Severe Thunderstorm Warning 10, NWS Bismarck, ND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
411 PM CDT SUN MAR 22 2009

.SHORT TERM...

THE 12 UTC ECMWF HAS FINALLY BEGUN TRENDING TOWARD COOLER SO THAT
THE US 83 CORRIDOR CHANGES OVER TO ALL SNOW BY MID MORNING ON
TUESDAY. THERE IS STILL SOME VARIATION ON AMOUNTS...SO USING
NCEP/HPC SNOW AMOUNTS ENCOMPASSES A CONSERVATIVE APPROACH TO SNOW
AMOUNTS AFTER SUNDAY AND MONDAY THUNDERSTORMS DELIVER A SHOT OF
RAIN WITH SOME THUNDERSTORMS TO ALREADY-FLOODING AREAS OF NORTH
DAKOTA. THERE IS AMPLE INSTABILITY PRESENT WITH THE MASSIVE WARM
CONVEYOR BELT ADVECTING VERY MOIST AIR ALL THE WAY FROM THE GULF
OF MEXICO INTO SOUTHERN CANADA. THEN...THE TROWAL DEVELOPS AS
SURFACE LOW PRESSURE MOVES FROM NORTHEASTERN COLORADO INTO
NORTHERN MINNESOTA AND OCCLUDES.

FOLLOWED THE NCEP/HPC WINTER WEATHER DESK FORECAST SNOW AMOUNTS
WITH THE MAIN BAND OF SNOW STRETCHING FROM BOWMAN AND HETTINGER
INTO THE GARRISON AREA. CANNOT RULE OUT THUNDER SNOW AS ELEVATED
INSTABILITY WRAPS INTO THE COLD SECTOR. THAT WOULD RESULT IN
CONSIDERABLY GREATER SNOW AMOUNTS IN THE HEAVIEST AXIS...BUT IS
VERY DIFFICULT TO FORECAST. SO...WILL RELY ON THE CONSENSUS
AMOUNTS THAT ARE RELATIVELY CONSERVATIVE.

WINDS GET GOING PRETTY SOON INTO THE EVENT...SO WIND DRIVEN RAIN
WILL CHANGE INTO BLOWING SNOW AND CAUSE VISIBILITIES TO DIVE TO
NEAR ZERO IN MODERATE TO HEAVY SNOW BANDS.

CONCERNING HAZARDS...LEFT BISMARCK AND NORTH IN A WATCH DUE TO
UNCERTAINTY WITH CHANGEOVER TO SNOW. WITH THE EVENT NOT FORECAST
TO OCCUR UNTIL TUESDAY MORNING...CAN AFFORD TO PUSH THAT BACK
ANOTHER PERIOD. UPGRADED MOST OF THE REMAINING WATCH TO A BLIZZARD
WARNING WITH THE EXPECTATION THAT THIS MODEL CONSENSUS IS AS GOOD
AS IT CAN GET IN TERMS OF WIND...COLD TEMPERATURES...MOISTURE
AVAILABILITY...AND AGGRESSIVE DYNAMICS. ADDED THE WINTER STORM
WATCH WHERE CHANGEOVER IS EXPECTED TO BE LATER...RESULTING IN LESS
SNOW ACCUMULATION AND LESS DROP IN VISIBILITY...BUT MORE FLOODING
POTENTIAL.

.LONG TERM...WEDNESDAY THROUGH SUNDAY...

OUR SIGNIFICANT WEATHER EVENT FROM EARLIER IN THE WEEK SHOULD BE
WINDING DOWN IF NOT ALL BUT OVER BY WEDNESDAY. MAY HAVE SOME
LINGERING AREAS OF LIGHT SNOW OVER CENTRAL AND EASTERN PORTIONS OF
THE FORECAST AREA DURING THE DAYTIME IN ADDITION TO GUSTY
NORTHWESTERLY WINDS CREATING LIKELY BLOWING AND DRIFTING SNOW.
CYCLONIC FLOW ALOFT INTO FRIDAY WILL ALSO WARRANT MAINTAINING SLIGHT
CHANCES FOR SNOW THURS/THURS NIGHT/FRIDAY. HAVE MAINTAINED LOWERED
DAYTIME AND NIGHTTIME TEMPS DAY 4 THROUGH DAY 7 TO ACCOUNT FOR THE
EXPECTED FRESH SNOW COVER AS WELL AS THE COLDER TEMPS ASSOCIATED
WITH THE LARGE UPPER LEVEL TROUGH/CLOSED LOW DEPICTED ACROSS SOUTH
CENTRAL CANADA/NORTHERN PLAINS. WE MAY SEE A SLIGHT WARM UP TOWARDS
THE WEEKEND...ALTHOUGH GIVEN THE PROGRESSIVE PATTERN DEPICTED THIS
MAY NEED TO BE SCALED BACK.

&&

.AVIATION...

PERIODS OF MVFR-IFR AND LOWER CIGS AND VIS CAN BE EXPECTED TODAY AND
TONIGHT DUE TO RA AND FG...THEN IFR AND LOWER CIGS AND VIS FOR ALL
TAF SITES THROUGHOUT MONDAY AND TUESDAY. A MAJOR SPRING STORM WILL
APPROACH THE NORTHERN PLAINS OVER THE NEXT 24 HOURS...THEN MOVE
THROUGH THE LOCAL REGION MONDAY AFTERNOON THROUGH TUESDAY NIGHT.
AREAS OF SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH TODAY AND
THIS EVENING. WIDESPREAD MODERATE TO HEAVY RAIN/SNOW WILL THEN
DEVELOP SOUTH MONDAY DAYTIME AND SPREAD NORTH AND EAST THROUGHOUT
THE DAY...THROUGH MONDAY NIGHT...AND THROUGH MUCH OF TUESDAY.

&&

.HYDROLOGY...

STEADY RAINS OVER OUR SOUTHEASTERN ZONES THIS AFTERNOON
HAS PROMPTED A FLASH FLOOD WARNING FOR LAMOURE AND DICKEY COUNTIES
THROUGH EARLY THIS EVENING. ALL OF CENTRAL AND WESTERN NORTH DAKOTA
WILL REMAIN UNDER AN AREAL FLOOD WARNING WITH SEVERAL RIVER POINT
FLOOD WARNINGS CONTINUING ALONG SPECIFIC RIVERS. PLEASE SEE
BISFLSBIS FOR SPECIFIC INFORMATION ON THE AREAL FLOOD WARNINGS AND
POINT RIVER FLOOD WARNINGS. PLEASE SEE BISRVSBIS FOR INFORMATION ON
HIGH WATER STATEMENTS. FOR ADDITIONAL INFORMATION ON THE FLASH FLOOD
WARNING OVER LAMOURE AND DICKEY COUNTIES PLEASE SEE BISFFWBIS.
INFORMATION IS ALSO AVAILABLE ON OUR WEBSITE 24/7 AT WEATHER.GOV/BIS

A LARGE STORM WILL BRING SIGNIFICANT PRECIPITATION TO WESTERN AND
CENTRAL NORTH DAKOTA TONIGHT THROUGH TUESDAY NIGHT...SEE THE SHORT
TERM DISCUSSION ABOVE. ADDITIONAL FLOODING WILL OCCUR DURING AND
AFTER THE STORM.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 9 PM CDT /8 PM MDT/ THIS EVENING FOR
NDZ002>005-010>013-018>023-025-033>037-042-045>048-050-051.

BLIZZARD WARNING FROM 7 PM CDT /6 PM MDT/ MONDAY TO 7 PM CDT /6
PM MDT/ TUESDAY FOR NDZ003-011-019>021-034-042-045.

BLIZZARD WARNING FROM 7 AM CDT /6 AM MDT/ MONDAY TO 7 PM CDT /6
PM MDT/ TUESDAY FOR NDZ010-018-031>033-040-041-043-044.

WINTER WEATHER ADVISORY FROM 7 AM MONDAY TO 7 PM CDT TUESDAY FOR
NDZ001-002-009-017.

WINTER STORM WATCH FROM MONDAY EVENING THROUGH TUESDAY EVENING
FOR NDZ005-013-023-025-036-037-047-050.

BLIZZARD WATCH FROM MONDAY EVENING THROUGH TUESDAY EVENING FOR
NDZ004-012-022-035-046.

&&

SCHECK/NH/KS