Area Forecast Discussion
Issued by NWS Hastings, NE

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000
FXUS63 KGID 230524
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
1224 AM CDT TUE SEP 23 2014

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 324 PM CDT MON SEP 22 2014

MAP ANALYSIS INDICATES UPPER TROPOSPHERIC RIDGING OVER THE
WESTERN CONUS AND A TROUGH OVER THE EAST. AN UPPER TROPOSPHERIC
SHORT WAVE IS ALSO NOTED OVER IDAHO. ENHANCED UPPER TROPOSPHERIC
FLOW EXTENDS FROM NORTHWESTERN CANADA...SOUTHEAST INTO THE GREAT
LAKES REGION AND OHIO RIVER VALLEY...AND THEN NORTHEAST INTO THE
NORTHEASTERN CONUS AND SOUTHEASTERN CANADA. UPPER TROPOSPHERIC
FLOW OVER OUR AREA MAXES OUT AT AROUND 50KTS NEAR 37000FT AGL PER
12Z SOUNDING DATA FROM KLBF AND KOAX. AT THE SURFACE AN AREA OF
HIGH BAROMETRIC PRESSURE IS NOTED OVER THE MISSISSIPPI
VALLEY...AND A TROUGH EXTENDS ALONG THE FRONT RANGE OF THE
ROCKIES. RESULTANT BOUNDARY-LAYER FLOW ACROSS OUR AREA REMAINS
FROM THE SOUTH/SOUTHEAST.

GUIDANCE FROM THE NAM...OPERATIONAL GFS AND EC ALL SUGGEST THE
UPPER TROPOSPHERIC SHORT WAVE...CURRENTLY OVER IDAHO...WILL MOVE
EAST/SOUTHEAST THROUGH THE NEXT 24 HOURS...LIKELY MOVING INTO THE
CENTRAL HIGH PLAINS BY 12Z TUESDAY AND INTO THE MISSOURI RIVER
VALLEY BY 00Z WEDNESDAY. AT THE SURFACE...THE AREA OF HIGH
BAROMETRIC PRESSURE OVER THE MISSISSIPPI VALLEY IS EXPECTED TO
MOVE EAST THROUGH THE NEXT 24 HOURS WHILE THE AFOREMENTIONED
SURFACE TROUGH LINGERS OVER THE CENTRAL HIGH PLAINS. THIS WILL
CONTINUE TO PROMOTE A SOUTH/SOUTHEAST BOUNDARY-LAYER WIND FIELD
ACROSS OUR AREA.

GUIDANCE SUGGESTS TROPOSPHERIC MOISTURE AND THERMAL
ADVECTION...AHEAD OF THE APPROACHING UPPER TROPOSPHERIC SHORT
WAVE...WILL BE SUFFICIENT FOR PRECIPITATION PRODUCTION ACROSS MUCH
OF THE REGION TONIGHT AND INTO THE DAY TUESDAY...WITH QPF FIELDS
FROM THE NAM...OPERATIONAL GFS AND EC...AS WELL AS SIMULATED
REFLECTIVITY FROM THE 1KM WRF-NMM...1KM WRF-ARW AND 4KM WRF-NMM
ALL SUGGESTING PRECIPITATION WILL BE REALIZED ACROSS OUR AREA
TONIGHT AND INTO THE DAY TUESDAY. THERE ARE ALSO INDICATIONS THAT
PRECIPITATION COULD CREEP INTO OUR FAR WESTERN CWA LATE THIS
AFTERNOON INTO THIS EVENING...BUT THE HEAVIEST PRECIPITATION WILL
LIKELY HOLD OFF UNTIL AFTER MIDNIGHT TONIGHT. GIVEN ALL
THIS...FELT IT PRUDENT TO CONTINUE THE VERY HIGH POPS FOR
OVERNIGHT TONIGHT WHICH WERE INHERITED FROM PREVIOUS SHIFTS. TO
START...WENT AHEAD WITH 20-30% POPS ACROSS OUR FAR WEST 21-00Z
THIS AFTERNOON/EVENING. POPS THEN STEADILY INCREASE THROUGH THE
OVERNIGHT HOURS...WITH 50-80% POPS ACROSS THE AREA 06-12Z. POPS
THEN TAPER OFF FROM WEST TO EAST DURING THE DAY TUESDAY AS THE
UPPER TROPOSPHERIC SHORT WAVE AXIS...AND PRIMARY BAND OF THERMAL
ADVECTION...ALSO MOVE EAST OF OUR AREA. TAKING AN EVEN-AVERAGE OF
THE NAM...OPERATIONAL GFS AND EC PRESENTS QPF AMOUNTS IN THE 0.25-
0.50" RANGE THROUGH THE DAY TUESDAY.

FOR TONIGHT...MEAGER LOWER TROPOSPHERIC MOISTURE AND UPPER
TROPOSPHERIC LAPSE RATES ARE EXPECTED TO KEEP POTENTIAL ENERGY
VALUES IN THE 100-200J/KG RANGE...IF NOT LOWER. WILL GO AHEAD WITH
ISOLATED THUNDER MENTION AS A RESULT. STEEPER UPPER TROPOSPHERIC
LAPSE RATES TUESDAY AFTERNOON COULD PROMOTE POTENTIAL ENERGY
VALUES CLOSER TO 1000J/KG TUESDAY AFTERNOON AND
EVENING...PRIMARILY WEST OF HIGHWAY 281. GIVEN THIS...WILL GO
AHEAD AND OUTLOOK THE POTENTIAL FOR NICKEL-SIZE HAIL ACROSS OUR
WEST FOR TUESDAY AFTERNOON AND EVENING IN THE HWO.

CONTINUED SOUTHERLY BOUNDARY-LAYER FLOW AND RESULTANT THERMAL
ADVECTION...ALONG WITH THE ANTICIPATED CLOUD COVER AND
PRECIPITATION... SHOULD PRESENT WARMER TEMPERATURE READINGS
TONIGHT WHEN COMPARED TO EARLY THIS MORNING...WITH LOWS IN THE MID
TO UPPER 50S CURRENTLY FORECAST FOR TONIGHT. PERSISTENT CLOUD
COVER AND POTENTIAL RAINFALL WILL LIKELY PRESENT LOWER TEMPERATURE
READINGS DURING THE DAY TUESDAY WHEN COMPARED TO TODAY...WITH
TUESDAY HIGHS IN THE UPPER 60S TO MID 70S CURRENTLY FORECAST FOR
MOST LOCATIONS.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 324 PM CDT MON SEP 22 2014

OVER THE NEXT 7 DAYS...THE MAIN BAND OF WESTERLIES WILL CURVE
AROUND AN E PACIFIC TROF AND THEN BECOME ZONAL OVER CANADA. THE
PACIFIC TROF WILL MOVE ONSHORE INTO THE WRN USA...CLOSE-OFF AND
CUT-OFF FRI- SAT. WHILE THE WESTERLIES WILL BECOME REESTABLISHED
ACROSS CANADA... THE NEXT TROF FCST TO MOVE INTO THE GULF OF AK
SHOULD BEGIN TO KICK THE LOW NE ACROSS THE INTERMOUNTAIN W...RE-
ABSORBING IT INTO THE WESTERLIES AND SWINGING IT THRU HERE
SOMETIME AROUND THE END OF THE MONTH. THIS IS THE HIGHEST
CONFIDENCE PORTION OF THIS FCST.

HOWEVER...THE FCST IS FRAUGHT WITH UNCERTAINTY IN THE DETAILS...
ESPECIALLY THRU SAT.

BOTTOM LINE IS THAT THRU MON...TEMPS WILL AVERAGE NEAR TO
SLIGHTLY WARMER THAN NORMAL ALONG WITH FAIRLY DRY CONDITIONS.

ALOFT: AT 00Z/WED THE CLOSED LOW WILL BE OVER SD WITH A TROF
EXTENDING S THRU THE PLAINS. THE TROF WILL SHIFT SLIGHTLY E WED.
IN THE MEANTIME...A SUBTROPICAL HIGH WILL FORM OVER THE ROCKIES
WITH THE APPROACH OF THE E PACIFIC TROF. THIS HIGH WILL ARC THRU
THE NRN PLAINS AND INTO THE GREAT LAKES THU-FRI. THIS CREATES
SUBSTANTIAL FCST UNCERTAINTY AS IT CALLS INTO QUESTION THE
DEPARTURE OF THE TROF. HOWEVER...ITS TAIL END WILL CUT-OFF
AGAIN...LINGERING UNDERNEATH THE HIGH OVER THE CNTRL PLAINS OR MID
MS VALLEY THU-SAT. WE COULD BE DEALING WITH THIS FCST PROBLEM FOR
SEVERAL DAYS UNTIL THE NEXT LOW APPROACHES EARLY NEXT WEEK.

MODELS: OVERALL THEY ARE IN UNISON THRU 00Z/THU. CONFLICT
DEVELOPS IN HOW THE TROF EVOLVES.

SURFACE: STRAIGHT-FORWARD AND BASIC. NO FRONTS THRU HERE THRU
NEXT MON. HIGH PRES WILL REMAIN PARKED OVER THE ERN USA THRU THU
WITH RETURN FLOW LOCKED IN. THE COOL FRONT WILL PROBABLY GET CLOSE
FROM THE W NEXT MON...ASSOCIATED WITH THE NEXT LOW.

THE DAILY DETAILS...

TOUGH TO PIN DOWN MANY DETAILS IN A STALL PATTERN LIKE THIS WITH
SO MUCH UNCERTAINTY.

TUE NIGHT: SHOWERY WX ALONG WITH EVENING TSTMS /W OF HWY 281/
WILL BE ON THE WANE AS THE TROF SHIFTS E OF THE REGION.

WED: MAINTAINED A VERY LOW PROB FOR A SHWR/TSTM E AND S OF THE
TRI- CITIES. OVERALL SHOULD BE DRY WITH DECREASING CLOUDS. DIURNAL
SHWR/ TSTM DEVELOPMENT SHOULD BE MAINLY E OF THE FCST AREA.

THU-SUN: THE MODEST COOL POCKET ALOFT COULD RESULT IN AN ISOLATED
BRIEF SHWR/TSTM EACH AFTERNOON/EVENING...BUT SYNOPTIC FORCING WILL
BE NIL. DIURNAL HEATING AND INDISCERNIBLE BOUNDARY LAYER FEATURES
WILL BE IN THE MAIN PLAYERS. NEARLY ALL OF THIS TIME FRAME LOOKS
DRY BASED ON CURRENT SIGNALS. AND AS LONG AS CLOUDS ARE NOT AN
ISSUE... THE WARM HEIGHTS ALOFT COULD RESULT IN A STRETCH OF VERY
NICE WX WITH TEMPS AVERAGING NEAR NORMAL.

SUN NIGHT: THE DIURNAL TSTMS THAT DEVELOP WITHIN THE LEE TROF
COULD HOLD TOGETHER AND MOVE INTO AREAS W OF HWY 281...SUSTAINED
BY THE LEAD WRN USA SHORTWAVE TROF.

MON: SCATTERED MAINLY AFTERNOON/EVENING STORMS?

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1219 AM CDT TUE SEP 23 2014

SHOWERS AND THUNDERSTORMS HAVE STARTED MOVING INTO THE AREA.
EXPECT THEM TO CONTINUE ON AND OFF THROUGH THE NIGHT AND INTO THE
MORNING HOURS. BY LATER IN THE MORNING THERE SHOULD BE A FEW
BREAKS IN THE CLOUDS.

&&

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

$$

SHORT TERM...BRYANT
LONG TERM...HALBLAUB
AVIATION...JCB



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