000 
FXUS63 KLBF 300745
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
245 AM CDT SAT OCT 30 2004

.DISCUSSION...
NORTHERN PLAINS SYSTEM MATURING NICELY THIS EVENING EVOLVING INTO A
CLASSIC STAGE II/III SHAPIRO-KEYSER CYCLONE WITH THE T-BONE AND
FRONTAL FRACTURE OCCURRING ACROSS NRN MN AND BENT BACK FRONT ACROSS
THE DAKOTAS AND HENCE A GOOD MID LEVEL F-GEN BAND GENERATING PRECIP
AS WELL. PRECIP TYPE HAS BEEN A CHALLENGE THIS EVENING AS COLDEST LOW
LEVEL TEMPS AND SNOWFALL COINCIDENT WITH BEST MESOSCALE LIFT.
SNOWFALL HAS LIMITED VSBYS ACROSS THE NRN MOST PORTION OF THE CWA TO
LESS THAN 2 MILES AT TIMES. THE EXCEPTION TO THIS HAS BEEN IN NRN
SHERIDAN AND NORTHWEST CHERRY COUNTIES. THE REASON FOR THIS HAS
BEEN THE MESOSCALE LIFT ASSOCIATED WITH STRONG NORTHWEST FLOW OVER
THE BLACK HILLS. WIND AND STABILITY PROFILE HAS GENERATED A FROUDE
NUMBER CONDUCIVE TO STRONG LIFT ON THE UPSLOPE (NW) SIDE OF THE
HILLS...THEN A RESULTANT DOWNSLOPE ON THE SWRN SIDE...THEN A
HDYRAULIC JUMP DOWNWIND FROM THAT. ETA HAS HANDLED THIS WELL...BUT
EVEN IT LIKELY UNDERESTIMATED THE INTENSITY OF THIS LIFT AND
ASSOCIATED COOLING OF THE LOWER ATMOS. REPORTS OF SNOW STICKING TO
THE GROUND IN NRN SHERIDAN...WITH POSSIBLY A COUPLE INCHES NEAR THE
SD BORDER. PRECIP WANING NOW.

WINDS HAVE BEEN A STRONG SUBHEADING TO THIS SCENARIO WITH WIND
GUSTS APPROACHING WARNING CRITERIA A TIME OR TWO. QUESTION BECOMES
IF AND HOW FAR TO EXTEND THE ADVISORY INTO THE MORNING HOURS.
UNLESS THE TREND DRAMATICALLY DECREASES BY ISSUANCE...WILL LIKELY
KEEP ADV GOING IN THE NERN ZONES. ETA BUFR SOUNDINGS INDICATE ADV
CRITERIA IN THE NERN ZONES UNTIL LATE MORNING/EARLY AFTERNOON SO
THE NPW WILL BE WORDED THAT WAY. WITH DECENT SUNSHINE BY AFTERNOON
GUIDANCE MAXES SHOULD BE REACHED.

NEXT COMES SUNDAY INTO MONDAY SYSTEM. MODELS SIMILAR IN THEIR
SYNOPTIC SCALE FEATURES...BUT DIFFER SOME ON STREGNTH OF MID LEVEL F-
GEN AND LOW LEVEL RH. GFS HAS BEEN FAIRLY CONSISTENT AS HAS THE ETA
TO SOME RESPECT. WILL NOT DEVIATE FROM GOING FCST TOO MUCH...BUT
JUST ADJUST RA/SN WORDING TIMING.

AS FOR THE MID WEEK SYSTEM...GFS HAS KEPT MOST OF THE ENERGY IN THE
NRN STREAM WITH THE LATEST RUN...AS OPPOSED TO DEVELOPING THE SWRN
STATES UPPER CUTOFF. WHILE MOST MEMBERS OF THE GFS ENSEMBLES AND
ALSO THE CANADIAN ENSEMBLES INDICATE THIS IS SO...THERE ARE A FEW
MEMBERS HOLDING ONTO THE PREVIOUS GFS SOLUTION. IF KEPT IN THE NRN
STREAM...IT WILL BE A QUICK MOVING SYSTEM AS THE UPPER FLOW BECOMES
MORE AMPLIFIED WITH THE BUILDING RIDGE OFF THE WEST COAST. THIS
SHOULD ALSO KEEP THE DOOR OPEN FOR REINFORCING SHOTS OF COLD AIR
THROUGH THE LAST HALF OF THE WEEK.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...WIND ADVISORY NEZ007-010-028>029-
038

&&

$$

JWS