RSS FeedsIssued by NWS North Platte, NE
000 FXUS63 KLBF 222327 AAA AFDLBF AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE NORTH PLATTE NE 527 PM CST SUN NOV 22 2009 .DISCUSSION... A QUICK UPDATE FOR FOG DEVELOPMENT EAST OF KIML-KOGA-KVTN. THE RUC AND 18Z NAM SOUNDINGS INDICATE A PRIME ENVIRONMENT FOR SHALLOW FOG BEGINNING AROUND MIDNIGHT. KLXN IS CARRYING A DEWPT OF 36F AT 23Z... KONL 35F. THIS SHALLOW MOISTURE SHOULD BE SWEPT WESTWARD OVERNIGHT AND COMBINED WITH STRONG RADIATIONAL COOLING...FOG IS LIKELY. .PREVIOUS DISCUSSION... AS SPECULATED YESTERDAY...THE PACIFIC STORM CAME ASHORE IN TIME FOR THE 12Z UA FLIGHT. THE NAM...GFS AND ECMWF WHERE INITIALIZED AND PRODUCED VERY SIMILAR MODEL RESULTS FOR THE DEVELOPING CLOSED LOW ACROSS THE CENTRAL PLAINS MONDAY. THUS FCST CONFIDENCE IS GOOD AND POPS HAVE BEEN RAISED TO THE LIKELY CATEGORY ACROSS PARTS OF WESTERN AND NCNTL NEB. THE PACIFIC FRONT ENTERING WRN WY THIS AFTN SHOULD BE ACROSS WRN NEB BY 12Z MONDAY MORNING. DRY AIR AHEAD OF THE FRONT WILL ALLOW TEMPERATURES TO RADIATE BELOW FREEZING TONIGHT IN TIME FOR THE FRONTAL PASSAGE MONDAY MORNING IN THE WEST. THUS SNOW IS LIKELY ACROSS WRN NEB MONDAY MORNING WITH RAIN CHANGING TO SNOW ALONG AND AHEAD OF THE FRONT ACROSS NCNTL NEB MONDAY AFTERNOON. THE FRONT SHOULD BE MOVING THROUGH EASTERN NEB MONDAY NIGHT WITH SNOW ENDING IN THE WEST. ALL THREE MODELS TRACK THE H7 LOW THROUGH SRN NEB WITH RAIN AND SNOW LIKELY RIGHT ALONG AND NORTH OF THIS TRACK. THE NAM12 AND GFS BUFKIT SOUNDINGS SHOW ABOUT 3 TO PERHAPS 6 HOURS OF DEEP LIFT TO 500 MB WHICH SHOULD SUPPORT MODERATE TO OCCASIONALLY HEAVY SNOW WITH RATES NEAR 1 INCH PER HOUR AT TIMES. SINCE THE STORM IS EXPECTED TO BEGIN DEEPENING AFTER 00Z TUESDAY...MONDAY EVENING EAST OF HIGHWAY 83...FCST QPF IS GENERALLY LESS THAN 1/3 OF AN INCH. THE SNOW SHOULD FALL DURING THE DAY ACROSS THE FCST AREA AND SNOWFALL TOTALS SHOULD BE 3 INCHES OR LESS. 500M WINDS INCREASE TO 20 KTS AND THIS SUPPORTS THE GUIDANCE OF 15 TO 25 MPH WINDS. THE OFFICIAL QPF FCST USES A 3 WAY BLEND OF THE 12Z RUNS OF THE ECMWF...GFS AND NAM12 WHICH WERE VERY SIMILAR AND A 10 TO 1 RATIO FOR SNOW WHICH PRODUCED UP TO 3 INCHES OF SNOW CENTERED OVER NWRN LINCOLN COUNTY STRETCHING NORTH AND SOUTH FROM MULLEN TO HAYES CENTER. THIS IS CLOSE TO THE HPC FCST OF 2 TO 4 INCHES OF SNOW ACROSS THE SAME LOCATION. THE STORM INTENSIFICATION PROCESS WILL NEED TO BE WATCHED VERY CLOSELY AS NEW MODEL DATA COME IN TONIGHT AND MONDAY. HEAVY RAIN AND SNOW IS FCST TO DEVELOP ACROSS SCNTL AND ERN NEB MONDAY NIGHT ONCE THE OCCLUSION PROCESS BEGINS AND IF THIS PROCESS BEGINS SOONER THAN FCST...VERY HEAVY WET SNOW COULD DEVELOP ACROSS WRN AND NCNL NEB ALONG AND WEST OF HIGHWAY 83. AS THE STORM MOVES TOWARD THE UPPER MIDWEST...A SECONDARY REINFORCING COLD FRONT IS EXPECTED TO MOVE THROUGH TUESDAY NIGHT PRODUCING SNOW SHOWERS AND FLURRIES. THIS AIR MASS IS A HYBRID OF PACIFIC AND CANADIAN HIGH PRESSURE WHICH SHOULD KEEP TEMPERATURES IN THE 40S WEDNESDAY AND MOST OF THURSDAY. A SIGNIFICANT WARM UP IS FCST BY BOTH THE ECMWF AND GFS FRIDAY WITH TEMPERATURES WARMING INTO THE 50S FOLLOWED BY ANOTHER COLD FRONT SATURDAY. THIS HYBRID CANADIAN PACIFIC HIGH SHOULD KEEP TEMPERATURES IN THE 40S SUNDAY. && .AVIATION... VISUAL FLIGHT RULES WILL CONTINUE FOR TERMINALS KLBF AND KVTN THROUGH 18Z MONDAY. MODELS ARE IN BETTER AGREEMENT TODAY WITH AVIATION FORECAST BASED ON RUC/NAM/GFS BLEND. THE VISIBLE SATELLITE LOOP OVERLAYED WITH THE WX DEPICTION ANALYSIS AT 19Z SHOW IFR CEILINGS OVER SOUTH CENTRAL NEB. SURFACE HIGH PRESSURE WAS RIDGING INTO WESTERN NEBRASKA THAT WEAKENS TONIGHT AS AN AREA OF LOW PRESSURE FURTHER DEVELOPS ON THE HIGH PLAINS. NORTHERLY WINDS WILL SHIFT TO THE SOUTHEAST THAT WILL ALLOW DEEPER BOUNDARY LAYER MOISTURE TO DEVELOP NORTHWEST. HOW FAR WEST THE STRATUS DEVELOPS WILL AGAIN BE A CONCERN. FOR NOW THE WINDS WILL DROP OFF BY MIDNIGHT WITH THE WESTWARD EXTENT TO THE STRATUS TO EXTEND NEAR A LINE FROM KANW TO KLBF. THE KVTN TERMINAL IS EXPECTED TO STAY IN THE CLEAR FOR VISUAL FLIGHT RULES UNTIL 18Z MONDAY. BEYOND CEILINGS ARE EXPECTED TO LOWER THROUGHOUT TO MARGINAL VISUAL FLIGHT RULES THEN DETERIORATE AS SNOW OR A MIXTURE OF RAIN AND SNOW DEVELOPS AND MOVES ACROSS WESTERN NEBRASKA. THE MODELS HAVE PUSHED THE IMPACTS OF THIS SYSTEM SOUTHWEST WHERE COLDER AIR GETTING DRAWN INTO THE SYSTEM. A MIXTURE OF PRECIPITATION IS EXPECTED UNTIL EVENING WHEN THE PRECIPITATION WILL TRANSITION TO ALL SNOW THAT COULD DROP VISIBILITIES BELOW 3 MILES. THE SYSTEM LIFTS OUT TUESDAY FOR CLEARING FROM WEST TO EAST THROUGH THE MORNING ATTM. THE MODELS HAVE HAD A HARD TIME RESOLVING THE STORM TRACK WITH SOME ADJUSTMENTS STILL POSSIBLE IN THE NEAR TERM FORECASTS. && .LBF WATCHES/WARNINGS/ADVISORIES...NONE. && $$ CDC/TLK
