FXUS63 KBIS 101011
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
411 AM CST THU DEC 10 2009
.SHORT TERM...TODAY THROUGH SATURDAY NIGHT...
COLD/WELL BELOW SEASONABLE TEMPERATURES CONTINUE TO BE THE MAIN
FORECAST HIGHLIGHT IN THE SHORT TERM PERIOD. MODELS ARE SHOWING A
LARGE SPREAD IN THEIR SOLUTIONS FRIDAY NIGHT INTO SATURDAY. WILL
SIDE WITH HPC GUIDANCE AND USE A MODEL COMPROMISE OF THE 00Z
GFS/ECMWF/GEFS MEAN.
CURRENTLY...THE POLAR VORTEX CONTINUES TO SLOWLY PUSH SOUTH ACROSS
NORTH CENTRAL CANADA...SPEWING S/WV IMPULSES SOUTH INTO/TOWARDS THE
NORTHERN PLAINS. ONE OF THESE IMPULSES IS NOW MOVING OVER
NORTHWESTERN ND...ALONG WITH AN ASSOCIATED WEAK SFC TROUGH
STRETCHING FROM SOUTHEASTERN MT NORTHEAST TOWARDS LAKE WINNIPEG.
THESE FEATURES ARE RESULTING IN INCREASING CLOUDS AND SCATTERED
FLURRIES OVER MY WEST AND CENTRAL COUNTIES...AS WELL AS CAA AND
INCREASING NORTHWESTERLY WINDS AS PRESSURE RISES BEHIND THE TROUGH
ADVANCE SOUTHEAST INTO THE STATE. LATEST SFC OBS SHOW THE
TEMPERATURE RISES AHEAD OF THE SFC TROUGH ACROSS MY SOUTHWEST
BEGINNING TO DROP AGAIN AS THE FRONT PUSHES SOUTHEAST. THUS WILL LET
THE WIND CHILL ADVISORY CONTINUE DUE TO THESE TEMPERATURE AND WIND
TRENDS.
BEHIND THE FIRST WAVE THIS MORNING ANOTHER S/WV IMPULSE SLIDES
ACROSS THE STATE THIS AFTERNOON SO WILL CONTINUE TO MENTION SCT
FLURRIES AREA WIDE. WILL SEE TEMPERATURES MODERATE SOME (ESPECIALLY
WEST AND SOUTH CENTRAL) AS THIS SECOND WAVE IS FURTHER EAST ALLOWING
WAA TO PUSH INTO THE SOUTHWESTERN HALF OF THE STATE. DAYTIME HIGHS
AS A RESULT WILL CLIMB INTO THE LOWER TEENS SOUTHWEST TO NEAR 5 TO
10 ABOVE NORTHWEST AND SOUTH CENTRAL. WEAK IMPULSES IN NORTHWESTERLY
FLOW ALOFT TONIGHT...ALONG WITH ANOTHER SURGE OF COLD AIR OVER MY
CENTRAL AND EAST THIS EVENING...WILL RESULT IN ME MAINTAINING SCT
FLURRIES THROUGH 12Z. THE DAY CREW MAY WISH TO REEVALUATE.
SEMI-ACTIVE PATTERN CONTINUES INTO FRIDAY DAYTIME AS ELONGATED
ENERGY EMBEDDED IN NORTHWEST FLOW STRETCHES INTO THE NORTHERN
PLAINS/SOUTH CENTRAL CANADA. THIS RESULTS IN WEAK LEE SIDE SFC LOW
PRESSURE DEVELOPING ON FRIDAY AND ADVANCING SOUTHEAST INTO THE
DAKOTAS FRIDAY NIGHT. WILL STAY THE COURSE WITH DRY WEATHER AHEAD OF
THE SFC LOW FRIDAY DAYTIME AND SLIGHT CHANCES FOR SNOW ACROSS THE
NORTH FRIDAY NIGHT WHERE THE BEST LOW/MID LEVEL FORCING WILL BE NEAR
THIS SYSTEMS COLD FRONT.
SURFACE LOW PRESSURE REDEVELOPS SATURDAY OFF TO OUR WEST ALONG WITH
OUR FLOW ALOFT BECOMING MORE ZONAL AS THE POLAR VORTEX ELONGATES
ACROSS MUCH OF SOUTHWEST AND SOUTH CENTRAL CANADA. IT IS UNCERTAIN
WHERE THE MAIN BAROCLINIC ZONE WILL SET UP (AND THUS CHANCES FOR
PRECIPITATION) WITH THE GFS AND SREF FURTHER SOUTH ACROSS THE
NORTHERN TWO THIRDS OF ND AND THE EC FURTHER NORTH ACROSS SOUTHERN
CANADA. HAVE OPTED TO USE A BLEND WHICH LEAVES ME WITH PRETTY MUCH
WHAT WAS INHERITED FROM WEDNESDAY'S DAY SHIFT WITH SLIGHT CHANCES
ACROSS THE NORTH AND WEST.
TEMPERATURES WILL CONTINUE TO SLOWLY MODERATE INTO FRIDAY AS WAA
AHEAD OF THE SFC LOW PUSHES INTO THE FORECAST AREA. SATURDAY IS LESS
CERTAIN AS MUCH DEPENDS ON THE AFFECTS FROM THE ARCTIC LOW OVER
CENTRAL CANADA. ONCE AGAIN USED A GFS/EC BLEND LEANING MORE TOWARDS
THE COLDER BIAS-CORRECTED GFS GUIDANCE. EVEN THIS METHOD RESULTED
IN WARMER TEMPS FROM WHAT WAS INHERITED.
.LONG TERM...SUNDAY THROUGH THURSDAY...
THE MAIN FORECAST UNCERTAINTY TONIGHT IS WITH MINIMUM TEMPERATURES
EARLY NEXT WEEK AS AN UPPER LEVEL LOW PASSES NORTH OF WINNIPEG AND
FORCES UPPER LEVEL NORTHWEST FLOW OVER THE NORTHERN PLAINS.
WHILE THE 00 UTC ECMWF/GFS/GEFS MEMBERS ARE IN RELATIVELY GOOD
AGREEMENT ON LARGE SCALE FEATURES THROUGH MONDAY NIGHT...THE
MESOSCALE NATURE OF VERY COLD MORNING TEMPERATURES MAKES FORECASTING
THEM QUITE DIFFICULT AT SUCH LONG TIME RANGES. THIS IS PRIMARILY
BECAUSE THE JUXTAPOSITION OF CLEAR SKIES AND LITTLE WIND IS GREATLY
TIED TO SURFACE HIGH PRESSURE...WHICH COULD EASILY BE OFF A BIT ON A
DAY 5 FORECAST. THAT SAID...WITH MODELS AGREEING ON SUCH A STRONG
SURFACE HIGH IT IS JUSTIFIED TO LOWER CONTINUITY TEMPERATURES IN
GRIDDED FORECAST FOR MONDAY AND TUESDAY.
AS MENTIONED IN YESTERDAYS DISCUSSION...THE MORE NORTHERN THE TRACK
OF THE AFOREMENTIONED VORTEX THE BETTER THE CHANCES FOR
PRECIPITATION AS WAVES EMBEDDED IN THE MAIN WESTERLY FLOW.
CONSEQUENTLY...THE PRECIPITATION CHANCES FOR SUNDAY AND MONDAY WERE
INCREASED FROM CONTINUITY.
&&
.AVIATION...
MVFR REPORTS OF HAZE DO NOT APPEAR TO BE THE RESULT OF SUSPENDED ICE
CRYSTALS...BUT PERHAPS EXCESSIVE VEHICLE EXHAUST. THERE IS ALSO SOME
RISK OF MVFR CONDITIONS WITH ANY OF THE MORE INTENSE SNOW SHOWERS
THAT HAVE SUFFICIENT SNOWFALL TO COMBINE WITH WINDS AND LIMIT
VISIBILITIES TO AROUND 2SM. MINOT AND WILLISTON ARE THE MOST LIKELY
TO EXPERIENCE THE OCCASIONAL IFR CEILING THROUGH THURSDAY MORNING.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL NOON CST /11 AM MST/ TODAY FOR
NDZ001>005-009>013-017>023-025-031>037-040>048-050-051.
&&
$$
SHORT TERM...NH
LONG TERM/AVIATION...SCHECK
