Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 230502
AFDLBF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
1202 AM CDT WED APR 23 2014

.UPDATE...
ISSUED AT 824 PM CDT TUE APR 22 2014

UPDATE INCLUDED FRESHENING UP CLOUD COVER ACROSS THE AREA FOR
TONIGHT. OTHERWISE...FORECAST LOOKS ON TRACK WITH ISOLATED
SHOWERS AND THUNDERSTORMS EXPECTED TONIGHT. CURRENTLY...ONLY A
FEW SHOWERS/THUNDERSTORMS EXIST ACROSS THE NORTHWEST. LATE
TONIGHT...THE POSSIBILITY EXISTS FOR ACTIVITY INCREASING IN THE
NORTHEAST IN RESPONSE TO THE LOW LEVEL JET. THE LATEST RAP HAS
400-700 J/KG OF MUCAPE IN THE NORTHEAST LATE. WILL WAIT FOR
LATEST NAM BEFORE MAKING CHANGES TO PRECIP FORECAST.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 400 PM  CDT TUE APR 22 2014

AT 20Z WATER VAPOR IMAGERY SHOWED AN AMPLIFIED PATTERN IN THE UPPER
LEVELS WITH A TROUGH OVER THE EASTERN CONUS...RIDGING OVER THE
PLAINS...AND A DEEP TROUGH OVER THE WEST COAST. A GOOD FETCH OF MID
AND HIGH LEVEL MOISTURE WAS SEEN AHEAD OF THE TROUGH WITH QUITE A
BIT OF CLOUD COVER MOVING INTO THE CENTRAL PLAINS. AT THE
SURFACE...A BROAD AREA OF LOW PRESSURE DEVELOPED ON THE LEE SIDE OF
THE ROCKIES THROUGH THE DAY WHICH TIGHTENED THE PRESSURE GRADIENT
ACROSS NEBRASKA. THIS BROUGHT BREEZY SOUTHERLY WINDS TO THE ENTIRETY
OF THE FORECAST AREA THROUGH THE DAY WITH FREQUENT SPEEDS OF 25 MPH
WITH GUSTS TO 35 MPH. THIS SOUTHERLY FLOW BROUGHT WARM AIR AND
MOISTURE NORTHWARD THROUGH THE DAY...WITH HIGHS INTO THE 70S FOR
MUCH OF THE AREA...WHILE DEW POINTS INCREASED INTO THE 40S IN PARTS
OF THE PANHANDLE. EVEN WITH THE INCREASE IN DEW POINTS...THE BOUNDARY
LAYER REMAINS VERY DRY. ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS HAD BEEN DEVELOPING OVER THE PANHANDLE AND NORTHEAST
COLORADO THIS AFTERNOON...BUT DUE TO THE DRY AIR...CLOUD BASES WERE
AT OR ABOVE 10K FEET.

FOR THE REMAINDER OF THE AFTERNOON...SPC MESOANALYSIS SHOWED AREAS
OVER THE PANHANDLE HAD BUILT UP TO 500 J/KG MUCAPE. WITH SUFFICIENT
LIFT ONGOING ACROSS THE AREA AND SOME INSTABILITY...EXPECT THE
SHOWER AND THUNDERSTORM ACTIVITY TO CONTINUE...AND WILL SLOWLY MAKE
AN EASTWARD PROGRESSION INTO THIS EVENING.

FORECAST MODELS SHOW THAT AS THE ENTIRE SYSTEM PROGRESSES EAST THIS
EVENING AND OVERNIGHT SOME INSTABILITY IN THE MID LEVELS WILL
MIGRATE EAST ACROSS THE FORECAST AREA. THE AMOUNT OF INSTABILITY
WILL BE QUITE WEAK THOUGH...WITH 100-200 J/KG. WITH THE LOSS OF
DAYTIME HEATING...AND WITH THE WEAKENING INSTABILITY EXPECT ANY
ACTIVITY TO DIMINISH THIS EVENING AS IT MOVES EAST. THE ONE THING TO
WATCH WILL BE IF THE INCREASE OF THE LOW LEVEL JET TONIGHT WILL BE
ENOUGH TO KEEP ACTIVITY GOING. AT THIS TIME...WITH THE AMOUNT OF DRY
AIR ACROSS THE AREA...DON/T THINK THE LLJ WILL BE ENOUGH TO OVERCOME
THE DRY AIR AND DON/T EXPECT MUCH FOR PRECIPITATION IN THE OVERNIGHT
HOURS. WINDS WILL STAY STRONG OVERNIGHT AS THE PRESSURE GRADIENT
STAYS TIGHT. THE STRONG WINDS WILL KEEP TEMPERATURES FROM DROPPING
TONIGHT...SO LOOKING AT LOWS IN THE UPPER 40S AND 50S.

ON WEDNESDAY...THE UPPER LEVEL TROUGH WILL LIFT NORTHEAST WHICH WILL
PUSH A COLD FRONT ACROSS THE FORECAST AREA BY THE END OF THE DAY.
WINDS WILL STAY STRONG AHEAD OF THE FRONT...WHICH BY 18Z LOOKS TO BE
ROUGHLY FROM KMCK TO KONL. THERE COULD BE A PERIOD OF TIME WHEN
WINDS APPROACH WIND ADVISORY CRITERIA OVER THE NORTHEAST PART OF THE
FORECAST AREA. THE PERIOD OF THE HIGHEST WINDS WOULD BE FROM AROUND
06Z TO 15Z...BUT WITH IT BEING IN AN AREA OF WARM AIR ADVECTION AND
NOT SUBSIDENT AIR...AND ALSO IT BEING IN THE OVERNIGHT HOURS...DON/T
KNOW IF THE STRONGEST WINDS WILL BE ABLE TO MAKE IT TO THE SURFACE.

THEN IN THE AFTERNOON...MOISTURE WILL POOL AHEAD OF THE FRONT WITH
DEW POINTS RISING UP AROUND 50 OR HIGHER. STORMS SHOULD DEVELOP ALONG
AND AHEAD OF THE FRONT LATER IN THE AFTERNOON...AND THE PLACEMENT OF
THE FRONT WILL DEPEND WHAT AREAS SEE RAINFALL. DID PUSH CHANCES EAST
SLIGHTLY...BUT THINK THE STORMS MAY SKIRT THE EASTERN PART OF THE
FORECAST AREA. WHEREVER STORMS DO FORM...THEY WILL LIKELY BE STRONG
TO EVEN SEVERE AS STRONGER INSTABILITY IS EXPECTED...ALONG WITH
STRONG DEEP LEVEL SHEAR AS THE SYSTEM IS QUITE DYNAMIC. WILL BE
WATCHING THESE CHANCES CLOSELY OVER THE NEXT 18 TO 24 HOURS.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 400 PM CDT TUE APR 22 2014

INITIAL UPPER PV ANOMALY ROTATING ACROSS MT THROUGH THE NEGATIVELY
TILTED UPPER LOW WILL ENHANCE CONVERGENCE ALONG THE WARM FRONT
LOCATED ACROSS THE UPPER MIDWEST AND NORTHERN PLAINS EARLY...BUT AS
THE NEXT ANOMALY MOVES THROUGH THE LONG WAVE TROUGH AS IT PROGRESSES
EWD IT WILL ENHANCE CONVERGENCE ALONG THE SWD ADVANCING COLD FRONT
ACROSS NEBRASKA WED NIGHT...AND ALONG THE DRYLINE IN WRN KS SWD INTO
WEST TX. BY WED NIGHT THE FRONT WILL BE THROUGH MOST OF THE LBF CWA
AND WILL TREND THE PRECIP CHCS EWD THROUGH EARLY MORNING...THEN DRY
WHICH THE CURRENT GFCST HAS HANDLED WELL.

UPPER LOW THEN MOVES INTO THE GREAT LAKES REGION AS TRANSITORY
RIDGING MOVES INTO THE CENTRAL ROCKIES. AS THIS OCCURS WESTERLY
DOWNSLOPE WINDS WILL REMAIN IN THE BREEZY CATEGORY WITH VERY DRY LOW
LEVELS REMAINING. THIS WILL MEAN ANOTHER DAY NEAR CRITICAL FIRE
WEATHER CONDITIONS...THOUGH AT THIS TIME WINDS SHOULD REMAIN JUST
BELOW CRITERIA THOUGH RH VALUES WILL DROP IN TO THE TEENS IN
PORTIONS OF THE SOUTHEAST PANHANDLE INTO SOUTHWEST NEBRASKA. DESPITE
THE AREA NEING IN A POST-FRONTAL ENVIRONMENT TEMPS WILL REACH ABOVE
AVERAGE IN MOST LOCATIONS UNDER FULL SUN. DRY CONDITIONS WILL
PREVAIL INTO FRIDAY AS WELL AS TRANSITORY RIDGE MOVES EAST INTO THE
PLAINS.

NEXT HIGH AMPLITUDE UPPER LOW MOVES ONSHORE OVER CA FRIDAY NIGHT.
BEYOND THIS PERIOD MODEL HAVE VARYING SOLUTIONS TO HOW THIS NEXT
SIGNIFICANT WEATHER MAKER EVOLVES. THE 22.12Z RUN OF THE ECMWF HAS
SIGNIFICANT DIFFERENCES FROM THE 22.00Z RUN...MOVING THE WARM FRONT
MUCH FURTHER NORTH WITH THE LATEST RUN...LOCATED OVER NRN NEB INTO
SRM SD. THE POSITION OF THIS WARM FRONT IS SIGNIFICANT BECAUSE WITH
THE SYSTEM EVOLVING TO BECOME NEGATIVELY TILTED OVER TIME AS ALL
MODELS DO...THE LEAD UPPER PV ANOMALY WITH ENHANCE CONVERGENCE ALONG
THE WARM FRONT INITIALLY AND WITH THE POTENTIAL FOR GOOD LOWER LEVEL
SHEAR ALONG AND NORTH OF THE WARM FRONT...POTENTIAL FOR SEVERE
WEATHER...BOTH AMOUNT AND TYPE OF SEVERE...RESTS HEAVILY WITH THE
POSITION OF THIS WARM FRONT. GFS POSITIONS THE WARM FRONT IN
KS...FURTHER SOUTH THAN THE ECMWF AND SIMILAR TO THE 22.12Z RUN OF
THE CANADIAN MODEL. SEVERE WEATHER WILL BE A DISTINCT POSSIBILITY IN
THE PLAINS THIS WEEKEND...THOUGH THE DETAILS OF WHICH WILL HAVE TO
BE IRONED OUT IN THE NEXT FEW DAYS. MODELS THEN CONTINUE TO CUT OFF
THE UPPER LOW FROM THE MAIN FLOW AND REDEVELOP IT ACROSS THE MID
MISSISSIPPI VALLEY IN SOME FASHION...BUT AGAIN TIMING AND LOCATION
DIFFERENCES ARE SIGNIFICANT BUT WILL LIKELY KEEP THE AREA
UNSETTLED...COOLER THAN AVERAGE AND BETTER CHANCES FOR PRECIP...INTO
THE FIRST PART OF NEXT WEEK. ALONG WITH THE POSITION DIFFERENCES ARE
SIGNIFICANT TEMPERATURE DIFFERENCES WITH THE ECMWF BEING MUCH
COLDER. THIS WILL ALSO LEAD TO A LOW CONFIDENCE IN PRECIPITATION
TYPE FOR THE OVERNIGHT PERIODS SUNDAY NIGHT INTO MONDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1202 PM CDT TUE APR 23 2014

BREEZY CONDITIONS ARE EXPECTED OVER THE NEXT 20 HOURS AT THE TAF
SITES AS GUSTY SOUTHERLY WINDS SWITCH TO THE NORTHWEST TOMORROW
EARLY IN THE AFTERNOON. A FEW SHOWERS...AND POSSIBLY A
THUNDERSTORM...MAY AFFECT THE TERMINALS TONIGHT. HOWEVER...THE
CHANCE IS RATHER LOW. THUNDERSTORMS MAY DEVELOP TOMORROW AFTERNOON
IN THE VICINITY OF KLBF EARLY IN THE AFTERNOON...DEPENDING ON THE
TIMING OF THE FRONT. WILL CONTINUE WITHOUT TS MENTION AT KLBF
UNTIL MODELS COME IN BETTER AGREEMENT WITH FRONTAL LOCATION/TIMING.

&&

.FIRE WEATHER...
ISSUED AT 433 PM CDT TUE APR 22 2014

FIRE WEATHER CONCERNS WILL HEIGHTEN ON WEDNESDAY BEHIND A COLD
FRONT AS DRY AIR PUSHES INTO THE AREA...ALONG WITH BREEZY WEST TO
NORTHWEST WINDS. AT THIS TIME...MINIMUM RELATIVE HUMIDITY IS
EXPECTED TO BE 15 TO 25 PERCENT WITH WINDS BLOWING AT 15 TO 25
MPH. THEN ON THURSDAY...DRY AIR WILL FILTER INTO THE AREA AS
DEW POINTS LOOK TO FALL INTO THE TEENS. TEMPERATURES IN THE 60S TO
LOW 70S WILL EQUATE TO RELATIVE HUMIDITY DROPPING TO NEAR 15
PERCENT. WINDS WILL BE BREEZY OUT OF THE WEST TO NORTHWEST...BUT
THERE IS UNCERTAINTY TO HOW STRONG THEY WILL GET. BOTH DAYS ARE
LOOKING TO HAVE NEAR HIGH FIRE WEATHER CONDITIONS...BUT MAY STAY
JUST UNDER CRITICAL LEVELS. WILL BE CLOSELY WATCHING THIS IN THE
FORECAST THROUGH THURSDAY.

&&

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

$$

UPDATE...KNUTSVIG
SHORT TERM...BROOKS
LONG TERM...JWS
AVIATION...KNUTSVIG
FIRE WEATHER...BROOKS






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