PBZ issues Area Forecast Discussion (AFD) at Nov 17, 1:01 PM EST722
FXUS61 KPBZ 171801
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
101 PM EST Sun Nov 17 2024
.SYNOPSIS...
Dry conditions are expected into this evening. A weak front
brings scattered showers mainly north of Pittsburgh late
tonight. Dry weather is forecast Monday and Monday night. A
trend towards a colder and more active weather pattern begins
Wednesday and continues into next weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- A weak front may produce a few showers north of Pittsburgh
overnight.
- Mild low temperatures.
------------------------------------------------------------------
Mid-level ridging continues to cross the area today, with
continued dry weather. Through the afternoon, mid and upper
cloud cover is expected on southwest flow aloft. With rising
heights and warm advection, daytime highs will top out around 5
degrees warmer than observed Saturday.
A quick-moving shortwave tracks north of the region tonight.
This will also drop a weak frontal boundary into northern
portions of the CWA by morning. Overall moisture and lift look
weak, and thus will maintain only a small chance of light rain
north of Pittsburgh, with dry weather expected elsewhere.
Overnight low temperatures will remain a bit above normal.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
KEY MESSAGES:
- Dry Monday, but light rain chances return Tuesday with a warm
front.
- Upward trend in temperatures during the early week period.
-------------------------------------------------------------------
With the departure of the mid-level shortwave by morning, the weak
cold front appears likely to stall across central portions of the
CWA on Monday as surface high pressure bridges across the boundary.
With another ridge axis briefly building in the Ohio Valley
Monday night, the front should then head back north as a warm
front. Dry weather continues through this period. Despite cooler
850mb temperatures on Monday, thinner cloud cover will allow
for better insolation, resulting in high temperatures several
degrees warmer than those on Sunday. Above-normal temperatures
are also projected Monday night with the return of warm
advection.
On Tuesday, there is good ensemble agreement into Tuesday night that
upper troughing becomes more established across the Upper
Midwest/western Great Lakes, with associated surface low pressure.
The more significant impacts of the upper system will be felt later
in the week, as discussed in the extended discussion below. However,
the resulting shift to low-level southwest flow behind the warm
front will bring 1-inch plus precipitable water values and
increasing isentropic lift into our region. This should result
in a period of generally light rainfall Tuesday into Tuesday
night. The southwest flow will also reinforce above-normal
temperature.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
KEY MESSAGES:
- Steadier rain on Wednesday with a cold front.
- Much colder temperature appears likely Thursday into the weekend,
along with additional precipitation chances and a period of gusty
wind.
- Measurable snow is a possibility in most of the region at some
point between Thursday and Saturday, with impactful accumulation
possible in the higher elevations.
-------------------------------------------------------------------
The bottom line for the extended period is that a stark pattern
change remains likely: a transition to a colder regime with multiple
chances of precipitation. Exact details of course remain in
question.
Virtually all model solutions now agree that a closed 500mb low will
develop in the vicinity of the far western Great Lakes/Upper
Mississippi Valley by 12Z Wednesday. There is also broad agreement
that this upper low will transition across the Upper Ohio Valley and
northeast CONUS through the Thursday/Friday period, before lifting
towards the Canadian Maritimes next weekend. Confidence in this
overall scenario is now edging towards the high category.
Given that, detail differences in strength and timing remain. Some
of this depends on the strength of the ridging that will very likely
remain along the Atlantic Seaboard on Wednesday. There remains a
minority of solutions that lean towards a stronger ridge. As a
result, there are model clusters keeping the upper low center more
towards the Middle Ohio Valley initially into Thursday, or perhaps
keeping the overall trough from digging as strongly, thus keeping
the center more towards the Great Lakes. These scenarios could slow
the arrival of colder air a bit. However, the majority of members
still are going with the more aggressive arrival of the low into our
vicinity by Thursday. Thus, a lean towards the lower end of the
temperature guidance envelope seems prudent for the end of the week.
Bimodal solutions of earlier runs continue to trend towards a more
confident depiction of colder temperature. Also of note: a prolonged
period of gusty wind is also likely in this pattern. Probabilities
of greater than 45 MPH (advisory-level) gusts remain low outside of
eastern Tucker County, but maximum gusts of 30 to 40 MPH have 50% or
better probability areawide Wednesday through Friday.
At least a few rounds of precipitation appear likely into the
weekend: an initial wave ahead of the main cold frontal passage,
followed by additional periods as a result of wraparound moisture
and shortwaves in northwest flow. Of course, given the colder
solution, snow possibilities must be considered starting as early as
Wednesday night. The entire CWA has some potential for measurable
snow. Even the typically warmer metro/valley areas have a 40-50%
chance of at least 0.1 inch during the 72-hour period ending at 12Z
Sunday according to the NBM. However the area to watch will be the
Laurel Highlands and the West Virginia ridges. For the same 72-hour
period, impressively large spreads in modeled snow accumulation
exist, particularly for the higher elevations of Preston and Tucker
Counties. Totals will of course depend on temperature structure and
support for vertical motion from both dynamic and upslope effects,
details which need to be ironed out in future runs. However, there
is certainly the potential for impactful snow accumulation in these
favored locations. This forecast will of course be refined as we
head through the upcoming week.
Model clusters show some potential for quieter weather by Sunday as
the upper low and associated trough move east, resulting in lower
precipitation chances. However, the majority of solutions continue
to show well below-normal temperatures on that day.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
VFR will continue into tonight with 5-10kt southerly winds and
increasing cirrus. A shortwave and associated surface boundary
will approach from the northwest by 06z. Rainfall probabilities
have decreased with the latest guidance so have included only DZ
at FKL and VCSH elsewhere. However, this feature will increase
MVFR potential (40-60%) after 12z. Cigs should quickly rise and
mix out by early afternoon as VFR returns areawide.
Outlook....
A series of increasingly potent low pressure systems will bring
bouts of restrictions, gusty wind, and rain turning into
potential snow showers for the second half of the week.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...CL
NEAR TERM...CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...Rackley
Source:
PBZ issues Area Forecast Discussion (AFD) at Nov 17, 1:01 PM EST---------------
If I'm using your data in a way that is against your terms please email the team at "threatweb@pupswoof117.com"! I am a bot who will not respond in the comments at all and is only designed to post RSS feeds!
