Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 272015
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
313 PM CDT MON OCT 27 2014

.SYNOPSIS...
ISSUED AT 311 PM CDT MON OCT 27 2014

AT 18Z WATER VAPOR IMAGERY SHOWED A POTENT UPPER LEVEL LOW OVER
WESTERN NORTH DAKOTA...WITH A TROUGH EXTENDING SOUTHWEST INTO THE
CENTRAL ROCKIES. ALSO SEEN WITH THIS TROUGH WAS A SIGNIFICANT PV
ANOMALY OVER NORTHERN COLORADO AND SOUTHEAST WYOMING. AHEAD OF THIS
SYSTEM A STRONG RIDGE REMAINED OVER THE EASTERN PART OF THE COUNTRY
WITH ANOTHER RIDGE IN PLACE OVER THE WEST COAST. LOOKING FURTHER
UPSTREAM...A STRONG UPPER LEVEL LOW /WITH THE REMNANTS OF HURRICANE
ANNA/ WAS MOVING TOWARDS BRITISH COLUMBIA. AT THE SURFACE...THE COLD
FRONT ASSOCIATED WITH THE LOCAL UPPER LEVEL SYSTEM HAS PUSHED WELL
THROUGH THE STATE OF NEBRASKA WHERE THE COLDER AIR ALOFT HAS BEEN
CONTINUOUSLY FILTERED INTO THE FORECAST AREA THROUGH THE DAY.
FRONTOGENESIS IN THE 700-500MB LAYER HAS BROUGHT SOME LIGHT RAIN
SHOWERS/VIRGA ACROSS MUCH OF THE AREA TODAY. THIS FORCING HAS
DIMINISHED THROUGH THE AFTERNOON WITH ONLY SCATTERED RADAR RETURNS
REMAINING AT MID AFTERNOON. WITH THE TIGHT PRESSURE GRADIENT BEHIND
THE FRONT AND WITH COLD AIR ALOFT STEEPENING THE LAPSE RATES BELOW
800MB GOOD MIXING WAS IN PLACE...KEEPING WINDS BREEZY ACROSS THE
FORECAST AREA. ALSO...WITH THE STEEP LAPSE RATES...HAVE SEEN SOME
WEAK SHOWERS DEVELOP THIS AFTERNOON UNDER THE COLD POOL.
TEMPERATURE/DEWPOINT SPREADS WERE 20 TO 25 DEGREES OVER MUCH OF THE
AREA WHICH HAS LITTLE IN TERMS OF PRECIPITATION ACCUMULATION...WITH
MOST LOCATIONS SEEING A FEW HUNDREDTHS OF AN INCH TO JUST VIRGA.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 311 PM CDT MON OCT 27 2014

THE MID LEVEL FRONTOGENETICAL FORCING OVER SOUTHWEST TO NORTH
CENTRAL NEBRASKA THIS AFTERNOON WILL DIMINISH AS THE COLD AIR ALOFT
TAKES OVER WHICH WILL BRING AN END TO THE RAIN SHOWERS/VIRGA IN
THESE AREAS. ALSO...WITH AN END TO DIURNAL HEATING LATER THIS
AFTERNOON THE BOUNDARY LAYER INVERSION WILL BEGIN TO SET UP WHICH
SHOULD BRING AN END TO ANY SCATTERED RAIN SHOWERS OVER THE REGION.
THE PRESSURE GRADIENT WILL WEAKEN OVERNIGHT...ALLOWING WINDS TO
DIMINISH FOR MOST AREAS. THERE MAY BE A SLIGHT INCREASE IN WINDS
AFTER MIDNIGHT TONIGHT OVER THE NORTHEAST PART OF THE FORECAST AREA
AS THE UPPER LEVEL PV ANOMALY THAT IS NOW OVER SOUTHEAST MONTANA
MOVES ACROSS NORTH CENTRAL NEBRASKA.

DRY AIR WILL CONTINUE TO FILTER INTO THE REGION OVERNIGHT AND WITH
DEWPOINTS UPSTREAM READING FROM THE LOW 20S TO LOW 30S EXPECTING
SIMILAR NUMBERS LOCALLY. WITH THE DRY AIR IN PLACE AND LIGHT WINDS
AND CLEAR SKIES ESPECIALLY OVER THE SOUTHWEST HALF OF THE FORECAST
AREA...LOOKING AT TEMPERATURES TO PLUMMET TONIGHT WITH LOWS LOOKING
TO FALL INTO THE MID AND UPPER 20S. WHERE THE WINDS STAY UP OVER
NORTH CENTRAL NEBRASKA EVEN SLIGHT BOUNDARY LAYER MIXING AND PERHAPS
A BIT OF CLOUD COVER SHOULD KEEP TEMPERATURES WARMER...IN THE LOW TO
MID 30S.

ON TUESDAY...THE COOLEST AIR ALOFT WILL BE IN PLACE OVER THE REGION
AS 18Z READINGS AT 850MB ARE LOOKING TO RANGE FROM -2C TO 5C ACROSS
THE FORECAST AREA. DRY AIR WILL BE IN PLACE...THEREFORE PLENTIFUL
SUNSHINE WILL HELP SURFACE WARMING AND WILL PROMOTE STEEP LAPSE
RATES IN THE BOUNDARY LAYER AND DECENT MIXING. FORECAST SOUNDINGS
SHOW MIXING TO AROUND 750-800MB WHICH WOULD MIX DOWN WINDS OF 20 TO
25KTS OVER MUCH OF THE FORECAST AREA. THE COOL AIR ALOFT WILL ALSO
LIMIT THE AMOUNT OF WARMING POTENTIAL...SO LOOKING AT HIGHS
GENERALLY IN THE 50S WITH THE COOLEST READINGS EXPECTED OVER THE
WESTERN SANDHILLS INTO NORTH CENTRAL NEBRASKA WHERE TEMPERATURES AT
850MB REMAIN BELOW 0C THROUGH 00Z WEDNESDAY.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 311 PM CDT MON OCT 27 2014

WITH WEST TO NORTHWEST FLOW ALOFT AND A SUCCESSION OF WEAK
SYSTEMS...TEMPERATURES ARE EXPECTED TO FLUCTUATE 5 TO 10 DEGREES
EVERY DAY OR TWO. EVEN WITH THE PERIODIC FLUCTUATION...DAYTIME
TEMPERATURES WILL CONTINUE TO BE ABOVE AVERAGE EXCEPT FOR FRIDAY AND
MONDAY WHEN THEY WILL BE NEAR AVERAGE. LOWS WILL BE COOL
BUT...EXCEPT FOR TUESDAY NIGHT...AT OR ABOVE AVERAGE.

ON FRIDAY...ANOTHER COLD AIR MASS IS EXPECTED. BETWEEN IT AND THE
DEVELOPING LEE SIDE TROUGH...PRESSURE GRADIENT WILL SUPPORT WINDY
CONDITIONS FRIDAY AND SATURDAY. FOLLOWING THAT...A STRONGER FRONT IS
EXPECTED OVER THE WEEKEND. THAT FRONT WILL BE ACCOMPANIED BY STRONG
FRONTOGENESIS WHICH...THOUGH PRECONDITIONS ARE DRY...MAY JUSTIFY AT
LEAST A MENTION OF PRECIPITATION SUNDAY NIGHT AND/OR MONDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1220 PM CDT MON OCT 27 2014

VFR CONDITIONS ARE EXPECTED ACROSS WESTERN AND NORTH CENTRAL
NEBRASKA THROUGH THE NEXT 24 HOURS. MAIN FORECAST CONCERNS WILL BE
STRONG NORTHWEST WINDS...AS WELL THE CHANCE FOR SHOWERS IN NORTHERN
NEBRASKA TODAY. SHOWERS SO FAR TODAY HAVE NOT PRODUCED ANY CIGS OR
VISBYS BELOW VFR THRESHOLDS...WHICH SHOULD BE THE CASE WITH ANY
ACTIVITY THROUGH THE REMAINDER OF THE DAY. HOWEVER..VIRGA AND SHOWER
ACTIVITY MAY TEMPORARILY MIX DOWN WIND GUSTS STRONGER THAN THE 30 KT
GUSTS ALREADY OCCURRING. THE AREA WILL DRY OUT AND CLEAR OUT TONIGHT
WITH RELAXING WINDS.


&&

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

$$

SYNOPSIS...BROOKS
SHORT TERM...BROOKS
LONG TERM...SPRINGER
AVIATION...MARTIN









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