Area Forecast Discussion
Issued by NWS North Platte, NE

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000
FXUS63 KLBF 120601 AAA
AFDLBF

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NORTH PLATTE NE
101 AM CDT FRI SEP 12 2014

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 328 PM CDT THU SEP 11 2014

SEVERAL FORECAST CONCERNS TONIGHT AS SURFACE HIGH MOVES SOUTHEAST.
THE PRIMARY FORECAST CHALLENGE IS TEMPERATURES WITH HEADLINES ISSUED
FOR THE EASTERN PANHANDLE AND NORTHWEST SANDHILLS FOR TONIGHT. MUCH
COLDER AIR WILL SETTLE SOUTH AS THE 1037 MB SURFACE HIGH OVER
MONTANA MOVES SOUTHEAST. TEMPERATURES HAVE STRUGGLED TO RISE TODAY
AS THE SURFACE RIDGE EXTENDS SOUTH ON THE HIGH PLAINS...KEEPING
MOISTURE FLOWING WESTWARD. THE UPSLOPE FLOW HAS KEPT THE AIR
SATURATED WITH TEMPERATURES AT 18Z IN THE UPPER 30S NORTHWEST TO
MIDDLE 40S SOUTHWEST. THIS EVENING A H5 SHORTWAVE TROUGH WILL MOVE
SOUTHEAST WITH INCREASING LIFT FOR RAIN CHANCES TO INCREASE THIS
EVENING...ESPECIALLY IN THE SOUTHWEST. BEFORE MIDNIGHT CRITICAL
TEMPERATURES WILL BE REACHED AND THE RAIN BECOMING MIXED WITH SNOW
IN THE WEST...WEST OF HIGHWAY 83. THEN THE FAR NORTHWEST
TRANSITIONING TO ALL SNOW OVERNIGHT BEFORE ENDING EARLY MORNING
FRIDAY. SNOW ACCUMULATIONS ARE POSSIBLE OVER SHERIDAN COUNTY WHERE
UP TO 2 INCHES OF SNOW ACCUMULATION MAY BE SEEN ON GRASSY SURFACES.
THEN AN INCH OR LESS FOR NEARBY COUNTIES AS THE MAIN FORCING LIFTS
OUT. THE WEATHER CONDITIONS WILL IMPROVE BY MID MORNING FRIDAY WITH
CLEARING FROM THE NORTHWEST TO SOUTHEAST AS THE SURFACE HIGH BUILDS
SOUTHEAST. THE CLOUDS WILL STEADILY CLEAR FOR MORE SUNSHINE INTO THE
AFTERNOON AND DAYTIME HIGHS ONLY IN THE 50S.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 328 PM CDT THU SEP 11 2014

THE MAIN CHALLENGE FOR THE FORECAST FRIDAY NIGHT IS TEMPERATURES.
WITH CLEAR SKY AND LIGHT WIND...TEMPERATURES IN THE 30S ARE
POSSIBLE. THE COLDEST AREAS...ACCORDING TO THE NAM AND GFS
STATISTICAL OUTPUT...WOULD BE IN THE PANHANDLE...THE WESTERN
SANDHILLS AND IN THE PLATTE RIVER VALLEY. THIS IS SUPPORTED BY THE
SURFACE ANALYSIS THIS MORNING WHICH INDICATED THE COLDEST AIR IN
THE NORTHWEST QUADRANT OF THE HIGH ON THE PLAINS OF ALBERTA AND
WESTERN SASKATCHEWAN. ALSO...THE 500 METER TEMPERATURES FROM THE
DETERMINISTIC OUTPUT SUPPORTS THAT RELATIVE LOCATION AS WELL...AND
IT INDICATES COLDEST TEMPERATURES IN THE UPPER 30S. ASSUMING THE
WIND DECOUPLES...WIDESPREAD SURFACE TEMPERATURES OF 30 TO 35 ARE
LIKELY WITH LOCALIZED COLDER TEMPERATURES POSSIBLE IN AREAS PRONE TO
COLD AIR BEING TRAPPED SUCH AS RIVER VALLEYS. CLIMATOLOGICAL LY...IT
IS NOT RARE THAT THE COLDEST TEMPERATURES OCCUR THE SECOND NIGHT OF
AN ARCTIC OUTBREAK. THERE ARE A FEW THINGS THAT REDUCE THE
LIKELIHOOD OF FROST. WITH THE SURFACE HIGH HAVING MOVED TO SOUTH
CENTRAL KANSAS...RETURN FLOW MAY HELP COUNTER THE DIURNAL
TEMPERATURE DECREASE AND...IF THE WIND DOES NOT COMPLETELY
DECOUPLE...LOWS WILL BE CLOSER TO 40. FINALLY...MOST OF THE AREA IS
AT THE 10 PERCENT PROBABILITY OF FIRST FROST OCCURRENCE...SO FROST
IS NOT FAVORED CLIMATOLOGICALLY. WEIGHING IT ALL...MY CONFIDENCE IS
ABOUT 60 PERCENT THAT FROST WILL OCCUR AND THAT IS HIGH ENOUGH TO
INCLUDE AREAS OF FROST IN THE FORECAST FOR THE PANHANDLE...THE
WESTERN HALF OF THE SANDHILLS AND THE PLATTE RIVER VALLEY AND PATCHY
FROST ELSEWHERE. THE HIGHER PROBABILITY OF FROST IS ROUGHLY ALONG
AND NORTH OF INTERSTATE 80 AND ALONG AND WEST OF U.S. HIGHWAY 83.
SINCE THERE ARE ALREADY ADVISORIES FOR FROST AND FREEZE TONIGHT...
WE WILL DEFER THE DECISION ON ISSUING ANY ADVISORY FRIDAY NIGHT TO
THE FRIDAY MORNING ISSUANCE. FOR THE TIME BEING...WE WILL COVER
FRIDAY NIGHT AND EARLY SATURDAY WITH A SPECIAL WEATHER STATEMENT.

A LOW COMING OUT OF WYOMING AND CROSSING THE PLAINS ALONG THE SOUTH
DAKOTA/NEBRASKA STATE LINE WILL GENERATE SOME ISENTROPIC LIFT OF
NEARLY SATURATED AIR OVER NORTHERN AND EASTERN NEBRASKA. THIS IS
APPARENT WITH THE GFS40 FORECAST FOR THE 300-315K THETA LAYER. THERE
IS SOME ELEVATED INSTABILITY INDICATED...SO THUNDERSTORMS ARE
POSSIBLE AT LEAST FOR THE AFTERNOON AND EVENING. THEN HIGH PRESSURE
WILL FORCE THE PRECIPITATION OUT OF THE AREA MONDAY MORNING.

THE NEXT CHANCE FOR PRECIPITATION WILL BE TUESDAY NIGHT AND
WEDNESDAY WITH THE BEST CHANCES IN CENTRAL...SOUTH CENTRAL AND
SOUTHWEST NEBRASKA AS A WARM FRONT COMES OUT OF THE COLORADO AND
WYOMING PLAINS INTO SOUTHWEST AND THEN WESTERN NEBRASKA. THAT SYSTEM
IS LIKELY TO BRING PRECIPITATION TO CENTRAL AND NORTH CENTRAL
NEBRASKA WEDNESDAY AFTERNOON AND NIGHT AS IT MOVES FARTHER INTO
CENTRAL AND WESTERN NEBRASKA. VERY UNSTABLE CONDITIONS ARE EXPECTED
IN CENTRAL NEBRASKA WEDNESDAY AFTERNOON AND EVENING. WITH CONVECTIVE
POTENTIAL ENERGY AT OR ABOVE 2000J/KG AND 0-6KM SHEAR 35-40KT...
STRONG THUNDERSTORMS ARE POSSIBLE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 100 AM CDT FRI SEP 12 2014

MVFR CEILINGS ACROSS WESTERN NEBRASKA WILL BECOME VFR FROM NORTH TO
SOUTH OVERNIGHT. SOME LIGHT RAIN/LIGHT SNOW OBSERVED AT KLBF SHOULD
END BY 09Z WITH CEILINGS IMPROVING TO VFR BETWEEN 12Z AND 15Z. SKIES
TO BECOME SKC AFTER 18Z WITH LIGHT WINDS THROUGH THE TAF PERIOD.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
FROST ADVISORY UNTIL 9 AM MDT FRIDAY FOR NEZ022>024-035-056-094.

FREEZE WARNING UNTIL 9 AM MDT FRIDAY FOR NEZ004.

&&

$$

SHORT TERM...KECK
LONG TERM...SPRINGER
AVIATION...POWER





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