FXUS63 KLBF 282114
AFDLBF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
315 PM CST SAT NOV 28 2009
.SYNOPSIS...
H5 ANALYSIS THIS MORNING...DEPICTING SPLIT FLOW ACROSS THE CONUS
WITH A CLOSED LOW OVER SRN CA...A CLOSED LOW OVER MAINE...AND A
DECENT SHORTWAVE OVER THE TX PANHANDLE. AT THE SURFACE...A COLD
FRONT WAS PRESENT FROM SWRN KS INTO FAR SERN NEBRASKA. WITH NRLY
WINDS AND INCREASING CLOUDINESS...TEMPERATURES RANGED FROM THE LOWER
40S IN NRN NEBRASKA TO THE UPPER 50S IN SRN NEBRASKA.
.DISCUSSION...
NEAR TERM...TONIGHT THROUGH TUESDAY...A COUPLE OF DRY ARCTIC FROPAS
HIGHLIGHT FORECAST CONCERNS THROUGH TUESDAY. OVER THE NEXT 24
HOURS...A GLANCING BLOW OF ARCTIC AIR WILL PUSH INTO THE NRN AND
CENTRAL PLAINS LATER TONIGHT AS AN UPPER LEVEL TROUGH OF LOW
PRESSURE MOVES EAST INTO THE NRN GREAT LAKES. INHERITED SOME LOW
POPS IN NRN AREAS FOR TONIGHT AND DECIDED TO ELIMINATE THESE IN THIS
FORECAST PACKAGE. NOT MUCH IN THE WAY OF LIFT NOTED WITH THE FRONT
TONIGHT AND AVAILABLE MOISTURE REMAINS WELL ABOVE THE DRY DENDRITIC
LAYER. MOST OF THE ARCTIC AIR WILL IMPACT THE CWA TONIGHT AND THE
FIRST HALF OF SUNDAY...AS WESTERLY WINDS WILL BEGIN TO SHIFT THIS
AIRMASS QUICKLY EAST SUNDAY AFTERNOON. HIGHS TOMORROW WILL BE
SEASONAL WITH READINGS IN THE LOWER TO MID 40S. LIGHT WESTERLY WINDS
AND VERY DRY BOUNDARY LAYER AIR WILL ALLOW FOR COLD MINIMUM TEMPS BY
MONDAY MORNING. WENT WITH THE COOLER MET GUIDANCE UNDER THIS
SCENARIO AND UNDERCUT THIS IN THE PLATTE RIVER VALLEY BASED ON THE
LIGHT WESTERLIES AND DRY BOUNDARY LAYER. MOST AREAS WILL SEE LOWS
AROUND 20 DEGREES WITH SOME LOWER TO MID TEENS IN THE PLATTE RIVER
VALLEY. ZONAL FLOW WILL DEVELOP SUNDAY NIGHT...PERSISTING THROUGH
TUESDAY. HIGHS WILL BE WARMEST DURING THE FORECAST PERIOD ON MONDAY
BASED ON H85 TEMPS...AND POSSIBLY WARMER IN THE SOUTH FOR TUESDAY IF
A SECOND ARCTIC FRONT DECIDES TO SLOW DOWN TUESDAY. FOR
NOW...FRONTAL TIMING APPEARS TO BE MIDDAY IN THE CENTRAL AND
NORTHERN CWA...WHICH WOULD FACILITATE COOLER HIGHS FOR TUESDAY.
LONG TERM...WEDNESDAY TROUGH SATURDAY...TRICKY EXTENDED FCST SHAPING
UP THIS MORNING AS SOME MID RANGE MODEL DIFFERENCES DEVELOP DURING
THE LATTER HALF OF THE WEEK. BOTH MODELS AGREE ON A DECENT ARCTIC
SURGE OF COLD AIR ENVELOPING THE EASTERN HALF OF THE CONUS BY THE
END OF THE WEEK. THE DIFFERENCES ARE WITH THE DEVELOPMENT OF
UPSTREAM RIDGING INTO THE NERN PACIFIC BY THURSDAY NIGHT. THE GFS IS
AMPLIFIED THE GREATEST...EXTENDING A POSITIVE TILTED RIDGE INTO THE
AK PANHANDLE AND YUKON BY LATE SATURDAY. THIS WOULD FAVOR ARCTIC AIR
PUSHING WELL TO THE SOUTH OF THE AREA DURING THIS TIME FRAME.
WITH DECREASED AMPLIFICATION...THE EURO SOLN WOULD ONLY DELIVER A
GLANCING BLOW OF ARCTIC AIR TO THE REGION DURING FRIDAY AND SATURDAY
TIME PERIOD. SNOW COVER CONTINUES TO BE LACKING ACROSS THE NRN
PLAINS AND PRAIRIE REGIONS OF SRN CANADA...SO A COLDER SOLN ISN'T
PREFERRED HERE. WITH THIS IN MIND...FAVORED A DRY FCST WITH
TEMPERATURES AT OR SLIGHTLY BLO NORMAL...WHICH EQUATES TO DAYTIME
HIGHS IN THE 30S TO LOWER 40S.
&&
.AVIATION...
FRONT CLEARING SOUTHWEST NEBRASKA THIS AFTERNOON WITH COOL AIR
FILTERING IN AND LEVELING TEMPERATURES IN THE MID 40S TO MID 50S
MOST AREAS. FAIRLY DRY AIR BEHIND FRONT AS WELL AND BELIEVE SOME OF
MODEL SOLNS OVER-DOING LOW LEVEL MOISTURE AND STRATUS PRODUCTION
THIS EVENING. NAM GUIDANCE HINTING AT MVFR CIGS AT KVTN AFTER 00Z
AND LOOKING UPSTREAM THIS PROBABLY IS NOT REALISTIC. IN TAF FORECAST
KEPT CIGS AOA 4KFT AGL DURING THE LATE EVENING HOURS...WITH VFR
CONDITIONS CONTINUING THROUGH SUNDAY. FOR KLBF CONFIDENCE STILL NOT
VERY HIGH FOR CONDITIONS BELOW VFR BUT WITH HIGHER SATURATION IN THE
LOWEST LAYERS DID HINT AT POSSIBLE LOWER CIG CRITERIA...OTHERWISE
VFR SHOULD PREVAIL OVER NEXT 24 HOURS AT KLBF TERMINAL AS WELL.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...NONE
$$
.SHORT AND LONG TERM...BUTTLER
.AVIATION...DP
