Freeze Warning 14, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
840 PM PDT MON SEP 29 2014

.DISCUSSION...THE COLD FRONT HAS MOVED EAST OF THE CASCADES AND
STRETCHES FROM BURNS SOUTHWEST THROUGH LAKEVIEW. BOTH COOS AND
DOUGLAS COUNTIES REPORTED MEASURABLE RAIN EARLIER THIS EVENING.
EXPECT SHOWERS TO CONTINUE IN UPSLOPE NORTHWEST FLOW ESPECIALLY IN
SOUTHERN JACKSON COUNTY. HAVE UPDATED TO FORECAST TO INCREASE
CLOUD COVER AND EXPAND SHOWERS AREA. LOW TEMPERATURES WILL BE MILD
TONIGHT DUE TO EXTENSIVE CLOUD COVER BUT TUESDAY NIGHT COULD SEE
LOWS DIPPING INTO THE FROST/FREEZE RANGE EAST OF THE CASCADES. /FB

&&

.AVIATION...FOR THE 30/00Z TAF CYCLE...
A WEAK COLD FRONT IS PUSHING AND WILL CONTINUE TO PUSH RAIN ACROSS
THE WEST SIDE AND ONTO THE CASCADES THIS EVENING INTO TONIGHT. THE
FRONT WILL WEAKEN AS IT MOVES ONTO THE EAST SIDE. MVFR AND IFR
ALONG THE COAST AND UMPQUA BASIN THIS EVENING WILL LOWER TO IFR WITH
ISOLATED LIFR OVERNIGHT INTO THE MORNING. FURTHER INLAND, IN THE
ROGUE VALLEY, MVFR IS EXPECTED TO DEVELOP. EXPECT PARTIAL TERRAIN
OBSCURATIONS FROM THE CASCADES WESTWARD TO BECOME NEAR TOTAL THIS
EVENING BEFORE BECOMING PARTIAL AGAIN OVERNIGHT. ON THE EAST SIDE
PARTIAL TERRAIN OBSCURATIONS WILL DEVELOP DURING THE EVENING AND
OVERNIGHT, BUT VALLEYS SHOULD REMAIN MOSTLY VFR. ON TUESDAY MVFR ON
THE WEST SIDE WILL BREAK UP LATE MORNING THROUGH MID-AFTERNOON.
BTL

&&

.MARINE...UPDATED 8 PM PDT MON 29 SEP 2014...
HIGH PRESSURE MOVING IN BEHIND THE COLD FRONT WILL CAUSE WINDS AND
SEAS TO INCREASE TUESDAY AND WEDNESDAY. WINDS WILL INCREASE
FURTHER WEDNESDAY NIGHT AS THE THERMAL TROUGH EXPANDS NORTHWARD
ALONG THE COAST. ON FRIDAY THE HIGH PRESSURE IS LIKELY TO WEAKEN
AS A COLD FRONT PASSING TO THE NORTH. THIS WILL CAUSE WINDS AND
SEAS TO DIMINISH SOME. /FB

&&

.PREV DISCUSSION... /ISSUED 437 PM PDT MON SEP 29 2014/

DISCUSSION...A WEAK COLD FRONT IS CURRENTLY MAKING ITS WAY
ONSHORE THIS AFTERNOON, PRODUCING SOME LIGHT SHOWERS ALONG THE
COAST AND INTO THE UMPQUA BASIN. THESE SHOULD CONTINUE TO SPREAD
EATS INTO THE CASCADES THROUGH THE EVENING AND TONIGHT, BUT OTHER
AREAS WILL LIKELY SEE VERY LITTLE TO NO PRECIPITATION FROM THIS
SYSTEM. THIS WILL BE MOSTLY DUE TO THE BULK OF THE ENERGY
REMAINING WELL TO OUR NORTH, AND THE SYSTEM ITSELF LACKING A DEEP
CONNECTION TO SUBTROPICAL MOISTURE. THE SHOWERS SHOULD BEGIN TO
DISSIPATE FROM THE FORECAST AREA OVERNIGHT, BUT SOME COULD LINGER
IN THE UMPQUA AND THE CASCADES INTO TUESDAY MORNING.

ALTHOUGH THE FRONT WILL NOT PROVIDE A SIGNIFICANT AMOUNT OF
MOISTURE, THERE WILL BE A NOTICEABLE TEMPERATURE CHANGE, WITH SOME
OF THE COOLEST TEMPERATURES SO FAR THIS SEASON LIKELY TO OCCUR
TUESDAY AND TUESDAY NIGHT. IN FACT, THERE ARE MANY LOCATIONS ON
THE EAST SIDE THAT COULD DROP NEAR OR BELOW FREEZING, ESPECIALLY
AS THE SKIES SHOULD BE CLEAR AND RADIATIVE COOLING SHOULD BE VERY
EFFICIENT. HAVE OPTED TO ISSUE A FREEZE WATCH FOR AREAS THAT LOOK
THE MOST LIKELY TO SEE A GOOD FROST OR A FREEZE. THERE IS SOME
UNCERTAINTY REGARDING THE EXACT TEMPERATURES THAT THE AREAS WILL
DROP TO, BUT FEEL THAT THE OFFICIAL FORECAST IS MORE LIKELY TO BE
TOO WARM THAN TOO COLD. WITH INCREASING CERTAINTY AND ANOTHER PAIR
OF EYES ON THE NEXT FORECAST CYCLE, CONFIDENCE SHOULD INCREASE,
AND THE WATCH CAN THEN BE UPGRADED TO THE NECESSARY FROST AND/OR
FREEZE HEADLINES.

FOR WEDNESDAY AND BEYOND, THERE IS NOT MUCH TO SPEAK OF OTHER
THAN WARMER TEMPERATURES AND DRY CONDITIONS. MODELS, DESPITE THEIR
CONTINUING INCONSISTENCIES IN THE LONG TERM, REMAIN FIRMLY
CONVINCED IN THE GENERAL PATTERN: THAT OF A LARGE BROAD TROUGH
OVER THE REGION BEGINNING MIDWEEK AND PERSISTING THROUGH THE
REMAINDER OF THE FORECAST PERIOD. THE SYNOPTIC MODELS SEEM TO BE
HAVING SOME DIFFICULTY COMING TO A CONSENSUS CONCERNING SOME
FEATURES WITHIN THE WESTERLIES UPSTREAM, AND THIS IS LEADING TO
THE INCREASED DISCREPANCIES BETWEEN RUNS. KEEPING THIS IN MIND, A
STRAY SHORTWAVE CAN NOT BE RULED OUT EARLY NEXT WEEK, BUT WITH THE
RETURN OF THE THERMAL TROUGH AND OFFSHORE FLOW, AND SUCH A LARGE
RIDGE OVERHEAD, A SMALLER WEAKER FEATURE WILL HAVE A TOUGH TIME
MAKING ANY SIGNIFICANT HEADWAY INTO THE FORECAST AREA. HAVE
THEREFORE KEPT PRECIPITATION OUT OF THE FORECAST AND KEPT
TEMPERATURES AT ROUGHLY 5 TO 10 DEGREES ABOVE NORMAL FOR THE
DURATION. -BPN

AVIATION...FOR THE 30/00Z TAF CYCLE...
A WEAK COLD FRONT IS PUSHING AND WILL CONTINUE TO PUSH RAIN ACROSS
THE WEST SIDE AND ONTO THE CASCADES THIS EVENING INTO TONIGHT. THE
FRONT WILL WEAKEN AS IT MOVES ONTO THE EAST SIDE. MVFR AND IFR
ALONG THE COAST AND UMPQUA BASIN THIS EVENING WILL LOWER TO IFR WITH
ISOLATED LIFR OVERNIGHT INTO THE MORNING. FURTHER INLAND, IN THE
ROGUE VALLEY, MVFR IS EXPECTED TO DEVELOP. EXPECT PARTIAL TERRAIN
OBSCURATIONS FROM THE CASCADES WESTWARD TO BECOME NEAR TOTAL THIS
EVENING BEFORE BECOMING PARTIAL AGAIN OVERNIGHT. ON THE EAST SIDE
PARTIAL TERRAIN OBSCURATIONS WILL DEVELOP DURING THE EVENING AND
OVERNIGHT, BUT VALLEYS SHOULD REMAIN MOSTLY VFR. ON TUESDAY MVFR ON
THE WEST SIDE WILL BREAK UP LATE MORNING THROUGH MID-AFTERNOON. BTL

MARINE...UPDATED 3PM PDT MON 29 SEP 2014...
A WEAK COLD FRONT WILL CONTINUE TO MOVE ONSHORE THROUGH THIS
EVENING. THIS WILL CAUSE WINDS TO BECOME NORTHERLY. THESE NORTH
WINDS WILL INCREASE AND SEAS WILL STEEPEN TUESDAY AND WEDNESDAY AS
HIGH PRESSURE BUILDS FROM THE WEST. THERE IS SOME UNCERTAINTY AS
TO WHETHER OR NOT WINDS WILL BEGIN TO DIMINISH ON THURSDAY. ON
FRIDAY A FRONT PUSHING INTO WESTERN CANADA IS LIKELY TO PUSH THE
OFFSHORE HIGH A BIT FURTHER EAST CAUSING WINDS AND SEAS TO
DIMINISH SOME BEFORE LIKELY INCREASING AGAIN OVER THE WEEKEND. BTL

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FREEZE WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY MORNING
     FOR ORZ029>031.

CA...FREEZE WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY MORNING
     FOR CAZ082-084-085.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS FROM 2 PM TUESDAY TO 11 AM PDT
     THURSDAY FOR PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 PM TUESDAY TO 11
     AM PDT THURSDAY FOR PZZ376.
     SMALL CRAFT ADVISORY FOR WINDS FROM 2 PM TUESDAY TO 11 PM PDT
     WEDNESDAY FOR PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 PM TUESDAY TO 11
     PM PDT WEDNESDAY FOR PZZ356.

FJB/FJB/BTL