Area Forecast Discussion
Issued by NWS Medford, 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 KMFR 211613
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
913 AM PDT SUN SEP 21 2014

.DISCUSSION...BIG STORY THIS MORNING WAS THE GLACIER THAT BROKE
FREE ON MOUNT SHASTA YESTERDAY, SENDING A DEBRIS FLOW DOWN THE
SOUTHEAST DRAINAGES...MUD AND PILGRIM CREEKS. PLEASE SEE THE
HYDROLOGY SECTION BELOW.

AN UPPER LOW MOVING NORTHEAST ACROSS NORTH-CENTRAL NEVADA WILL
BRING ISOLATED TO SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
FROM ABOUT THE SHASTA REGION NORTHWARD ALONG THE CASCADES AND
EASTWARD TODAY. THERE IS MORE CLOUD COVER FARTHER WEST THIS
MORNING AND ISOLATED SHOWERS SHOWING UP ON RADAR OVER
MODOC/SISKIYOU COUNTIES, SO AN UPDATE TO THE FORECAST FOR
INCREASED SKY COVER/POPS WAS MADE EARLIER. NO OTHER CHANGES ARE
PLANNED THIS MORNING. FOR THE AFTERNOON PACKAGE, WE`LL BE TAKING
A CLOSER LOOK AT WIND/RAIN POTENTIAL WITH THE INCOMING SYSTEM
TUESDAY/WEDNESDAY. SPILDE

&&

.AVIATION...BASED ON THE 21/12Z TAF CYCLE...ALONG THE COAST...IFR
CIGS/VSBYS ALONG THE COAST...IN THE COASTAL VALLEYS...AND IN THE
LOWER UMPQUA BASIN WILL CLEAR TO VFR BY LATE MORNING BUT THE LOWER
CONDITIONS WILL REMAIN JUST OFFSHORE AND MOVE BACK ONSHORE EARLY
THIS EVENING THEN PERSIST INTO MONDAY MORNING. INLAND...VFR
CONDITIONS WILL PREVAIL THROUGH THIS EVENING...EXCEPT FOR LOCAL MVFR
VSBYS IN SMOKE NEAR WILDFIRES IN JOSEPHINE COUNTY AND THE WESTERN
PORTION OF SISKIYOU COUNTY. ALSO, ISOLATED SHOWERS AND THUNDERSTORMS
MAY DEVELOP THIS AFTERNOON AND EVENING OVER THE CASCADES...EASTERN
SISKIYOU COUNTY...SOUTHERN LAKE COUNTY...AND MODOC COUNTY WITH THE
HIGHEST PROBABILITY OVER THE WARNER MOUNTAINS IN MODOC COUNTY
NORTHWARD TO THE HIGHER TERRAIN OF LAKE COUNTY. /DW

&&

.MARINE...UPDATED 600 AM PDT SUN 21 SEP 2014...HIGH PRESSURE
WILL REMAIN OVER THE WATERS INTO EARLY MONDAY WITH LIGHT TO
MODERATE SOUTHERLY WINDS AND SWELL DOMINATED SEAS OF 5 TO 6 FEET AT
10 TO 11 SECONDS. SOUTHERLY WINDS INCREASE MONDAY AHEAD OF
A COLD FRONT. THE FRONT WILL ARRIVE MONDAY NIGHT AND BE THE FIRST
IN A SERIES OF FRONTS THAT WILL BRING PERIODS OF RAIN WITH
INCREASED WINDS AND STEEP TO VERY STEEP SEAS THROUGH THE WEEK. SMALL
CRAFT ADVISORY CONDITIONS ARE LIKELY TO DEVELOP LATE MONDAY NIGHT
WITH SEAS BECOMING WIND WAVE DOMINATED INTO TUESDAY NIGHT. WINDS ARE
FORECAST TO REMAIN MODERATE TO STRONG THROUGH THURSDAY NIGHT AND BE
ACCOMPANIED BY A HIGH AND STEEP WEST SWELL WEDNESDAY THROUGH FRIDAY.
/DW

&&

.HYDROLOGY...FOREST SERVICE REPORTS THIS MORNING ARE THAT FLOOD
WATERS AND DEBRIS FLOWS HAVE EASED SINCE YESTERDAY. EVEN SO...HAVE
MAINTAINED THE FLASH FLOOD WATCH THROUGH THIS AFTERNOON JUST IN
CASE WE GET REPORTS OF ADDITIONAL FLOODING. THERE IS AN ISOLATED
THUNDER THREAT TOO, WHICH IF A THUNDERSTORM WERE TO OCCUR, COULD
EXACERBATE THE FLOOD THREAT. DEBRIS CONTINUES TO ACCUMULATE
UPSTREAM AND COULD STILL BREAK FREE AND FLOW DOWNSTREAM AT ANY
TIME. THE MUD AND PILGRIM CREEK DRAINAGES FLOW PAST HIGHWAY 89
APPROXIMATELY 4 TO 5 MILES EAST OF MCCLOUD...WHICH IS WHERE THE
FLOOD THREAT EXISTS. FLOOD WATERS MAY BE SWIFT MOVING AND VERY
DANGEROUS. MOTORISTS ON HIGHWAY 89 EAST OF MCCLOUD ARE URGED TO
USE EXTREME CAUTION. SPILDE

.PREV DISCUSSION... /ISSUED 246 AM PDT SUN SEP 21 2014/

DISCUSSION...AN UPPER LOW CURRENTLY CENTERED OVER CENTRAL
CALIFORNIA WILL MOVE NORTHEAST ACROSS NEVADA TODAY. AMPLE MOISTURE
IS FLOWING NORTHWEST AHEAD OF THE LOW, AND THIS MOISTURE HELPED
PRODUCE A LOT OF SHOWER AND THUNDERSTORM ACTIVITY TO OUR SOUTH
YESTERDAY AND LAST NIGHT. AS IT CONTINUES TO MOVE NORTH TODAY,
SOME OF THIS WILL WORK INTO THE EASTERN HALF OF OUR FORECAST AREA.
MITIGATING THIS THREAT, HOWEVER, IS A TROUGH COMING IN FROM THE
WEST WHICH WILL SERVE TO NUDGE THIS SYSTEM FAR ENOUGH TO THE EAST
TO PRECLUDE A MAJOR THUNDERSTORM OUTBREAK. NEVERTHELESS, WE
INCREASED POPS A BIT ACROSS MODOC COUNTY AND INTO SOUTHERN LAKE
COUNTY. CLOUDS AHEAD OF THE DYNAMICS WILL ALSO HELP TO LIMIT
INSTABILITY, SO WE WENT WITH SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS IN THESE AREAS FOR TODAY. ELSEWHERE, WE`LL SEE A BIT
MORE CLOUDS AND COOLER TEMPERATURES AS A RESULT, BUT LITTLE ELSE.
THE EXCEPTION WILL BE AT THE COAST WHERE STRATUS IS ALREADY IN
PLACE AND SHOULD MOVE LITTLE TODAY. THIS WILL RESULT IN A COOL
CLOUDY DAY.

TOMORROW WILL BE A TRANSITION DAY WITH LOWERING HEIGHTS AND
CONTINUED COOLING AREA-WIDE. THERE MAY BE SOME LIGHT RAIN OR
DRIZZLE ALONG THE COAST TOMORROW AND THE POTENTIAL FOR A
THUNDERSTORM IN THE CASCADES, BUT NO OTHER PRECIPITATION IS
EXPECTED. THE COOLING TREND CONTINUES INTO TUESDAY AS A LARGE
TROUGH MOVES INSIDE OF 140W. THE DEEP, SUBTROPICAL MOISTURE TAP
AHEAD OF THE SYSTEM MAY PRODUCE SOME RAIN OVER THE WATERS OR COAST
LATE TUESDAY, BUT MOST OF US WILL STILL BE DRY. WE WILL SEE
SOUTHWESTERLY WINDS START TO PICK UP ON TUESDAY, ESPECIALLY ACROSS
THE EAST SIDE.

THE MAJOR CHANGE BEGINS TUESDAY NIGHT AND WEDNESDAY. THE MODELS
ARE IN GOOD AGREEMENT THAT AS THE UPPER TROUGH APPROACHES 130W, A
JUICY COLD FRONT WILL MOVE ASHORE OVER OUR AREA. THE ONLY QUESTION
LEFT NOW IS THE TIMING OF THE ASSOCIATED RAINFALL. THE ECMWF IS
THE FASTEST WITH RAIN ARRIVING AT THE NORTH COAST TUESDAY NIGHT,
WHEREAS THE AMERICAN MODELS HOLD OFF UNTIL WEDNESDAY MORNING.
EITHER WAY, WEDNESDAY IS LIKELY TO BE WET OVER MUCH OF THE WEST
SIDE, WITH HEAVY RAIN (ON THE ORDER OF SEVERAL INCHES) POSSIBLE AT
THE CURRY COAST AND MOUNTAINS. THE USUAL WORRY OF RAIN SHADOWING
WILL EXIST IN MEDFORD, BUT EVEN THEY WILL GET PROBABLY GET RAIN AT
SOME POINT WEDNESDAY. THE EAST SIDE AND SHASTA VALLEY WILL BE
BREEZY TO WINDY ON WEDNESDAY WITH LITTLE RAIN MAKING IT ACROSS
UNTIL WEDNESDAY NIGHT OR THURSDAY.

THE UPPER TROUGH WILL REMAIN IN THE AREA THROUGH FRIDAY THEN MOVE
INLAND SATURDAY. THIS WILL KEEP SHOWERY, COOL WEATHER GOING OVER
OUR AREA. WE WILL START TO WARM UP AND DRY OUT SUNDAY AS THE
TROUGH MOVES EAST AND A WEAK RIDGE BUILDS IN. -WRIGHT

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

CA...FLASH FLOOD WATCH UNTIL 5 PM PDT THIS AFTERNOON FOR CAZ082.

PACIFIC COASTAL WATERS...NONE.

$$

MAS/TRW/DW/SBN





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