Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 240235
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
935 PM CDT THU OCT 23 2014

.UPDATE...
ISSUED AT 935 PM CDT THU OCT 23 2014

STILL TRYING TO GET A GOOD FEEL FOR THE FOG SITUATION TONIGHT.
TEMPERATURE DROPS POST-SUNSET RESULTED IN RAPID FOG DEVELOPMENT
EARLIER THIS EVENING...BUT THUS FAR THE FOG HAS NOT BEEN ALL THAT
IMPRESSIVE WITH VISIBILITY RESTRICTION GENERALLY IN THE 3-5SM
RANGE. AS OF 02Z THE ONLY EXCEPTION IS KPHG WHICH IS AT 1/4SM.

THE BOUNDARY-LAYER WIND FIELD ACROSS OUR AREA IS GENERALLY FROM
THE SOUTH/SOUTHEAST AT 5KTS OR LESS...AND WITH NEAR-ZERO DEW POINT
DEPRESSIONS AT THE SURFACE...WHAT FOG DEVELOPMENT WE HAVE SEEN SO
FAR ISNT TOO SURPRISING. THAT SAID...SURFACE ANALYSIS DOES
INDICATE MORE OF A WEST/SOUTHWEST BOUNDARY-LAYER WIND FIELD ACROSS
WESTERN NEBRASKA...AND GUIDANCE SUGGESTS THIS WEST/SOUTHWESTERLY
WIND WILL WORK INTO WEST/NORTHWEST PORTIONS OF THE CWA LATER
TONIGHT...PERHAPS INCREASING TO AROUND 10KTS. ADD TO THAT...THE
BOUNDARY-LAYER AIR MASS IS MUCH DRIER TO OUR NORTHWEST WITH DEW
POINT READINGS IN THE 40S...AND THIS DRIER AIR IS ALSO EXPECTED TO
MOVE INTO WEST/NORTHWESTERN PORTIONS OF OUR AREA LATER TONIGHT.
GIVEN ALL THIS...IT SEEMS UNLIKELY WE WILL OBSERVE SIGNIFICANT
VISIBILITY RESTRICTION ACROSS ROUGHLY THE NORTHWESTERN ONE-THIRD
TO ONE-HALF OF THE CWA. FARTHER SOUTHEAST ACROSS THE AREA
HOWEVER...THE BOUNDARY-LAYER WIND FIELD IS EXPECTED TO REMAIN
WEAKER AND FROM THE SOUTH/SOUTHEAST FOR A LONGER PERIOD OF
TIME...AND WITH SURFACE DEW POINT READINGS LIKELY REMAINING IN THE
50S THROUGH MUCH OF THE NIGHT...IT STANDS TO REASON FOG
DEVELOPMENT...AND PERHAPS SIGNIFICANT VISIBILITY RESTRICTION...IS
MORE LIKELY ACROSS THAT AREA.

SO...GIVEN ALL THIS...OPTED TO MODIFY THE FORECAST SOMEWHAT FOR
TONIGHT. DID GO AHEAD WITH PATCHY FOG FOR THE ENTIRE CWA NOW
THROUGH 06Z TO ACCOUNT FOR CURRENT OBSERVATIONS. AFTER
06Z...STRONGLY CONSIDERED PULLING ANY MENTION OF FOG FROM OUR
NORTHWEST...BUT IF THE BOUNDARY-LAYER WIND FIELD DOESNT TRANSITION
TO THE WEST/SOUTHWEST AND/OR THE BOUNDARY-LAYER AIR MASS DOESNT
DRY OUT AS MUCH AS CURRENTLY FORECAST...THEN THERE COULD CERTAINLY
STILL BE SOME PATCHY FOG BEYOND 06Z. TO PLAY IT SAFE...KEPT PATCHY
FOG GOING ACROSS THE NORTHWESTERN ONE-HALF OF THE CWA THROUGH
TONIGHT. FARTHER SOUTHEAST ACROSS THE CWA...WENT AHEAD WITH AREAS
OF FOG AND VISIBILITY RESTRICTION TO AROUND 1SM. OBVIOUSLY THIS
WILL NEED TO BE MONITORED THROUGH THE OVERNIGHT HOURS AS TRENDS
CONTINUE TO UNFOLD.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 353 PM CDT THU OCT 23 2014

THE MAJOR ISSUE FOR TONIGHT/FRIDAY MORNING WILL BE DETERMINING
CHANCE OF FOG AND STRATUS. ALSO WE ARE LOOKING AT POTENTIALLY LOW
ENOUGH RELATIVE HUMIDITY TO BRING UP FIRE WEATHER CONCERNS.

STRATUS AND FOG TOOK A LONG TIME TO CLEAR THE CWA TODAY AS AN UPPER
SURFACE RIDGE TRIES TO NUDGE EAST TOWARD THE CENTRAL PLAINS. MODELS
ARE GENERALLY PAINTING A CLEAR AND FOG FREE NIGHT...BUT SINCE WE HAD
STRATUS LINGER SO LONG INTO THE AFTERNOON OVER A GOOD CHUNK OF THE
CWA...I HAVE A STRONG SUSPICION THAT MODELS ARE VERY WRONG. BASED ON
PATTERN RECOGNITION...I WILL HAVE TO STRAY FAR FROM MODELS HERE AND
INTRODUCE A CLOUDY SKY OVERNIGHT ALONG WITH AREAS OF FOG...LOCALLY
DENSE. AREAS ALONG THE EDGE OF STRATUS WILL BE ESPECIALLY PRONE TO
DENSE FOG. THE SREF DOES INDICATE SOME FOG DEVELOPMENT POSSIBLE IN
THE CWA TONIGHT...AS WELL AS SYNTHETIC GOES-R IMAGERY FROM THE WRF-
ARW. I RAISED TEMPERATURES A BIT FOR LOWS TONIGHT DUE TO ANTICIPATED
SKY COVER...AND LOWERED TEMPERATURES A BIT...ESPECIALLY
NORTH/CENTRAL DUE TO ANTICIPATED LINGERING STRATUS...DESPITE THE
RIDGING ALOFT THAT WILL BE OCCURRING. IT STILL SHOULD BE A
RELATIVELY WARM DAY.

AS FOR FIRE WEATHER CONCERNS...THE LOWER HUMIDITY SHOULD BE
CONCENTRATED IN OUR WESTERN CWA...WHERE WE COULD DROP DOWN TO NEAR
20 PERCENT. THIS WILL HINGE A LOT ON HOW MUCH STRATUS MAY HANG
AROUND...WHICH MAY KEEP TEMPERATURES DOWN AND DEW POINTS A LITTLE
HIGHER...RAISING RELATIVE HUMIDITY. ALSO...BY THE TIME HUMIDITY
BECOMES POTENTIALLY LOW ENOUGH TO BE A POSSIBLE ISSUE...WIND SHOULD
BEGIN TO DIE OFF AS A COLD FRONT APPROACHES FROM THE NORTH. WITH
THESE THINGS IN MIND...I DO NOT THINK WE WILL HAVE MUCH OF A FIRE
WEATHER ISSUE FOR THURSDAY...SO I AM NOT MENTIONING THIS IN THE HWO.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 353 PM CDT THU OCT 23 2014

PATTERN: THE MULTI-DAY 500 MB ENSEMBLE MEAN HEIGHT ANOMALIES FROM
THE ECMWF/JMA ALL INDICATE SOME PROGRESSION WILL OCCUR IN THE
LONGWAVES OVER THE NEXT 10 DAYS. THE CNTRL USA RIDGE WILL RELOCATE
INTO THE ERN USA...ALLOWING THE E PACIFIC TROF TO MOVE TO THE W
COAST. THE NCEP/GFS ENSEMBLE MEAN IS NOT AS PROGRESSIVE...KEEPING
THE TROF OVER THE E PACIFIC AND TRYING TO MAINTAIN MORE OF A TROF
OVER THE CNTRL USA. THE CANADIAN ENSEMBLE MEAN APPEARS TO HAVE
MEMBERS IN BOTH CAMPS. SO NOT A CLEAR SIGNAL OF WHAT WILL TRANSPIRE
...BUT THE EC/JMA IS PREFERRED. THIS IS ALSO THE CPC PREFERENCE.
INTERESTING TO NOTE THAT THE 12Z EC DID COME IN MUCH SIMILAR TO THE
GFS.

THIS SUGGESTS TEMPS WILL CONT TO AVERAGE WARMER THAN NORMAL FOR THE
NEXT 2 WEEKS /SEE THE CPC 6-10 AND 8-14 DAY OUTLOOKS/...BUT THERE
WILL BE INTERRUPTIONS OF NEAR NORMAL TEMPS WITH A DAY OR TWO OF
BELOW NORMAL AUTUMN CHILL. BOTTOM LINE IS NO BIG/EXTENDED COOLDOWN
ARE FORESEEN HERE THRU THE END OF THE MONTH AND PROBABLY THE FIRST
WEEK OF NOV AS WELL.

IF THE TROF DOES EVOLVE ALONG THE W COAST...CONDITIONS WOULD BECOME
MORE FAVORABLE FOR SOME RAIN IN EARLY NOV WITH HIGH PRES OVER THE
ERN USA CIRCULATING GULF AIR NORTHWARD. THIS IS REFLECTED IN THE CPC
8-14 DAY LOOK...WITH PROBABILITIES FAVORING ABOVE NORMAL RAINFALL.

OVERALL FCST CONFIDENCE: ABOVE AVERAGE.

ALOFT: THE MEAN RIDGE WILL ADVANCE ACROSS THE PLAINS THIS WEEKEND AS
THE E PACIFIC TROF GETS KICKED ONSHORE. SW FLOW WILL DEVELOP SUN
WITH THE TROF PASSAGE MON-TUE. IT IS INTERESTING TO SEE THE
SIGNIFICANT MODEL DISAGREEMENT OFF THE COAST OF BRITISH COLUMBIA AT
00Z/TUE. THE NON-GFS MODELS ARE ALL APPRECIABLY DEEPER WITH THE
KICKER TROF WITH HEIGHT DIFFERENCES OF 130M. THIS HAS IMPLICATIONS
FOR THE POTENCY OF THE TROF MOVING THRU HERE MON-TUE. NW FLOW SHOULD
DEVELOP TUE WITH ZONAL FLOW WED BEFORE THE TRANSITION TO BUILDING
HEIGHTS OCCURS THU.

SURFACE: A WEAK COOL FRONT WILL SLIDE THRU FRI NIGHT AND BRIEFLY
BECOME STATIONARY NEAR I-70 SAT...AS WEAK HIGH PRES QUICKLY RACES
THRU THE NRN PLAINS. THE NEXT SYSTEM WILL BE MOVING THRU THE
INTERMOUNTAIN W. IT WILL FORCE THE WRN END OF THE FRONT TO LIFT
SLIGHTLY BACK N AS A WARM FRONT SUN. THE NEXT COOL FRONT WILL MOVE
THRU SUN NIGHT. HIGH PRES WILL GRADUALLY BUILD IN TUE WITH RETURN
FLOW DEVELOPING WED AS THE HIGH EXITS TO THE E. A WEAK CLIPPER WILL
BE HEADING E ALONG THE US-CANADA BORDER. ITS COOL FRONT IS SLATED TO
MOVE THRU HERE WED.

THE DAILY DETAILS...

FRI NIGHT: UNEVENTFUL/DRY COOL FRONTAL PASSAGE. COOLED THE PREVIOUS
FCST BY 1-3F SINCE THE FRONTAL TROF WILL ALLOW FOR GOOD RADIATING.

SAT: CONTINUED VERY NICE WITH SUBSIDENCE/RIDGE OVERHEAD. HIGH PRES
SLIDES BY TO THE N. NOT AN APPRECIABLE COOLDOWN S OF HWY 6. TEMPS
SHOULD BE FAIRLY SIMILAR TO FRI. ANOTHER DAY OF A SOLID 10-15F
WARMER THAN NORMAL.

SAT NIGHT-SUN MORNING: AM STILL NOT CONVINCED THE FCST SHOULD BE
DRY. A 40KT LOW-LVL JET WILL DEVELOP AND WARM AIR ADVECTION AND
ASCENT SHOULD MOISTEN THE LOW-LVLS ENOUGH TO CREATE AN INSTABILITY
BURST AND POSSIBLE MID-LVL SHWR/TSTM ACTIVITY. FCST SOUNDINGS SHOW
SIGNIFICANT CINH...BUT I HAVE SEEN THIS BEFORE WHERE THE ATMOSPHERE
STILL PRODUCES. MUCAPE OF 500-800 J/KG WILL BE AVAILABLE IF ACCAS
CAN FORM.

ONLY ONE 09Z SREF MEMBER OUTPUTS MEASURABLE QPF. THE 00Z/06Z/12Z
GFS CONT TO DO THE SAME BUT THIS MAY JUST BE A WEAKNESS IN ITS
SHALLOW CONVECTIVE SCHEME AS IT HAS NO DEEP MOISTURE IN THE
COLUMN. A QUICK CHECK OF THE 15Z SREF AND ITS DRY.

SUN: SOME MID-LVL ACCAS MAY BE LIFTING NE ACROSS THE FCST AREA IN
THE MORNING. OTHERWISE ANOTHER VERY NICE DAY.

SUN NIGHT: A DECENT COLD FRONTAL PASSAGE. THIS FRONT WILL DELIVER
THE FIRST SUBSTANTIAL COOL DOWN SINCE THE 17TH-18TH.

MON: COLD AIR ADVECTION. BREEZY AND COOLER. TEMPS BACK CLOSER TO
NORMAL. INCREASING CLOUDS WITH A LOW PROBABILITY FOR POST FRONTAL
SHWRS.

SHOWERS: "BEST" CHANCE 4 PM MON-4 AM TUE TIME FRAME. RAINFALL AMTS
LOOK VERY LIGHT. 00Z EC ENSEMBLE 24 HR QPF PROBABILITIES FOR .10
ENDING 12Z/TUE ARE LOW. ONLY 20-30%...LOWEST SE THIRD OF THE FCST
AREA. 40% FAR NW FROM LXN-ORD.

TUE: TROF OVERHEAD. THE COOLEST DAY OF THE FCST AND TEMPS WILL BE
CHILLIER THAN NORMAL. THAT HAS BEEN AN INFREQUENT OCCURRENCE THIS
MONTH.

THE MONTHLY AVERAGE TEMP AT GRI IS RUNNING 1.9 ABOVE NORMAL BUT THAT
ACCOUNTS FOR BOTH HIGH AND LOW TEMPS EACH CALENDAR DAY.

WED: TEMPS SHOULD RETURN TO NEAR NORMAL HERE. POSSIBLE COOL FRONTAL
PASSAGE.

THU: HIGH PRES BUILDS IN. TEMPS STAY SEASONABLE.

&&

.AVIATION...(FOR THE 00Z KGRI/KEAR TAFS THROUGH 00Z FRIDAY
EVENING) ISSUED AT 935 PM CDT THU OCT 23 2014

UPDATE...FOG QUICKLY DEVELOPED ACROSS THE AREA POST-SUNSET AND IS
IMPACTING EAR WITH A VISIBILITY RESTRICTION OF AROUND 3SM. GRI IS
SOMEWHAT BETTER WITH A VISIBILITY RESTRICTION OF AROUND 5SM. WENT
AHEAD AND AMENDED BOTH TAFS TO REFLECT THESE CURRENT CONDITIONS.
AT THIS TIME IT IS STILL BELIEVED A SOMEWHAT STRONGER
WEST/SOUTHWEST BOUNDARY-LAYER WIND FIELD...SUSTAINED AT AROUND
08KTS...WILL APPROACH THE AREA FROM WESTERN NEBRASKA AND...ALONG
WITH A SOMEWHAT DRIER BOUNDARY LAYER AIR MASS ALSO ADVECTING IN
FROM THE NORTHWEST...HELP FOG DISSIPATE DURING THE EARLY MORNING
HOURS ON FRIDAY. GIVEN THIS...WENT AHEAD WITH MVFR VISIBILITY AT
EAR AND GRI THROUGH 06Z...WITH VFR CONDITIONS THEREAFTER. AS
MENTIONED IN THE PREVIOUS AVIATION DISCUSSION...IT IS BELIEVED THE
WORST VISIBILITY RESTRICTION WILL REMAIN SOUTHEAST OF GRI AND EAR.
THAT SAID...THE SITUATION WILL NEED TO BE CLOSELY MONITORED IN
CASE THE NORTHWESTERN PERIPHERY OF SIGNIFICANT VISIBILITY
RESTRICTION CAN REACH AS FAR NORTHWEST AS GRI AND/OR EAR.

&&

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

$$

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



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