FXUS63 KBIS 152142
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
342 PM CST TUE DEC 15 2009
.SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT
CONCERNS WITH THE FORECAST TONIGHT AND WEDNESDAY DEAL WITH CURRENT
WIND CHILL ADVISORY...WARMING TEMPERATURES AND CHANCES FOR SOME
FREEZING PRECIPITATION.
LATEST LOOK AT THE SURFACE CONDITIONS SHOW RIDGING OF BITTERLY COLD
AIR OVER MAINLY EASTERN NORTH DAKOTA FROM HIGH PRESSURE OVER ERN
NEBRASKA. TEMPERATURES RANGE FROM ZERO TO 5 BELOW IN THE
NORTHEASTERN COUNTIES TO ZERO TO 5 ABOVE IN THE FAR SOUTHWEST. HIGH
CLOUDS HAVE OVERSPREAD MAINLY WESTERN AREAS OF CWA. LOW PRESSURE
WAS OBSERVED OVER NORTHERN MONTANA. THE LIGHT WINDS AND SOME
MODERATION OF TEMPERATURES THIS AFTERNOON WILL RESULT IN
LETTING THE WIND CHILL ADVISORY EXPIRE WITH THE 4 PM ZONES.
LOOKING AT THE MODELS TODAY INDICATE COLD UPPER TROUGH OVER THE
EASTERN GREAT LAKES REGION WITH UPPER RIDGING IN THE NORTHERN
ROCKIES. THE TREND IS FOR THE RIDGING TO COLLAPSE DUE TO WEAK
SHORTWAVES MOVING OVER THE TOP THE NEXT FEW DAYS. GFS...NAM AND
ECMWF SHOW H850 WARM ADVECTION GRADUALLY MOVING ACROSS THE CWA
TONIGHT AND WEDNESDAY. MODELS SHOW RELATIVLY WEAK SURFACE FLOW
DURING THIS PERIOD SO ADVECTION AT BEST WILL BE WEAK AND GRADUAL.
H850 TEMPERATURES THIS EVENING WILL RANGE FROM -10C IN THE
NORTHEAST TO AROUND ZERO IN THE SOUTHWEST. ON WEDNESDAY THESE
TEMPERATURES CONTINUE TO WARM FROM AROUND ZERO IN THE SOUTH
CENTRAL TO NEAR 5 ABOVE IN THE SOUTHWEST. THIS WARMING MAY LEAD TO
LIGHT FREEZING DRIZZLE OR LIGHT FREEZING RAIN MAINLY IN THE NORTH
AROUND MINOT TO THE CANADIAN BORDER. THE GFS QPF SHOWS /0.06/
INCHES WITH THE NAM AND ECMWF INDICATING ABOUT /0.02/ INCHES. IN
ANY CASE REAL LIGHT AMOUNTS. WHILE THE MODELS DO NOT SHOW ANY
CHANCE OF FREEZING PRECIPITATION OCCURRING IN THE SOUTHWEST AND
SOUTH CENTRAL...I CANT RULE IT OUT. WILL LEAVE ANY MENTION OF THIS
IN THOSE AREAS OF THE ZONES TONIGHT AND LET THE EVENING SHIFT
DECIDE IF THIS POSSIBLE FOR WEDNESDAY.
MOS TEMPERATURES SHOW THE MODERATION IN THE RANGE OF 25 TO 30
DEGREES IN THE WEST AND CENTRAL WITH MID TEENS IN THE EASTERN
COUNTIES. FEEL THAT THIS WARMING IS A BIT OVERDONE AND THUS HAVE
TAPERED THE MAX TEMPERATURES BACK A FEW DEGREES. THE SHALLOW COLD
DENSE AIR AT THE SURFACE WILL NOT BE MOVED OUT BY LIGHT WINDS AND
WEAK ADVECTION. THE WARMING WILL BE MAINLY ALOFT AND IF THIS
HAPPENS SOME FREEZING PRECIPITATION WILL BE POSSIBLE.
FOR THURSDAY AND FRIDAY...ANOTHER WEAK RIPPLE WILL MOVE ALONG THE
UPPER FLOW AND RESULT IN SOME LIGHT SNOW SHOWERS IN THE NORTH
AGAIN. TEMPERATURES WILL AGAIN RANGE FROM 25 TO 30 DEGREES FOR
HIGHS BOTH DAYS.
OVERALL...THE WARMING WILL BE A WELCOME CHANGE.
.LONG TERM...SATURDAY THROUGH TUESDAY...
THE LONG TERM PERIOD START OUT ON SATURDAY WITH SHORT WAVE RIDGING
OVER THE REGION. AN APPROACHING SHORTWAVE TROUGH IN A NORTHWEST
UPPER FLOW WILL BRING SOME MID LEVEL FORCING AND WEAK SURFACE
DEVELOPMENT OVER WESTERN AND CENTRAL NORTH DAKOTA BY SATURDAY
EVENING. AT THIS TIME ANY PRECIPITATION LOOKS TO BE LIGHT...BUT THE
GFS/ECMWF AND GEM ALL PRODUCE SOME QPF OVER NORTH DAKOTA. WILL
INTRODUCE SOME SLIGHT CHANCE POPS ACROSS THE CENTRAL ON SATURDAY
NIGHT.
ON SUNDAY AND SUNDAY NIGHT...THE SURFACE AND UPPER SYSTEMS MOVE
THROUGH THE AREA. SHORTWAVE ENERGY MOVES ACROSS THE NORTHERN ROCKIES
AS WELL AS FROM THE NORTHWEST...OVER THE TOP OF THE UPPER RIDGE. THE
GFS DEVELOPS AN UPPER LOW JUST NORTH OF THE STATE BY 12Z MONDAY. THE
ECMWF IS NOT AS STRONG WITH THIS FEATURE...BUT DOES KEEP SOME UPPER
LEVEL TROUGHINESS FROM THE GREAT LAKES REGION...BACK INTO THE
NORTHERN PLAINS. THE GLOBAL GEM DOES NOT BRING THE CANADIAN VORTEX
SOUTH LIKE THE OTHER TWO MODELS...AND THUS BRINGS UPPER RIDGING OVER
THE AREA AFTER THE PASSAGE OF THE SHORTWAVE MOVING THROUGH THE
NORTHERN ROCKIES. FAVOR A GFS/ECMWF BLEND HERE AND WILL KEEP A
CHANCE OF SNOW IN THE FORECAST BOTH SUNDAY AND SUNDAY NIGHT.
BEYOND MONDAY...MODELS CONTINUE TO RETROGRADE AN UPPER LOW WEST
ACROSS THE CANADIAN PROVINCES...BUT THEIR PLACEMENT OF THE LOW
DIFFERS QUITE A BIT. THUS ANY TIMING AND PLACEMENT OF INDIVIDUAL
FEATURES WILL BE PROBLEMATIC. THERE IS AGREEMENT THAT TEMPERATURES
WILL REMAIN BELOW NORMAL THROUGH THE FIRST HALF OF NEXT WEEK.
&&
.AVIATION...
CURRENTLY...SURFACE HIGH PRESSURE IS SLIDING EAST AND WARMER
TEMPERATURES ARE TRYING TO PUSH INTO NORTH DAKOTA. A WEAK SHORTWAVE
COMBINED WITH WARM ADVECTION ON THE BACK SIDE OF THE SURFACE HIGH
WILL COMBINE TO PRODUCE SOME LIGHT PRECIPITATION ACROSS NORTHERN
NORTH DAKOTA. AT THIS TIME EXPECT MAINLY VFR CONDITIONS WITH PERHAPS
A BRIEF PERIOD OF MVFR CEILINGS FROM ISN TO MOT TONIGHT. FOR NOW
WILL LIKELY NOT MENTION MVFR CIGS TONIGHT. WEAK SOUTHERLY FLOW WILL
CONTINUE LATE TONIGHT THROUGH THE DAY ON WEDNESDAY.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
VJ/TWH
