TROUGH EXTENDING FROM SOUTHEAST SASKATCHEWAN INTO EASTERN MT SO IT
IS PLAUSIBLE MORE THAN JUST THAT INITIAL SHOWER MAY FORM. THAT
BEING SAID...RECENT HRRR RUNS ARE LIKELY OVERDONE WITH EXPECTED
DEVELOPMENT BASED ON THAT MODEL/S RECENT AND LONGER-TERM BIASES.

OTHERWISE...WE ARE CONTINUING THE RED FLAG WARNING IN EAST CENTRAL
ND FOR NOW GIVEN LATE-AFTERNOON OBSERVATIONS AND ONGOING FIRES.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 235 PM CDT THU MAY 5 2016

THE MAIN IMPACTS IN THE SHORT TERM ARE CRITICAL FIRE CONDITIONS
TODAY AND A COLD FRONT TOMORROW.

AN UPPER LEVEL RIDGE...COMBINED WITH A SURFACE TROUGH AND
SOUTHWESTERLY MIXING WINDS...HAVE ALLOWED TEMPERATURES THIS
AFTERNOON TO RISE RAPIDLY INTO THE 80S AND LOW 90S. THESE WARM
TEMPERATURES HAVE FURTHER EXACERBATED DRY BOUNDARY LAYER
CONDITIONS. WITH VERY DRY AIR MIXING DOWN RELATIVE HUMIDITY VALUES
HAVE PLUMMETED INTO THE TEENS AND LOW 20S. WIND SPEEDS HAVE BEEN A
BIT BREEZY ACROSS THE JAMES VALLEY. THIS IS WHAT PROMPTED THE
ISSUANCE OF THE RED FLAG WARNING. WIND SPEEDS AROUND 20
MPH...COMBINED WITH HUMIDITY 20 PERCENT OR LESS AND DRY FUELS IS
PRODUCING CRITICAL FIRE CONDITIONS ACROSS THE JAMES VALLEY.

A COLD FRONT WILL SWEEP THROUGH TONIGHT INTO FRIDAY MORNING. WINDS
WILL SHIFT OUT OF THE NORTH BETWEEN 20 AND 30 MPH. TOMORROW
AFTERNOON MINIMUM RELATIVE HUMIDITY AROUND 20 PERCENT IS EXPECTED
IN NORTHWEST AND PORTIONS OF NORTH CENTRAL NORTH DAKOTA BY LATE
AFTERNOON. HOWEVER...BY THIS TIME THE STRONGEST WINDS SHOULD HAVE
PASSED TO THE SOUTH. THEREFORE...THESE AREAS MAY ESCAPE CRITICAL
FIRE CONDITIONS. MODELS CONTINUE TO INDICATE A MAINLY DRY FRONTAL
PASSAGE...WITH A FEW ISOLATED SHOWERS POSSIBLE. HOWEVER...WITH A
PERSISTANT DRY BOUNDARY LAYER...THE LIKELIHOOD OF ANY
PRECIPITATION ACTUALLY REACHING THE GROUND IS RATHER MINIMAL.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 235 PM CDT THU MAY 5 2016

COOLER AIR WILL SETTLE INTO THE AREA THIS WEEKEND IN THE WAKE OF
FRIDAYS COLD FRONT. HOWEVER... PLEASANT TEMPERATURES ARE STILL
EXPECTED WITH HIGHS MAINLY IN THE 70S. DRY CONDITIONS WILL REMAIN.

CHANGES APPEAR ON THE HORIZON FOR THE START THE WORK WEEK AS
AN UPPER LOW CURRENTLY OFF THE CALIFORNIA COAST DEEPENS OVER THE
FOUR CORNERS REGION THIS WEEKEND AND LIFTS INTO THE PLAINS ON
MONDAY...BRINGING CHANCES FOR RAIN AND THUNDERSTORMS.

CHANCES FOR RAIN AND THUNDERSTORMS WILL LINGER OVER THE AREA
THROUGH THE WEEK AS THE GFS AND ECMWF HAVE THE LOW REMAINING
NEARBY THROUGH FRIDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1237 AM CDT FRI MAY 6 2016

VFR CONDITIONS ARE FORECAST OVERNIGHT THROUGH FRIDAY...BUT THERE IS
A LOW PROBABILITY OF SUB-VFR SMOKE AFFECTING PARTS OF THE AREA. THE
MAIN AVIATION WEATHER ISSUE WILL BE A COLD FRONTAL PASSAGE THAT HAS
ARRIVED AT KISN...WHICH HAS SHIFTED WINDS TO THE NORTH. EXPECT WINDS
TO BEGIN INCREASING A FEW HOURS AFTER FRONTAL PASSAGE WITH NORTHERLY
WIND GUSTS TO AROUND 30 KT EXPECTED TO OCCUR FRIDAY LATE MORNING AND
AFTERNOON ACROSS ALL OF WESTERN AND CENTRAL ND.

&&

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

$$

UPDATE...JV
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...JV


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