Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 252328
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
628 PM CDT MON APR 25 2016

.UPDATE...
ISSUED AT 611 PM CDT MON APR 25 2016

TEMPERATURES REMAIN NEAR THE RAIN/SNOW THRESHOLD ACROSS SOUTHWEST
AND WEST CENTRAL NORTH DAKOTA THIS EVENING. WHILE THERE MAY BE A
SPOT OR TWO OF SLEET MIXED IN FOR THE MOST PART A MIX OF RAIN AND
SNOW LOOKS TO PREDOMINATE. TWEAKED THE TEMPERATURES A BIT COOLER
THROUGH THE EVENING HOURS WHICH WILL MAINTAIN MORE SNOW AS A
WEATHER ELEMENT WEST. OTHERWISE SINCE TEMPERATURES BOTTOM OUT IN
THE LOWER 30S DONT EXPECT ACCUMULATIONS MORE THAN AN INCH ON
GRASSY AREAS WEST CENTRAL TONIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 400 PM CDT MON APR 25 2016

OUR FOCUS THROUGH TUESDAY IS ON THE LINGERING LIGHT RAIN...AND IN
PARTS OF WESTERN ND THE POTENTIAL FOR LIGHT SNOW.

AS OF 20 UTC...A MID-LEVEL LOW BASED NEAR 700 MB IS SPINNING OVER
SOUTHEAST ND PER SATELLITE...RADAR...AND RAP ANALYSES. RAIN
MOVING WESTWARD THROUGH CENTRAL AND SOUTHWEST ND AT MID AFTERNOON
IS TIED TO THE FORCING ASSOCIATED WITH THIS FEATURE...AND BROAD
MID-LEVEL DEFORMATION THAT STRETCHES BACK INTO NORTHEAST MT. MODEL
GUIDANCE FROM 12 UTC SUGGESTS THE MID-LEVEL LOW WILL SLOWLY WASH
OUT BY 12 UTC TUESDAY...BUT THE LINGERING DEFORMATION-AIDED
FORCING WILL BE ENOUGH TO SUSTAIN THE PRECIPITATION ACROSS WESTERN
ND TONIGHT. THE 12 UTC GFS...NAM AND ECMWF ARE IN GOOD AGREEMENT
WITH THAT...AS AS THE MORE RECENT RAPID-REFRESH /RAP AND HRRR/
GUIDANCE. THE THERMAL PROFILE MAY MARGINALLY SUPPORT SOME LIGHT
SNOW ACROSS WESTERN ND TONIGHT AND TUESDAY MORNING. THE 12 UTC NAM
WAS MORE ROBUST IN ITS ADVERTISEMENT OF QPF FALLING AS SNOW /BASED
ON THE NCEP DOMINANT PRECIPITATION-TYPE ALGORITHM APPLIED TO ITS
MASS FIELDS/ THAN MOST OTHER GUIDANCE...BUT EVEN THE MULTI-MODEL
CONSENSUS WE UTILIZED TO CONSTRUCT THE FORECAST YIELDED UP TO
ABOUT AN INCH OF SNOW IN SOME PARTS OF WESTERN ND BY TUESDAY
MORNING.

OTHERWISE...ON THE LARGE SCALE...AFTERNOON MOISTURE CHANNEL /WATER
VAPOR/ IMAGES SHOW THE NEXT IN WHAT HAS BEEN A SERIES OF SHORTWAVE
TROUGHS/CLOSED UPPER-LEVEL LOWS DIGGING INTO THE FOUR CORNERS. THE
IMPACTS FROM THIS WAVE WILL MOSTLY HOLD OFF UNTIL TUESDAY NIGHT OR
WEDNESDAY...BUT IT WILL REINFORCE BROAD DIFFLUENT FLOW ALOFT OVER
THE AREA DURING THE DAY TUESDAY. THAT IS SUPPORTIVE OF A CONTINUED
CHANCE OF RAIN AND SNOW...ESPECIALLY WEST OF HIGHWAY 83. HIGHS ARE
FORECAST TO BE IN THE 40S F WITH EASTERLY FLOW AND CLOUD COVER.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 400 PM CDT MON APR 25 2016

ANOTHER WAVE OF PRECIPITATION IS EXPECTED WEDNESDAY AND WEDNESDAY
NIGHT...WITH YET ONE MORE CHANCE OF RAINFALL THIS WEEKEND.

THE 12 UTC MODEL GUIDANCE IS IN RELATIVE SYNC ADVERTISING A 500-MB
LOW MOVING ACROSS NEB ON WEDNESDAY...WITH DEEP EAST-SOUTHEAST FLOW
ALOFT OVER THE NORTHERN PLAINS TO ITS NORTH. THE CONSENSUS OF THAT
GUIDANCE TAKES A WELL-DEFINED BATCH OF PRECIPITATION NORTHWARD AND
INTO SOUTHERN AND WESTERN ND BY DAYTIME WEDNESDAY. TWO CHALLENGES
WITH THAT PRECIPITATION SHIELD WILL BE 1/ DETERMINING ITS PHASE IN
WESTERN AND PERHAPS SOUTH CENTRAL ND WHERE SOME WET SNOW MAY OCCUR
AND 2/ DECIDING HOW FAR NORTH IT WILL REACH. WHERE THE FIRST ISSUE
IS CONCERNED...MODEL GUIDANCE HAS CONSISTENTLY BEEN CALLING FOR AN
AREA OF SUB-FREEZING 850-MB TEMPERATURES DEVELOPING WEDNESDAY WITH
THE ONSET OF THE PRECIPITATION...WHICH IS LIKELY SUGGESTS WET BULB
COOLING WILL BE NECESSARY TO DRIVE TEMPERATURES LOW ENOUGH FOR ANY
SNOWFALL. THAT IS SOMEWHAT OF A LOW-CONFIDENCE ITEM...AND MOST OF
THE 12 UTC GUIDANCE PRECIPITATION-TYPE ALGORITHM OUTPUT BACKED OFF
ON SNOWFALL POTENTIAL. THUS...WE HELD WITH A MIX OF RAIN AND SNOW
IN THE FORECAST FOR NOW. FINALLY...NOTE THAT THE PRECIPITATION ON
WEDNESDAY APPEARS TO EMANATE IN THE MODELS OUT OF THE DEEP MOIST
CONVECTION THAT ERUPTS LATE TUESDAY IN THE CENTRAL PLAINS. THAT IS
A REASONABLE SOLUTION...BUT WHEN DEEP CONVECTION IS INVOLVED THERE
IS ALWAYS SOME INHERENT UNCERTAINTY IN DOWNSTREAM PRECIPITATION.

OTHERWISE...MEAN WESTERN UNITED STATES TROUGHING WILL PERSIST INTO
THE WEEKEND...WITH ANOTHER CHANCE OF RAINFALL SATURDAY AND SUNDAY.
THE 12 UTC ECMWF LIFTED THE WEEKEND SHORTWAVE A BIT FURTHER NORTH
THAN ITS PREVIOUS RUNS AND 12 UTC GFS AND GFS ENSEMBLE...WHICH IS
INDICATIVE OF SOME UNCERTAINTY AS TO WHETHER OR NOT THE STATE WILL
JUST BE GRAZED BY THAT WAVE OR NOT. TEMPERATURES WILL REMAIN COOL
WITH HIGHS MAINLY IN THE 40S AND 50S F DURING THE LONG TERM.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 611 PM CDT MON APR 25 2016

BROAD AREA OF COOL MOIST AIR REMAINS IN PLACE ACROSS NORTH DAKOTA WITH
IFR CEILINGS FROM KDIK- KBIS- KJMS TONIGHT AND TUESDAY. MVFR EXPECTED
KISN-KMOT BECOMING IFR AFTER 12Z.

&&

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

$$

UPDATE...WAA
SHORT TERM...CJS
LONG TERM...CJS
AVIATION...WAA



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