Area Forecast Discussion
Issued by NWS Pendleton, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KPDT 301810 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
1109 AM PDT THU OCT 30 2014

UPDATED AVIATION DISCUSSION

.UPDATE...A WARM FRONT WAS MOVING NORTH ACROSS THE REGION WITH AN
AREA OF RAIN FOLLOWING IT. THE BULK OF THE PCPN IS LOCATED ACROSS
NORTHERN OREGON AND SOUTHERN WA INCLUDING THE EAST SLOPES OF THE WA
CASCADES. MOST OF THE PCPN SHOULD CONTINUE MOVING NORTH. BY MIDDAY
PORTIONS OF THE REGION SHOULD BREAK INTO SOME SUNSHINE AND HIGH
TEMPERATURES SHOULD WARM ABOVE NORMAL. THEREFORE AFTERNOON
TEMPERATURES HAVE BEEN INCREASED A FEW DEGREES AND THE PRESENT SHORT
TERM FORECAST APPEARS ON TRACK FOR NOW.

&&

.AVIATION...18Z TAFS...A WARM FRONT MOVING NORTH IS STILL BRINGING
LIGHT RAIN TO KYKM, WHICH SHOULD END BY 21Z THIS AFTERNOON. MVFR
WILL CONTINUE AT KYKM AND KALW UNTIL 20Z-21Z TODAY, THEN IMPROVE TO
VFR. OTHERWISE, VFR CONDITIONS WILL PREVAIL THROUGH THIS EVENING.
CONDITIONS DETERIORATE TO VFR/IFR AT KDLS, KYKM, KRDM AND KBDN
OVERNIGHT DUE THE COLD FRONT BRINGING LOWERING CIGS WITH STEADY RAIN
SPREADING EAST ACROSS REGION. RAIN STARTS AT KDLS AROUND 31ST/01Z,
THEN AT KYKM BY 04Z, KRDM AND KBDN BY 08Z, KPSC AND KPDT BY 13Z, AND
KALW BY 14Z. WINDS AOB 10 KTS ARE EXPECTED DURING THE TAF PERIOD.
POLAN

&&

.PREVIOUS DISCUSSION... /ISSUED 420 AM PDT THU OCT 30 2014/

SHORT TERM...TODAY THROUGH SATURDAY...A WARM FRONT ASSOCIATED WITH
A DEVELOPING WEATHER SYSTEM ALONG THE COAST IS MOVING NORTHWARD
ACROSS THE FORECAST AREA THIS MORNING. MOST OF THE PRECIPITATION
WITH THIS FRONT IS OVER WESTERN AREAS FROM THE BLUE MOUNTAINS
WESTWARD AND NORTHWARD. HOWEVER DID NOT RULE OUT POSSIBLE LIGHT RAIN
OVER THE WALLOWA AND ELKHORN MOUNTAINS. THE WARM FRONT WILL BE TO
THE NORTH OF THE CWA BY 00Z THIS AFTERNOON. AFTER THAT A COLD FRONT
WILL BEGIN TO PUSH EASTWARD WITH THE WINDS SWITCHING TO THE
SOUTHWEST TO NORTHWEST TONIGHT. THIS WILL BE A SLOW MOVING COLD
FRONT WITH AN UPPER LEVEL JET STREAM PARALLEL TO IT. AS A RESULT
THERE WILL BE SIGNIFICANT RAINFALL OVER AND JUST TO THE EAST OF THE
CASCADES TONIGHT AND FRIDAY. ON FRIDAY THE FRONT WILL MAKE AN
ADVANCE TO THE EAST WITH THE PRECIPITATION SPREADING INTO THE LOWER
COLUMBIA BASIN SOUTHWARD ACROSS CENTRAL AND NORTH CENTRAL OREGON.
THE COLD FRONT WILL CONTINUE TO MOVE EASTWARD FINALLY REACHING THE
IDAHO BORDER BY FRIDAY EVENING (00Z-06Z SATURDAY) WITH LIKELY POPS
MOVING INTO THE BLUE MOUNTAINS EASTWARD LATE FRIDAY AFTERNOON AND
EVENING. AT THAT TIME THE LOW LEVEL FLOW WILL BECOME SOUTHWEST TO
NORTHWEST BEHIND THE COLD FRONT WHICH WILL BE DOWNSLOPE OFF THE
CASCADES. THIS WILL CAUSE RAIN SHADOWING OVER THE SIMCOE HIGHLANDS
NORTHWARD ACROSS THE YAKIMA AND KITTITAS VALLEYS WITH DECREASING
POPS THERE. DRYING WILL CONTINUE OVERNIGHT FRIDAY INTO SATURDAY
MORNING FROM WEST TO EAST. LIKELY TO CATEGORICAL POPS WILL CONTINUE
FROM THE BLUE MOUNTAINS EASTWARD ON SATURDAY. WEST OF THE BLUE
MOUNTAINS DRYING WILL TAKE PLACE WITH THE RAIN ENDING OVER THE LOWER
COLUMBIA BASIN AND CENTRAL/NORTH CENTRAL OREGON AS WELL AS THE
YAKIMA/KITTITAS VALLEYS. THE GFS MODEL HAS THE BEST HANDLE ON THE
TIMING OF THE COLD FRONT AND LEANED MOSTLY TO IT FOR THIS FORECAST
PACKAGE. THE AIR BEHIND THE COLD FRONT WILL BE SUBSTANTIALLY COOLER
WITH SNOW LEVELS DROPPING TO AROUND 4500 FEET OVER WESTERN
AREAS...CAUSING THE PRECIPITATION TO CHANGE OVER TO SNOW ABOVE THIS
LEVEL IN THE CASCADES BEFORE TAPING OFF. SINCE MOST OF THE
PRECIPITATION WILL HAVE MOVED EAST BY THAT TIME ANY SNOW
ACCUMULATIONS WILL BE VERY LIGHT IF ANY OVER THE HIGHER CASCADES.
DRYING WILL CONTINUE FROM WEST TO EAST IN THE EARLY EXTENDED PERIOD.
WINDS WILL BE LIGHT THROUGH THE SHORT TERM WITH THE EXCEPTION THAT
THEY WILL INCREASE OVER NORTH CENTRAL OREGON AND THE EASTERN
COLUMBIA RIVER GORGE SATURDAY AFTERNOON DUE TO MIXING OF HIGHER
WINDS ALOFT DOWN TO THE SURFACE BEHIND THE COLD FRONT. TEMPERATURES
WILL BE ABOVE NORMAL TODAY BY A FEW DEGREES...BUT COOLING TO NEAR
NORMAL ON FRIDAY AND THEN ABOUT 3 TO 6 DEGREES BELOW NORMAL ON
SATURDAY. THE MOST DRAMATIC COOLING WILL TAKE PLACE OVER THE WESTERN
CWA ON FRIDAY AND SATURDAY BEHIND THE SLOW MOVING COLD FRONT. 88

LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY NIGHT...AN EXITING
UPPER LEVEL TROUGH WILL RESULT IN A GRADUAL DECREASE IN
PRECIPITATION CHANCES ACROSS THE LOWER COLUMBIA BASIN.  WRAPAROUND
MOISTURE AND NORTHERLY FLOW BEHIND THE EXITING SYSTEM MAY KEEP RAIN
BELOW 3500 FEET AND SNOW ABOVE 3500 FEET GOING THROUGH THE DAY
SUNDAY MAINLY OVER THE HIGHLANDS OF CENTRAL TO NORTHEAST OREGON.
ANOTHER WEATHER SYSTEM WILL APPROACH THE REGION WITH AN ASSOCIATED
WARM FRONT THAT WILL MOVE ACROSS THE AREA MONDAY AFTERNOON AND
EVENING.  THIS WILL RESULT GRADUALLY INCREASING CHANCES OF
PRECIPITATION AGAIN WITH SNOW LEVELS RISING THROUGH THE DAY MONDAY
TO ABOUT 6500 FEET.  THE UPPER LEVEL SHORTWAVE TROUGH WILL MOVE
ACROSS THE REGION HEADING INTO TUESDAY BRINGING AT LEAST A SLIGHT
CHANCE OF RAIN WITH SNOW LEVELS CONTINUING TO RISE TO ABOUT 7500
FEET GIVEN THE SUBTROPICAL MOISTURE SOURCE.  MODEL SOLUTIONS DIVERGE
SOMEWHAT TUESDAY NIGHT AND WEDNESDAY WITH SOME INDICATIONS OF DRYING
FROM THE GFS AND THE DGEX...BUT THE ECMWF BRINGS ANOTHER MOISTURE
LADEN SHORTWAVE TROUGH TO THE REGION.  HAVE OPTED TO LOWER POPS SOME
BY BLENDING CLIMO TO THE PRIOR FORECAST.  TEMPERATURES DURING THE
PERIOD WILL BE NEAR NORMAL SUNDAY...WITH GRADUAL WARMING INCREASING
THE TEMPERATURES UP TO 10 DEGREES ABOVE NORMAL BY WEDNESDAY.  BIEDA

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  60  46  56  40 /  20  10  70  70
ALW  61  49  58  44 /  20  10  60  70
PSC  58  45  58  42 /  30  10  60  60
YKM  56  42  55  36 /  80  70  70  20
HRI  59  43  57  40 /  30  10  60  60
ELN  55  43  52  36 /  90  80  70  20
RDM  63  39  51  31 /  20  20  80  70
LGD  62  44  58  39 /  20  10  50  70
GCD  64  44  57  38 /  10  10  60  70
DLS  60  46  55  42 / 100  80  80  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.

&&

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON

$$

97/99/88/98






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.