Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 181820
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1220 PM CST TUE NOV 18 2014

.SYNOPSIS...
ISSUED AT 403 AM CST TUE NOV 18 2014

H5 ANALYSIS FROM EARLIER THIS EVENING CONTINUES TO SHOW A
BLOCKING RIDGE EXTENDING UP THE WEST COAST OF THE CONUS INTO THE
YUKON AND ALASKA. FURTHER EAST...A BROAD AREA OF LOW PRESSURE
EXTENDED FROM HUDSON BAY...SOUTH TO LAKE SUPERIOR. A TROUGH
EXTENDED SOUTH OF THIS FEATURE INTO TEXAS AND THE GULF COAST
STATES. ON THE WESTERN PERIPHERY OF THE UPPER LEVEL LOW...A NICE
SHORTWAVE WAS NOTED OVER NRN SASKATCHEWAN AND NRN ALBERTA. THIS
FEATURE IS EXPECTED TO DROP QUICKLY SOUTH SOUTHEAST TODAY AND
TONIGHT...AND WILL FORCE AN ARCTIC COLD FRONT INTO THE REGION
TONIGHT. MORE ABOUT THAT BELOW. AT THE SURFACE...A WEAK RIDGE OF
HIGH PRESSURE EXTENDED FROM NERN OKLAHOMA INTO EASTERN MONTANA.
WEST OF THIS FEATURE...A SURFACE TROUGH OF LOW PRESSURE EXTENDED
ALONG THE FRONT RANGES OF WYOMING INTO NERN COLORADO. SKIES ACROSS
WESTERN AND NORTH CENTRAL NEBRASKA WERE MAINLY CLEAR THIS MORNING
WITH THE EXCEPTION OF THE NERN CWA WHERE CLOUDS WERE PRESENT ALONG
AND EAST OF A LINE FROM SPRINGVIEW TO ERICSON. TEMPERATURES AS OF
3 AM CST RANGED FROM -8 AT VALENTINE...TO 14 AT ONEILL.

&&

.UPDATE...
ISSUED AT 1215 PM CST TUE NOV 18 2014

DOWN SLOPING WESTERLY WINDS /10 TO 20 KTS/ BEHIND TROUGH/WARM
FRONT PUSHING ACROSS THE AREA ALLOWING FOR BETTER MIXING THAN
PREVIOUSLY THOUGHT. IML HAS ALREADY JUMPED TO 48 DEGREES WITH
LOWER 50S IN NORTHEAST COLORADO. RUC AND HRRR HAVE JUMPED ON THE
WARMER TEMPS AND BRING HIGHS INTO THE LOWER 50S FOR FAR SW. STILL
CHILLY ACROSS THE SNOWPACK OF THE NORTH AND NORTHEAST. FORECAST
UPDATE HAS A CONSERVATIVE CATEGORY OR TWO TREND UP FOLLOWING A
BLEND OF THE RUC/HRRR.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 403 AM CST TUE NOV 18 2014

TEMPERATURES TODAY...FOLLOWED BY THE THREAT OF FLURRIES/LIGHT
SNOW TONIGHT ARE THE MAIN FORECAST CONCERNS OVER THE NEXT 24
HOURS. FOR TODAY SURFACE RIDGING WILL MOVE EAST OF THE
AREA...ALLOWING A SURFACE TROUGH OF LOW PRESSURE TO PUSH INTO THE
CENTRAL CWA BY MID AFTERNOON. WARMER H85 TEMPS WILL PUSH INTO THE
FORECAST AREA LATER THIS AFTERNOON WITH 00Z H85 TEMPS RANGING FROM
-3 IN THE NORTHEAST TO AROUND 5C IN THE SOUTHWEST. INTERPOLATING
THESE 00Z TEMPS TO THE 18Z H85 TEMPS...YIELDS AROUND 2 TO 3C FOR
NORTH PLATTE AT 21Z THIS AFTERNOON. WITH MIXING...THIS YIELDS THE
LOWER TO MIDDLE 40S...WHICH IS SLIGHTLY ABOVE THE MAV GUIDANCE OF
41 THIS AFTERNOON. THE MET IS MUCH COOLER AND CONTINUES TO HAVE A
SNOW COVER BIAS ACROSS THE AREA AND WAS DISREGARDED FOR TDYS FCST.
OTHER ASPECTS WHICH MAY HOLD DOWN HIGHS TODAY ARE THE COLD
START...IE STARTING TEMPS AROUND ZERO...AND THE FROZEN GROUND
CONDS...EVEN IN AREAS WHICH ARE NOT SNOW COVERED. IN
ADDITION...MIXING WINDS SHOULD BE ON THE LIGHT SIDE TDY WITH A
SURFACE TROUGH FORECAST ACROSS THE FORECAST AREA. WITH THIS IN
MIND...UTILIZED GFS H85 TEMPS AT 21Z FOR FORECAST HIGHS TDY. THIS
YIELDED HIGHS RANGING FROM AROUND FREEZING IN THE FAR
NORTHEAST...TO AROUND 47 FOR IMPERIAL. FOR TONIGHT...A STRONG
UPPER LEVEL DISTURBANCE WILL DROP SOUTH INTO WESTERN
ONTARIO...FORCING A REINFORCING SHOT OF COLD AIR INTO THE FORECAST
AREA OVERNIGHT. LOWS WILL BE IN THE TEENS HOWEVER...AS LOW CLOUDS
AND BREEZY CONDS WILL SET IN BEHIND THE FRONT. THE MODELS CONTINUE
TO INDICATE A SHALLOW MOIST LAYER BEHIND THE FROPA IN THE SURFACE
TO H850 LAYER WHICH EXTENDS FROM NORTH CENTRAL INTO CENTRAL
NEBRASKA OVERNIGHT. LIFT WITHIN THIS LAYER IS WEAK AT BEST...WITH
THE BEST DENDRITIC GROWTH TEMPERATURES ABOVE THE MOIST LAYER. EVEN
WITH LIMITED LIFT...HARD TO RULE OUT FLURRIES GIVEN THE STRONG CAA
AND LOW LEVEL MOISTURE BEHIND THE FRONT...AND WILL CONTINUE TO
MENTION THAT THREAT WITH THIS FCST PACKAGE.


.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 403 AM CST TUE NOV 18 2014

PRIMARY FORECAST CONCERNS THROUGH THE FIRST PART OF NEXT WEEK ARE
PRIMARILY WITH TEMPERATURES EACH DAY...AND THEN WITH PRECIPITATION
CHANCES OVER THE WEEKEND AS THE LARGE SCALE PATTERN SHIFTS FROM THE
ANOMALOUSLY AMPLIFIED PATTERN THAT HAS BEEN IN PLACE OVER NORTH
AMERICA THIS PAST WEEK.

MODELS CONTINUE TO BE IN GOOD AGREEMENT GOING INTO THE MIDDLE AND
LATER PARTS OF THIS WEEK. THE PERIOD BEGINS ON WEDNESDAY WITH THE
VERY AMPLIFIED LARGE-SCALE PATTERN STILL IN PLACE...THEN AS
THE POTENT LOW PRESSURE SYSTEM NOW OVER THE EASTERN PACIFIC MOVES
ONSHORE LATER IN THE DAY THE RIDGE OVER THE WEST COAST BEGINS TO
BREAK DOWN MEANWHILE THE UPPER LOW OVER SOUTHEAST CANADA WHICH HAS
BEEN DRIVING TROUGH ALSO BEGINS TO MAKE SOME EASTWARD PROGRESS TO
CONTINUE THE PROCESS OF FLATTENING THE UPPER LEVEL PATTERN. THE
MODEL SOLUTIONS ARE ALL ON BOARD WITH THIS OCCURRING AND ARE QUITE
SIMILAR IN FORECASTING SPLIT FLOW TAKING SHAPE...AND WITH THE
GENERAL TRACK AND SPEED OF SYSTEMS MOVING THROUGH BOTH THE NORTHERN
AND SOUTHERN STREAM. THAT BEING SAID...THERE ARE ENOUGH DIFFERENCES
IN SOME OF THE DETAILS TO KEEP SOME UNCERTAINTY IN THE SENSIBLE
WEATHER IN THE FORECAST AT THIS TIME.

WEDNESDAY BEGINS WITH THE FORECAST AREA IN THE WAKE OF YET ANOTHER
COLD FRONTAL PASSAGE WITH COLD ARCTIC AIR ONCE AGAIN TAKING
RESIDENCE ACROSS THE NORTHERN AND CENTRAL PLAINS. HIGH PRESSURE
BUILDS IN THROUGH THE DAY WHICH WILL ALLOW THE SURFACE PRESSURE
GRADIENT TO RELAX. EVEN WITH A WEAKENING PRESSURE GRADIENT...THE
COLD AIR ADVECTION REGIME WILL KEEP THE BOUNDARY LAYER MIXED WITH
FORECAST SOUNDINGS SHOWING THE MIXED LAYER UP TO 825-850MB. WINDS
ALOFT /AT THE TOP OF THE MIXED LAYER/ STAY HIGHER THROUGH THE
AFTERNOON...WITH VALUES STILL AT 20-25KTS AT PEAK HEATING. DO HAVE
THE WINDS DECREASING SLIGHTLY IN AFTERNOON...BUT EXPECT GUSTS TO
CONTINUE SO IT WILL BE A BREEZY DAY UNTIL EVENING WHEN THE INVERSION
BEGINS TO SET UP. ALTHOUGH THE COLDEST AIR BEHIND THE COLD FRONT
WILL BE UP OVER THE UPPER MISSISSIPPI RIVER VALLEY
REGION...TEMPERATURES AT 850MB WILL BE 5-10 DEGREES COOLER THAT WILL
BE SEEN TODAY. THE SOUTHWEST WILL BE WARMER WHERE 850MB TEMPS LOOK
TO BE RIGHT AROUND 0C. NOT REAL CONFIDENT ON HOW WARM IT WILL GET.
STRONG SUPER-ADIABATIC MIXING TO 850MB WOULD PUT HIGHS UP AROUND 50
DEGREES OVER THE SOUTHWEST PARTS OF THE FORECAST AREA. JUST DON/T
HAVE A GOOD FEEL IF MIXING WILL BE UP TO THAT LEVEL AND WITH
STATISTICAL GUIDANCE IN THE LOW 40S IN A COLD AIR ADVECTION PATTERN
DIDN/T WANT TO GO TOO MUCH ABOVE THAT AT THIS TIME. IN THE NORTHEAST
PART OF THE FORECAST AREA...TEMPERATURES WILL BE COOLER...MOST
LIKELY STAYING IN THE MID TO UPPER 20S. IT LOOKS LIKE THERE WILL BE
A STREAM OF CLOUD COVER MOVING ACROSS THIS AREA IN THE NORTHWEST
FLOW WHICH ALONG WITH THE COLDER AIR IN PLACE WILL INHIBIT
TEMPERATURES FROM RISING MUCH. ANOTHER THING TO LOOK AT FOR
WEDNESDAY IS POTENTIAL FOR FLURRIES MAINLY IN THE AFTERNOON. THIS
WOULD BE ASSOCIATED WITH THE CLOUD COVER JUST MENTIONED. FORECAST
SOUNDINGS SHOW SUFFICIENT MOISTURE AND COLD ENOUGH FOR SNOW...BUT
THE LIFT IN THE LAYER IS VERY LIGHT OR EVEN NEGLIGIBLE. THE GEM IS
THE MODEL THE MOST EXCITED ABOUT SNOW WEDNESDAY WITH THE NAM BEING
THE ONLY OTHER MODEL TO EVEN DEVELOP SOME QPF. WENT THE CONSERVATIVE
ROUTE AND KEPT THE FORECAST DRY AS THERE ISN/T ENOUGH OF A SIGNAL TO
ADD SNOW IN RIGHT NOW.

FOR WEDNESDAY NIGHT AND THURSDAY THE PATTERN SHIFT ALOFT IS ONGOING.
A MID LEVEL SHORTWAVE TROUGH MOVES INTO THE SOUTHERN PLAINS AND AS
THE EASTERN CONUS LARGEWAVE TROUGH PROGRESSES A BIT FURTHER EAST
WARM AIR ADVECTION BEGINS OVER THE HIGH PLAINS. WEDNESDAY
NIGHT...THE SURFACE HIGH WILL BE DIRECTLY OVER EASTERN NEBRASKA WITH
CALM TO LIGHT WINDS EXPECTED OVERNIGHT. THIS AND CLEAR SKIES WILL
BRING STRONG RADIATIONAL COOLING AND ALTHOUGH THE AIRMASS ISN/T AS
COLD...EXPECT TEMPERATURES TO BE ABLE TO DROP INTO THE SINGLE DIGITS
AND LOW TEENS. THE HIGH THEN MOVES OFF TO THE EAST THURSDAY BRINGING
SOUTHERLY RETURN FLOW BACK TO THE PLAINS. THIS IS A SLOW PROGRESSION
THOUGH SO REALLY DON/T START SEEING GOOD WARM AIR ADVECTION UNTIL
THURSDAY NIGHT. THIS WOULD KEEP THURSDAY COOLER WITH HIGHS AGAIN
FROM THE MID 20S TO THE MID 40S. EVEN IF THE WARMER AIR ALOFT DOES
START TO MOVE IN...LIGHT WINDS AT THE SURFACE WILL INHIBIT GOOD
MIXING FROM OCCURRING SO WANTED TO KEEP TEMPERATURES ON THE COOLER
SIDE AND IF THE TREND BEGINS TO BE WARMER LATER SHIFTS CAN MAKE
ADJUSTMENTS.

THE MODELS HAVE TRENDED FURTHER SOUTH AND EAST WITH THE SOUTHERN
PLAINS SYSTEM GOING INTO THE WEEKEND. A SECOND UPPER LEVEL SHORTWAVE
ALSO MOVES THROUGH THE SOUTHERN STREAM AND CATCHES UP ON SATURDAY
OVER TEXAS. IT THEN LIFTS NORTHEAST AND THE MODELS ARE IN GOOD
AGREEMENT WITH ITS TRACK KEEPING ALL PRECIPITATION OVER THE
MISSISSIPPI RIVER VALLEY REGION AND GENERALLY ENTIRELY OUT OF
NEBRASKA. ALSO...THE MODELS HAVE SLOWED WITH A SYSTEM MOVING THROUGH
THE NORTHERN STREAM OUT OF THE PACIFIC NORTHWEST AND INTO THE
NORTHERN AND CENTRAL PLAINS FOR SUNDAY. THIS SLOWDOWN HAS ALLOWED
PRECIPITATION CHANCES TO BE BACKED OFF FOR SUNDAY AND SUNDAY NIGHT.
THE SYSTEM TO THE EAST BASICALLY ROBS THE NORTHERN STREAM OF
MOISTURE SO THERE ISN/T MUCH TO WORK WITH AS IT MOVES INTO NEBRASKA.
BOTH SYSTEMS BEGIN TO PHASE TOGETHER ON MONDAY WITH MOISTURE BEING
ABLE TO BE PULLED FAR ENOUGH WEST AROUND THE LOW TO KEEP CHANCES FOR
PRECIPITATION OVER PARTS OF NORTHERN NEBRASKA. THE PATTERN SHIFT TO
WHICH OCCURS LATER THIS WEEK WILL BE SHORT LIVED AS THE MODELS ARE
INDICATING THE LONGWAVE PATTERN WILL RETURN TO RIDGING OVER THE WEST
AND TROUGHING TO THE EAST AS THE UPPER LOW GETS ANCHORED OVER THE
GREAT LAKES EARLY NEXT WEEK. SO LOOKING AT A SLIGHT WARM-UP /TO
AROUND NORMAL IN SOME PLACES/ FOR THE WEEKEND BUT COLDER AIR SHOULD
RETURN NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1215 PM CST TUE NOV 18 2014

VFR AFTERNOON WITH SOME PASSING HIGH CLOUDS AND WEST/SOUTHWEST
WINDS AROUND 10 TO 15 KTS. TONIGHT AN ARCTIC COLD FRONT WILL BACK
INTO THE REGION...BRINGING A CHANCE FOR LOW /MVFR/ CIGS. THE LOWER
CIGS ARE EXPECTED INTO KVTN BEFORE MIDNIGHT...WITH THE LOWEST CIGS
TOWARDS SUNRISE. MORNING FORECAST IS CONSERVATIVE AND DOES
INCREASE THE CEILING HEIGHT FOR KVTN. MEANWHILE THE FRONT REACHES
KLBF IN THE MORNING HOURS. DID INTRODUCE A BKN025 CIG INTO THE
TAF...ALTHOUGH CONFIDENCE IS LOW ON THE HEIGHT OF THE CIG...WHICH
COULD BE IN THE LOWER.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

UPDATE...MASEK
SYNOPSIS...CLB
SHORT TERM...CLB
LONG TERM...BROOKS
AVIATION...MASEK





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