Area forecast discussion
National Weather Service Medford or
828 PM PDT Thursday may 23 2013
Discussion...no updates planned this evening. A steady stream of
moisture remains aimed at the north coast and Umpqua areas this
evening. While webcams generally show dry roads and many area observation
haven't recorded rain in a while, there is another plume of deeper
moisture moving south along the coast, so rain ought to start up
over these areas this evening and continue tonight. The rest of
US are currently dry and will likely only be dodging scattered
showers tonight. The current forecast covers this well. -Wright
&&
Aviation...low pressure to the north will continue to bring some
light rain along with a mix of VFR and MVFR north of the Umpqua
Divide and along the north coast through tonight. Mostly VFR is
expected south of the Umpqua Divide through tonight, but cannot
rule out some MVFR in isolated areas overnight...then again toward
sunrise over the valleys. Partial mountain obscuration is also
likely, especially across the northern half of the County Warning Area. East of
the Cascades...some scattered showers could result in brief
periods of MVFR through tonight. Otherwise...VFR will prevail.
-Bpn
&&
Previous discussion... /issued 235 PM PDT Thursday may 23 2013/
Short term...the upper low remains over the region today and
tonight. As the center of the low swings southward along the
coast today then inland this evening and tonight expect additional
showers to move into the area. On Friday the low center will shift
northeast then a broad trough remains over the region on Saturday
and Sunday. Embedded with the trough...another shortwave is
forecast to move towards the coast Saturday and inland Saturday
night and Sunday. This will bring additional showers Saturday with
increasing shower activity on Sunday. Also during the afternoon
and evening today and again on Saturday and Sunday there is a
slight chance for thunderstorms for location east of the Cascades.
Scattered showers and isolated thunderstorms have develop east of
the Cascades this afternoon while from the Cascades west...showers
are expected to develop late this afternoon into this evening as
the upper low center moves into central Oregon. The best chances
for shower activity will be over Coos and Douglas counties as well
as into the southern Oregon Cascades with isolated to scattered
showers in other areas of the County Warning Area. Also of note is that another
cool night is expected east of the Cascades tonight into early
Friday morning with low temperatures expected near or just above
freezing. In the Klamath basin...do not expect widespread freezing
conditions tonight and areas that reach freezing may just briefly
dip into the low 30s so have not issued a freeze warning for this
area.
As the low center tracks to the northeast on Friday expect
decreasing showers across the area by afternoon. Models continue to
indicate a broad trough will remain over the region through the
weekend. This is expected to bring mild temperatures with highs
near or just below normal. Chances for showers will continue as
well on the weekend. Another shortwave is forecast to move towards
the area Saturday then inland Sunday. Ahead of the shortwave
expect some scattered showers to develop Saturday afternoon and
evening. A slight chance of thunderstorms is also
possible...mainly east of the Cascades on Saturday. By Sunday
models indicate continued moisture and increasing instability.
Expect most areas to see a chance for showers Sunday with
thunderstorms possible in the afternoon and evening from the
Cascades east.
Long term...Memorial Day through Thursday...confidence remains high
in the overall weather pattern in the extended as gefs/European model (ecmwf)
ensemble means both focus a trough over the western United States
with below normal heights. While it won't be as cool as it was
earlier this week, temperatures overall for the period will likely
remain slightly below normal. That translates to upper 60s and lower
70s for highs in Medford. Timing and strength details of individual
short waves moving into the northwest will be difficult, but the
strongest is likely to arrive at the coast Monday morning, then push
inland during the afternoon/evening. The 00z deterministic run of
the European model (ecmwf) was weaker and farther south with this feature, but the
12z run has come more in line with the 12z GFS (though still is a
bit weaker and farther south). Even so, felt confident enough here
to increase probability of precipitation during this time, since that is where the focus of
precipitation likely will be. Heights will rise a bit Tuesday, but remain
below normal, so have maintained slight chance to chance probability of precipitation. Models
showing another short wave approaching the coast Wednesday into
Thursday in the moist westerly onshore flow. This should keep the
probability of showers highest along and west of the Cascades.
Beyond that, the GFS ensembles carve another deep trough/closed low
over the area/just offshore next weekend, while the European model (ecmwf) is flatter
and more zonal. Spilde
&&
Mfr watches/warnings/advisories...
or...none.
California...none.
Pacific coastal waters...Small Craft Advisory for hazardous seas until
5 am PDT Friday for pzz370-376.
Small Craft Advisory for hazardous seas until 2 am PDT Friday
for pzz350.
$$
