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  Forecast Discussion for Southern Oregon and Northern California  

Forecast: Forecast Discussion | 7 Day Forecast

Forecast Discussion for MFR NWS Office

000
FXUS66 KMFR 220016 AAA
AFDMFR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MEDFORD OR
516 PM PDT TUE APR 21 2015

UPDATED AVIATION SECTION

.SHORT TERM...VISIBLE SATELLITE SHOWS THE ATMOSPHERE HAS
DESTABILIZED AS EXPECTED WITH NUMEROUS CUMULUS BUILDUPS OVER THE
HIGHER TERRAIN AND EAST SIDE. RADAR IS ALREADY SHOWING RETURNS IN
EASTERN SISKIYOU, NORTHERN KLAMATH, AND CENTRAL LAKE COUNTIES.
THERE HAS EVEN BEEN A STRIKE OR TWO RECORDED IN EASTERN SISKIYOU
COUNTY JUST WEST OF TENANT. AND NUMEROUS STRIKES RECORDED JUST
SOUTH OF THE CWA IN LASSEN COUNTY. HI-RES, NEAR TERM MODELS LIKE
THE HRRR (HIGH RESOLUTION RAPID REFRESH) SHOW MOST OF THE ACTION
OVER MODOC, LAKE, AND FAR EASTERN KLAMATH COUNTIES LATER THIS
AFTERNOON. STEERING WINDS ARE FAIRLY LIGHT SO THESE STORMS WILL
LIKELY BE SLOW MOVERS RESULTING IN THE POTENTIAL FOR SOME HEAVIER
DOWNPOURS UNDER THE CORE OF THESE STORMS. ALSO EXPECT SOME GUSTY
OUTFLOW WINDS WITH THE STRONGER STORMS ALONG WITH THE POTENTIAL
FOR SMALL HAIL. MODELS CONTINUE TO SHOW THE ATMOSPHERE STABILIZING
WITH THE LOSS OF DIURNAL HEATING SO CONVECTION SHOULD DIMINISH BY
TONIGHT. THE ATMOSPHERE WEST OF THE CASCADES IS MORE STABLE WITH
WEAKER LAPSE RATES SO NOT EXPECTING ANY THUNDERSTORMS FOR THAT
AREA.

ASIDE FROM THE RAIN EXPECTED WITH THE CONVECTION PREVIOUSLY MENTIONED,
MOST AREAS WILL REMAIN DRY WITH THE PASSAGE OF THE COLD FRONT.
WINDS WILL BE QUITE BREEZY THROUGH THE AFTERNOON IN RESPONSE TO
THIS COLD FRONT MOVING THROUGH THE AREA. THE UPPER LEVEL TROUGH
MOVES THROUGH OVERNIGHT INTO TOMORROW AND DRIER, MORE STABLE AIR
MOVES IN BEHIND IT FOR WEDNESDAY. WEAK RIDGING STARTS TO BUILD
OVER THE AREA WEDNESDAY NIGHT, BUT THIS IS SHORT LIVED AS A WEAK
TROUGH APPROACHES THE AREA THURSDAY MORNING. THERE IS A CHANCE FOR
SOME SHOWERS THURSDAY AFTERNOON, BUT THIS LOOKS MOSTLY CONFINED
FROM THE UMPQUA DIVIDE AND NORTH.

AN UPPER LOW MOVES IN OVER BRITISH COLUMBIA THURSDAY EVENING AND
SHORTWAVES ROTATING AROUND IT CONTINUE THE CHANCE FOR PRECIPITATION
FOR MOST OF THE AREA THROUGH SATURDAY MORNING. MND

.LONG TERM...SATURDAY THROUGH TUESDAY...THE OPERATIONAL EC AND
GFS ARE IN SIMILAR AGREEMENT WITH THE OVERALL PATTERN FRIDAY INTO
NEXT WEEKEND. HOWEVER THERE IS DISAGREEMENT WITH THE PLACEMENT AND
STRENGTH OF THE UPPER LOW FRIDAY. THE EC IS STRONGER AND FURTHER
SOUTH WITH THE UPPER LOW AND WETTER. HAVE KEPT IN A CHANCE OF
SHOWERS FOR MOST OF THE FORECAST AREA...THOUGH RAIN AND MOUNTAIN
SNOW AMOUNTS SHOULD BE LIGHT. THE TROUGH AXIS SHIFTS EAST FRIDAY
NIGHT AND RIDGING WILL ATTEMPT TO MOVE IN FROM THE SOUTHWEST. THE
GFS SHOWS MORE OF A DIRTY RIDGE SCENARIO WITH WARM FRONTAL
PRECIPITATION MOVING INTO THE AREA. THE EC HAS A MORE PRONOUNCED
RIDGE AND THUS SHOWS A DRY AND MILDER SOLUTION. SUSPECT THE WARM
FRONTAL PRECIPITATION IS OVERDONE, BUT DID NOT WANT TO DISCOUNT IT
COMPLETELY, SO WITH WITH A BLEND BETWEEN THE EC AND GFS WITH A
SLIGHTLY DRIER BIAS.

A DIRTY RIDGE REMAIN OVER THE AREA SUNDAY WITH THE BEST CHANCE FOR
PRECIPITATION OVER THE NORTHERN PART OF THE CWA. ESPECIALLY WEST OF
THE CASCADES AND NORTH OF THE UMPQUA DIVIDE.

SIGNIFICANT UPPER TROUGHING THAT`S BEEN HANGING OVER THE NORTHEAST
PACIFIC FINALLY REACHES THE FORECAST AREA WITH SIGNIFICANT RAIN
POTENTIALLY MONDAY INTO TUESDAY. THAT SAID...THERE IS SOME
UNCERTAINTY AS TO WHEN THIS TROUGHING REACHES THE AREA. ENSEMBLE
MEMBERS ARE OUT OF PHASE...BUT NOT AS MUCH AS YESTERDAY WITH THE
TROUGH AXIS STARTING TO DROP SOUTH. IN CONTRAST, THE OPERATIONAL EC
SHOWS MORE OF A SPLIT FLOW PATTERN NEAR 150 W AND MORE RIDGING IN
OUR AREA, THUS DELAYING ANY SIGNIFICANT PRECIPITATION.

IN SHORT...CONFIDENCE IS LOW TO MODERATE IN THE EXTENDED PERIOD AND
DID NOT MAKE ANY SIGNIFICANT CHANGES. -PETRUCELLI

&&

.AVIATION...FOR THE 22/00Z TAF CYCLE...SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS WILL PERSIST THIS EVENING FROM ABOUT THE
SHASTA REGION EASTWARD TO THE WARNERS...THEN NORTHWARD INTO LAKE AND
EASTERN KLAMATH COUNTIES. MOST OF THE ACTIVITY WILL BE SOUTH AND
EAST OF KLMT. OVERALL, CIGS IN THESE AREAS WILL BE VFR, THOUGH
TERRAIN MAY BE PARTLY OBSCURED WITH TEMPORARY MVFR IN HEAVIER
SHOWERS/THUNDERSTORMS.

ALONG THE COAST NORTH OF PORT ORFORD, EXPECT MVFR CIGS WITH AN
ISOLATED SHOWER THROUGH THIS EVENING. MVFR CIGS WILL GRADUALLY LIFT
TO VFR LATER WEDNESDAY MORNING OR AFTERNOON. OFFSHORE FLOW WILL
RESULT IN VFR ALONG THE SOUTH COAST THROUGH WEDNESDAY.

THE REST OF THE WEST SIDE TO THE CASCADES WILL BE MOSTLY VFR THROUGH
LATE THIS EVENING WITH JUST ISOLATED SHOWERS...THOUGH AREAS OF MVFR
AND PARTIAL TERRAIN OBSCURATIONS WILL DEVELOP AND LAST THROUGH ABOUT
MID-LATE MORNING WEDNESDAY. SPILDE

&&

.MARINE...UPDATED 300 PM PDT TUESDAY APR 21, 2015...HIGH PRESSURE
WILL BUILD INTO THE AREA TONIGHT BUT THIS WILL RESULT IN GUSTY NORTH
WINDS AND STEEP TO VERY STEEP SEAS. GALES AND WARNING LEVEL SEAS ARE
EXPECTED AT TIMES SOUTH OF CAPE BLANCO TONIGHT THROUGH WEDNESDAY
NIGHT. THURSDAY THROUGH THE WEEKEND...A SERIES OF FRONTAL SYSTEMS IS
LIKELY TO MOVE THROUGH WITH BUILDING SWELL. NORTHWEST WINDS
WEDNESDAY NIGHT THROUGH FRIDAY ARE EXPECTED TO BECOME SOUTHWESTERLY
THIS WEEKEND. SPILDE

&&

.FIRE WEATHER...UPDATED 3 PM PDT TUESDAY, APRIL 21ST, 2015... THE
ATMOSPHERE IS ALREADY STARTING TO BECOME UNSTABLE AHEAD OF A
RATHER SHARP, BUT NOT STRONG, INCOMING TROUGH OF LOW PRESSURE. A
FEW ISOLATED STORMS HAVE DEVELOPED IN NORTHERN CAL AND NORTHERN
KLAMATH COUNTY NORTHEAST OF CHEMULT. THE LATEST HRRR REFLECTIVITY
PRODUCT SHOWS MOST OF THE ACTIVITY DEVELOPING IN NORTHERN CAL,
THEN MIGRATING NORTH INTO PARTS OF LAKE AND KLAMATH COUNTIES LATE
THIS AFTERNOON THROUGH THIS EVENING. UNLIKE THE HIGH IMPACT
LIGHTNING EVENTS THAT SOMETIMES AFFECT OUR REGION MAINLY IN THE
SUMMER, FORCING WITH THE INCOMING SYSTEM IS WEAK IN THAT THERE IS
NO CLEAR COLD POOL MOVING THROUGH. INSTEAD, A WEAK SURFACE FRONT
IS EXPECTED TO DEVELOP ALONG AND NEAR THE CASCADES THIS AFTERNOON.
THIS SHOULD GIVE RISE TO BUILD-UPS ALONG AND NEAR THE TRINITY ALPS
AND CASCADE CREST THIS AFTERNOON, SHIFTING EASTWARD TO THE LEE OF
THE CASCADES TOWARDS THE EVENING. CONDITIONS ARE MOST FAVORABLE
FOR SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS IN THESE LEE AND
EAST SIDE AREAS. MOST GUIDANCE FOCUSES ACTIVITY THIS EVENING IN
THE WARNER MOUNTAINS OF LAKE COUNTY AND ANOTHER IN NORTHERN LAKE
COUNTY THIS EVENING. WHILE FIRE DANGER DID REACH HIGH IN PORTIONS
OF THE MODOC ON MONDAY, FORECAST FIRE DANGER FOR TODAY IS
MODERATE. ADDITIONALLY, DEPARTURE FROM AVERAGE GREENNESS IS SPOTTY
IN TERMS OF DEFICITS, SO SUSPECT THERE`S SOME GREEN-UP COMPONENT
TO THE LIVE FUELS NOW. MODELS INDICATE THAT ANY STORMS THAT DO GET
GOING WILL PRODUCE GUSTY OUTFLOW WINDS MAINLY IN THE 20 TO 30 MPH
RANGE, BUT ALSO SOME MEASURABLE RAINFALL. THUS, DESPITE UNUSUALLY
DRY CONDITIONS DUE TO THE ONGOING DROUGHT, WE HAVE DECIDED THAT
THIS EVENT DOES NOT WARRANT ANY WARNINGS. INSTEAD, A HEADS-UP TYPE
OF HEADLINE WILL BE MAINTAINED IN THE FORECAST. BTL/PETRUCELLI

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 AM PDT
     THURSDAY FOR PZZ350-356-370-376.
 HAZARDOUS SEAS WARNING UNTIL 5 AM PDT THURSDAY FOR PZZ356-376.
 GALE WARNING UNTIL 5 AM PDT THURSDAY FOR PZZ356-376.
 SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 AM PDT THURSDAY
 FOR PZZ350-356-370-376.

$$

MAS/MND/MAP

NWS MFR Office Area Forecast Discussion