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000
FXUS63 KBIS 021635
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
1035 AM CST MON DEC 2 2013

.UPDATE...
ISSUED AT 1035 AM CST MON DEC 2 2013

A COMPLEX WEATHER SCENARIO CONTINUES TO DEVELOP OVER THE NORTHERN
PLAINS TODAY. A LEADING SHORTWAVE/SHEAR AXIS CONTINUES TO PIVOT
FROM NORTHWESTERN NORTH DAKOTA INTO SOUTHEASTERN NORTH DAKOTA.
PRECIPITATION IS DEVELOPING AHEAD OF THIS FEATURE. THERMODYNAMIC
PROFILES AND DUAL POL DATA INDICATE FREEZING RAIN OVER THE
SOUTHERN JAMES RIVER BASIN CONTINUING THIS MORNING. AS A
RESULT...EXTENDED THE FREEZING RAIN ADVISORY FOR THE JAMES RIVER
BASIN COUNTIES UNTIL 1 PM CST. NORTH OF I-94...THE BULK OF THE
PRECIPITATION IS FALLING AS SNOW. AS A RESULT...CONTINUED WITH THE
WINTER WEATHER ADVISORY FOR SNOW ACROSS NORTHERN NORTH DAKOTA.

PATCHY DENSE FOG/DRIZZLE/FREEZING DRIZZLE HAS BEEN REPORTED ACROSS
SOUTHWESTERN NORTH DAKOTA THIS MORNING. ADDED SAID SENSIBLE WEATHER TO
THE GRIDS THROUGH THIS AFTERNOON. SNOW SHOULD BEGIN TO TAKE OVER
SOUTHWESTERN NORTH DAKOTA AFTER SUNSET TONIGHT AS THE LOW
APPROACHES.

THE MEDIUM RANGE MODELS CONTINUE TO STRUGGLE WITH THE STRENGTH OF
THE SECOND WAVE THROUGH NORTH DAKOTA TUESDAY AND WEDNESDAY. WILL
KEEP THE WATCH GOING FOR THIS UPDATE AS A RESULT.

UPDATE
ISSUED AT 645 AM CST MON DEC 2 2013

LEAD S/WV AND STRONG OVERRUNNING PRECIPITATION CONTINUE EAST
ACROSS THE DAKOTAS EARLY THIS MORNING. WEST EDGE OF PRECIPITATION
EXTENDS NORTHWEST FROM CENTRAL SIOUX COUNTY INTO WEST CENTRAL
NORTH DAKOTA. AT THE MOMENT DRY OVER THE SOUTHWEST. TRICKY
PRECIPITATION TYPE FORECAST...BUT IT APPEARS THE SNOW/FREEZING
RAIN LINE IS FROM NORTH OF JAMESTOWN BACK WEST- NORTHWEST TO
BETWEEN WILLISTON AND TIOGA. CURRENT WINTER HEADLINES LOOK OK AS
OF THIS FORECAST ISSUANCE.

OTHER UPDATES MINOR...JUST TRENDING HOURLY WEATHER ELEMENTS BASED
ON CURRENT OBS AND NEAR TERM HR MODEL OUTPUT.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY NIGHT)

ISSUED AT 515 AM CST MON DEC 2 2013

THE SHORT TERM PERIOD HAS BEEN EXTENDED THROUGH TUESDAY NIGHT TO
BETTER MATCH MORE OF THE STORM POTENTIAL IMPACTS. OTHER SHIFT
DUTIES OF THE SHORT TERM WERE TURNED OVER TO THE LONG TERM DESK.

THIS IS A VERY COMPLEX CASE AS VARIOUS MODEL OUTPUT IS NOT COMING
INTO AGREEMENT ON PLACEMENT OR INTENSITY OF IMPACTS. IF ANYTHING
THE GROWING FORECASTER CONFIDENCE OF THE PAST 24 HOURS HAS NOW
REVERSED. CONFIDENCE AT THIS POINT IS NOT HIGH. FOR THAT REASON
THE FORECAST PHILOSOPHY THIS SHIFT HAS BEEN TO WEATHER ADVISORY
THE FIRST PERIOD OR TWO OF THE FORECAST AS NECESSARY...AND
CONTINUE THE WATCH FOR THE LATER PERIODS...NAMELY VERY LATE MONDAY
NIGHT THROUGH WEDNESDAY. THIS PHILOSOPHY WILL DECREASE LEAD TIME
ON ANY STORM WARNINGS SHOULD THEY BECOME NEEDED...BUT WILL BETTER
SERVE LATER SHIFTS BY NOT ATTEMPTING TO LOCK THEM IN TO A LOW
CONFIDENCE FORECAST.

THESE MODEL DIFFERENCES SHOW UP AT VARIOUS OUTPUT LEVELS FROM
PLACEMENT OF THE SURFACE LOW TO THE MID LEVEL WAVE BEING CLOSED
OFF OVER WESTERN MONTANA TO IT COMING THROUGH NORTH DAKOTA AS AN
OPEN WAVE. PLACEMENT OF FEATURES THEN IMPACTS THE THERMAL PROFILE
AND TIMING AND INTENSITY OF THE COLD AIR ADVECTION.

AN ALL BLEND APPROACH FAVORS THE IMPACTS BEING ADVISORY LEVEL FOR
TODAY AND TONIGHT...AND BORDERLINE ADVISORY / WARNING LEVEL FOR
TUESDAY AND WEDNESDAY...THUS THE WATCH. A NAM SOLUTION BRINGS THE
BRUNT OF THE SNOW ACROSS SIOUX AND EMMONS COUNTIES AND THEN
NORTHEAST FROM THERE WHILE A GFS SOLUTION WOULD KEEP THE HEAVIEST
SNOW ON THE SOUTH DAKOTA SIDE OF THE STATE LINE.

REGARDLESS...THERE SHOULD BE SOME SNOW ACROSS THE ENTIRE FORECAST
AREA...AND WIND WITH BLOWING SNOW...AND THAT FRESH SNOW WILL
ALLOW FOR A VERY COLD END TO THIS WEEK.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)

ISSUED AT 515 AM CST MON DEC 2 2013

FORECAST HIGHLIGHTS IN THE LONG TERM PERIOD WILL BE LINGERING
CHANCES FOR ACCUMULATING SNOW AND LIKELY BLOWING SNOW ON
WEDNESDAY...AND VERY COLD AIR SURGING INTO THE REGION THROUGH THE
PERIOD.

THE LONG TERM PERIOD BEGINS 12Z WEDNESDAY. STILL LOTS OF UNCERTAINTY
REGARDING HOW FAST THE STORM SYSTEM WILL PUSH EAST ACROSS THE
REGION. LATEST NAM/SREF/ECMWF LINGER SNOW ACROSS WEST AND CENTRAL
NORTH DAKOTA THROUGH WEDNESDAY AFTERNOON WITH CHANCES DIMINISHING
WEDNESDAY NIGHT...WHILE THE CONSISTENTLY MORE PROGRESSIVE GFS ENDS
MOST IF NOT ALL PRECIPITATION BY LATE TUESDAY NIGHT. OPTED TO LEAN
ON FORECAST CONSISTENCY AND A MODEL BLEND...MAINTAINING CHANCE POPS
WEDNESDAY DAYTIME...FOLLOWED BY SLIGHT CHANCE POPS WEDNESDAY NIGHT.
THE WINTER STORM WATCH WILL CONTINUE WITH THIS FORECAST PACKAGE ALL
LOCATIONS WEDNESDAY MORNING AND AFTERNOON. EVEN IF WE DO NOT REALIZE
MUCH ACCUMULATING SNOW ON WEDNESDAY...NORTHWEST WINDS GUSTING TO 30
MPH OR MORE (DEPENDING ON HOW DEEP THE SFC LOW EVENTUALLY WILL BE
AND HOW FAST IT MOVES EAST) WILL LIKELY CREATE AREAS OF BLOWING SNOW
FOR THOSE LOCATIONS THAT ACCUMULATE. CONFIDENCE IS NOT THE GREATEST
AS MODELS ARE STILL MAKING THE SNOWFALL PREDICTION CHALLENGING TO
SAY THE LEAST.

WITH THE EXCEPTION OF THE NORTH...WHICH MAY SEE WRAP AROUND LIGHT
SNOW THURSDAY DAYTIME IF THE LATEST ECMWF IS CORRECT...ALL LOCATIONS
SHOULD BE DRY BY THURSDAY MORNING. A DRY FORECAST WILL REMAIN UNTIL
LATER THIS WEEKEND...WHEN A COLORADO LOW IS FORECAST TO LIFT THROUGH
THE CENTRAL PLAINS SUNDAY...AND INTO THE UPPER MISSISSIPPI VALLEY
SUNDAY NIGHT. MOST IF NOT ALL PRECIPITATION ASSOCIATED WITH THIS
STORM SYSTEM IS DEPICTED TO BE OFF TO OUR SOUTH AND EAST BY MOST
MODELS.

THE MAIN HIGHLIGHT BESIDES THE LINGERING SNOW CHANCES AND BLOWING
SNOW POTENTIAL WILL BE THE ARCTIC AIR MASS SETTLING OVER THE
NORTHERN PLAINS BRINGING THE COLDEST AIR SO FAR THIS FALL/WINTER.
DAYTIME TEMPERATURES WILL STRUGGLE TO REACH ZERO ACROSS THE SOUTH ON
THURSDAY...AND WILL EVEN STRUGGLE TO REACH WARMER THAN 10 BELOW ZERO
NORTHWEST ON FRIDAY. CURRENT FORECAST LOWS THURSDAY/FRIDAY/SATURDAY
NIGHTS ARE THE COLDEST...NEAR 25 BELOW ZERO NORTH AND 10-15 BELOW
ZERO SOUTH. WOULD NOT BE SURPRISED TO SEE COLDER THAN 30 BELOW ONE
OF THOSE NIGHTS. WIND CHILLS THURSDAY AND FRIDAY NIGHTS WILL BE NEAR
45 BELOW ZERO NORTH AND 30 BELOW ZERO SOUTH. THUS WIND CHILL
HEADLINES WILL BE LIKELY.

LOOKING FURTHER AHEAD WITH THE 00Z GFS/ECMWF...THE AIR MASS MODERATES
SLIGHTLY NEXT SUNDAY...BUT ANOTHER SURGE OF ARCTIC AIR LOOKS TO
ARRIVE THE FOLLOWING MONDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)

ISSUED AT 645 AM CST MON DEC 2 2013

MULTIPLE HAZARDS TO AVIATION FOR THE 12Z TAF PERIOD. A DEVELOPING
WINTER STORM ACROSS MONTANA WILL BRING AN INITIAL SURGE OF
FREEZING RAIN ACROSS NORTHWEST AND SOUTH CENTRAL NORTH DAKOTA
THROUGH THIS MORNING. THIS WILL IMPACT MAINLY KBIS AND
KJMS...POSSIBLY KISN. SUFFICIENT WARM AIR SHOULD MAINTAIN RAIN AT
KDIK THIS MORNING IF PRECIPITATION FALLS. SNOW WILL DEVELOP ACROSS
NORTHERN NORTH DAKOTA INTO EASTERN NORTH DAKOTA AFTER DAYBREAK
MONDAY. THIS WILL IMPACT KISN-KMOT-KJMS WITH LOW IFR CONDITIONS
IN SNOW. KDIK-KBIS LIKELY TO SEE MVFR-IFR CONDITIONS DUE TO
CEILINGS...WITH SOME SNOW DEVELOPING AT KDIK LATER THIS AFTERNOON.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM LATE TONIGHT THROUGH WEDNESDAY AFTERNOON
FOR NDZ017>020-031>036-040>048-050-051.

WINTER WEATHER ADVISORY UNTIL 6 AM CST TUESDAY FOR NDZ001>005-
009>013-021>023-025.

WINTER STORM WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY
AFTERNOON FOR NDZ001>005-009>013-021>023-025-037.

WINTER WEATHER ADVISORY UNTIL 6 AM CST TUESDAY FOR NDZ037.

FREEZING RAIN ADVISORY UNTIL 1 PM CST THIS AFTERNOON FOR NDZ036-
037-047-048-050-051.

&&

$$

UPDATE...TM
SHORT TERM...JPM
LONG TERM...NH
AVIATION...NH