Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 301126
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
626 AM CDT WED JUL 30 2014

.UPDATE...
ISSUED AT 626 AM CDT WED JUL 30 2014

JUST PUBLISHED A MUCH-NEEDED VERY SHORT-TERM UPDATE THRU 9 AM AS
FCST HOURLY TEMPS HAD FALLEN OFF THE TRACK N OF I-80. THE PAST 3
HRS OF IR SATELLITE SHOWS THE CIRRUS SHIELD CONTINUING TO THIN AND
DROP S. THIS HAS ALLOWED FOR SOME RADIATING. THE OBSERVED TEMP AT
ORD WAS RUNNING 5F BELOW THE FCST.

SHOULD BE A BEAUTIFUL SUNRISE WHERE THE CLOUDS ARE DEPARTING. PEAK
COLORS WILL OCCUR WITHIN THE NEXT 30-40 MIN.

WE MAY HAVE A BRIEF FOG PROBLEM AS WELL. THE CROSS-OVER TEMP AT
ORD IS 57F AND THE ASOS IS AT 54F AT 11Z WITH THE VSBY DROPPING.
HAVE ADDED SOME PATCHY FOG N OF HWY 92.

THE NARROW BAND OF SHWRS SINKING THRU N-CNTRL KS HAS SLOWED ITS
FORWARD PROGRESS. THIS HAS BEEN BETTER DEPICTED IN THE HOURLY
POP/WX GRIDS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 626 AM CDT WED JUL 30 2014

...FAIRLY UNEVENTFUL WX PATTERN CONTS AS WE GRAPPLE WITH MINOR
DISTURBANCES THAT REDUCE FCSTR CONFIDENCE...

THERE IS ESSENTIALLY NO CHANGE IN THE SYNOPTIC FEATURES. THAT
LEAVES US TO DEAL WITH MESOSCALE FEATURES WHICH HAVE LESS
PREDICTABILITY AND LOWER FCST CONFIDENCE.

ALOFT: NW FLOW ALOFT REMAINS. A WEAK AND SHEARED SHORTWAVE TROF
WAS OVER ND IN WATER VAPOR IMAGERY AND DROPPING S INTO SD. THIS
TROF WAS ASSOCIATED WITH SOME VERY SPOTTY TSTM ACTIVITY YESTERDAY
AFTERNOON AND EVEN A COUPLE SHWRS OVERNIGHT. IT WILL CONT DROPPING
S AND ARRIVE HERE IN NEB TONIGHT.

SURFACE: OVERALL HIGH PRES WILL REMAIN PARKED FROM THE CANADIAN
PRAIRIES SE INTO THE ERN USA. THE APPROACHING TROF WILL INDUCE A
WEAK LOW OVER WRN SD AND 07Z MSAS ANALYSIS SHOWS CONVERGENCE AND
FALLING PRES THERE. THIS LOW IS FCST TO DROP SE INTO THE SANDHILLS
BY TONIGHT.

TODAY: M/CLOUDY TO START BUT GRADUALLY DECREASING CLOUDS FROM THE
N. OVERALL...TURNING P/CLOUDY. THE CO SHORTWAVE TROF RESPONSIBLE
FOR THE BAND OF FGEN SHWRS OVER N-CNTRL KS AND THE MORE EXTENSIVE
RAIN/TSTMS TO THE S AND W WILL DIVE INTO OK TODAY. THIS SHOULD
ALLOW FOR THE GRADUAL IMPROVEMENT. USED CONSENSUS OF MODEL 2M
TEMPS FOR HIGHS WITH A BIAS CORRECTION WHICH OFFERS 75-80F...
COOLEST OVER N-CNTRL KS WHERE CLOUDS WILL HANG ON THE LONGEST.

FCST CONFIDENCE: MEDIUM

TONIGHT: PROBABLY JUST SOME PATCHY THIN CIRROSTRATUS IN THE
EVENING THEN INCREASING CLOUDS. LOW TEMPS ARE CONSENSUS OF MODEL
2M TEMPS WITH NO BIAS CORRECTION /55-60F/. HOWEVER...WITH NEARLY
CALM WINDS EXPECTED SOME AREAS THAT STAY OUT OF THE CLOUD COVER
LONGEST COULD END UP A LITTLE COOLER.

A FEW SHWRS MAY TRY TO DEVELOP N OF I-80 IN THE BURST OF MODEST
WARM AIR ADVECTION AND FRONTOGENESIS ASSOCIATED WITH THE WEAK
LOW/TROF. THE 18Z/00Z/06Z NAM RUNS HAVE CONTINUITY WITH THEIR
SPOTTY/LOW QPF. ALL OTHER MODELS HAVE NO CONSISTENCY OR NO QPF.

THE SATURATION THAT OCCURS IN THE 6-8K FT LAYER DOES LEAD TO
POTENTIAL INSTABILITY. ALL MODELS FCST A WEAK CAP BETWEEN 600-500
MB. THE MOST UNSTABLE PARCEL IN THE NAM SOUNDINGS DOES GET PAST
THIS WITH A VERY SKINNY CAPE PROFILE /MAYBE 400 J/KG CAPE?/ AND
AN EQUILIBRIUM LVL NEAR 29K FT.

FOR NOW...A 20% POP HAS BEEN INSERTED INTO THE FCST N OF I-80
AFTER MIDNIGHT WITH NO THUNDER. THIS MAY CHANGE IF THE DAY SHIFT
HAS HIGHER CONFIDENCE IN THE PROBABILITY OF OCCURRENCE.

FCST CONFIDENCE: MEDIUM


.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 357 AM CDT WED JUL 30 2014

THE AMPLIFIED RIDGE TO THE WEST AND TROUGH TO THE EAST REMAIN
PERSISTENT IN UPPER LEVELS. THIS PATTERN DEAMPLIFIES BY EARLY NEXT
WEEK. MAIN FORECAST ISSUE WILL BE CHANCE OF PRECIPITATION
THURSDAY...THEN AGAIN MONDAY INTO TUESDAY.

THE MAIN ISSUE FOR THURSDAY WILL BE A SHOT AT SOME SHOWERS AND
THUNDERSTORMS THURSDAY AFTERNOON...MAINLY NORTH/NORTHEASTERN CWA
AS A PERTURBATION MOVES NEARBY WITHIN UPPER LEVEL NORTHWEST FLOW.
THE FOCUS HAS BEEN CONSISTENTLY FORECAST MORE TOWARD THE
NORTH/NORTHEASTERN CWA FOR THE PAST COUPLE OF DAYS. NUMERICAL
MODELS ARE NOT IN WIDESPREAD AGREEMENT...WITH THE ECMWF REMAINING
DRY FOR THURSDAY...WHEREAS THE NAM HAS BEEN CONSISTENTLY
FORECASTING SOME SPOTTY CONVECTION AS THE WAVE MOVES THROUGH.
THERE SHOULD BE ENOUGH INSTABILITY TO ALLOW THUNDER...BUT NOT
ENOUGH FOR SEVERE WEATHER AS BULK SHEAR WILL BE MODERATE AT AROUND
25 TO 30 KTS TOPS AND CONVECTIVE AVAILABLE POTENTIAL ENERGY NOT
MUCH MORE THAN 750 J/KG.

AFTER THE THURSDAY WAVE...WE HAVE A DRY FORECAST THROUGH THE
WEEKEND FOR THE MOST PART...SAVE A SLIGHT CHANCE OF PRECIPITATION
IN OUR FAR NORTHWEST ON FRIDAY AFTERNOON WITH ANOTHER POTENTIAL
PERTURBATION WITHIN NORTHWEST FLOW. I DID NOT EXPAND THIS FARTHER
SOUTHEAST AS TIMING OF THE PERTURBATION IS IN QUESTION.. THERE MAY
NOT BE ENOUGH INSTABILITY BY FRIDAY NIGHT TO GET MUCH OF ANYTHING
GOING AS THE PERTURBATION MOVES OVER OUR AREA...AS PREDICTED BY
SOME NUMERICAL MODELS SUCH AS THE NAM.

AS THE PATTERN DE-AMPLIFIES...THERE WILL BE MORE OF A SHOT AT
SOME PRECIPITATION AND THIS IS REFLECTED IN THE FORECAST FOR EARLY
NEXT WEEK AS A SHORTWAVE TROUGH CUTS THROUGH THE DE-AMPLIFIED
RIDGE TO THE WEST. TEMPERATURES MAKE A GRADUAL REBOUND TO MORE
NORMAL CONDITIONS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 626 AM CDT WED JUL 30 2014

TODAY: MULTI-LAYERED VFR MID-LEVEL CLOUDS ARE DEPARTING TO THE S.
THIS WILL LEAVE JUST CIRROSTRATUS CEILINGS AROUND 20K FT. LIGHT
NE WINDS UNDER 10 KTS. CONFIDENCE: HIGH

TONIGHT: VFR WITH A FEW PATCHES OF CIRROSTRATUS IN THE EVENING.
MID-LEVEL CEILINGS SHOULD INVADE AROUND 7K AFTER MIDNIGHT. LIGHT
OR CALM WINDS WILL SHIFT TO THE SW LATE. CONFIDENCE: HIGH

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&

$$

UPDATE...HALBLAUB
SHORT TERM...HALBLAUB
LONG TERM...HEINLEIN
AVIATION...HALBLAUB



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