FXUS63 KGID 050835
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
235 AM CST SUN FEB 5 2012

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT. 11-3.9 MICRON
SATELLITE IMAGERY EARLY THIS MORNING SHOWED A LARGE AREA OF
STRATUS DROPPING SOUTH FROM EASTERN SOUTH DAKOTA AND MINNESOTA
INTO EASTERN NEBRASKA. THE MODELS OVERALL HAVE NOT DONE A GOOD JOB
IN CAPTURING THIS AREA...THOUGH THE HRRR DOES SEEM TO HAVE AN IDEA
OF ITS PRESENCE. FOLLOWING THE HRRR WOULD SUGGEST THE WESTERN EDGE
OF THE STRATUS COULD MAKE A RUN FOR FAR EASTERN PORTIONS OF THE
FORECAST AREA. WILL INCREASE CLOUDS ACCORDINGLY...BUT IT WILL BE A
SHARPLY DEFINED LINE BETWEEN CLOUDS VS. SUN.

THE NEXT ISSUE WILL BE TEMPERATURES...AND THE MAIN MESSAGE IN THE
FORECAST THE NEXT COUPLE OF DAYS WILL BE TO CUT GUIDANCE
VALUES...ESPECIALLY IN THE HEART OF THE DEEPER SNOWPACK. AM NOT
OVERLY CONFIDENT ABOUT HOW FAR BELOW GUIDANCE TO GO...AND WILL STAY
FAIRLY CLOSE TO THE GOING FORECAST WHICH IS ABOUT 5 TO 10 DEGREES
BELOW BOTH MET AND MAV HIGH TEMPERATURE FORECASTS.

DEBATED ADDING AT LEAST SOME PATCHY FOG TO THE FORECAST TONIGHT WITH
THE 05.00Z NAM SHOWING REDUCED VISIBILITIES OVERNIGHT INTO MONDAY
MORNING. THE MAIN THING THAT KEPT US FROM JUMPING ON IT AT THIS
POINT IS THAT BOUNDARY LAYER RELATIVE HUMIDITY VALUES ARE NOT VERY
HIGH OVERNIGHT...AND PROXIMITY SOUNDINGS ONLY SHOW A VERY SHALLOW
AREA OF NEAR SATURATION. THINK WE MAY SEE SOME VERY SHALLOW GROUND
FOG...BUT WILL LET THE DAY SHIFT TAKE ANOTHER LOOK AT IT BEFORE
ADDING.

THE NEXT CHANCE FOR SNOW COULD ARRIVE MONDAY NIGHT INTO TUESDAY DUE
TO THE ARRIVAL OF THE NEXT MID LEVEL WAVE. CURRENTLY THE SYSTEM IS
SPINNING ACROSS THE INTERMOUNTAIN WEST...AND THE MODELS HAVE COME
INTO GENERAL AGREEMENT THAT IT WILL OPEN UP AND SHIFT ACROSS THE
CENTRAL AND SOUTHERN PLAINS MONDAY INTO TUESDAY. THE FINER DETAILS
REMAIN A BIT DIFFERENT...BUT THE OVERALL MESSAGE FROM THE
DETERMINISTIC MODEL RUNS ALONG WITH THE SREF IS THAT CHANCES OF SNOW
WILL INCREASE MONDAY EVENING IN WESTERN PARTS OF THE FORECAST
AREA...WITH THE CHANCES SPREADING SOUTH AND EAST OVERNIGHT MONDAY
INTO TUESDAY. DISCREPANCIES REMAIN IN THE MODEL GENERATED QPF
FIELDS...BUT BASED ON THE SPEED AND STRENGTH OF THIS SYSTEM IT
APPEARS IT COULD TRY TO GENERATE AN INCH OR SO OF SNOW...PRIMARILY
ACROSS PARTS OF NORTH CENTRAL KANSAS INTO FAR SOUTHERN NEBRASKA.

.LONG TERM...WEDNESDAY THROUGH SATURDAY. CONFIDENCE IS REASONABLY
HIGH FOR DRY WEATHER THROUGH THIS 4-DAY PERIOD...ALTHOUGH
CONFIDENCE IN TEMPERATURE TRENDS IS A BIT SHAKY OWING NOT ONLY TO
MODEL DIFFERENCES...BUT ALSO TO UNCERTAINTY IN HOW MUCH IMPACT THE
FRESH SNOW PACK WILL HAVE ON HIGHS. THAT BEING SAID...IT CERTAINLY
LOOKS LIKE AT LEAST SLIGHTLY BELOW-NORMAL TEMPS WILL PERSIST
THROUGH THE PERIOD...AND CURRENT FORECAST MAY NOT BE COLD ENOUGH
AT TIMES...ESPECIALLY OVER THE DEEPER SNOW NEAR/NORTH OF HIGHWAY
6.

STARTING THINGS OUT WEDNESDAY/WEDNESDAY NIGHT...00Z GFS AND ECMWF
RUNS ARE IN REASONABLE AGREEMENT DEPICTING A GENERAL NORTHWEST
FLOW ALOFT OVER THE CENTRAL PLAINS...WITH THE PRIMARY SYNOPTIC LOW
PRESSURE SYSTEMS CONSISTING OF A HUDSON BAY VORTEX WELL TO THE
NORTHEAST...AND A SLOW-MOVING CLOSED LOW OFF BAJA WELL TO THE
SOUTHWEST. MEANWHILE...A LOWER AMPLITUDE MID LEVEL WAVE WILL BE
MOVING AWAY FROM IA EASTWARD. AT THE SURFACE...THERE IS GENERAL
AGREEMENT IN SURFACE HIGH PRESSURE SLIDING EAST DURING THE
DAY...INDUCING SOUTHERLY BREEZES...WHICH THEN TURN MORE WESTERLY
OR POSSIBLY NORTHERLY OVERNIGHT AS THE NEXT COLD FRONT MOVES
IN...BUT THE GFS SOLUTION IS DEFINITELY MUCH MORE AGGRESSIVE WITH
THIS FRONTAL INVASION THAN THE ECMWF. FOR HIGH TEMPS WED...CHANGED
VERY LITTLE FROM PREVIOUS FORECAST...REMAINING A SOLID 3-4 DEGREES
BELOW 00Z MEX GUIDANCE MAINLY TO ACCOUNT FOR SNOW PACK. THIS KEEPS
MOST NEB ZONES ONLY IN THE UPPER 20S...WITH LOW-MID 30S MORE
PREVALENT IN KS ZONES.

THURSDAY/THURSDAY NIGHT...ECMWF/GFS SOLUTIONS AGREE THAT A HIGHLY
AMPLIFIED MID-UPPER RIDGE WILL BUILD OVER THE WESTERN CONUS...BUT
EAST OF THIS FEATURE...THE GFS IS MUCH MORE AGGRESSIVE MOVING A
SHORTWAVE SOUTHWARD THROUGH THE PLAINS...ROTATING AROUND THE MAIN
HUDSON BAY REGION VORTEX. THIS IN TURN MAKES THE GFS MUCH MORE
AGGRESSIVE WITH LOW LEVEL COLD AIR ADVECTION INTO THE CWA. FOR
MOST AREAS KEPT HIGH TEMPS SIMILAR TO BOTH PREVIOUS FORECAST AND
00Z MEX GUIDANCE...WITH LOW 30S OVER DEEPER SNOW AND MID 30S
SOUTH.

FRIDAY/FRIDAY NIGHT...DIFFERENCES WITH SYNOPTIC FEATURES ALOFT
BETWEEN 00Z ECMWF/GFS SOLUTIONS CONTINUE TO MAGNIFY...WITH THE
ECMWF TRYING TO BUILD A SHORTWAVE RIDGE INTO THE CENTRAL PLAINS
MAINLY FRIDAY NIGHT...WHILE THE GFS DROPS AN AMPLIFYING SHORTWAVE
SOUTH THROUGH THE UPPER MS VALLEY/MIDWEST. THIS RESULTS IN A
DRAMATIC DIFFERENCE IN 850MB TEMPS ACROSS THE CWA...AND ALSO WIND
DIRECTION...ESPECIALLY FOR FRIDAY NIGHT WITH THE ECWMF SUGGESTING
OVERNIGHT WARM AIR ADVECTION. THE 00Z GFS ENSEMBLE MEAN 500MB
HEIGHT IS A MIDDLE GROUND BETWEEN THE DETERMINISTIC ECMWF/GFS
SOLUTIONS...AND THUS FOR HIGHS FRIDAY STUCK CLOSE TO MODEL
CONSENSUS WITH MID-UPPER 20S MOST NEB ZONES...AND MID 30S FARTHER
SOUTH. THIS UNDERCUTS 00Z MEX HIGHS BY 2-3 DEGREES MOST AREAS.

FINALLY FOR SATURDAY...CONFIDENCE REALLY GOES IN THE TANK ON THE
SYNOPTIC SCALE PATTERN...WITH THE GFS SHOWING AN EXPANSIVE
COLD SURFACE RIDGE OVER THE PLAINS...WHILE THE ECMWF HAS
IMPRESSIVE WARM ADVECTION AND SOUTHERLY BREEZES AHEAD OF A
SHORTWAVE CROSSING THE CENTRAL ROCKIES. THIS IMPLIES HIGH
TEMPERATURES COULD EASILY RANGE ANYWHERE FROM 20S TO AT LEAST 40S
ACROSS PARTS OF THE CWA...AND FOR NOW WILL PLAY CONSENSUS MIDDLE
GROUND WITH LOW 30S NORTHEAST TO LOW 40S SOUTHWEST. LOTS TO IRON
OUT AT THIS RANGE.

DESPITE THE UPCOMING STRETCH OF BELOW NORMAL TEMPERATURES...EXTENDED
MODELS SHOW NO SIGN OF A LEGITIMATE ARCTIC INVASION. ON ONE FINAL
NOTE...NOW THAT PLENTY OF SNOW IS ON THE GROUND AND LOOKS TO BE
SLOW TO FULLY MELT...THERE COULD EASILY BE POTENTIAL FOR FOG
AND/OR LOW STRATUS DURING THE NEXT WEEK...WITH THE DETAILS JUST
TOO MURKY TO RESOLVE AT THIS TIME.

&&

.PREV DISCUSSION... /ISSUED 1124 PM CST SAT FEB 4 2012/

AVIATION...06Z KGRI TAF. VFR CEILING/VISIBILITY ARE CURRENTLY
ADVERTISED THROUGHOUT THE PERIOD...WITH LIGHT WEST-NORTHWEST
BREEZES ONLY AVERAGING AROUND 7KT OR SO. THAT BEING SAID...NOW
THAT EXTENSIVE SNOW COVER IS ON THE GROUND...THE NEXT SEVERAL DAYS
AND ESPECIALLY NIGHTS WILL HAVE TO BE CLOSELY MONITORED FOR THE
POTENTIAL FOR FOG AND/OR LOW STRATUS TO MATERIALIZE. AT THIS
TIME...ONE OF THESE FAIRLY EXTENSIVE IFR/LIFR STRATUS DECKS IS
LURKING ROUGHLY 140 MILES NORTH-NORTHEAST OF THE TERMINAL...AND IS
SHOWING SOME SIGNS OF SAGGING SOUTH TOWARD THE AREA OVER THE NEXT
12-18 HOURS WITH THE LOW LEVEL STEERING FLOW. AT THIS
TIME...TRADITIONAL NUMERICAL GUIDANCE AND MOST SHORT TERM MODEL
DATA KEEP THESE LOW CLOUDS AT LEAST SLIGHTLY EAST OF KGRI...BUT
THIS WILL NEED CLOSELY MONITORED. EVEN IF LOW STRATUS STAYS
AWAY...THE BEGINNING STAGES OF SNOW MELT AND CONTINUED LIGHT WINDS
COULD PROMOTE AT LEAST PATCHY FOG DEVELOPMENT MAINLY FOR SUNDAY
EVENING/OVERNIGHT. ALL THESE CAVEATS BEING SAID...GIVEN LACK OF
SUPPORT FROM CURRENT MODEL GUIDANCE...WILL MAINTAIN VFR CONDITIONS
FOR NOW BUT AT LEAST HINT AT POSSIBLE ISSUES BY INSERTING A
SCATTERED LOW STRATUS GROUP FOR MUCH OF THE PERIOD...AND A LIGHT
VFR VISIBILITY RESTRICTION SUNDAY EVENING. BOTTOM LINE...THIS
FORECAST MAY NOT BE QUITE AS STRAIGHTFORWARD AS CURRENT GUIDANCE
WOULD SUGGEST.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&

$$

SHORT TERM...KING
LONG TERM/AVIATION...PFANNKUCH


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