HAMweather.com Area Forecast Discussion for County Warning Area ARX

Thu, 16 Feb 2012 06:53:21 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1128 PM CST WED FEB 15 2012

.SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT
304 PM CST WED FEB 15 2012

MAIN FORECAST CONCERNS THIS PACKAGE...SMALL -SN CHANCE NORTH
TONIGHT...-SN CHANCE LATE FRI/FRI NIGHT...TEMPERATURES THRU THE
PERIOD.

18Z DATA ANALYSIS HAD LOW PRESSURE OVER HUDSONS BAY WITH A TROUGH TO
THE SOUTH-SOUTHWEST ACROSS WESTERN MN TO ANOTHER LOW OVER OK. PLENTY
OF BOUNDARY LAYER MOISTURE TRAPPED ACROSS THE REGION UNDER A SHALLOW
INVERSION NEAR 950MB. MANY VSBYS REMAINED IN THE 2-6SM RANGE IN FOG
AS OF NOON. A WEAK SHORTWAVE MOVING OUT OF EASTERN SD COMBINED WITH
THE SFC-700MB TROUGH AND SOME 700MB MOISTURE PROVIDING THE FORCING/
LIFT FOR SOME -RA/-SN OVER EASTERN SD/SOUTHWEST MN. THIS PRECIP
LIFTING NORTHEAST TOWARD/INTO CENTRAL MN. MID-DAY TEMPS AGAIN
SEASONABLY MILD FOR MID FEB...IN THE 30S TO LOWER 40S OVER MUCH OF
MN/IA/WI.

15.12Z MODELS LOOK TO HAVE INITIALIZED WELL. THEIR SOLUTIONS
REASONABLY SIMILAR THRU TONIGHT THRU THU NIGHT BEFORE DIVERGING ON
STRENGTH/TIMING/TRACK DETAILS OF A NORTHWEST FLOW SHORTWAVE ACROSS
THE REGION FRI THRU SAT. DPROG/DT OF 500MB HGTS AT 15.12Z SHOWED
MODEL RUNS OF 13.12Z AND 14.12Z VERIFIED QUITE WELL ACROSS MOST OF
NOAM/EASTERN PAC. TREND FAVORED FASTER/STRONGER OF EARLIER
SOLUTIONS WITH THE SHORTWAVE OVER CA/NV. BETWEEN MODEL CONSISTENCY
IMPROVING OVER THE CONUS TONIGHT/THU BUT STILL PLENTY OF DETAIL
DIFFERENCES WITH THE SHORTWAVE DROPPING TOWARD ND BY 00Z FRI. FOR
THU/THU NIGHT MODELS MOVE INTO 2 CAMPS WITH A SHORTWAVE TROUGH AS
IT DROPS INTO THE DAKOTAS/MN...GFS/UKMET SLOWER/STRONGER...NAM/GEM/
ECMWF FASTER/FURTHER EAST AT 00Z SAT. THESE TIMING/STRENGTH
DIFFERENCES CONTINUE TO GROW WITH GFS/UKMET REMAINING SLOWER. ECMWF/
GEM STRONGER WITH YET ANOTHER COMPACT SHORTWAVE TO DROP TOWARD/INTO
NORTHWEST MN LATE SAT/SAT NIGHT. RUN-TO-RUN CONSISTENCY ON THE
DETAILS LEAVES QUITE A BIT TO BE DESIRED BY FRI NIGHT AND BEYOND.
CHECK OF OBS VS. MODEL DATA AT 18Z SHOW ALL QUITE REASONABLE WITH
THE SFC MASS FIELDS OVER CENTRAL NOAM. PER WV IMAGERY ALL ALSO
LOOKED TO HAVE A GOOD HANDLE ON THE SHORTWAVES OF SIGNIFICANCE OVER
NOAM. NAM WAS MISSING ON THE LIGHT PRECIP MOVING NORTHEAST ACROSS MN
TODAY. WITH NO CLEAR MODEL FAVORITE AND THE INCREASING DETAIL
DIFFERENCES THRU THE SHORT TERM...FAVORED THE MODEL/ENSEMBLE
CONSENSUS THIS CYCLE. GIVEN THE WEAK SYSTEM AND ANY IMPACTS ON THE
SENSIBLE WEATHER LOOKING TO BE MINOR...SHORT-TERM FCST CONFIDENCE
AVERAGE THIS CYCLE.

IN THE SHORT TERM...THE SD/SOUTHWEST MN SHORTWAVE WILL CONTINUE TO
LIFT NORTHEAST ACROSS MN/LK SUPERIOR TONIGHT. BULK OF THE MOISTURE/
FORCING/LIFT WITH THIS FEATURE IS ABOVE 700MB AND WILL PASS
NORTHWEST OF THE FCST AREA. THIS WHILE THE COLUMN BELOW 700MB
STRUGGLES TO SATURATE. DID ADD A SMALL -SN /MIXED WITH -RA EARLY IN
THE EVENING/ ACROSS THE FAR NORTH END OF THE FCST AREA TONIGHT. AS
FOR THE SYSTEM LOOKING TO GRAZE THE FAR SOUTH END OF THE FCST AREA
WITH A LITTLE -RA/-SN THIS EVENING. THE TREND CONTINUES WEAKER AS
THIS FEATURE MOVES INTO RIDGING OVER THE EASTERN CONUS AND GENERALLY
CONFLUENT FLOW. MAIN FORCING/LIFT/SATURATION OVER THE SOUTH END OF
THE FCST AREA WITH THIS SYSTEM ALSO GENERALLY ABOVE 700MB. DID LEAVE
A 20-50 PERCENT -RA/-SN CHANCE OVER THE FAR SOUTHEAST END OF THE
FCST AREA THIS EVENING...WITH SEVERAL MODELS/SREF MEAN SHOWING
POTENTIAL FOR A FEW HUNDRETHS OF PRECIP MAINLY OVER SOUTHERN
GRANT/CLAYTON CTYS. BY LATER TONIGHT DEEPER COLD ADVECTION...
ANTICYCLONIC FLOW AND DRYING SPREAD ACROSS THE FCST AREA AS THE MID
LEVEL TROUGH AXIS PASSES AND HIGH PRESSURE BUILDS EAST ACROSS THE
CENTRAL PLAINS. SFC GRADIENT INCREASES FOR TONIGHT/THU WITH
NORTHWEST WINDS AND SUBSIDENCE EXPECTED TO SCOUR OUT THE LOW LEVEL
MOISTURE. WITH CLOUDS THIS EVENING THEN THE NORTHWEST GRADIENT WINDS
LATER TONIGHT...LEFT FOG MENTION OUT OF GRIDS. QUIET THU/THU NIGHT
WITH A DEEPER/DRIER AIRMASS OVER THE AREA. SUNSHINE LOOKS TO OFF-SET
THE WEAK LOW LEVEL COLD ADVECTION THU WITH 925MB TEMPS REMAINING IN
THE 0C TO -4C RANGE. MID/HIGH LEVEL MOISTURE INCREASES OVER THE AREA
FRI...AHEAD OF THE SHORTWAVE ENERGY DROPPING INTO THE DAKOTAS OR MN.
WITH ALL THE SHORTWAVE AND LOWER LEVEL MOISTURE DETAIL DIFFERENCES
BY FRI/FRI NIGHT...WHERE THE LIFT MAY BE AND THE COLUMN MAY
SATURATE...LEFT FRI DRY FOR NOW. APPEARS MUCH OF THE LIFT WITH THE
FRI/FRI NIGHT SHORTWAVE TROUGH WILL AGAIN GO INTO TRYING TO SATURATE
THE COLUMN BEFORE ANY PRECIP WOULD OCCUR. BETTER MODEL CONSENSUS FOR
SATURATION IN THE SFC-700MB LAYER TO OCCUR OVER THE NORTH/EAST ENDS
OF THE FCST AREA FRI NIGHT...AHEAD OF THE SFC-MID LEVEL LOW/TROUGH
AXIS. ADDED A SMALL -SN CHANCE FRI NIGHT MAINLY ALONG/NORTH-EAST OF
I-94. HIGH PRESSURE...ANTICYCLONIC LOW LEVEL FLOW AND LOW LEVEL COLD
ADVECTION BUILD IN FOR FRI NIGHT INTO SAT. 925-850MB WARM ADVECTION
ALREADY RETURNS SAT NIGHT AS HGTS FALL ACROSS THE NORTHERN PLAINS
AHEAD OF THE NEXT LEE TROUGH. 925MB TEMPS ON SAT IN THE -6C TO -10C
RANGE WITH SAT HIGHS LOOKING TO BE CLOSER TO NORMAL.

FAVORING THE MODEL/ENSEMBLE CONSENSUS...TRENDED TOWARD A BLEND OF
THE NUMERICAL MAX/MIN GUIDANCE FOR TONIGHT THRU SAT NIGHT. WITH
MINIMAL SNOW COVER AND SOME SUNSHINE AT LEAST THU AND SAT...DID
FAVOR WARMER OF GUIDANCE HIGHS THESE DAYS.

.LONG TERM...SUNDAY THROUGH WEDNESDAY
304 PM CST WED FEB 15 2012

MEDIUM RANGE MODEL RUNS OF 15.00Z IN REASONABLY GOOD AGREEMENT SUN
WITH SHORTWAVE RIDGING TO BE BUILDING EAST OVER THE NORTH-CENTRAL
CONUS AND STRONGER TROUGHING TO BE DIGGING THRU THE ROCKIES.
CONSISTENCY REMAINS RATHER GOOD MON/TUE AS THE ROCKIES TROUGH MOVES
INTO THE CENTRAL CONUS MON THEN LIFTS ACROSS THE UPPER MIDWEST MON
NIGHT/TUE. TREND IS A BIT SLOWER TOWARD A COMPROMISE OF THE EARLIER
RUNS. TREND IS FOR LONG-WAVE TROUGHING TO DEVELOP OVER THE NORTH-
CENTRAL CONUS LATE TUE/WED. WITH BETTER THAN AVERAGE BETWEEN MODEL
AND RUN-TO-RUN CONSISTENCY...LONG-TERM FCST CONFIDENCE AVERAGE TO
GOOD THIS CYCLE. GOOD CONSENSUS FOR HIGH PRESSURE/MILD AIRMASS TO
DRIFT EAST ACROSS THE UPPER MIDWEST SUN. TROUGH APPROACHES MON BUT
THE SLIGHT SLOWING TREND KEEPS THE DEEPER MOISTURE/STRONGER LIFT
WEST OF THE FCST AREA UNTIL MON NIGHT. PRESENT MODEL CONSENSUS LIFTS
A SFC LOW AND MID LEVEL TROUGH AXIS ACROSS THE MID/UPPER MS VALLEY
MON NIGHT/TUE. LOWER LEVEL THERMAL PROFILES INDICATE POTENTIAL FOR
-RA OR -SN OVER AT LEAST THE SOUTHEAST HALF OF THE FCST WITH THIS
PASSING SYSTEM. 15.12Z MODELS TREND TOWARD A NORTH/SOUTH STREAM
SPLIT OF THE TROUGH/ENERGY AND A WEAKER SYSTEM MON/TUE. 20-40
PERCENT SN OR RA/SN CHANCES MON NIGHT/TUE LOOK GOOD FOR NOW. TROUGH
IS PROGRESSIVE WITH DRIER GENERALLY WESTERLY FLOW FOR TUE NIGHT INTO
WED. PLENTY OF DETAIL DIFFERENCES BY WED WITH TIMING/STRENGTH OF
SHORTWAVES IN THE DEVELOPING CENTRAL NOAM LONGWAVE TROUGH...AND
TIMING/STRENGTH OF THE NEXT LOW TO TRACK ALONG THE US/CAN BORDER.
15.06Z GFS SLOWER LIKE 00Z ECMWF...KEEPING THE NEXT LOW WELL WEST OF
THE REGION AND A DRY FCST FOR THE AREA WED...WHILE 15.12Z GFS A
FASTER SOLUTION FOR WED. FAVORED THE MODEL/ENSEMBLE CONSENSUS ON DAY
7 FOR NOW WITH A SMALL -RA/-SN CHANCE. WITH THE MAIN COMPONENT OF
THE MID LEVEL FLOW WESTERLY...ARCTIC AIR REMAINS WELL NORTH IN CAN
WITH SEASONABLY MILD TEMPS CONTINUING OVER THE AREA WELL INTO NEXT
WEEK. WITH THE UNCERTAINTY IN THE FINER DAY 4-7 DETAILS...A BLEND OF
THE NUMERICAL MAX/MIN GUIDANCE FOR SUN-WED REASONABLE AT THIS TIME.

.AVIATION...THROUGH 06Z FRIDAY
1128 PM CST WED FEB 15 2012

SURFACE OBSERVATIONS THIS EVENING INDICATE THE WEAK SURFACE TROUGH
OF LOW PRESSURE HAS MOVED INTO CENTRAL WISCONSIN WITH THE WINDS
SLOWLY COMING AROUND TO THE NORTHWEST BEHIND THE TROUGH. THE BACK
EDGE OF THE CLOUDS TRAILS WELL BEHIND THE TROUGH BUT IS MAKING
STEADY EASTWARD PROGRESS AND IS NOW OVER SOUTH CENTRAL MINNESOTA.
TIMING THIS OUT WITH SATELLITE SUGGESTS THE CLOUDS WILL CLEAR KRST
BY 10Z AND KLSE AROUND 13Z. ONCE THESE CLOUDS CLEAR OUT...IT LOOKS
LIKE MUCH OF THURSDAY WILL BE CLOUD FREE. THE NEXT NORTHERN STREAM
SHORT WAVE TROUGH WILL START TO APPROACH THE AREA THURSDAY
EVENING. THE 16.00Z NAM IS QUICKER THAN THE 16.00Z GFS TO BRING IN
SOME MID LEVEL MOISTURE AND WOULD HAVE A HIGH VFR CEILING IN PLACE
BY 06Z FRIDAY. FOR NOW HAVE GONE WITH THE SLOWER TIMING OF THE GFS
AND JUST BROUGHT IN SOME HIGH LEVEL CLOUDS DURING THE EVENING
THINKING ANY VFR CEILINGS WILL HOLD OFF UNTIL AFTER 06Z FRIDAY.

.ARX WATCHES/WARNINGS/ADVISORIES...
304 PM CST WED FEB 15 2012

WI...NONE.
MN...NONE.
IA...NONE.